Energies

2024

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15 pages, 6866 KiB

Open AccessArticle

Analysis of the Possibility of Applying Biochars from Biowaste as Adsorbents to Eliminate Odors from Wastewater Treatment

by Jacek Piekarski, Katarzyna Ignatowicz, Tomasz Dąbrowski and Bartosz Dąbrowski

Energies 2024, 17(16), 4129; https://doi.org/10.3390/en17164129 - 19 Aug 2024

Cited by 1 | Viewed by 683

Abstract

Due to its nitrogen, phosphorus, and magnesium content, sewage sludge is used, among other things, to grow plants for energy purposes or to intensify biogas production. These processes are always accompanied by odor emissions, which are treated as pollution according to European legislation [...] Read more.

Due to its nitrogen, phosphorus, and magnesium content, sewage sludge is used, among other things, to grow plants for energy purposes or to intensify biogas production. These processes are always accompanied by odor emissions, which are treated as pollution according to European legislation and are subject to legal regulations in many countries. Therefore, this publication presents the results of a study on the removal of odor from sewage sludge by adsorption on biochars produced from selected biowaste. Beekeeping waste (grain) and coffee brewing residues (spent coffee grounds) were selected for the study. Both materials were pyrolyzed to produce biochar which was applied for adsorption of odors from sewage sludge. Commercial Organosorb 200-1 Wi activated carbon was used as a comparison material. The odors were taken from dried sewage sludge from a municipal wastewater treatment plant. The obtained biochars are suitable for odor adsorption and can be an alternative to commercial adsorbents. The biochar from beekeeping waste showed the highest efficiency, allowing 100% odor removal. Slightly worse results were obtained for biochar from spent coffee grounds. Full article

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23 pages, 2109 KiB

Open AccessArticle

Improving the Methodology for Determining the Biomass/Coal Co-Combustion Ratio: Predictive Modeling of the ¹⁴C Activity of Pure Biomass

by Yinchen Wang, Zhongyang Luo, Chunjiang Yu, Sheng Wang, Xiaohuan Wang and Peiliang Zhu

Energies 2024, 17(4), 942; https://doi.org/10.3390/en17040942 - 17 Feb 2024

Viewed by 1188

Abstract

Sampling and ¹⁴C detection of biomass are now essential steps to ensure the accuracy of the ¹⁴C method, but they require additional time and economic investment. When there are multiple types of biomass fuels, it is not possible to guarantee the [...] Read more.

Sampling and ¹⁴C detection of biomass are now essential steps to ensure the accuracy of the ¹⁴C method, but they require additional time and economic investment. When there are multiple types of biomass fuels, it is not possible to guarantee the uniformity of sampling. The ¹⁴C activity of biomass fuels exhibits variability, and this value significantly impacts the precision of the ¹⁴C method. Therefore, this study aims to investigate the influencing factors of ¹⁴C activity in biomass fuels. It also provides predicted values of ¹⁴C activity for different types of biomass fuels for each year from 2020 to 2030. Additionally, this study discusses the potential blending ratio measurement errors that may arise due to the uncertainties of the predicted values. The reduction in the ¹⁴C activity of biomass fuels can occur due to the utilization of fossil fuels, human activities, and the photosynthesis mode of C3 plants. This study presents a prediction method for determining the reduction factor. The other component of the prediction methodology involves determining the original ¹⁴C activity of biomass fuels. The ¹⁴C activity of the annual biomass is equal to the ¹⁴CO₂ activity (the ¹⁴C activity of CO₂) of the surrounding environment, and it experiences a decline of 0.355 pMC/year. The ¹⁴C activity has ranges of five types of perennial biomass fuels, including wood chips and branches, bark, leaves, wasted furniture, and abandoned building wood, for the time period between 2020 and 2030, are 97.34~102.84, 96.35~106.27, 96.35~102.64, 111.00~118.60, and 111.32~129.47 pMC, respectively. Based on these, this study introduces a new formula for calculating blending ratios, which enhances the current methodology. The calculation errors of blending ratios caused by the uncertainties of the predicted values are generally negligible, with the exception of wasted furniture and construction wood. The annual decrease in the blending ratio calculation error, caused by the uncertainty associated with the predicted value, can be observed. This study aims to reduce the implementation time and economic cost of the ¹⁴C method while ensuring the accuracy of biomass blending ratio detection. Full article

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19 pages, 4511 KiB

Open AccessArticle

Calibration Techniques for Water Content Measurements in Solid Biofuels

by Henrik Kjeldsen, Peter Friis Østergaard, Helena Strauss, Jan Nielsen, Bayan Tallawi, Eric Georgin, Pierre Sabouroux, Jan G. Nielsen and Jens Ole Hougaard

Energies 2024, 17(3), 635; https://doi.org/10.3390/en17030635 - 28 Jan 2024

Viewed by 1214

Abstract

This paper presents methodologies and equipment for SI-traceable inline measurements of water content (a critical quality parameter) in solid biofuels. Inline measurement systems for water content are commonly used at CHP plants, providing continuous real-time data. However, the accuracy of these systems is [...] Read more.

This paper presents methodologies and equipment for SI-traceable inline measurements of water content (a critical quality parameter) in solid biofuels. Inline measurement systems for water content are commonly used at CHP plants, providing continuous real-time data. However, the accuracy of these systems is in most cases unsatisfactory, mainly because the systems are not calibrated representatively for the relevant material, and until now, calibrations traceable to the SI system have not been available. To provide reliable and accurate inline water content data, new procedures and equipment for calibrating measurement systems were developed. Two reference methods for the determination of water content were developed; one measures the airflow and dewpoint of desorbed water in the air passing a test sample, while the other uses a P₂O₅-sensor. Additionally, a transfer standard based on a cavity resonance sensor was developed for fast onsite calibration of the inline sensor at the power plant. This new instrument allows for quick and accurate measurements. The transfer standard is made metrologically traceable to the primary measurement standards. The entire system was demonstrated by calibrating an inline microwave-based (MW) sensor at the CHP plant of VERDO in Randers, Denmark. Thus, a complete metrological traceability chain was established from an industrial to a primary standard. Full article

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2023

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15 pages, 2695 KiB

Open AccessArticle

Experimental Investigation of Single-Cylinder Engine Performance Using Biodiesel Made from Waste Swine Oil

by Ramozon Khujamberdiev, Haeng Muk Cho and Md. Iqbal Mahmud

Energies 2023, 16(23), 7891; https://doi.org/10.3390/en16237891 - 3 Dec 2023

Cited by 4 | Viewed by 1218

Abstract

The global push towards sustainable energy solutions has intensified research into alternative fuels, such as biodiesel. This study investigates the performance and emission characteristics of biodiesel derived from waste swine oil in comparison to traditional diesel fuel. Using an engine running at 75% [...] Read more.

The global push towards sustainable energy solutions has intensified research into alternative fuels, such as biodiesel. This study investigates the performance and emission characteristics of biodiesel derived from waste swine oil in comparison to traditional diesel fuel. Using an engine running at 75% load across a range of speeds (1200 rpm to 1800 rpm), various metrics such as Brake-Specific Fuel Consumption (BSFC), Brake Thermal Efficiency (BTE), and emissions including Carbon Monoxide (CO), Hydrocarbon (HC), Carbon Dioxide (CO₂₎, Nitrogen Oxide (NOx), and smoke opacity were measured. The biodiesel demonstrated a higher BSFC (270 g/kWh) compared to diesel (245 g/kWh) but showed reduced Brake Thermal Efficiency (28.5% vs. 29.8%) compared to diesel. In terms of emissions, biodiesel blends recorded lower levels of CO, HC, and smoke opacity, but elevated levels of CO₂ and NOx. The results indicate that while biodiesel from waste swine oil presents some environmental benefits, such as reduced CO, HC, and smoke emissions, challenges remain in terms of higher NOx emissions and less efficient fuel consumption. Full article

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28 pages, 9899 KiB

Open AccessArticle

Optimization of Welding Process of Geomembranes in Biodigesters Using Design of Factorial Experiments

by Rocio Camarena-Martinez, Roberto Baeza-Serrato and Rocio A. Lizarraga-Morales

Energies 2023, 16(18), 6583; https://doi.org/10.3390/en16186583 - 13 Sep 2023

Viewed by 1104

Abstract

This research focuses on the optimization of the thermofusion process in the construction of biodigesters as it has a direct influence on their quality and durability. The study utilizes factorial experiments and statistical analysis, with particular emphasis on the innovative application of the [...] Read more.

This research focuses on the optimization of the thermofusion process in the construction of biodigesters as it has a direct influence on their quality and durability. The study utilizes factorial experiments and statistical analysis, with particular emphasis on the innovative application of the arcsine transformation. Two

2^{k}

factorial designs were developed to account for warm and cold weather. The experiments evaluated factors such as the operator’s experience, wedge sealing temperature, sealing speed, and extruder temperature. The effects on the response variables were analyzed, which included overheating, resistance, and leaks. The study identified significant influences of the operator and the temperature of the wedge sealer in warm weather conditions, while the operator’s influence remained prominent in resistance and leakage tests in cold weather. Data transformation techniques, including the arcsine transformation, were employed to ensure statistical validity. Optimal input variable combinations were identified to maximize resistance and minimize overheating and air leaks. The research emphasizes the importance of optimizing the thermofusion process for biodigester construction, highlighting the role of arcsine transformation in improving statistical analysis. The findings enable practitioners to make informed decisions, leading to improvements in welding processes and overall biodigester quality. Full article

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22 pages, 20262 KiB

Open AccessArticle

Investigation of Pyrolysis Kinetic Triplet, Thermodynamics, Product Characteristics and Reaction Mechanism of Waste Cooking Oil Biodiesel under the Influence of Copper Slag

by Tianhao Shen, Fengxia Zhang, Shiliang Yang, Hua Wang and Jianhang Hu

Energies 2023, 16(5), 2137; https://doi.org/10.3390/en16052137 - 22 Feb 2023

Cited by 1 | Viewed by 1883

Abstract

WCO-Biodiesel can be used as a fuel instead of fossil energy for the copper smelting industry will not only save resources but also protect the environment. The pyrolysis of WCO-Biodiesel in the melting pool is influenced to some extent by the copper slag [...] Read more.

WCO-Biodiesel can be used as a fuel instead of fossil energy for the copper smelting industry will not only save resources but also protect the environment. The pyrolysis of WCO-Biodiesel in the melting pool is influenced to some extent by the copper slag (CS) generated during the copper smelting process. In this study, the effects of CS on the kinetic triplet, thermodynamics, product characteristics and reaction mechanism of WCO-Biodiesel are comprehensively investigated via a thermogravimetric analyzer and pyrolysis experimental system. Firstly, the apparent activation energy (E_α) is calculated using STR, and E_α decreased at different α under the influence of CS. Then, the trend of the WCO-Biodiesel pyrolysis mechanism with α is determined by the master plots method based on 18 commonly used models similar to the Pn and D1 models. The analysis of WCO-Biodiesel pyrolysis gas products shows that more flammable gases containing H are formed under the influence of CS. The analysis of the liquid products shows that more PAHs and more small molecule products are generated under the influence of CS. Two coke products are produced at high temperatures, which differ significantly in microscopic morphology, spherical carbon particle size and chemical structure. Finally, the mechanism of pyrolysis of the main components in WCO-Biodiesel in the high-temperature environment of melt pool melting is explored. Full article

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20 pages, 10110 KiB

Open AccessArticle

Assessment of Irregular Biomass Particles Fluidization in Bubbling Fluidized Beds

by David Bannon, Mirka Deza, Masoud Masoumi and Bahareh Estejab

Energies 2023, 16(4), 2051; https://doi.org/10.3390/en16042051 - 19 Feb 2023

Cited by 4 | Viewed by 2049

Abstract

Biomass as a clean and renewable source of energy has immense potential to aid in solving the energy crisis in the world. In order to accurately predict the fluidization behavior of biomass particles using the Eulerian–Eulerian approach and the kinetic theory for granular [...] Read more.

Biomass as a clean and renewable source of energy has immense potential to aid in solving the energy crisis in the world. In order to accurately predict the fluidization behavior of biomass particles using the Eulerian–Eulerian approach and the kinetic theory for granular flows (KTGF), employing appropriate models that adapt to irregularly shaped particles and can precisely predict the interaction between particles is crucial. In this study, the effects of varying radial distribution functions (RDF), frictional viscosity models (FVM), angles of internal friction (

ϕ

), and stress blending functions (SBF) on the performance of two-fluid models (TFM) were investigated. Simulation predictions were compared and validated with the previous experiments in the literature on Geldart B biomass particles of walnut shells. When applying sphericity to account for size irregularities of biomass particles, the results of this study demonstrated that predictions of both the Ma–Ahmadi and the Carnahan–Starling RDFs along with the Schaeffer FVM agree with experimental data. More specifically, the bubbling behavior prediction slightly favored the use of the Ma–Ahmadi RDF for biomass particles. The results also revealed the importance of using FVM regardless of the initial void fraction. The use of the Schaeffer FVM became more important as time proceeded and particle bulk density decreased. With the change of

ϕ

and the application of SBF, no significant differences in the time-averaged results were observed. However, when

ϕ

ranges were between 30 and 40, the predictions of bubbling behavior became more greatly aligned with experimental results. Full article

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10 pages, 1958 KiB

Open AccessArticle

Automatic Fed-Batch Cultivation Enhances Microbial Lipid Production from Volatile Fatty Acids

by Subin Shin, Jae Hee Go, Myounghoon Moon and Gwon Woo Park

Energies 2023, 16(4), 1996; https://doi.org/10.3390/en16041996 - 17 Feb 2023

Cited by 2 | Viewed by 1617

Abstract

Organic waste is generated worldwide, and its disposal and recycling are becoming a challenge. Due to its high carbon content, however, it may be converted into valuable products. Carbon neutrality is essential, and unstable international oil prices stress the increasing importance of biofuels [...] Read more.

Organic waste is generated worldwide, and its disposal and recycling are becoming a challenge. Due to its high carbon content, however, it may be converted into valuable products. Carbon neutrality is essential, and unstable international oil prices stress the increasing importance of biofuels significantly. Volatile fatty acids (VFA) derived from organic waste can be converted to microbial lipids by oleaginous yeast using it as a carbon source. When VFA is consumed by oleaginous yeast, the pH of the medium rises; hence, acidic agents have to be added to the medium to maintain the broth’s pH. In this study, we enhanced microbial lipid productivity by automatic fed-batch cultivation using VFA as an acidic agent, and the modified cultivation showed 48.9% and 69.0% higher biomass and lipid productivity than manual multi-fed culture. At a VFA concentration of 5 g/L and pH 7.0, a lipid yield of 0.25 g/g alongside lipid productivity of 0.11 g/L/h was obtained from an automatic fed-batch system. Oleic acid accounted for the largest proportion of microbial lipids, and the fatty acid composition was suitable for biodiesel production. Full article

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2021

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24 pages, 14796 KiB

Open AccessArticle

Modelling of a Torrefaction Process Using Thermal Model Object

by Alok Dhaundiyal and Laszlo Toth

Energies 2021, 14(9), 2481; https://doi.org/10.3390/en14092481 - 27 Apr 2021

Viewed by 1745

Abstract

So far, the torrefaction process has been merely discussed based on the physical and chemical characteristics of the final product, but the mechanism has not been yet pondered and investigated. Thus far, microwave torrefaction has been predominately used for thermal pre-treatment; therefore, a [...] Read more.

So far, the torrefaction process has been merely discussed based on the physical and chemical characteristics of the final product, but the mechanism has not been yet pondered and investigated. Thus far, microwave torrefaction has been predominately used for thermal pre-treatment; therefore, a paradigm shift in the methodology has been introduced by using a Joule heating system. The article mainly focuses on the thermal engineering aspect of the torrefaction process. The densified black pine underwent thermal pre-treatment at a temperature of 523 K. The furnace used for torrefaction was initially improvised to carry out thermal degradation at quasi-static/dynamic conditions. A 3D PDE thermal model was developed to determine the numerical solution and temperature distribution across a black pine pellet. To compare the effect of the linear ramping profile, time-dependent as well as fixed Dirichlet conditions were applied to the proposed model. The mass distribution, duration of the torrefaction process, the effect of Nusselt and Reynold’s number of inert gas, and thermal history are some of the factors whose influence on the numerical solution was investigated. The simulation of thermal pre-treatment and its effect on the heat transfer characteristic was examined with help of a PDE thermal model, whereas the numerical solution of diffusion of the product of reactions was determined by solving the partial differential equations with the help of the discretisation method (PDEPE). The densification of black pine was performed in a ring die, whereas initial milling of biomass was carried out using a 1.5 mm sieve size. The system was found to have a homogeneous distribution in energy and temperature with time, whereas the amplitude of heat flux along the radial direction was reduced by 15% if the same pellet underwent torrefaction for a duration of 5 min in dynamic mode. Similarly, a 64.46% drop in amplitude of heat flux along the azimuth plane could be seen while performing torrefaction in a time-dependent thermal history. However, the relative amplitude of the heat flux at the centre of the pellet was estimated to be lowered by 98.41% along the vertical axis for heating a pellet in a quasi-static condition. The net change in the mass fraction of carbon dioxide across the boundary film was seen to be 40% higher than that of carbon monoxide. The rate of change of mass fraction of carbon monoxide across the boundary film was increased by 7–11% with the increase in torrefaction time. A 6.8% rise in the evaporation of water was noticed during the first half interval of torrefaction (from 5 min to 10 min). In the second half, from 10 min to 15 min, it was merely increased by 5.8%. A relative drop of 17.24% in water evaporation was estimated in the dynamic state of the system. Full article

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2020

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19 pages, 5015 KiB

Open AccessArticle

A Methodology for Measuring the Heat Release Efficiency in Bubbling Fluidised Bed Combustors

by Dominik Müller, Thomas Plankenbühler and Jürgen Karl

Energies 2020, 13(10), 2420; https://doi.org/10.3390/en13102420 - 12 May 2020

Cited by 14 | Viewed by 2352

Abstract

Differences in the densities of bed material and—especially biogenic—solid fuels prevent an ideal mixture within bubbling fluidised bed (BFB) combustors. So, the presence of fuel particles is usually observed mainly near the surface of the fluidised bed. During their thermal conversion, this leads [...] Read more.

Differences in the densities of bed material and—especially biogenic—solid fuels prevent an ideal mixture within bubbling fluidised bed (BFB) combustors. So, the presence of fuel particles is usually observed mainly near the surface of the fluidised bed. During their thermal conversion, this leads to a release of unburnt pyrolysis products to the freeboard of the combustion chamber. Within the further oxidation, these species will not transfer their heat-of-reaction to the inert bed material in the way of a convective heat transfer, but rather increase the gas phase temperature providing probably some additional radiative heat transfer to the dense bed. In this case, the so-called heat release efficiency to the fluidised bed, being the ratio of transferred heat to the fuel input, will be reduced. This paper presents a methodology to quantify this heat release efficiency with lab-scale experiments and the observed effects of common operating parameters like bed temperature, fluidisation ratio and fuel-to-air ratio. Experimental results show that the air-to-fuel ratio dominates the heat release efficiency, while bed temperature and fluidisation ratio have minor influences. Full article

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13 pages, 1612 KiB

Open AccessArticle

Effects of Nitrogen Forms and Supply Mode on Lipid Production of Microalga Scenedesmus obliquus

by Mei An, Li Gao, Wen Zhao, Weiguang Chen and Ming Li

Energies 2020, 13(3), 697; https://doi.org/10.3390/en13030697 - 6 Feb 2020

Cited by 48 | Viewed by 4625

Abstract

Optimization of the microalgae culture conditions could significantly reduce the production costs of microalgae-derived biodiesel. In the current study, a new process of adding different forms using the multiple small-dose method was employed. The effects of different forms of nitrogen (NaNO₃, [...] Read more.

Optimization of the microalgae culture conditions could significantly reduce the production costs of microalgae-derived biodiesel. In the current study, a new process of adding different forms using the multiple small-dose method was employed. The effects of different forms of nitrogen (NaNO₃, NH₄Cl, and CH₄N₂O) and their concentrations (0.1, 0.5, 1, and 2 mg L⁻¹) on the growth and lipid production of Scenedesmus obliquus were studied. Algae density and lipid production increased with increasing nitrogen concentration for all different forms of nitrogen except NH₄Cl. The Scenedesmus obliquus growth was promoted by adding NaNO₃ and CH₄N₂O, but was inhibited by adding NH₄Cl. Adding 2 mg N L⁻¹ of CH₄N₂O daily yielded the highest cell density (1.7 × 10⁷ cells mL⁻¹) and lipid production (242.4 mg L⁻¹). These conditions can thus maintain the biomass of Scenedesmus obliquus, increase its lipid accumulation, and decrease the costs of biodiesel production. Full article

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2019

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12 pages, 3253 KiB

Open AccessArticle

Factors Affecting the Corrosive Behavior of Used Cooking Oils and a Non-Edible Fish Oil That Are in Contact with Ferrous Metals

by Nina Bruun, Abayneh Getachew Demesa, Fiseha Tesfaye, Jarl Hemming and Leena Hupa

Energies 2019, 12(24), 4812; https://doi.org/10.3390/en12244812 - 17 Dec 2019

Cited by 6 | Viewed by 4924

Abstract

The corrosion behavior of three used cooking oils and one non-edible fish oil was experimentally investigated by the immersion test of iron rods at room temperature. The corrosivity of the tested oils was indirectly determined from the amount of the dissolved iron in [...] Read more.

The corrosion behavior of three used cooking oils and one non-edible fish oil was experimentally investigated by the immersion test of iron rods at room temperature. The corrosivity of the tested oils was indirectly determined from the amount of the dissolved iron in the tested oils after the immersion test. Different factors that affect the corrosive behavior of the tested oils were assessed. Among the tested oils, the fish oil showed the highest amount of dissolved iron owing to its chemical properties such as high water content and acid number. In general, water content and acid number have direct effects on the amount of dissolved iron. The addition of oleic acid to the used cooking oil resulted in a 60% less amount of dissolved iron. It was suggested that the addition of oleic acid prompted the formation of a monolayer, which inhibited the permeation of oxygen and water to the surface of the iron rod. Moreover, the addition of glycerol gave the lowest amount of dissolved iron in the oil sample owing to its ability to bind water molecules and form microemulsions in the presence of a surfactant (for example, oleic acid). Full article

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11 pages, 1081 KiB

Open AccessArticle

The Effect of Lignin Content in Birch and Beech Kraft Cellulosic Pulps on Simple Sugar Yields from the Enzymatic Hydrolysis of Cellulose

by Kamila Przybysz Buzała, Halina Kalinowska, Edyta Małachowska, Piotr Boruszewski, Krzysztof Krajewski and Piotr Przybysz

Energies 2019, 12(15), 2952; https://doi.org/10.3390/en12152952 - 31 Jul 2019

Cited by 19 | Viewed by 3537

Abstract

The results of enzymatic hydrolysis of birch and beech kraft cellulosic pulps indicate that they may be promising feedstocks for fermentation processes including biofuel manufacturing. The aim of this study was to investigate whether birch and beech wood require the same degree of [...] Read more.

The results of enzymatic hydrolysis of birch and beech kraft cellulosic pulps indicate that they may be promising feedstocks for fermentation processes including biofuel manufacturing. The aim of this study was to investigate whether birch and beech wood require the same degree of delignification by kraft pulping as pine wood. The differences observed in the efficiency of hydrolysis for the raw materials tested suggest that the differences in the anatomical structure of the examined wood in relation to pine wood is essential for the efficiency of the enzymatic hydrolysis process. The yields of glucose and other reducing sugars obtained from the birch and beech cellulosic pulps were similar (up to around 75% and 98.3% dry weight, and 76% and 98.6% dry weight, respectively). The highest glucose yields from cellulose contained in the birch and beech pulp were around 81.2% (at a Kappa number of 28.3) and 83.1% (at a Kappa number of 30.4), respectively. The maximum glucose yields and total reducing sugars of birch wood on a dry weight basis (39.8% and 52.1%, respectively) were derived from the pulp at a Kappa number of 28.3, while the highest yields of glucose and total reducing sugars of beech wood on a dry weight basis (around 36.9% and 48.2%, respectively) were reached from the pulp at a Kappa number of 25.3. To obtain the highest glucose yields and total reducing sugars of a wood on a dry weight basis, total lignin elimination from the birch and beech pulps was not necessary. However more in-depth delignification of birch and beech wood is required than for pine wood. Full article

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14 pages, 2428 KiB

Open AccessArticle

Floating Membrane Bioreactors with High Gas Hold-Up for Syngas-to-Biomethane Conversion

by Konstantinos Chandolias, Enise Pekgenc and Mohammad J. Taherzadeh

Energies 2019, 12(6), 1046; https://doi.org/10.3390/en12061046 - 18 Mar 2019

Cited by 15 | Viewed by 4668

Abstract

The low gas-to-liquid mass transfer rate is one of the main challenges in syngas biomethanation. In this work, a new concept of the floating membrane system with high gas hold-up was introduced in order to enhance the mass transfer rate of the process. [...] Read more.

The low gas-to-liquid mass transfer rate is one of the main challenges in syngas biomethanation. In this work, a new concept of the floating membrane system with high gas hold-up was introduced in order to enhance the mass transfer rate of the process. In addition, the effect of the inoculum-to-syngas ratio was investigated. The experiments were conducted at 55 °C with an anaerobic mixed culture in both batch and continuous modes. According to the results from the continuous experiments, the H₂ and CO conversion rates in the floating membrane bioreactor were approximately 38% and 28% higher in comparison to the free (suspended) cell bioreactors. The doubling of the thickness of the membrane bed resulted in an increase of the conversion rates of H₂ and CO by approximately 6% and 12%, respectively. The highest H₂ and CO consumption rates and CH₄ production rate recorded were approximately 22 mmol/(L·d), 50 mmol/(L·d), and 34.41 mmol/(L·d), respectively, obtained at the highest inoculum-to-syngas ratio of 0.2 g/mL. To conclude, the use of the floating membrane system enhanced the syngas biomethanation rates, while a thicker membrane bed resulted in even higher syngas conversion rates. Moreover, the increase of the inoculum-to-syngas ratio of up to 0.2 g/mL favored the syngas conversion. Full article

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18 pages, 7872 KiB

Open AccessArticle

Experimental Investigation on Performance of a Compression Ignition Engine Fueled with Waste Cooking Oil Biodiesel–Diesel Blend Enhanced with Iron-Doped Cerium Oxide Nanoparticles

by Meshack Hawi, Ahmed Elwardany, Mohamed Ismail and Mahmoud Ahmed

Energies 2019, 12(5), 798; https://doi.org/10.3390/en12050798 - 27 Feb 2019

Cited by 74 | Viewed by 6908

Abstract

The effect of iron-doped cerium oxide (FeCeO₂) nanoparticles as a fuel additive was experimentally investigated with waste cooking oil methyl ester (WCOME) in a four-stroke, single cylinder, direct injection diesel engine. The study aimed at the reduction of harmful emissions of [...] Read more.

The effect of iron-doped cerium oxide (FeCeO₂) nanoparticles as a fuel additive was experimentally investigated with waste cooking oil methyl ester (WCOME) in a four-stroke, single cylinder, direct injection diesel engine. The study aimed at the reduction of harmful emissions of diesel engines including oxides of nitrogen (NO_x) and soot. Two types of nanoparticles were used: cerium oxide doped with 10% iron and cerium oxide doped with 20% iron, to further investigate the influence of the doping level on the nanoparticle activity. The nanoparticles were dispersed in the tested fuels at a dosage of 90 ppm with the aid of an ultrasonic homogenizer. Tests were conducted at a constant engine speed of 2000 rpm and varying loads (from 0 to 12 N.m) with neat diesel (D100) and biodiesel–diesel blends of 30% WCOME and 70% diesel by volume (B30). The engine combustion, performance, and emission characteristics for the fuel blends with nanoparticles were compared with neat diesel as the base fuel. The test results showed improvement in the peak cylinder pressure by approximately 3.5% with addition of nanoparticles to the fuel. A reduction in NO_x emissions by up to 15.7% were recorded, while there was no noticeable change in unburned hydrocarbon (HC) emissions. Carbon monoxide (CO) emission was reduced by up to 24.6% for B30 and 15.4% for B30 with nano-additives. Better engine performance was recorded for B30 with 20% FeCeO₂ as compared to 10% FeCeO₂, in regard to cylinder pressure and emissions. The brake specific fuel consumption was lower for the fuel blend of B30 with 10% FeCeO₂ nanoparticles, in low-to-medium loads and comparable to D100 at high loads. Hence, a higher brake thermal efficiency was recorded for the blend in low-to-medium loads compared to D100. Full article

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31 pages, 1126 KiB

Open AccessReview

A Holistic Review on Biomass Gasification Modified Equilibrium Models

by Sérgio Ferreira, Eliseu Monteiro, Paulo Brito and Cândida Vilarinho

Energies 2019, 12(1), 160; https://doi.org/10.3390/en12010160 - 3 Jan 2019

Cited by 67 | Viewed by 6807

Abstract

Biomass gasification is realized as a settled process to produce energy in a sustainable form, between all the biomass-based energy generation routes. Consequently, there are a renewed interest in biomass gasification promoting the research of different mathematical models to enlighten and comprehend gasification [...] Read more.

Biomass gasification is realized as a settled process to produce energy in a sustainable form, between all the biomass-based energy generation routes. Consequently, there are a renewed interest in biomass gasification promoting the research of different mathematical models to enlighten and comprehend gasification process complexities. This review is focused on the thermodynamic equilibrium models, which is the class of models that seems to be more developed. It is verified that the review articles available in the literature do not address non-stoichiometric methods, as well as an ambiguous categorization of stoichiometric and non-stoichiometric methods. Therefore, the main purpose of this article is to review the non-stoichiometric equilibrium models and categorize them, and review the different stoichiometric equilibrium model’s categorization available in the literature. The modeling procedures adopted for the different modeling categories are compared. Conclusion can be drawn that almost all equilibrium models are modified by the inclusion of empirical correction factors that improves the model prediction capabilities but with loss of generality. Full article

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2018

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11 pages, 2119 KiB

Open AccessArticle

Evaluation of Biogas Production from the Co-Digestion of Municipal Food Waste and Wastewater Sludge at Refugee Camps Using an Automated Methane Potential Test System

by Mohammad Al-Addous, Motasem N. Saidan, Mathhar Bdour and Mohammad Alnaief

Energies 2019, 12(1), 32; https://doi.org/10.3390/en12010032 - 22 Dec 2018

Cited by 35 | Viewed by 6623

Abstract

The potential benefits of the application of a circular economy—converting biomass at Za’atari Syrian refugee camps into energy—was investigated in this study. Representative organic waste and sludge samples were collected from the camp, mixed in different ratios, and analyzed in triplicate for potential [...] Read more.

The potential benefits of the application of a circular economy—converting biomass at Za’atari Syrian refugee camps into energy—was investigated in this study. Representative organic waste and sludge samples were collected from the camp, mixed in different ratios, and analyzed in triplicate for potential biogas yield. Numerous calorific tests were also carried out. The tangential benefit of the co-digestion that was noticed was that it lowered the value of the total solid content in the mixture to the recommended values for wet digestion without the need for freshwater. To test the potential methane production, the automated methane potential test system (AMPTS) and the graduated tubes in the temperature-controlled climate room GB21 were utilized. Also, calorific values were determined for the organic waste and sludge on both a dry and a wet basis. The maximum biogas production from 100% organic waste and 100% sludge using AMPTS was 153 m³ ton⁻¹ and 5.6 m³ ton⁻¹, respectively. Methane yield reached its maximum at a Vs sub/Vs inoculum range of 0.25–0.3. In contrast, the methane yield decreased when the Vs sub/Vs inoculum exceeded 0.46. The optimum ratio of mixing of municipal food waste to sludge must be carefully selected to satisfy the demands of an energy production pilot plant and avoid the environmental issues associated with the sludge amount at wastewater treatment plants (WWTPs). A possible ratio to start with is 60–80% organic waste, which can produce 21–65 m³· biogas ton⁻¹ fresh matter (FM). The co-digestion of organic waste and sludge can generate 38 Nm³/day of methane, which, in theory, can generate about 4 MW in remote refugee camps. Full article

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9 pages, 1022 KiB

Open AccessArticle

Laboratory Testing of the Innovative Low-Cost Mewar Angithi Insert for Improving Energy Efficiency of Cooking Tasks on Three-Stone Fires in Critical Contexts

by Jacopo Barbieri, Fabio Parigi, Fabio Riva and Emanuela Colombo

Energies 2018, 11(12), 3463; https://doi.org/10.3390/en11123463 - 11 Dec 2018

Cited by 6 | Viewed by 5014

Abstract

Currently, about 2.7 billion people across the world still lack access to clean cooking means. Humanitarian emergencies and post-emergencies are among the most critical situations: the utilization of traditional devices such as three-stone fires have a huge negative impact not only on food [...] Read more.

Currently, about 2.7 billion people across the world still lack access to clean cooking means. Humanitarian emergencies and post-emergencies are among the most critical situations: the utilization of traditional devices such as three-stone fires have a huge negative impact not only on food security but also on the socio-economic status of people, their health and the surrounding environment. Advanced Cooking Stoves may constitute better systems compared to actual ones, however, financial, logistic and time constraints have strongly limited the interventions in critical contexts until now. The innovative, low-cost Mewar Angithi insert for improving energy efficiency of three-stone fires may play a role in the transition to better cooking systems in such contexts. In this paper, we rely on the Water Boiling Test 4.2.3 to assess the performances of the Mewar Angithi insert respect to a traditional three-stone fire and we analyse the results through a robust statistical procedure. The potentiality and suitability of this novel solution is discussed for its use in critical contexts. Full article

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23 pages, 35669 KiB

Open AccessArticle

An Experimental and Theoretical Study of the Gasification of Miscanthus Briquettes in a Double-Stage Downdraft Gasifier: Syngas, Tar, and Biochar Characterization

by Tejasvi Sharma, Diego M. Yepes Maya, Francisco Regis M. Nascimento, Yunye Shi, Albert Ratner, Electo E. Silva Lora, Lourival Jorge Mendes Neto, Jose Carlos Escobar Palacios and Rubenildo Vieira Andrade

Energies 2018, 11(11), 3225; https://doi.org/10.3390/en11113225 - 21 Nov 2018

Cited by 17 | Viewed by 6069

Abstract

The goal of this work is to understand the gasification process for Miscanthus briquettes in a double-stage downdraft gasifier, and the impact of different Equivalence Ratios (ER) on syngas, biochar, and tar characteristics. The optimal ER was found to be 0.35, which yielded [...] Read more.

The goal of this work is to understand the gasification process for Miscanthus briquettes in a double-stage downdraft gasifier, and the impact of different Equivalence Ratios (ER) on syngas, biochar, and tar characteristics. The optimal ER was found to be 0.35, which yielded a syngas maximum heating value of 5.5 MJ/Nm³ with a syngas composition of 20.29% CO, 18.68% H₂, and 0.86% CH₄. To better understand the observed behavior, an equilibrium reaction model was created and validated using the experimental data. The model showed that the heating value decreased with increasing ER, and that hydrogen production peaked at ER = 0.37, while methane (CH₄) became negligible above ER = 0.42. Tar and particle content in the gas produced at a certain temperature can now be predicted. To assess the biochar characteristics, surface structure image analysis and a surface area porosity analysis were carried out. Employing images from a scanning electron microscope (SEM), the biochar cell bonds and pore structures were examined and analyzed. By using the Brunauer-Emmett-Teller (BET) analysis of the surface porosity, the surface area to be 186.06 m²/g and the micro pore volume was calculated to be 0.07 m³/g. The final aspect of the analysis involved an evaluation of tar production. Combining current and prior data showed a logarithmic relationship between the amount of tar produced and the gasifier bed temperature, where the amount of tar produced decreased with increasing bed temperature. This results in very low tar levels, which is one of the known advantages for a double-stage downdraft gasifier over a single-stage system. Full article

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13 pages, 1884 KiB

Open AccessArticle

Co-Digestion of Napier Grass with Food Waste and Napier Silage with Food Waste for Methane Production

by Suriyan Boonpiyo, Sureewan Sittijunda and Alissara Reungsang

Energies 2018, 11(11), 3200; https://doi.org/10.3390/en11113200 - 18 Nov 2018

Cited by 15 | Viewed by 6051

Abstract

Enhancement of methane production by co-digestion of Napier grass and Napier silage with food waste was investigated in batch and repeated batch modes. First, the ratios of Napier grass to food waste and Napier silage to food waste were varied at different g-volatile [...] Read more.

Enhancement of methane production by co-digestion of Napier grass and Napier silage with food waste was investigated in batch and repeated batch modes. First, the ratios of Napier grass to food waste and Napier silage to food waste were varied at different g-volatile solids (VS) to g-VS at an initial substrate concentration of 5 g-VS/L. The optimum ratios of Napier grass to food waste and Napier silage to food waste were 1:4 and 3:2 (g-VS/g-VS), respectively. This gave maximum methane yields (MY) of 411 and 362 mL-CH₄/g-VS_added, respectively. Subsequently, the suitable ratios were used to produce methane at various substrate concentrations. A maximal MY of 403 and 353 mL CH₄/g-VS were attained when concentrations of Napier grass co-digested with food waste and Napier silage co-digested with food waste were 15 g-VS/L and 20 g-VS/L, respectively. Under the optimum substrate concentration, the maximum MY from co-digestion of Napier grass with food waste was 1.14 times higher than that of Napier silage with food waste. Thus, co-digestion of Napier grass with food waste was further investigated at various organic loading rates (OLRs) in a 10.25 L horizontal reactor with a working volume of 5 L at an optimal ratio of 1:4 (g-VS/g-VS) and substrate concentration of 15 g VS/L. An OLR of 1.5 g-VS/L∙d gave a maximum methane production rate and MY of 0.5 L CH₄/L∙d and 0.33 L-CH₄/g-VS_added, respectively. Under the optimum OLR, the predominant methane producers were Methanoregula sp., Methanotorris sp., Methanobacterium sp., Methanogenium sp. and Methanosarcina sp. An energy production of 11.9 kJ/g-VS_added was attained. Full article

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20 pages, 5966 KiB

Open AccessArticle

Physicochemical, Performance, Combustion and Emission Characteristics of Melaleuca Cajuputi Oil-Refined Palm Oil Hybrid Biofuel Blend

by Sharzali Che Mat, Mohamad Yusof Idroas, Yew Heng Teoh and Mohd Fadzli Hamid

Energies 2018, 11(11), 3146; https://doi.org/10.3390/en11113146 - 14 Nov 2018

Cited by 12 | Viewed by 5030

Abstract

To reduce the economic impact caused by the fossil fuel crisis and avoid relying on existing biofuels, it is important to seek locally available and renewable biofuel throughout the year. In the present work, a new light biofuel—Melaleuca Cajuputi oil (MCO)—was introduced to [...] Read more.

To reduce the economic impact caused by the fossil fuel crisis and avoid relying on existing biofuels, it is important to seek locally available and renewable biofuel throughout the year. In the present work, a new light biofuel—Melaleuca Cajuputi oil (MCO)—was introduced to blend with refined palm oil (RPO). The physicochemical properties, combustion characteristics, engine performance, and exhaust emissions were comprehensively examined. It was found that the higher the percentage of MCO, the lower the viscosity and density of the blends obtained. Calorific value (CV) was increased with the increase of MCO fraction in the blend. Regression analysis has suggested that the blend of 32% (v/v) of RPO and 68% (v/v) of MCO (RPO32MCO68) is optimal to obtain viscosity and density in accordance with ASTM 6751/EN 14214 standards. The experimental results show that the in-cylinder pressure, brake torque, and brake power of the optimal blend were slightly lower than those of baseline diesel fuel. Brake specific fuel consumption (BSFC), carbon monoxide (CO), and unburnt hydrocarbon (HC) were found to be slightly higher compared to diesel fuel. Notably, nitrogen oxides (NO_x) and smoke opacity were found to be decreased over the entire range of the test. Overall, the optimal blend of RPO32MCO68 has shown a decent result which marks it as a potential viable source of biofuel. Full article

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15 pages, 523 KiB

Open AccessArticle

Chemical Characteristics of Biomass Ashes

by Grzegorz Zając, Joanna Szyszlak-Bargłowicz, Wojciech Gołębiowski and Małgorzata Szczepanik

Energies 2018, 11(11), 2885; https://doi.org/10.3390/en11112885 - 24 Oct 2018

Cited by 171 | Viewed by 7735

Abstract

The aim of the conducted research was to obtain information on the main components of ashes from 35 biomass species used in combustion processes to obtain reference data for the development of utility possibilities for these ashes, with particular emphasis on agricultural use. [...] Read more.

The aim of the conducted research was to obtain information on the main components of ashes from 35 biomass species used in combustion processes to obtain reference data for the development of utility possibilities for these ashes, with particular emphasis on agricultural use. The examined biomass samples were divided into groups depending on origin: woody biomass and energetic woody plants I-WWB, herbaceous and grassy energy plants II-EC, agricultural waste III-AR, forest waste IV-FR and waste from the agri-food industry V-AFIW. The analysis of the studied elements contents was carried out in the designated groups. The chemical composition of ash was dominated by the macroelements Ca, K, P and S, which suggests the possibility of their agricultural use. At the same time, the low content of toxic elements such as As and Pb should not be a limiting feature in their use, with the exception of wood biomass. In addition, ashes obtained from the biomass combustion were enriched with microelements such as Zn, Cu and Mn, which further increases their possibilities of fertilizer use. The potential use of ash from each type of biomass in the aspect of its chemical composition should be considered individually, regardless of the division into groups depending on the origin of biomass. Full article

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15 pages, 3330 KiB

Open AccessArticle

Effects of Pore Fluid Chemistry and Saturation Degree on the Fracability of Australian Warwick Siltstone

by Mandadige Samintha Anne Perera, Kadinappuli Hewage Suresh Madushan Sampath, Pathegama Gamage Ranjith and Tharaka Dilanka Rathnaweera

Energies 2018, 11(10), 2795; https://doi.org/10.3390/en11102795 - 17 Oct 2018

Cited by 9 | Viewed by 3256

Abstract

Fracability of unconventional gas reservoirs is an important parameter that governs the effectiveness of subsequent gas extraction. Since reservoirs are saturated with various pore fluids, it is essential to evaluate the alteration of fracability of varyingly saturated rocks. In this study, varyingly saturated [...] Read more.

Fracability of unconventional gas reservoirs is an important parameter that governs the effectiveness of subsequent gas extraction. Since reservoirs are saturated with various pore fluids, it is essential to evaluate the alteration of fracability of varyingly saturated rocks. In this study, varyingly saturated (dry, water, and brine with 10%, 20% and 30% NaCl by weight) siltstone samples were subjected to uniaxial compressive loading to evaluate their fracability variation. Acoustic emission (AE) and ARAMIS photogrammetry analyses were incorporated to interpret the crack propagation. SEM analysis was carried out to visualize the micro-structural alterations. Results show that siltstone strength and brittleness index (BI) are reduced by 31.7% and 46.7% after water saturation, due to water-induced softening effect. High NaCl concentrations do not reduce the siltstone strength or brittleness significantly but may contribute to a slight re-gain of both values (about 3–4%). This may be due to NaCl crystallization in rock pore spaces, as confirmed by SEM analysis. AE analysis infers that dry siltstone exhibits a gradual fracture propagation, whereas water and brine saturated specimens exhibit a hindered fracturing ability. ARAMIS analysis illustrates that high NaCl concentrations causes rock mass failure to be converted to shear failure from splitting failure, which is in favour of fracability. Full article

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13 pages, 3726 KiB

Open AccessArticle

Optimizing Waste Heat Utilization in Vehicle Bio-Methane Plants

by Feng Zhen, Jia Zhang, Wenzhe Li, Yongming Sun and Xiaoying Kong

Energies 2018, 11(6), 1518; https://doi.org/10.3390/en11061518 - 11 Jun 2018

Cited by 2 | Viewed by 3955

Abstract

Current vehicle bio-methane plants have drawbacks associated with high energy consumption and low recovery levels of waste heat produced during the gasification process. In this paper, we have optimized the performance of heat exchange networks using pinch analysis and through the introduction of [...] Read more.

Current vehicle bio-methane plants have drawbacks associated with high energy consumption and low recovery levels of waste heat produced during the gasification process. In this paper, we have optimized the performance of heat exchange networks using pinch analysis and through the introduction of heat pump integration technology. Optimal results for the heat exchange network of a bio-gas system producing 10,000 cubic meters have been calculated using a pinch point temperature of 50 °C, a minimum heating utility load of 234.02 kW and a minimum cooling utility load of 201.25 kW. These optimal parameters are predicted to result in energy savings of 116.08 kW (19.75%), whilst the introduction of new heat pump integration technology would afford further energy savings of 95.55 kW (16.25%). The combined energy saving value of 211.63 kW corresponds to a total energy saving of 36%, with economic analysis revealing that these reforms would give annual savings of 103,300 USD. The installation costs required to introduce these process modifications are predicted to require an initial investment of 423,200 USD, which would take 4.1 years to reach payout time based on predicted annual energy savings. Full article

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23 pages, 9566 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Comprehensive Overview of CO₂ Flow Behaviour in Deep Coal Seams

by Mandadige Samintha Anne Perera

Energies 2018, 11(4), 906; https://doi.org/10.3390/en11040906 - 12 Apr 2018

Cited by 21 | Viewed by 4638

Abstract

Although enhanced coal bed methane recovery (ECBM) and CO₂ sequestration are effective approaches for achieving lower and safer CO₂ levels in the atmosphere, the effectiveness of CO₂ storage is greatly influenced by the flow ability of the injected CO₂ [...] Read more.

Although enhanced coal bed methane recovery (ECBM) and CO₂ sequestration are effective approaches for achieving lower and safer CO₂ levels in the atmosphere, the effectiveness of CO₂ storage is greatly influenced by the flow ability of the injected CO₂ through the coal seam. A precious understanding of CO₂ flow behaviour is necessary due to various complexities generated in coal seams upon CO₂ injection. This paper aims to provide a comprehensive overview on the CO₂ flow behaviour in deep coal seams, specifically addressing the permeability alterations associated with different in situ conditions. The low permeability nature of natural coal seams has a significant impact on the CO₂ sequestration process. One of the major causative factors for this low permeability nature is the high effective stresses applying on them, which reduces the pore space available for fluid movement with giving negative impact on the flow capability. Further, deep coal seams are often water saturated where, the moisture behave as barriers for fluid movement and thus reduce the seam permeability. Although the high temperatures existing at deep seams cause thermal expansion in the coal matrix, reducing their permeability, extremely high temperatures may create thermal cracks, resulting permeability enhancements. Deep coal seams preferable for CO₂ sequestration generally are high-rank coal, as they have been subjected to greater pressure and temperature variations over a long period of time, which confirm the low permeability nature of such seams. The resulting extremely low CO₂ permeability nature creates serious issues in large-scale CO₂ sequestration/ECBM projects, as critically high injection pressures are required to achieve sufficient CO₂ injection into the coal seam. The situation becomes worse when CO₂ is injected into such coal seams, because CO₂ movement in the coal seam creates a significant influence on the natural permeability of the seams through CO₂ adsorption-induced swelling and hydrocarbon mobilisation. With regard to the temperature, the combined effects of the generation of thermal cracks, thermal expansion, adsorption behaviour alterations and the associated phase transition must be considered before coming to a final conclusion. A reduction in coal’s CO₂ permeability with increasing CO₂ pressure may occur due to swelling and slip-flow effects, both of which are influenced by the phase transition in CO₂ from sub- to super-critical in deep seams. To date, many models have been proposed to simulate CO₂ movement in coal considering various factors, including porosity, effective stress, and swelling/shrinkage. These models have been extremely useful to predict CO₂ injectability into coal seams prior to field projects and have therefore assisted in implementing number of successful CO₂ sequestration/ECBM projects. Full article

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15 pages, 15784 KiB

Open AccessArticle

Performance and Combustion Characteristics Analysis of Multi-Cylinder CI Engine Using Essential Oil Blends

by S. M. Ashrafur Rahman, Md. Nurun Nabi, Thuy Chu Van, Kabir Suara, Mohammad Jafari, Ashley Dowell, Md. Aminul Islam, Anthony J. Marchese, Jessica Tryner, Md. Farhad Hossain, Thomas J. Rainey, Zoran D. Ristovski and Richard J. Brown

Energies 2018, 11(4), 738; https://doi.org/10.3390/en11040738 - 24 Mar 2018

Cited by 20 | Viewed by 8995

Abstract

Essential oils are derived from not-fatty parts of plants and are mostly used in aromatherapy, as well as cosmetics and perfume production. The essential oils market is growing rapidly due to their claimed health benefits. However, because only therapeutic grade oil is required [...] Read more.

Essential oils are derived from not-fatty parts of plants and are mostly used in aromatherapy, as well as cosmetics and perfume production. The essential oils market is growing rapidly due to their claimed health benefits. However, because only therapeutic grade oil is required in the medicinal sector, there is a substantial low-value waste stream of essential oils that can be used in the transportation and agricultural sectors. This study investigated the influence of orange, eucalyptus, and tea tree oil on engine performance and combustion characteristics of a multi-cylinder compression ignition engine. Orange, eucalyptus, and tea tree oil were blended with diesel at 10% by volume. For benchmarking, neat diesel and 10% waste cooking biodiesel-diesel blend were also tested. The selected fuels were used to conduct engine test runs with a constant engine speed (1500 RPM (revolutions per minute)) at four loads. As the load increased, frictional power losses decreased for all of the fuel samples and thus mechanical efficiency increased. At higher loads (75% and 100%), only orange oil-diesel blends produced comparable power to diesel and waste cooking biodiesel-diesel blends. Fuel consumption (brake and indicated) for the essential oil-diesel blends was higher when compared to base diesel and waste cooking biodiesel-diesel blends. Thermal efficiency for the essential oil-diesel blends was comparable to base diesel and waste cooking biodiesel-diesel blends. At higher loads, blow-by was lower for essential oil blends as compared to base diesel and waste cooking biodiesel-diesel blends. At 50% and 100% load, peak pressure was lower for all of the essential oil-diesel blends when compared to base diesel and waste cooking biodiesel-diesel blends. From the heat release rate curve, the essential oil-diesel blends ignition delay times were longer because the oils have lower cetane values. Overall, the low-value streams of these essential oils were found to be suitable for use in diesel engines at 10% blends by agricultural producers of these oils. Full article

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23 pages, 1007 KiB

Open AccessArticle

Relative Greenhouse Gas Abatement Cost Competitiveness of Biofuels in Germany

by Markus Millinger, Kathleen Meisel, Maik Budzinski and Daniela Thrän

Energies 2018, 11(3), 615; https://doi.org/10.3390/en11030615 - 9 Mar 2018

Cited by 15 | Viewed by 5783

Abstract

Transport biofuels derived from biogenic material are used for substituting fossil fuels, thereby abating greenhouse gas (GHG) emissions. Numerous competing conversion options exist to produce biofuels, with differing GHG emissions and costs. In this paper, the analysis and modeling of the long-term development [...] Read more.

Transport biofuels derived from biogenic material are used for substituting fossil fuels, thereby abating greenhouse gas (GHG) emissions. Numerous competing conversion options exist to produce biofuels, with differing GHG emissions and costs. In this paper, the analysis and modeling of the long-term development of GHG abatement and relative GHG abatement cost competitiveness between crop-based biofuels in Germany are carried out. Presently dominant conventional biofuels and advanced liquid biofuels were found not to be competitive compared to the substantially higher yielding options available: sugar beet-based ethanol for the short- to medium-term least-cost option and substitute natural gas (SNG) for the medium to long term. The competitiveness of SNG was found to depend highly on the emissions development of the power mix. Silage maize-based biomethane was found competitive on a land area basis, but not on an energetic basis. Due to land limitations, as well as cost and GHG uncertainty, a stronger focus on the land use of crop-based biofuels should be laid out in policy. Full article

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13 pages, 799 KiB

Open AccessCommunication

Polarization Potential Has No Effect on Maximum Current Density Produced by Halotolerant Bioanodes

by Muriel González-Muñoz, Xochitl Dominguez-Benetton, Jorge Domínguez-Maldonado, David Valdés-Lozano, Daniella Pacheco-Catalán, Otto Ortega-Morales and Liliana Alzate-Gaviria

Energies 2018, 11(3), 529; https://doi.org/10.3390/en11030529 - 1 Mar 2018

Cited by 5 | Viewed by 4047

Abstract

Halotolerant bioanodes are considered an attractive alternative in microbial electrochemical systems, as they can operate under higher conductive electrolytes, in comparison with traditional wastewater and freshwater bioanodes. The dependency between energetic performance and polarization potential has been addressed in several works; however the [...] Read more.

Halotolerant bioanodes are considered an attractive alternative in microbial electrochemical systems, as they can operate under higher conductive electrolytes, in comparison with traditional wastewater and freshwater bioanodes. The dependency between energetic performance and polarization potential has been addressed in several works; however the vast majority discusses its effect when wastewater or freshwater inocula are employed, and fewer reports focus on inocula from highly-saline environments. Moreover, the effect of the polarization potential on current production is not fully understood. To determine if the polarization potential has a significant effect on current production, eight bioanodes were grown by chronoamperometry at positive and negative potentials relative to the reference electrode (+0.34 V/SHE and −0.16 V/SHE), in a three-electrode set-up employing sediments from a hyperhaline coastal lagoon. The maximum current density obtained was the same, despite the differences in the applied potential. Our findings indicate that even if differences in organic matter removal and coulombic efficiency are obtained, the polarization potential had no statistically significant effect on overall current density production. Full article

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13 pages, 1345 KiB

Open AccessArticle

Hydrothermal Disintegration and Extraction of Different Microalgae Species

by Michael Kröger, Marco Klemm and Michael Nelles

Energies 2018, 11(2), 450; https://doi.org/10.3390/en11020450 - 20 Feb 2018

Cited by 32 | Viewed by 6312

Abstract

For the disintegration and extraction of microalgae to produce lipids and biofuels, a novel processing technology was investigated. The utilization of a hydrothermal treatment was tested on four different microalgae species (Scenedesmus rubescens, Chlorella vulgaris, Nannochloropsis oculata and Arthorspira platensis (Spirulina)) [...] Read more.

For the disintegration and extraction of microalgae to produce lipids and biofuels, a novel processing technology was investigated. The utilization of a hydrothermal treatment was tested on four different microalgae species (Scenedesmus rubescens, Chlorella vulgaris, Nannochloropsis oculata and Arthorspira platensis (Spirulina)) to determine whether it has an advantage in comparison to other disintegration methods for lipid extraction. It was shown, that hydrothermal treatment is a reasonable opportunity to utilize microalgae without drying and increase the lipid yield of an algae extraction process. For three of the four microalgae species, the extraction yield with a prior hydrothermal treatment elevated the lipid yield up to six times in comparison to direct extraction. Only Scenedesmus rubescens showed a different behaviour. Reason can be found in the different cell wall of the species. The investigation of the differences in cell wall composition of the used species indicate that the existence of algaenan as a cell wall compound plays a major role in stability. Full article

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14 pages, 3002 KiB

Open AccessArticle

Energy Analysis of a Rotary Drum Bioreactor for Composting Tomato Plant Residues

by Fahad N. Alkoaik, Ahmed M. Abdel-Ghany, Mohamed A. Rashwan, Ronnel B. Fulleros and Mansour N. Ibrahim

Energies 2018, 11(2), 449; https://doi.org/10.3390/en11020449 - 19 Feb 2018

Cited by 23 | Viewed by 8283

Abstract

Energy produced from plant residue composting has stimulated great interest in heat recovery and utilization. Composting is an exothermic process often controlled through temperature measurements. However, energy analysis of the overall composting system, especially the rotary bioreactors, is generally not well known and [...] Read more.

Energy produced from plant residue composting has stimulated great interest in heat recovery and utilization. Composting is an exothermic process often controlled through temperature measurements. However, energy analysis of the overall composting system, especially the rotary bioreactors, is generally not well known and very limited. This study presents detailed energy analysis in a laboratory-scale, batch-operated, rotary bioreactor used for composting tomato plant residues. The bioreactor was considered as a thermodynamic system operating under unsteady state conditions. The composting process was described, the input generated and lost energy terms as well as the relative importance of each term were quantitatively evaluated, and the composting phases were clearly identified. Results showed that the compost temperature peaked at 72 h of operation reaching 66.7 °C with a heat generation rate of 9.3 W·kg⁻¹ of organic matter. During the composting process, the accumulated heat generation was 1.9 MJ·kg⁻¹of organic matter; only 4% of this heat was gained by the composting material, and 96% was lost outside the bioreactor. Contributions of thermal radiation, aeration, cylindrical, and side-walls surfaces of the reactor on the total heat loss were 1%, 2%, 69%, and 28%, respectively. The information obtained is applicable in the design, management, and control of composting operations and in improvement of bioreactor effectiveness and productivity. Full article

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12 pages, 2532 KiB

Open AccessArticle

Improving Vegetable Oil Properties by Transforming Fatty Acid Chain Length in Jatropha Oil and Coconut Oil Blends

by Wahyudi, I.N.G. Wardana, Agung Widodo and Widya Wijayanti

Energies 2018, 11(2), 394; https://doi.org/10.3390/en11020394 - 8 Feb 2018

Cited by 40 | Viewed by 7716

Abstract

Efforts to improve the physical and chemical properties of vegetable oils as diesel fuels such as viscosity and calorific value are indispensable with the depletion of fossil oil reserves. Jatropha oil with long chain fatty acids and high degree of unsaturation is mixed [...] Read more.

Efforts to improve the physical and chemical properties of vegetable oils as diesel fuels such as viscosity and calorific value are indispensable with the depletion of fossil oil reserves. Jatropha oil with long chain fatty acids and high degree of unsaturation is mixed with short chain saturated fatty acid coconut oil in various compositions. The mixture was heated and stirred for 30 min at 90 °C. This mixing leads to a decrease in viscosity which allows for the breaking of the bond. The fatty acid molecule structure undergoes transformation that changes the degree of unsaturation and the average length of the carbon chain. Consequently, the kinematic viscosity and flash point of the mixture decreases while its calorific value increases. Full article

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20 pages, 2738 KiB

Open AccessFeature PaperArticle

Technoeconomic and Policy Drivers of Project Performance for Bioenergy Alternatives Using Biomass from Beetle-Killed Trees

by Robert M. Campbell, Nathaniel M. Anderson, Daren E. Daugaard and Helen T. Naughton

Energies 2018, 11(2), 293; https://doi.org/10.3390/en11020293 - 26 Jan 2018

Cited by 17 | Viewed by 4727

Abstract

As a result of widespread mortality from beetle infestation in the forests of the western United States, there are substantial stocks of biomass suitable as a feedstock for energy production. This study explored the financial viability of four production pathway scenarios for the [...] Read more.

As a result of widespread mortality from beetle infestation in the forests of the western United States, there are substantial stocks of biomass suitable as a feedstock for energy production. This study explored the financial viability of four production pathway scenarios for the conversion of beetle-killed pine to bioenergy and bioproducts in the Rocky Mountains. Monte Carlo simulation using data obtained from planned and existing projects was used to account for uncertainty in key technoeconomic variables and to provide distributions of project net present value (NPV), as well as for sensitivity analysis of key economic and production variables. Over a 20-year project period, results for base case scenarios reveal mean NPV ranging from a low of −$8.3 million for electric power production to a high of $76.0 million for liquid biofuel with a biochar co-product. However, under simulation, all scenarios had conditions resulting in both positive and negative NPV. NPV ranged from −$74.5 million to $51.4 million for electric power, and from −$21.6 million to $246.3 million for liquid biofuels. The potential effects of economic trends and public policies that aim to promote renewable energy and biomass utilization are discussed for each production pathway. Because the factors that most strongly affect financial viability differ across projects, the likely effects of particular types of policies are also shown to vary substantially. Full article

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17 pages, 3116 KiB

Open AccessArticle

The Effect of Using Ethanol-Gasoline Blends on the Mechanical, Energy and Environmental Performance of In-Use Vehicles

by Juan E. Tibaquirá, José I. Huertas, Sebastián Ospina, Luis F. Quirama and José E. Niño

Energies 2018, 11(1), 221; https://doi.org/10.3390/en11010221 - 17 Jan 2018

Cited by 72 | Viewed by 10412

Abstract

The use of ethanol in gasoline has become a worldwide tendency as an alternative to reduce net CO₂ emissions to the atmosphere, increasing gasoline octane rating and reducing dependence on petroleum products. However, recently environmental authorities in large urban centers have expressed [...] Read more.

The use of ethanol in gasoline has become a worldwide tendency as an alternative to reduce net CO₂ emissions to the atmosphere, increasing gasoline octane rating and reducing dependence on petroleum products. However, recently environmental authorities in large urban centers have expressed their concerns on the true effect of using ethanol blends of up to 20% v/v in in-use vehicles without any modification in the setup of the engine control unit (ECU), and on the variations of these effects along the years of operation of these vehicles. Their main concern is the potential increase in the emissions of volatile organic compounds with high ozone formation potential. To address these concerns, we developed analytical and experimental work testing engines under steady-conditions. We also tested carbureted and fuel-injected vehicles every 10,000 km during their first 100,000 km of operation. We measured the effect of using ethanol-gasoline blends on the power and torque generated, the fuel consumption and CO₂, CO, NOx and unburned hydrocarbon emissions, including volatile organic compounds (VOCs) such as acetaldehyde, formaldehyde, benzene and 1,3-butadiene which are considered important ozone precursors. The obtained results showed statistically no significant differences in these variables when vehicles operate with a blend of 20% v/v ethanol and 80% v/v gasoline (E20) instead of gasoline. Those results remained unchanged during the first 100,000 km of operation of the vehicles. We also observed that when the vehicles operated with E20 at high engine loads, they showed a tendency to operate with greater values of λ (ratio of the actual air-fuel ratio to the stoichiometric air-fuel ratio) when compared to their operation with gasoline. According to the Eco-Indicator-99, these results represent a minor reduction (<1.3%) on the impact to human health, and on the deterioration of the ecosystem. However, it implies a 12.9% deterioration of the natural resources. Thermal equilibrium analysis, at the tailpipe conditions (~100 °C), showed that ethane, formaldehyde, ethylene and ethanol are the most relevant VOCs in terms of the amount of mass emitted. The use of ethanol in the gasoline reduced 20–40% of those emissions. These reductions implied an average reduction of 17% in the ozone formation potential. Full article

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15 pages, 1759 KiB

Open AccessArticle

Esterification Optimization of Crude African Palm Olein Using Response Surface Methodology and Heterogeneous Acid Catalysis

by Francisco Anguebes-Franseschi, Mohamed Abatal, Ali Bassam, Mauricio A. Escalante Soberanis, Oscar May Tzuc, Lauro Bucio-Galindo, Atl Victor Cordova Quiroz, Claudia Alejandra Aguilar Ucan and Miguel Angel Ramirez-Elias

Energies 2018, 11(1), 157; https://doi.org/10.3390/en11010157 - 9 Jan 2018

Cited by 13 | Viewed by 5214

Abstract

In this work, the effect of zeolite montmorillonite KSF in the esterification of free fatty acids (FFAs) of crude African palm olein (Eleaias guinnesis Jacq) was studied. To optimize the esterification of FFAs of the crude African palm olein (CAPO), the response [...] Read more.

In this work, the effect of zeolite montmorillonite KSF in the esterification of free fatty acids (FFAs) of crude African palm olein (Eleaias guinnesis Jacq) was studied. To optimize the esterification of FFAs of the crude African palm olein (CAPO), the response surface methodology (RSM) that was based on a central composite rotatable design (CCRD) was used. The effects of three parameters were investigated: (a) catalyst loading (2.6–9.4 wt %), (b) reaction temperature (133.2–166.2 °C), and (c) reaction time (0.32–3.68 h). The Analysis of variance (ANOVA) indicated that linear terms of catalyst loading (X₁), reaction temperature (X₂), the quadratic term of catalyst loading (

X_{1}^{2}

), temperature reaction (

X_{2}^{2}

), reaction time (

X_{3}^{2}

), the interaction catalyst loading with reaction time (

X_{1}^{*}

X₃), and the interaction reaction temperature with reaction time (

X_{2}^{*}

X₃) have a significant effect (p < 0.05 with a 95% confidence level) on Fatty Methyl Ester (FAME) yield. The result indicated that the optimum reaction conditions to esterification of FFAs were: catalyst loading 9.4 wt %, reaction temperature 155.5 °C, and 3.3 h for reaction time, respectively. Under these conditions, the numerical estimation of FAME yield was 91.81 wt %. This result was experimentally validated obtaining a difference of 1.7% FAME yield, with respect to simulated values. Full article

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12 pages, 1839 KiB

Open AccessArticle

Evolving Microbial Communities in Cellulose-Fed Microbial Fuel Cell

by Renata Toczyłowska-Mamińska, Karolina Szymona, Patryk Król, Karol Gliniewicz, Katarzyna Pielech-Przybylska, Monika Kloch and Bruce E. Logan

Energies 2018, 11(1), 124; https://doi.org/10.3390/en11010124 - 4 Jan 2018

Cited by 53 | Viewed by 7002

Abstract

The abundance of cellulosic wastes make them attractive source of energy for producing electricity in microbial fuel cells (MFCs). However, electricity production from cellulose requires obligate anaerobes that can degrade cellulose and transfer electrons to the electrode (exoelectrogens), and thus most previous MFC [...] Read more.

The abundance of cellulosic wastes make them attractive source of energy for producing electricity in microbial fuel cells (MFCs). However, electricity production from cellulose requires obligate anaerobes that can degrade cellulose and transfer electrons to the electrode (exoelectrogens), and thus most previous MFC studies have been conducted using two-chamber systems to avoid oxygen contamination of the anode. Single-chamber, air-cathode MFCs typically produce higher power densities than aqueous catholyte MFCs and avoid energy input for the cathodic reaction. To better understand the bacterial communities that evolve in single-chamber air-cathode MFCs fed cellulose, we examined the changes in the bacterial consortium in an MFC fed cellulose over time. The most predominant bacteria shown to be capable electron generation was Firmicutes, with the fermenters decomposing cellulose Bacteroidetes. The main genera developed after extended operation of the cellulose-fed MFC were cellulolytic strains, fermenters and electrogens that included: Parabacteroides, Proteiniphilum, Catonella and Clostridium. These results demonstrate that different communities evolve in air-cathode MFCs fed cellulose than the previous two-chamber reactors. Full article

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Open AccessArticle

Co-Digestion of Napier Grass and Its Silage with Cow Dung for Bio-Hydrogen and Methane Production by Two-Stage Anaerobic Digestion Process

by Wipa Prapinagsorn, Sureewan Sittijunda and Alissara Reungsang

Energies 2018, 11(1), 47; https://doi.org/10.3390/en11010047 - 26 Dec 2017

Cited by 26 | Viewed by 6840

Abstract

The objective of this study was to efficiently utilize the napier grass and its silage to produce bio-hydrogen and methane by a two-stage process in batch mode. First, the production of hydrogen from a co-digestion of grass with cow dung and silage with [...] Read more.

The objective of this study was to efficiently utilize the napier grass and its silage to produce bio-hydrogen and methane by a two-stage process in batch mode. First, the production of hydrogen from a co-digestion of grass with cow dung and silage with cow dung by Clostridium butyricum Thailand Institute of Scientific and Technological Research (TISTR) 1032 was conducted. The results indicated that bio-hydrogen production by C. butyricum TISTR 1032 gave a higher hydrogen yield (HY) than without C. butyricum addition. The HY of 6.98 and 27.71 mL H₂/g-Volatile solid_added (VS_added), were obtained from a co-digestion of grass with cow dung and silage with cow dung by C. butyricum, respectively. The hydrogenic effluent and solid residue left over after hydrogen fermentation were further used as substrates for methane production (Batch I). Methane yield (MY) from hydrogenic effluent of grass with cow dung and silage with cow dung were 169.87 and 141.33 mL CH₄/g-COD_added (COD: chemical oxygen demand), respectively. The maximum MY of 210.10 and 177.79 mL CH₄/g-VS_added, respectively, were attained from solid residues left over after bio-hydrogen production pretreated by enzyme (cellulase cocktail) and alkali (NaOH). Afterward, solid residue left over after methane production (Batch I) was used as the substrate for methane production (Batch II). A maximum MY of 370.39 and 370.99 mL CH₄/g-VS_added were achieved from solid residue repeatedly pretreated by alkaline plus enzyme, respectively. The overall energy yield in the two-stage bio-hydrogen and methane production process was derived from a bio-hydrogen production, a methane production from hydrogenic effluent, methane production of pretreated solid residue (Batch I) and methane production of repeatedly pretreated solid residue (Batch II), which yielded 480.27 and 204.70 MJ/g-VS_added, respectively. Full article

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5442 KiB

Open AccessArticle

The Lubricity of Ternary Fuel Mixture Blends as a Way to Assess Diesel Engine Durability

by Abul Kalam Azad, Mohammad Golam Rasul, Subhash Chandra Sharma and Mohammad Masud Kamal Khan

Energies 2018, 11(1), 33; https://doi.org/10.3390/en11010033 - 24 Dec 2017

Cited by 14 | Viewed by 4167

Abstract

The study deals with the lubrication characteristics of ternary fuel mixture blends to assess diesel engine durability by using better performing fuels, namely Mandarin Crambe and Paraffin (ManCr_Pa) and Avocado Bush nut and Paraffin (AvBn_Pa). Tribological parameters of friction coefficient, wear, and lubrication [...] Read more.

The study deals with the lubrication characteristics of ternary fuel mixture blends to assess diesel engine durability by using better performing fuels, namely Mandarin Crambe and Paraffin (ManCr_Pa) and Avocado Bush nut and Paraffin (AvBn_Pa). Tribological parameters of friction coefficient, wear, and lubrication stability were measured to assess the impact of these fuels on engine durability. The tests were conducted on a four-ball tribotester using the American Society for Testing Materials (ASTM) D4172 standard; friction coefficient and wear scar diameter for the fuels were measured. The wear scar surface morphology of the ball metals was evaluated by a high-performance scanning electron microscope with energy dispersive X-ray SEM/EDX analysis. The corrosive behaviour of the fuels was also assessed by evaluating images from the SEM/EDX tests. Finally, the engine durability, reliability, and longevity were also evaluated based on the measured tribological parameters. Full article

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5488 KiB

Open AccessArticle

Floor Heave Mechanism of Gob-Side Entry Retaining with Fully-Mechanized Backfilling Mining

by Peng Gong, Zhanguo Ma, Xiaoyan Ni and Ray Ruichong Zhang

Energies 2017, 10(12), 2085; https://doi.org/10.3390/en10122085 - 8 Dec 2017

Cited by 47 | Viewed by 6542

Abstract

Serious floor heave in gob-side entry retaining (GER) with fully-mechanized gangue backfilling mining affects the transportation and ventilation safety of the mine. A theoretical mechanical model for the floor of gob-backfilled GER was established. The effects of the mechanical properties of floor strata, [...] Read more.

Serious floor heave in gob-side entry retaining (GER) with fully-mechanized gangue backfilling mining affects the transportation and ventilation safety of the mine. A theoretical mechanical model for the floor of gob-backfilled GER was established. The effects of the mechanical properties of floor strata, the granular compaction of backfilling area (BFA), the vertical support of roadside support body (RSB), and the stress concentration of the solid coal on the floor heave of the gob-backfilled GER were studied. The results show that the floor heave increases with the increase of the coal seam buried depth, and decreases with the increase of the floor rock elastic modulus. The development depth of the plastic zone decreases with the increase of the c and φ value of the floor rock, and increases with the increase of the stress concentration factor of the solid coal. The development depth of the plastic zone in the test mine reached 2.68 m. The field test and monitoring results indicate that the comprehensive control scheme of adjusting backfilling pressure, deep grouting reinforcement, shallow opening stress relief slots, and surface pouring can effectively control the floor heave. The roof-floor displacement is reduced by 73.8% compared to that with the original support scheme. The roadway section meets the design and application requirements when the deformation stabilizes, demonstrating the rationality of the mechanical model. The research results overcome the technical bottleneck of floor heave control of fully-mechanized backfilling GER, providing a reliable basis for the design of a floor heave control scheme. Full article

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1603 KiB

Open AccessArticle

Sludge Acts as a Catalyst for Coal during the Co-Combustion Process Investigated by Thermogravimetric Analysis

by Wendi Chen, Fei Wang and Altaf Hussain Kanhar

Energies 2017, 10(12), 1993; https://doi.org/10.3390/en10121993 - 1 Dec 2017

Cited by 19 | Viewed by 4760

Abstract

Sewage sludge in China has the characteristics of low organic content and low heating value compared with other developed countries. Self-sustaining combustion of Chinese sludge cannot be achieved when the moisture content is high. Co-combusting a small amount of sludge in the existing [...] Read more.

Sewage sludge in China has the characteristics of low organic content and low heating value compared with other developed countries. Self-sustaining combustion of Chinese sludge cannot be achieved when the moisture content is high. Co-combusting a small amount of sludge in the existing coal-fired boilers is a usual sludge disposal method in China. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis of a bituminous coal, three different sewage sludges, and their blends have been carried out. Fitted curves by linear calculation and actual curves of blends were compared to study the interaction between sludge and coal in their co-combustion process. The results indicate that the interaction between the two fuels takes place during the devolatilization and combustion period. Sludge acts as a catalyst for coal during the co-combustion process because of the large amount of inorganic salts contained in the sludge. Co-combustion of coal and sludge is more efficient than single burning of the two fuels. Full article

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3447 KiB

Open AccessArticle

Supercritical Water Gasification of Biomass in a Ceramic Reactor: Long-Time Batch Experiments

by Daniele Castello, Birgit Rolli, Andrea Kruse and Luca Fiori

Energies 2017, 10(11), 1734; https://doi.org/10.3390/en10111734 - 30 Oct 2017

Cited by 37 | Viewed by 7145

Abstract

Supercritical water gasification (SCWG) is an emerging technology for the valorization of (wet) biomass into a valuable fuel gas composed of hydrogen and/or methane. The harsh temperature and pressure conditions involved in SCWG (T > 375 °C, p > 22 MPa) are [...] Read more.

Supercritical water gasification (SCWG) is an emerging technology for the valorization of (wet) biomass into a valuable fuel gas composed of hydrogen and/or methane. The harsh temperature and pressure conditions involved in SCWG (T > 375 °C, p > 22 MPa) are definitely a challenge for the manufacturing of the reactors. Metal surfaces are indeed subject to corrosion under hydrothermal conditions, and expensive special alloys are needed to overcome such drawbacks. A ceramic reactor could be a potential solution to this issue. Finding a suitable material is, however, complex because the catalytic effect of the material can influence the gas yield and composition. In this work, a research reactor featuring an internal alumina inlay was utilized to conduct long-time (16 h) batch tests with real biomasses and model compounds. The same experiments were also conducted in batch reactors made of stainless steel and Inconel 625. The results show that the three devices have similar performance patterns in terms of gas production, although in the ceramic reactor higher yields of C₂₊ hydrocarbons were obtained. The SEM observation of the reacted alumina surface revealed a good resistance of such material to supercritical conditions, even though some intergranular corrosion was observed. Full article

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5439 KiB

Open AccessFeature PaperArticle

Biodiesel from Mandarin Seed Oil: A Surprising Source of Alternative Fuel

by A. K. Azad

Energies 2017, 10(11), 1689; https://doi.org/10.3390/en10111689 - 26 Oct 2017

Cited by 41 | Viewed by 7395

Abstract

Mandarin (Citrus reticulata) is one of the most popular fruits in tropical and sub-tropical countries around the world. It contains about 22–34 seeds per fruit. This study investigated the potential of non-edible mandarin seed oil as an alternative fuel in Australia. The seeds [...] Read more.

Mandarin (Citrus reticulata) is one of the most popular fruits in tropical and sub-tropical countries around the world. It contains about 22–34 seeds per fruit. This study investigated the potential of non-edible mandarin seed oil as an alternative fuel in Australia. The seeds were prepared after drying in the oven for 20 h to attain an optimum moisture content of around 13.22%. The crude oil was extracted from the crushed seed using 98% n-hexane solution. The biodiesel conversion reaction (transesterification) was designed according to the acid value (mg KOH/g) of the crude oil. The study also critically examined the effect of various reaction parameters (such as effect of methanol: oil molar ratio, % of catalyst concentration, etc.) on the biodiesel conversion yield. After successful conversion of the bio-oil into biodiesel, the physio-chemical fuel properties of the virgin biodiesel were measured according to relevant ASTM standards and compared with ultra-low sulphur diesel (ULSD) and standard biodiesel ASTM D6751. The fatty acid methyl esters (FAMEs) were analysed by gas chromatography (GC) using the EN 14103 standard. The behaviour of the biodiesel (variation of density and kinematic viscosity) at various temperatures (10–40 °C) was obtained and compared with that of diesel fuel. Finally, mass and energy balances were conducted for both the oil extraction and biodiesel conversion processes to analyse the total process losses of the system. The study found 49.23 wt % oil yield from mandarin seed and 96.82% conversion efficiency for converting oil to biodiesel using the designated transesterification reaction. The GC test identified eleven FAMEs. The biodiesel mainly contains palmitic acid (C16:0) 26.80 vol %, stearic acid (C18:0) 4.93 vol %, oleic acid (C18:1) 21.43 vol % (including cis. and trans.), linoleic acid (C18:2) 4.07 vol %, and less than one percent each of other fatty acids. It is an important source of energy because it has a higher heating value of 41.446 MJ/kg which is close to ULSD (45.665 MJ/kg). In mass and energy balances, 49.23% mass was recovered as crude bio-oil and 84.48% energy was recovered as biodiesel from the total biomass. Full article

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2335 KiB

Open AccessArticle

Co-Digestion of Napier Grass and Its Silage with Cow Dung for Methane Production

by Wipa Prapinagsorn, Sureewan Sittijunda and Alissara Reungsang

Energies 2017, 10(10), 1654; https://doi.org/10.3390/en10101654 - 19 Oct 2017

Cited by 34 | Viewed by 8153

Abstract

Methane production from co-digestion of grass with cow dung and silage with cow dung was conducted by a bioaugmentation technique. For self-fermentation, maximum methane yield (MY) of 176.66 and 184.94 mL CH₄/g-VS_added were achieved at a ratio of grass to [...] Read more.

Methane production from co-digestion of grass with cow dung and silage with cow dung was conducted by a bioaugmentation technique. For self-fermentation, maximum methane yield (MY) of 176.66 and 184.94 mL CH₄/g-VS_added were achieved at a ratio of grass to cow dung and silage to cow dung of 1:1, respectively. A higher maximum MY of 179.59 and 208.11 mL CH₄/g-VS_added was obtained from co-digestion of grass with cow dung and silage with cow dung bioaugmented with anaerobic sludge at a ratio of 3:1. The solid residue left over after co-digestion at a ratio of 3:1 was pretreated by alkaline plus enzyme before used to produce methane and a maximum MY of 333.63 and 301.38 mL CH₄/g-VS_added, respectively, was achieved. Overall power generated from co-digestion of grass with cow dung plus pretreated solid residues and co-digestion of silage with cow dung plus pretreated solid residues were 0.0397 and 0.007 watt, respectively. Full article

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6862 KiB

Open AccessArticle

Diesel/CNG Mixture Autoignition Control Using Fuel Composition and Injection Gap

by Firmansyah, A. Rashid A. Aziz, Morgan Raymond Heikal and Ezrann Z. Zainal A.

Energies 2017, 10(10), 1639; https://doi.org/10.3390/en10101639 - 18 Oct 2017

Cited by 8 | Viewed by 5366

Abstract

Combustion phasing is the main obstacle to the development of controlled auto-ignition based (CAI) engines to achieve low emissions and low fuel consumption operation. Fuel combinations with substantial differences in reactivity, such as diesel/compressed natural gas (CNG), show desirable combustion outputs and demonstrate [...] Read more.

Combustion phasing is the main obstacle to the development of controlled auto-ignition based (CAI) engines to achieve low emissions and low fuel consumption operation. Fuel combinations with substantial differences in reactivity, such as diesel/compressed natural gas (CNG), show desirable combustion outputs and demonstrate great possibility in controlling the combustion. This paper discusses a control method for diesel/CNG mixture combustion with a variation of fuel composition and fuel stratification levels. The experiments were carried out in a constant volume combustion chamber with both fuels directly injected into the chamber. The mixture composition was varied from 0 to 100% CNG/diesel at lambda 1 while the fuel stratification level was controlled by the injection phasing between the two fuels, with gaps between injections ranging from 0 to 20 ms. The results demonstrated the suppressing effect of CNG on the diesel combustion, especially at the early combustion stages. However, CNG significantly enhanced the combustion performance of the diesel in the later stages. Injection gaps, on the other hand, showed particular behavior depending on mixture composition. Injection gaps show less effect on combustion phasing but a significant effect on the combustion output for higher diesel percentage (≥70%), while it is contradictive for lower diesel percentage (<70%). Full article

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3499 KiB

Open AccessArticle

Biodiesel Production Potential from Littered Edible Oil Fraction Using Directly Synthesized S-TiO₂/MCM-41 Catalyst in Esterification Process via Non-Catalytic Subcritical Hydrolysis

by Md Sufi Ullah Siddik Bhuyan, Abul Hasnat Md Ashraful Alam, Younghwan Chu and Yong Chan Seo

Energies 2017, 10(9), 1290; https://doi.org/10.3390/en10091290 - 29 Aug 2017

Cited by 11 | Viewed by 4955

Abstract

Due to uncontrolled consumption of fossil fuel it is necessary to use alternative resources as renewable energy. Among all the available liquid fuels biodiesel has drawn attention for producing less emissions and having less aromatic contents than diesel and because it can also [...] Read more.

Due to uncontrolled consumption of fossil fuel it is necessary to use alternative resources as renewable energy. Among all the available liquid fuels biodiesel has drawn attention for producing less emissions and having less aromatic contents than diesel and because it can also be obtained from inferior grade feedstocks. Since the various uses of fats and oils have increased, a significant amount of waste animal fat and used edible oil is generated every year. In this work, we produced biodiesel from littered edible oil fraction (LEOF) via hydrolysis followed by catalytic esterification. Nearly 90% free fatty acids (FFA) content was achieved at 275 °C, after 45 min during hydrolysis and linoleic acid (C18:2) was observed to be the highest component. Compared to refined soybean oil (SBO) the reaction rate was accelerated by the auto-catalytic behavior of free fatty acids (FFA) in littered edible oil fraction (LEOF). For catalytic esterification, S-TiO₂/MCM-41 catalyst was directly synthesized and characterized by using XRD, SEM, NH₃-TPD and Brunauer Emmett Teller (B.E.T). The parameters such as; SO₄⁻² content, TiO₂ loading and calcination temperature were varied to get optimum free fatty acids (FFA) conversion. Fatty acid methyl ester (FAME) conversion was 99.29% using 1% S-TiO₂/MCM-41 catalyst at 240 °C whereas 86.18% was observed with 3.5% catalyst at 180 °C with 20 min. Thus, using S-TiO₂/MCM-41 catalyst in esterification via hydrolysis would be a better option for treating low quality feedstocks. Full article

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Open AccessArticle

Combustion and Heat Release Characteristics of Biogas under Hydrogen- and Oxygen-Enriched Condition

by Jun Li, Hongyu Huang, Huhetaoli, Yugo Osaka, Yu Bai, Noriyuki Kobayashi and Yong Chen

Energies 2017, 10(8), 1200; https://doi.org/10.3390/en10081200 - 13 Aug 2017

Cited by 31 | Viewed by 7754

Abstract

Combustion and heat release characteristics of biogas non-premixed flames under various hydrogen-enriched and oxygen-enriched conditions were investigated through chemical kinetics simulation using detailed chemical mechanisms. The heat release rates, chemical reaction rates, and molar fraction of all species of biogas at various methane [...] Read more.

Combustion and heat release characteristics of biogas non-premixed flames under various hydrogen-enriched and oxygen-enriched conditions were investigated through chemical kinetics simulation using detailed chemical mechanisms. The heat release rates, chemical reaction rates, and molar fraction of all species of biogas at various methane contents (35.3–58.7%, mass fraction), hydrogen addition ratios (10–50%), and oxygen enrichment levels (21–35%) were calculated considering the GRI 3.0 mechanism and P1 radiation model. Results showed that the net reaction rate of biogas increases with increasing hydrogen addition ratio and oxygen levels, leading to a higher net heat release rate of biogas flame. Meanwhile, flame length was shortened with the increase in hydrogen addition ratio and oxygen levels. The formation of free radicals, such as H, O, and OH, are enhanced with increase in hydrogen addition ratio and oxygen levels. Higher reaction rates of exothermic elementary reactions, especially those with OH free radical are increased, are beneficial to the improvement in combustion and heat release characteristics of biogas in practical applications. Full article

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Open AccessArticle

Influence of Catalytic Formulation and Operative Conditions on Coke Deposition over CeO₂-SiO₂ Based Catalysts for Ethanol Reforming

by Vincenzo Palma, Concetta Ruocco, Eugenio Meloni and Antonio Ricca

Energies 2017, 10(7), 1030; https://doi.org/10.3390/en10071030 - 19 Jul 2017

Cited by 29 | Viewed by 4540

Abstract

In this work, a series of CeO₂-SiO₂ (30 wt % of ceria)-based catalysts was prepared by the wetness impregnation method and tested for ESR (ethanol steam reforming) at 450–500 °C, atmospheric pressure and a water/ethanol ratio increasing from 4 to [...] Read more.

In this work, a series of CeO₂-SiO₂ (30 wt % of ceria)-based catalysts was prepared by the wetness impregnation method and tested for ESR (ethanol steam reforming) at 450–500 °C, atmospheric pressure and a water/ethanol ratio increasing from 4 to 6 (the ethanol concentration being fixed to 10 vol %); after every test, coke gasification measurements were performed at the same water partial pressure, and the temperature of the test and the gasified carbon was measured from the areas under the CO and CO₂ profiles. Finally, oxidation measurements under a 5% O₂/N₂ stream made it possible to calculate the total carbon deposited. In an attempt to improve the coke resistance of a Pt-Ni/CeO₂-SiO₂ catalyst, the effect of support basification by alkali addition (K and Cs), as well as Pt substitution by Rh was investigated. The novel catalysts, especially those containing Rh, displayed a lowering in the carbon formation rate; however, a faster reduction of ethanol conversion with time-on-stream and lessened hydrogen selectivities were recorded. In addition, no significant gain in terms of coke gasification rates was observed. The most active catalyst (Pt-Ni/CeO₂-SiO₂) was also tested under different operative conditions, in order to study the effect of temperature and water/ethanol ratio on carbon formation and gasification. The increase in the water content resulted in an enhanced reactor-plugging time due to reduced carbonaceous deposits formation; however, no effect of steam concentration on the carbon gasification rate were recorded. On the other hand, the increase in temperature from 450–500 °C lowered the coke selectivity by almost one order of magnitude improving, at the same time, the contribution of the gasification reactions. Full article

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Open AccessArticle

Production of Torrefied Solid Bio-Fuel from Pulp Industry Waste

by Michael Huang, Chia-Chi Chang, Min-Hao Yuan, Ching-Yuan Chang, Chao-Hsiung Wu, Je-Lueng Shie, Yen-Hau Chen, Yi-Hung Chen, Chungfang Ho, Wei-Ren Chang, Tzu-Yi Yang and Far-Ching Lin

Energies 2017, 10(7), 910; https://doi.org/10.3390/en10070910 - 3 Jul 2017

Cited by 17 | Viewed by 4435

Abstract

The pulp industry in Taiwan discharges tons of wood waste and pulp sludge (i.e., wastewater-derived secondary sludge) per year. The mixture of these two bio-wastes, denoted as wood waste with pulp sludge (WPS), has been commonly converted to organic fertilizers for agriculture application [...] Read more.

The pulp industry in Taiwan discharges tons of wood waste and pulp sludge (i.e., wastewater-derived secondary sludge) per year. The mixture of these two bio-wastes, denoted as wood waste with pulp sludge (WPS), has been commonly converted to organic fertilizers for agriculture application or to soil conditioners. However, due to energy demand, the WPS can be utilized in a beneficial way to mitigate an energy shortage. This study elucidated the performance of applying torrefaction, a bio-waste to energy method, to transform the WPS into solid bio-fuel. Two batches of the tested WPS (i.e., WPS1 and WPS2) were generated from a virgin pulp factory in eastern Taiwan. The WPS1 and WPS2 samples contained a large amount of organics and had high heating values (HHV) on a dry-basis (H_HD) of 18.30 and 15.72 MJ/kg, respectively, exhibiting a potential for their use as a solid bio-fuel. However, the wet WPS as received bears high water and volatile matter content and required de-watering, drying, and upgrading. After a 20 min torrefaction time (t_T), the H_HD of torrefied WPS1 (WPST1) can be enhanced to 27.49 MJ/kg at a torrefaction temperature (T_T) of 573 K, while that of torrefied WPS2 (WPST2) increased to 19.74 MJ/kg at a T_T of 593 K. The corresponding values of the energy densification ratio of torrefied solid bio-fuels of WPST1 and WPST2 can respectively rise to 1.50 and 1.25 times that of the raw bio-waste. The H_HD of WPST1 of 27.49 MJ/kg is within the range of 24–35 MJ/kg for bituminous coal. In addition, the wet-basis HHV of WPST1 with an equilibrium moisture content of 5.91 wt % is 25.87 MJ/kg, which satisfies the Quality D coal specification of the Taiwan Power Co. requiring a value of above 20.92 MJ/kg. Full article

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Open AccessArticle

A Computational Tool for Comparative Energy Cost Analysis of Multiple-Crop Production Systems

by Efthymios Rodias, Remigio Berruto, Dionysis Bochtis, Patrizia Busato and Alessandro Sopegno

Energies 2017, 10(7), 831; https://doi.org/10.3390/en10070831 - 22 Jun 2017

Cited by 13 | Viewed by 5492

Abstract

Various crops can be considered as potential bioenergy and biofuel production feedstocks. The selection of the crops to be cultivated for that purpose is based on several factors. For an objective comparison between different crops, a common framework is required to assess their [...] Read more.

Various crops can be considered as potential bioenergy and biofuel production feedstocks. The selection of the crops to be cultivated for that purpose is based on several factors. For an objective comparison between different crops, a common framework is required to assess their economic or energetic performance. In this paper, a computational tool for the energy cost evaluation of multiple-crop production systems is presented. All the in-field and transport operations are considered, providing a detailed analysis of the energy requirements of the components that contribute to the overall energy consumption. A demonstration scenario is also described. The scenario is based on three selected energy crops, namely Miscanthus, Arundo donax and Switchgrass. The tool can be used as a decision support system for the evaluation of different agronomical practices (such as fertilization and agrochemicals application), machinery systems, and management practices that can be applied in each one of the individual crops within the production system. Full article

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Open AccessArticle

Watching the Smoke Rise Up: Thermal Efficiency, Pollutant Emissions and Global Warming Impact of Three Biomass Cookstoves in Ghana

by George Y. Obeng, Ebenezer Mensah, George Ashiagbor, Owusu Boahen and Daniel J. Sweeney

Energies 2017, 10(5), 641; https://doi.org/10.3390/en10050641 - 6 May 2017

Cited by 30 | Viewed by 8324

Abstract

In Ghana, about 73% of households rely on solid fuels for cooking. Over 13,000 annual deaths are attributed to exposure to indoor air pollution from inefficient combustion. In this study, assessment of thermal efficiency, emissions, and total global warming impact of three cookstoves [...] Read more.

In Ghana, about 73% of households rely on solid fuels for cooking. Over 13,000 annual deaths are attributed to exposure to indoor air pollution from inefficient combustion. In this study, assessment of thermal efficiency, emissions, and total global warming impact of three cookstoves commonly used in Ghana was completed using the International Workshop Agreement (IWA) Water Boiling Test (WBT) protocol. Statistical averages of three replicate tests for each cookstove were computed. Thermal efficiency results were: wood-burning cookstove: 12.2 ± 5.00% (Tier 0); coalpot charcoal stove: 23.3 ± 0.73% (Tier 1–2); and Gyapa charcoal cookstove: 30.00 ± 4.63% (Tier 2–3). The wood-burning cookstove emitted more CO, CO₂, and PM_2.5 than the coalpot charcoal stove and Gyapa charcoal cookstove. The emission factor (EF) for PM_2.5 and the emission rate for the wood-burning cookstove were over four times higher than the coalpot charcoal stove and Gyapa charcoal cookstove. To complete the WBT, the study results showed that, by using the Gyapa charcoal cookstove instead of the wood-burning cookstove, the global warming impact could be potentially reduced by approximately 75% and using the Gyapa charcoal cookstove instead of the coalpot charcoal cookstove by 50%. We conclude that there is the need for awareness, policy, and incentives to enable end-users to switch to, and adopt, Gyapa charcoal cookstoves for increased efficiency and reduced emissions/global warming impact. Full article

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Open AccessArticle

Experimental Investigations of Physical and Chemical Properties for Microalgae HTL Bio-Crude Using a Large Batch Reactor

by Farhad M. Hossain, Jana Kosinkova, Richard J. Brown, Zoran Ristovski, Ben Hankamer, Evan Stephens and Thomas J. Rainey

Energies 2017, 10(4), 467; https://doi.org/10.3390/en10040467 - 5 Apr 2017

Cited by 45 | Viewed by 6403

Abstract

As a biofuel feedstock, microalgae has good scalability and potential to supply a significant proportion of world energy compared to most types of biofuel feedstock. Hydrothermal liquefaction (HTL) is well-suited to wet biomass (such as microalgae) as it greatly reduces the energy requirements [...] Read more.

As a biofuel feedstock, microalgae has good scalability and potential to supply a significant proportion of world energy compared to most types of biofuel feedstock. Hydrothermal liquefaction (HTL) is well-suited to wet biomass (such as microalgae) as it greatly reduces the energy requirements associated with dewatering and drying. This article presents experimental analyses of chemical and physical properties of bio-crude oil produced via HTL using a high growth-rate microalga Scenedesmus sp. in a large batch reactor. The overarching goal was to investigate the suitability of microalgae HTL bio-crude produced in a large batch reactor for direct application in marine diesel engines. To this end we characterized the chemical and physical properties of the bio-crudes produced. HTL literature mostly reports work using very small batch reactors which are preferred by researchers, so there are few experimental and parametric measurements for bio-crude physical properties, such as viscosity and density. In the course of this study, a difference between traditionally calculated values and measured values was noted. In the parametric study, the bio-crude viscosity was significantly closer to regular diesel and biodiesel standards than transesterified (FAME) microalgae biodiesel. Under optimised conditions, HTL bio-crude’s high density (0.97–1.04 kg·L⁻¹) and its high viscosity (70.77–73.89 mm²·s⁻¹) had enough similarity to marine heavy fuels. although the measured higher heating value, HHV, was lower (29.8 MJ·kg⁻¹). The reaction temperature was explored in the range 280–350 °C and bio-crude oil yield and HHV reached their maxima at the highest temperature. Slurry concentration was explored between 15% and 30% at this temperature and the best HHV, O:C, and N:C were found to occur at 25%. Two solvents (dichloromethane and n-hexane) were used to recover the bio-crude oil, affecting the yield and chemical composition of the bio-crude. Full article

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Open AccessArticle

Economic and Environmental Study of Wineries Powered by Grid-Connected Photovoltaic Systems in Spain

by Daniel Gómez-Lorente, Ovidio Rabaza, Fernando Aznar-Dols and María José Mercado-Vargas

Energies 2017, 10(2), 222; https://doi.org/10.3390/en10020222 - 14 Feb 2017

Cited by 19 | Viewed by 6140

Abstract

This research developed a system that can make factories more independent from the grid. The system enhances efficiency since factory operation is powered by the renewable energy generated during the production process. Winemaking is a key sector that can profit from such a [...] Read more.

This research developed a system that can make factories more independent from the grid. The system enhances efficiency since factory operation is powered by the renewable energy generated during the production process. Winemaking is a key sector that can profit from such a system because wineries can recycle much of the waste from the raw materials employed in wine production. Moreover, the solar energy collected at winemaking facilities can also be used to reduce electricity consumption and thus increase energy efficiency. This study investigated the feasibility of using renewable energy sources, such as solar energy, in wineries in Spain, given the quantity of renewable energy produced in the country. For this purpose, cost-effectiveness, power generation, CO₂ emissions and the renewable energy fraction were taken into account. The assumption was that the photovoltaic system was grid-connected. Research results showed a reduction in electrical power costs ranging from 4% to 36%. This reduction was accompanied by an increase in the use of renewable energy of up to 57%. The results obtained are based on self-consumption or net metering policy as well as the production capacity of the winery. Full article

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Open AccessArticle

Used Cooking Oils in the Biogas Chain: A Technical and Economic Assessment

by Erika Carnevale, Giovanni Molari and Matteo Vittuari

Energies 2017, 10(2), 192; https://doi.org/10.3390/en10020192 - 9 Feb 2017

Cited by 6 | Viewed by 5866

Abstract

The current concerns on global energy security, climate change, and environmental pollution represent some of the major elements of the growing interest on renewable energy. In this framework agro-food energy systems are at the center of a twofold debate: on the one hand [...] Read more.

The current concerns on global energy security, climate change, and environmental pollution represent some of the major elements of the growing interest on renewable energy. In this framework agro-food energy systems are at the center of a twofold debate: on the one hand they represent a key option for energy production while on the other their sustainability is threatened by the expansion of the bioenergy market that could lead to negative social and environmental consequences. The aim of this work is to evaluate—through a case study—the technical and economic feasibility of the replacement of energy crops (ECs) with used cooking oil (UCO) in an anaerobic digestion (AD) full-scale plant. At this purpose, a full-scale plant performing AD was monitored for two years. Three scenarios were developed and compared to evaluate the impacts and the potential benefits in terms of land saving in case of a substitution of ECs with UCO. Results highlighted a reduction of land use of over 50% if UCO is introduced in co-digestion with ECs. The lack of an appropriate legislative framework limits the utilization of used cooking oils (UCOs) in AD with a consequently missed opportunity for biogas owners that could find an important alternative in UCO. Full article

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978 KiB

Open AccessEditor’s ChoiceArticle

An Improvement in Biodiesel Production from Waste Cooking Oil by Applying Thought Multi-Response Surface Methodology Using Desirability Functions

by Marina Corral Bobadilla, Rubén Lostado Lorza, Rubén Escribano García, Fátima Somovilla Gómez and Eliseo P. Vergara González

Energies 2017, 10(1), 130; https://doi.org/10.3390/en10010130 - 21 Jan 2017

Cited by 57 | Viewed by 7022

Abstract

The exhaustion of natural resources has increased petroleum prices and the environmental impact of oil has stimulated the search for an alternative source of energy such as biodiesel. Waste cooking oil is a potential replacement for vegetable oils in the production of biodiesel. [...] Read more.

The exhaustion of natural resources has increased petroleum prices and the environmental impact of oil has stimulated the search for an alternative source of energy such as biodiesel. Waste cooking oil is a potential replacement for vegetable oils in the production of biodiesel. Biodiesel is synthesized by direct transesterification of vegetable oils, which is controlled by several inputs or process variables, including the dosage of catalyst, process temperature, mixing speed, mixing time, humidity and impurities of waste cooking oil that was studied in this case. Yield, turbidity, density, viscosity and higher heating value are considered as outputs. This paper used multi-response surface methodology (MRS) with desirability functions to find the best combination of input variables used in the transesterification reactions to improve the production of biodiesel. In this case, several biodiesel optimization scenarios have been proposed. They are based on a desire to improve the biodiesel yield and the higher heating value, while decreasing the viscosity, density and turbidity. The results demonstrated that, although waste cooking oil was collected from various sources, the dosage of catalyst is one of the most important variables in the yield of biodiesel production, whereas the viscosity obtained was similar in all samples of the biodiesel that was studied. Full article

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Open AccessArticle

Study on the Tribological Characteristics of Australian Native First Generation and Second Generation Biodiesel Fuel

by Md Mofijur Rahman, Mohammad Rasul and Nur Md Sayeed Hassan

Energies 2017, 10(1), 55; https://doi.org/10.3390/en10010055 - 5 Jan 2017

Cited by 36 | Viewed by 5988

Abstract

Biodiesels are a renewable energy source, and they have the potential to be used as alternatives to diesel fuel. The aim of this study is to investigate the wear and friction characteristics of Australian native first generation and second generation biodiesels using a [...] Read more.

Biodiesels are a renewable energy source, and they have the potential to be used as alternatives to diesel fuel. The aim of this study is to investigate the wear and friction characteristics of Australian native first generation and second generation biodiesels using a four-ball tribo tester. The biodiesel was produced through a two-step transesterification process and characterized according to the American Society for Testing and Materials (ASTM) standards. The tribological experiment was carried out at a constant 1800 rpm and different loads and temperatures. In addition, the surface morphology of the ball was tested by scanning electron microscope (SEM)/energy dispersive X-ray spectroscopy (EDX) analysis. The test results indicated that biodiesel fuels have a lower coefficient of frictions (COF) and lower wear scar diameter (WSD) up to 83.50% and 41.28%, respectively, compared to conventional diesel fuel. The worn surface area results showed that biodiesel fuel has a minimum percentage of C and O, except Fe, compared to diesel. In addition, the worn surface area for diesel was found (2.20%–27.92%) to be higher than biodiesel. The findings of this study indicated that both first and second generation biodiesel fuels have better tribological performance than diesel fuel, and between the biodiesel fuels, macadamia biodiesel showed better lubrication performance. Full article

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Open AccessArticle

Optimization of Reducing Sugar Production from Manihot glaziovii Starch Using Response Surface Methodology

by Abdi Hanra Sebayang, Masjuki Haji Hassan, Hwai Chyuan Ong, Surya Dharma, Arridina Susan Silitonga, Fitranto Kusumo, Teuku Meurah Indra Mahlia and Aditiya Harjon Bahar

Energies 2017, 10(1), 35; https://doi.org/10.3390/en10010035 - 1 Jan 2017

Cited by 38 | Viewed by 6892

Abstract

Bioethanol is known as a viable alternative fuel to solve both energy and environmental crises. This study used response surface methodology based on the Box-Behnken experimental design to obtain the optimum conditions for and quality of bioethanol production. Enzymatic hydrolysis optimization was performed [...] Read more.

Bioethanol is known as a viable alternative fuel to solve both energy and environmental crises. This study used response surface methodology based on the Box-Behnken experimental design to obtain the optimum conditions for and quality of bioethanol production. Enzymatic hydrolysis optimization was performed with selected hydrolysis parameters, including substrate loading, stroke speed, α-amylase concentration and amyloglucosidase concentration. From the experiment, the resulting optimum conditions are 23.88% (w/v) substrate loading, 109.43 U/g α-amylase concentration, 65.44 U/mL amyloglucosidase concentration and 74.87 rpm stroke speed, which yielded 196.23 g/L reducing sugar. The fermentation process was also carried out, with a production value of 0.45 g ethanol/g reducing sugar, which is equivalent to 88.61% of ethanol yield after fermentation by using Saccharomyces cerevisiae (S. cerevisiae). The physical and chemical properties of the produced ethanol are within the specifications of the ASTM D4806 standard. The good quality of ethanol produced from this study indicates that Manihot glaziovii (M. glaziovii) has great potential as bioethanol feedstock. Full article

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1175 KiB

Open AccessArticle

A Simple Method for the Detection of Long-Chain Fatty Acids in an Anaerobic Digestate Using a Quartz Crystal Sensor

by Takuro Kobayashi, Hidetoshi Kuramochi, Kouji Maeda and Kaiqin Xu

Energies 2017, 10(1), 19; https://doi.org/10.3390/en10010019 - 24 Dec 2016

Cited by 8 | Viewed by 5540

Abstract

In anaerobic digestion (AD), long-chain fatty acids (LCFAs) produced by hydrolysis of lipids, exhibit toxicity against microorganisms when their concentration exceeds several millimolar. An absorption detection system using a quartz crystal microbalance (QCM) was developed to monitor the LCFA concentration during an anaerobic [...] Read more.

In anaerobic digestion (AD), long-chain fatty acids (LCFAs) produced by hydrolysis of lipids, exhibit toxicity against microorganisms when their concentration exceeds several millimolar. An absorption detection system using a quartz crystal microbalance (QCM) was developed to monitor the LCFA concentration during an anaerobic digester’s operation treating oily organic waste. The dissociation of the LCFAs considerably improved the sensor response and, moreover, enabled it to specifically detect LCFA from the mixture of LCFA and triglyceride. Under alkaline conditions, the frequency-shift rates of the QCM sensor linearly increased in accordance with palmitic acid concentration in the range of 0–100 mg/L. Frequency changes caused by anaerobic digestate samples were successfully measured after removing suspended solids and adjusting the pH to 10.7. Finally, the QCM measurements for digestate samples demonstrated that frequency-shift rates are highly correlated with LCFA concentrations, which confirmed that the newly developed QCM sensor is helpful for LCFA monitoring in terms of rapidness and usability. Full article

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Open AccessArticle

Realistic Quantum Control of Energy Transfer in Photosynthetic Processes

by Reda M. El-Shishtawy, Robert Haddon, Saleh Al-Heniti, Bahaaudin Raffah, Sayed Abdel-Khalek, Kamal Berrada and Yas Al-Hadeethi

Energies 2016, 9(12), 1063; https://doi.org/10.3390/en9121063 - 15 Dec 2016

Cited by 3 | Viewed by 4415

Abstract

The occurrence of coherence phenomenon as a result of the interference of the probability amplitude terms is among the principle features of quantum mechanics concepts. Current experiments display the presence of quantum techniques whose coherence is supplied over large interval times. Specifically, photosynthetic [...] Read more.

The occurrence of coherence phenomenon as a result of the interference of the probability amplitude terms is among the principle features of quantum mechanics concepts. Current experiments display the presence of quantum techniques whose coherence is supplied over large interval times. Specifically, photosynthetic mechanisms in light-harvesting complexes furnish oscillatory behaviors owing to quantum coherence. In this manuscript, we study the coherent quantum energy transfer for a single-excitation and nonlocal correlation in a dimer system (donor+acceptor) displayed by two-level systems (TLSs), interacting with a cavity field with a time-dependent coupling effect considering the realistic situation of coupling between each TLS and the cavity field. We analyze and explore the specific conditions which are viable with real experimental realization for the ultimate transfer of quantum energy and nonlocal quantum correlation. We show that the enhancement of the probability for a single-excitation energy transfer greatly benefits from the energy detuning, photon-number transition, classicality of the field, and the time-dependent coupling effect. We also find that the entanglement between the donor and acceptor is very sensitive to the physical parameters and it can be generated during the coherent energy transfer. Full article

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Open AccessArticle

A Principal Component Analysis in Switchgrass Chemical Composition

by Mario Aboytes-Ojeda, Krystel K. Castillo-Villar, Tun-hsiang E. Yu, Christopher N. Boyer, Burton C. English, James A. Larson, Lindsey M. Kline and Nicole Labbé

Energies 2016, 9(11), 913; https://doi.org/10.3390/en9110913 - 4 Nov 2016

Cited by 9 | Viewed by 6802

Abstract

In recent years, bioenergy has become a promising renewable energy source that can potentially reduce the greenhouse emissions and generate economic growth in rural areas. Gaining understanding and controlling biomass chemical composition contributes to an efficient biofuel generation. This paper presents a principal [...] Read more.

In recent years, bioenergy has become a promising renewable energy source that can potentially reduce the greenhouse emissions and generate economic growth in rural areas. Gaining understanding and controlling biomass chemical composition contributes to an efficient biofuel generation. This paper presents a principal component analysis (PCA) that shows the influence and relevance of selected controllable factors over the chemical composition of switchgrass and, therefore, in the generation of biofuels. The study introduces the following factors: (1) storage days; (2) particle size; (3) wrap type; and (4) weight of the bale. Results show that all the aforementioned factors have an influence in the chemical composition. The number of days that bales have been stored was the most significant factor regarding changes in chemical components due to its effect over principal components 1 and 2 (PC1 and PC2, approximately 80% of the total variance). The storage days are followed by the particle size, the weight of the bale and the type of wrap utilized to enclose the bale. An increment in the number of days (from 75–150 days to 225 days) in storage decreases the percentage of carbohydrates by −1.03% while content of ash increases by 6.56%. Full article

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Open AccessReview

Scrap Tyre Management Pathways and Their Use as a Fuel—A Review

by Amir Rowhani and Thomas J. Rainey

Energies 2016, 9(11), 888; https://doi.org/10.3390/en9110888 - 29 Oct 2016

Cited by 140 | Viewed by 12620

Abstract

This article provides a review of different methods for managing waste tyres. Around 1.5 billion scrap tyres make their way into the environmental cycle each year, so there is an extreme demand to manage and mitigate the environmental impact which occurs from landfilling [...] Read more.

This article provides a review of different methods for managing waste tyres. Around 1.5 billion scrap tyres make their way into the environmental cycle each year, so there is an extreme demand to manage and mitigate the environmental impact which occurs from landfilling and burning. Numerous approaches are targeted to recycle and reuse the tyre rubber in various applications. Among them, one of the most important methods for sustainable environmental stewardship is converting tyre rubber components into bio-oil. In this study, scrap tyre management techniques including landfill, retreading, recycling, combustion, and conversion to liquid fuels was reviewed (including gasification, hydrothermal liquefaction, and pyrolysis). The effects of parameters such as reactor types, pyrolysis temperature, and catalyst on the oil, gas and solid products in pyrolysis process were investigated. Full article

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Open AccessArticle

The BioSCWG Project: Understanding the Trade-Offs in the Process and Thermal Design of Hydrogen and Synthetic Natural Gas Production

by Mohamed Magdeldin, Thomas Kohl, Cataldo De Blasio, Mika Järvinen, Song Won Park and Reinaldo Giudici

Energies 2016, 9(10), 838; https://doi.org/10.3390/en9100838 - 18 Oct 2016

Cited by 20 | Viewed by 6983

Abstract

This article presents a summary of the main findings from a collaborative research project between Aalto University in Finland and partner universities. A comparative process synthesis, modelling and thermal assessment was conducted for the production of Bio-synthetic natural gas (SNG) and hydrogen from [...] Read more.

This article presents a summary of the main findings from a collaborative research project between Aalto University in Finland and partner universities. A comparative process synthesis, modelling and thermal assessment was conducted for the production of Bio-synthetic natural gas (SNG) and hydrogen from supercritical water refining of a lipid extracted algae feedstock integrated with onsite heat and power generation. The developed reactor models for product gas composition, yield and thermal demand were validated and showed conformity with reported experimental results, and the balance of plant units were designed based on established technologies or state-of-the-art pilot operations. The poly-generative cases illustrated the thermo-chemical constraints and design trade-offs presented by key process parameters such as plant organic throughput, supercritical water refining temperature, nature of desirable coproducts, downstream indirect production and heat recovery scenarios. The evaluated cases favoring hydrogen production at 5 wt. % solid content and 600 °C conversion temperature allowed higher gross syngas and CHP production. However, mainly due to the higher utility demands the net syngas production remained lower compared to the cases favoring BioSNG production. The latter case, at 450 °C reactor temperature, 18 wt. % solid content and presence of downstream indirect production recorded 66.5%, 66.2% and 57.2% energetic, fuel-equivalent and exergetic efficiencies respectively. Full article

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1800 KiB

Open AccessBrief Report

Comparison of Nitrogen Depletion and Repletion on Lipid Production in Yeast and Fungal Species

by Shihui Yang, Wei Wang, Hui Wei, Stefanie Van Wychen, Philip T. Pienkos, Min Zhang and Michael E. Himmel

Energies 2016, 9(9), 685; https://doi.org/10.3390/en9090685 - 29 Aug 2016

Cited by 14 | Viewed by 6602

Abstract

Although it is well known that low nitrogen stimulates lipid accumulation, especially for algae and some oleaginous yeast, few studies have been conducted in fungal species, especially on the impact of different nitrogen deficiency strategies. In this study, we use two promising consolidated [...] Read more.

Although it is well known that low nitrogen stimulates lipid accumulation, especially for algae and some oleaginous yeast, few studies have been conducted in fungal species, especially on the impact of different nitrogen deficiency strategies. In this study, we use two promising consolidated bioprocessing (CBP) candidates to examine the impact of two nitrogen deficiency strategies on lipid production, which are the extensively investigated oleaginous yeast Yarrowia lipolytica, and the commercial cellulase producer Trichoderma reesei. We first utilized bioinformatics approaches to reconstruct the fatty acid metabolic pathway and demonstrated the presence of a triacylglycerol (TAG) biosynthesis pathway in Trichoderma reesei. We then examined the lipid production of Trichoderma reesei and Y. lipomyces in different media using two nitrogen deficiency strategies of nitrogen natural repletion and nitrogen depletion through centrifugation. Our results demonstrated that nitrogen depletion was better than nitrogen repletion with about 30% lipid increase for Trichoderma reesei and Y. lipomyces, and could be an option to improve lipid production in both oleaginous yeast and filamentous fungal species. The resulting distinctive lipid composition profiles indicated that the impacts of nitrogen depletion on yeast were different from those for fungal species. Under three types of C/N ratio conditions, C16 and C18 fatty acids were the predominant forms of lipids for both Trichoderma reesei and Y. lipolytica. While the overall fatty acid methyl ester (FAME) profiles of Trichoderma reesei were similar, the overall FAME profiles of Y. lipolytica observed a shift. The fatty acid metabolic pathway reconstructed in this work supports previous reports of lipid production in T. reesei, and provides a pathway for future omics studies and metabolic engineering efforts. Further investigation to identify the genetic targets responsible for the effect of nitrogen depletion on lipid production improvement will facilitate strain engineering to boost lipid production under more optimal conditions for productivity than those required for nitrogen depletion. Full article

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Open AccessArticle

Environment-Friendly Heterogeneous Alkaline-Based Mixed Metal Oxide Catalysts for Biodiesel Production

by Hwei Voon Lee, Joon Ching Juan, Taufiq-Yap Yun Hin and Hwai Chyuan Ong

Energies 2016, 9(8), 611; https://doi.org/10.3390/en9080611 - 3 Aug 2016

Cited by 48 | Viewed by 7405

Abstract

The critical problem arising from the depletion of fossil fuels has stimulated recent interests in alternative sources for petroleum-based fuel. An alternative fuel should be technically feasible, readily available, sustainable, and techno-economically competitive. Biodiesel is considered as a potential replacement of conventional diesel [...] Read more.

The critical problem arising from the depletion of fossil fuels has stimulated recent interests in alternative sources for petroleum-based fuel. An alternative fuel should be technically feasible, readily available, sustainable, and techno-economically competitive. Biodiesel is considered as a potential replacement of conventional diesel fuel, which is prepared from non-edible and high-acid feedstock via transesterification technology. The focus of this study is to investigate the catalytic activity of mixed metal oxides (MMOs) as catalysts for biodiesel production by using non-edible jatropha oil as feedstock. Various types of MMOs (CaO-MgO, CaO-ZnO, CaO-La₂O₃, and MgO-ZnO) were synthesized via a co-precipitation method. In this study, transesterification activities are closely related to the physicochemical properties of catalysts. The presence of different active metals in the binary system greatly influenced the surface area, basicity, and the stability of catalysts. The catalytic activity of MMO catalysts was increased in the order of CaO-ZnO (94% ± 1%) > CaO ~ CaO-MgO ~ CaO-La₂O₃ (~90% ± 2%) > MgO-ZnO (83% ± 2%) > MgO (64% ± 1%) > ZnO (41% ± 2%) > La₂O₃ (23% ± 1%). In addition, the MMO catalysts, especially CaO-ZnO, demonstrated high reusability and catalyst stability for four cycles of transesterification reaction of jatropha oil. Full article

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Open AccessReview

A Review of CO₂-Enhanced Oil Recovery with a Simulated Sensitivity Analysis

by Mandadige Samintha Anne Perera, Ranjith Pathegama Gamage, Tharaka Dilanka Rathnaweera, Ashani Savinda Ranathunga, Andrew Koay and Xavier Choi

Energies 2016, 9(7), 481; https://doi.org/10.3390/en9070481 - 23 Jun 2016

Cited by 153 | Viewed by 15899

Abstract

This paper reports on a comprehensive study of the CO₂-EOR (Enhanced oil recovery) process, a detailed literature review and a numerical modelling study. According to past studies, CO₂ injection can recover additional oil from reservoirs by reservoir pressure increment, oil [...] Read more.

This paper reports on a comprehensive study of the CO₂-EOR (Enhanced oil recovery) process, a detailed literature review and a numerical modelling study. According to past studies, CO₂ injection can recover additional oil from reservoirs by reservoir pressure increment, oil swelling, the reduction of oil viscosity and density and the vaporization of oil hydrocarbons. Therefore, CO₂-EOR can be used to enhance the two major oil recovery mechanisms in the field: miscible and immiscible oil recovery, which can be further increased by increasing the amount of CO₂ injected, applying innovative flood design and well placement, improving the mobility ratio, extending miscibility, and controlling reservoir depth and temperature. A 3-D numerical model was developed using the CO₂-Prophet simulator to examine the effective factors in the CO₂-EOR process. According to that, in pure CO₂ injection, oil production generally exhibits increasing trends with increasing CO₂ injection rate and volume (in HCPV (Hydrocarbon pore volume)) and reservoir temperature. In the WAG (Water alternating gas) process, oil production generally increases with increasing CO₂ and water injection rates, the total amount of flood injected in HCPV and the distance between the injection wells, and reduces with WAG flood ratio and initial reservoir pressure. Compared to other factors, the water injection rate creates the minimum influence on oil production, and the CO₂ injection rate, flood volume and distance between the flood wells have almost equally important influence on oil production. Full article

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Open AccessArticle

Effect of Coal Rank on Various Fluid Saturations Creating Mechanical Property Alterations Using Australian Coals

by Mandadige Samintha Anne Perera, Ashani Savinda Ranathunga and Pathegama Gamage Ranjith

Energies 2016, 9(6), 440; https://doi.org/10.3390/en9060440 - 8 Jun 2016

Cited by 35 | Viewed by 5411

Abstract

During CO₂ sequestration in deep coal seams, the coal mass may be subjected to various fluid (CO₂, N₂, etc.) saturations. Therefore, in order to maintain the long-term integrity of the process, it is necessary to identify the [...] Read more.

During CO₂ sequestration in deep coal seams, the coal mass may be subjected to various fluid (CO₂, N₂, etc.) saturations. Therefore, in order to maintain the long-term integrity of the process, it is necessary to identify the mechanical responses of preferable coal seams for various fluid saturations. To date, many studies have focused on the CO₂ saturation effect on coal mass strength and less consideration has been given to the influence of other saturation mediums. Hence, this study aims to investigate coal’s mechanical responses to water and N₂ saturations compared to CO₂ saturation and to determine the effect of coal-rank. A series of unconfined compressive strength (UCS) tests was conducted on Australian brown and black coal samples saturated with water and N₂ at various saturation pressures. An advanced acoustic emission (AE) system was utilized to identify the changes in crack propagation behaviors under each condition. According to the results, both CO₂ and water act similarly with coal by enhancing the ductile properties of the coal mass and this mechanical weakening is greater for high-rank coal. Conversely, N₂ saturation slightly enhances coal strength and delays crack propagation in coal and this strength enhancement can be improved by increasing the N₂ saturation pressure. Full article

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Open AccessArticle

Cathode Assessment for Maximizing Current Generation in Microbial Fuel Cells Utilizing Bioethanol Effluent as Substrate

by Guotao Sun, Anders Thygesen and Anne S. Meyer

Energies 2016, 9(5), 388; https://doi.org/10.3390/en9050388 - 20 May 2016

Cited by 5 | Viewed by 6190

Abstract

Implementation of microbial fuel cells (MFCs) for electricity production requires effective current generation from waste products via robust cathode reduction. Three cathode types using dissolved oxygen cathodes (DOCs), ferricyanide cathodes (FeCs) and air cathodes (AiCs) were therefore assessed using bioethanol effluent, containing 20.5 [...] Read more.

Implementation of microbial fuel cells (MFCs) for electricity production requires effective current generation from waste products via robust cathode reduction. Three cathode types using dissolved oxygen cathodes (DOCs), ferricyanide cathodes (FeCs) and air cathodes (AiCs) were therefore assessed using bioethanol effluent, containing 20.5 g/L xylose, 1.8 g/L arabinose and 2.5 g/L propionic acid. In each set-up the anode and cathode had an electrode surface area of 88 cm², which was used for calculation of the current density. Electricity generation was evaluated by quantifying current responses to substrate loading rates and external resistance. At the lowest external resistance of 27 Ω and highest substrate loading rate of 2 g chemical oxygen demand (COD) per L·day, FeC-MFC generated highest average current density (1630 mA/m²) followed by AiC-MFC (802 mA/m²) and DOC-MFC (184 mA/m²). Electrochemical impedance spectroscopy (EIS) was used to determine the impedance of the cathodes. It was thereby confirmed that the FeC-MFC produced the highest current density with the lowest internal resistance for the cathode. However, in a setup using bioethanol effluent, the AiC-MFC was concluded to be the most sustainable option since it does not require ferricyanide. The data offer a new add-on option to the straw biorefinery by using bioethanol effluent for microbial electricity production. Full article

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789 KiB

Open AccessArticle

Assessment of the Variability of Biogas Production from Sugar Beet Silage as Affected by Movement and Loss of the Produced Alcohols and Organic Acids

by Ali Heidarzadeh Vazifehkhoran, Jin Mi Triolo, Søren Ugilt Larsen, Kasper Stefanek and Sven G. Sommer

Energies 2016, 9(5), 368; https://doi.org/10.3390/en9050368 - 16 May 2016

Cited by 16 | Viewed by 5952

Abstract

The biochemical methane potential and composition of sugar beet pulp silage were investigated using samples taken from six different depths in both open and closed silos (height 3.6 m). The biochemical methane potential (BMP) of pulp silage in open silos ranged from 337 [...] Read more.

The biochemical methane potential and composition of sugar beet pulp silage were investigated using samples taken from six different depths in both open and closed silos (height 3.6 m). The biochemical methane potential (BMP) of pulp silage in open silos ranged from 337 to 420 normal litre (NL) CH₄/kg volatile solids (VS), while the BMP of pulp silage in closed silos varied between 411 and 451 NL CH₄/kg VS. The biochemical methane potential peaked at a depth of 1.45 m with 420 NL CH₄/kg VS for open silos and 451 NL CH₄/kg VS for closed silos. The ethanol concentration and biochemical methane potential showed the same trend with depth throughout the silos. The energy loss correlated to the loss of volatile solids, and the depths described a linear relationship between them for both the open and closed silos (R² = 0.997 for the open silo and R² = 0.991 for the closed silo). The energy potentials and composition of beet pulp silage were highly stratified and there was a risk that the silage samples were not representative in investigations of biomass quality for energy production. Full article

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Open AccessArticle

Techno-Economic Analysis of Integrating First and Second-Generation Ethanol Production Using Filamentous Fungi: An Industrial Case Study

by Karthik Rajendran, Sreevathsava Rajoli and Mohammad J. Taherzadeh

Energies 2016, 9(5), 359; https://doi.org/10.3390/en9050359 - 12 May 2016

Cited by 30 | Viewed by 9406

Abstract

The 2nd generation plants producing ethanol from lignocelluloses demand risky and high investment costs. This paper presents the energy- and economical evaluations for integrating lignocellulose in current 1st generation dry mill ethanol processes, using filamentous fungi. Dry mills use grains and have mills, [...] Read more.

The 2nd generation plants producing ethanol from lignocelluloses demand risky and high investment costs. This paper presents the energy- and economical evaluations for integrating lignocellulose in current 1st generation dry mill ethanol processes, using filamentous fungi. Dry mills use grains and have mills, liquefactions, saccharifications, fermentation, and distillation to produce ethanol, while their stillage passes centrifugation, and evaporation to recycle the water and dry the cake and evaporated syrup into animal feed. In this work, a bioreactor was considered to cultivate fungi on the stillage either before or after the centrifugation step together with pretreated lignocellulosic wheat bran. The results showed that the integrated 1st and 2nd generation ethanol process requires a capital investment of 77 million USD, which could yield NPV of 162 million USD after 20 years. Compared to the fungal cultivation on thin stillage modified 1st generation process, the integrated process resulted in 53 million USD higher NPV. The energy analysis showed that the thin stillage modified 1st generation process could reduce the overall energy consumption by 2.5% and increase the ethanol production by 4%. Such modifications in the 1st generation processes and integration concepts could be interesting for the ethanol industries, as integrating lignocelluloses to their existing setup requires less capital investment. Full article

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898 KiB

Open AccessArticle

Regionalized Techno-Economic Assessment and Policy Analysis for Biomass Molded Fuel in China

by Jie Xu, Shiyan Chang, Zhenhong Yuan, Yang Jiang, Shuna Liu, Weizhen Li and Longlong Ma

Energies 2015, 8(12), 13846-13863; https://doi.org/10.3390/en81212399 - 4 Dec 2015

Cited by 23 | Viewed by 6554

Abstract

As a relatively mature technology, biomass molded fuel (BMF) is widely used in distributed and centralized heating in China and has received considerable government attention. Although many BFM incentive policies have been developed, decreased domestic traditional fuel prices in China have caused BMF [...] Read more.

As a relatively mature technology, biomass molded fuel (BMF) is widely used in distributed and centralized heating in China and has received considerable government attention. Although many BFM incentive policies have been developed, decreased domestic traditional fuel prices in China have caused BMF to lose its economic viability and new policy recommendations are needed to stimulate this industry. The present study built a regionalized net present value (NPV) model based on real production process simulation to test the impacts of each policy factor. The calculations showed that BMF production costs vary remarkably between regions, with the cost of agricultural briquette fuel (ABF) ranging from 86 US dollar per metric ton (USD/t) to 110 (USD/t), while that of woody pellet fuel (WPF) varies from 122 USD/t to 154 USD/t. The largest part of BMF’s cost composition is feedstock, which accounts for up 50%–60% of the total; accordingly a feedstock subsidy is the most effective policy factor, but in consideration of policy implementation, it would be better to use a production subsidy. For ABF, the optimal product subsidy varies from 26 USD/t to 57 USD/t among different regions of China, while for WPF, the range is 36 USD/t to 75 USD/t. Based on the data, a regional BMF development strategy is also proposed in this study. Full article

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Open AccessArticle

Effects of Alkali and Alkaline Earth Metals on N-Containing Species Release during Rice Straw Pyrolysis

by Pan Gao, Lu Xue, Qiang Lu and Changqing Dong

Energies 2015, 8(11), 13021-13032; https://doi.org/10.3390/en81112356 - 17 Nov 2015

Cited by 26 | Viewed by 5965

Abstract

To study the effects of inherent and external alkali and alkaline earth metallic species (AAEMs, i.e., K, Ca and Mg) on the behavior of N-containing species release during rice straw (RS) pyrolysis, different pretreatments were applied in numerous experiments. Results indicate that [...] Read more.

To study the effects of inherent and external alkali and alkaline earth metallic species (AAEMs, i.e., K, Ca and Mg) on the behavior of N-containing species release during rice straw (RS) pyrolysis, different pretreatments were applied in numerous experiments. Results indicate that ammonia (NH₃) and hydrogen cyanide (HCN) are the major N-containing species and that the yields of isocyanic acid (HNCO) and nitric oxide (NO) are relatively low. The removal of inhert AAEMs shifts N-containing species release to a high-temperature zone according to volatile release behavior because of the increase in activation energy. The formation selectivity of NH₃, HNCO, and NO increases by demineralized pretreatment, whereas HCN selectivity decreases. The formation of HNCO is mainly affected by alkaline earth metal. N-containing species release occurs in low temperatures with the addition of external AAEMs. The activation energy of samples impregnated with CaCl₂ and MgCl₂ sharply decreases compared to the original RS. The total yields of N-containing species are reduced significantly in the presence of KCl, CaCl₂, and MgCl₂ as additives. The inhibition ability of AAEMs follows the sequence MgCl₂ > CaCl₂ > KCl. The inhibition effect of MgCl₂ can be improved by solution immersion compared with solid powder mixing. The clean biomass pyrolysis and gasification technology with low N-containing species content may be developed according to the results. Full article

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Open AccessArticle

Eicosapentaenoic Acid from Porphyridium Cruentum: Increasing Growth and Productivity of Microalgae for Pharmaceutical Products

by Maryam Asgharpour, Brigitte Rodgers and Jamie A. Hestekin

Energies 2015, 8(9), 10487-10503; https://doi.org/10.3390/en80910487 - 22 Sep 2015

Cited by 40 | Viewed by 9071

Abstract

An alternative source of eicosapentaenoic acid (EPA) or omega-3 could be microalgae lipids instead of fish oils. However, EPA and lipid contents extracted from microalgae vary at different growth conditions. Therefore, it is of paramount importance to optimize the growth conditions of microalgae [...] Read more.

An alternative source of eicosapentaenoic acid (EPA) or omega-3 could be microalgae lipids instead of fish oils. However, EPA and lipid contents extracted from microalgae vary at different growth conditions. Therefore, it is of paramount importance to optimize the growth conditions of microalgae to maximize EPA production. In this paper, the effects of temperature (16 °C and 20 °C), light intensity (140 µE m⁻² s⁻¹ and 180 µE m⁻² s⁻¹) and nitrate level (0.075, 0.3, 0.5, and 0.7 g/L) on the cell growth, lipid productivity, and omega-6/omega-3 ratio of Porphyridium cruentum, one of the most promising oil-rich species of microalgae, are investigated. The ratio of the fatty acids with omega-6 and omega-3 groups at various growth conditions were compared, since an appropriate proportion of ω-6 (arachidonic acid (ARA)) to ω-3 (EPA) is vital for healthy nutrition. Lower EPA production and consequently a higher ARA/EPA ratio occurred when 5% CO₂/air was utilized as CO₂ supplementation compared to pure CO₂. The highest EPA (13.08% (w/w) of total fatty acids) and biomass productivity (143 mg L⁻¹ day⁻¹) was achieved at 140 µE m⁻² s⁻¹, 20 °C, and 0.3 g/L nitrate, while lipid content was the lowest (0.5% w/w) at this condition. The optimal condition with minimum ARA/EPA ratio (2.5) was identified at 20 °C, 140 µE m⁻² s⁻¹, and 0.5 g/L nitrate concentration. Full article

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Open AccessArticle

Influence of Combustion Parameters on Fouling Composition after Wood Pellet Burning in a Lab-Scale Low-Power Boiler

by Lara Febrero, Enrique Granada, Araceli Regueiro and José Luis Míguez

Energies 2015, 8(9), 9794-9816; https://doi.org/10.3390/en8099794 - 9 Sep 2015

Cited by 34 | Viewed by 6513

Abstract

The present study aims to evaluate the effect of different operating conditions on fouling composition after woody biomass combustion in an experimental low-power fixed-bed boiler. The boiler was built specifically for research purposes and allows easy removal of areas susceptible to fouling and [...] Read more.

The present study aims to evaluate the effect of different operating conditions on fouling composition after woody biomass combustion in an experimental low-power fixed-bed boiler. The boiler was built specifically for research purposes and allows easy removal of areas susceptible to fouling and the control, modification and registry of combustion parameters. The influences of the total airflow supplied and the deposition probe temperature were studied in fouling; differentiating between the layers of fouling adhered to the tube and those deposited over the tube. Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS) were performed in order to determine a relationship between the fouling composition and the combustion parameters used. Upon increasing the total airflow supplied and the deposition probe temperature, the amount of organic matter, namely unburned carbon, decreased, indicating a better combustion efficiency. Chemical analysis results of fouling deposits showed that inorganic elements presented different behaviors depending on the collection area and the combustion parameters. Non-volatile elements such as Si and Ca were mostly found in the coarse fraction of the bottom ash and minor amounts were deposited over the tube. Small amounts of Cl in biomass generated serious deposition problems, especially during combustions with low airflow rates. Full article

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Open AccessArticle

Chemical Composition of Apricot Pit Shells and Effect of Hot-Water Extraction

by Derek B. Corbett, Neil Kohan, Grazielle Machado, Chengyan Jing, Aditi Nagardeolekar and Biljana M. Bujanovic

Energies 2015, 8(9), 9640-9654; https://doi.org/10.3390/en8099640 - 3 Sep 2015

Cited by 39 | Viewed by 8663

Abstract

Agricultural residues, such as corn stover, wheat straw, and nut shells show promise as feedstocks for lignocellulosic biorefinery due to their relatively high polysaccharide content and low or no nutritional value for human consumption. Apricot pit shells (APS) were studied in this work [...] Read more.

Agricultural residues, such as corn stover, wheat straw, and nut shells show promise as feedstocks for lignocellulosic biorefinery due to their relatively high polysaccharide content and low or no nutritional value for human consumption. Apricot pit shells (APS) were studied in this work to assess their potential for use in a biorefinery. Hot water extraction (HWE; 160 °C, 2 h), proposed to remove easily accessible hemicelluloses, was performed to evaluate the susceptibility of APS to this mild pretreatment process. The chemical composition of APS before and after HWE (EAPS) was analyzed by standard methods and ¹H-NMR. A low yield of the remaining HW-extracted APS (~59%) indicated that APS are highly susceptible to this pretreatment method. ¹H-NMR analysis of EAPS revealed that ~77% of xylan present in raw APS was removed along with ~24% of lignin. The energy of combustion of APS was measured before and after HWE showing a slight increase due to HWE (1.61% increase). Near infrared radiation spectroscopy (NIRS), proposed as a quick non-invasive method of biomass analysis, was performed. NIRS corroborated results of traditional analysis and ¹H-NMR. Determination of antioxidizing activity (AOA) of APS extracts was also undertaken. AOA of organic APS extracts were shown to be more than 20 times higher than that of a synthetic antioxidizing agent. Full article

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Open AccessArticle

Bio-Wastes as an Alternative Household Cooking Energy Source in Ethiopia

by Gudina Terefe Tucho and Sanderine Nonhebel

Energies 2015, 8(9), 9565-9583; https://doi.org/10.3390/en8099565 - 2 Sep 2015

Cited by 41 | Viewed by 11840

Abstract

Up to the present day, wood has been used to supply the needs for cooking in rural Africa. Due to the ongoing deforestation, households need to change to other energy sources. To cover this need, a large amount of people are using residues [...] Read more.

Up to the present day, wood has been used to supply the needs for cooking in rural Africa. Due to the ongoing deforestation, households need to change to other energy sources. To cover this need, a large amount of people are using residues from agriculture (straw, manure) instead. However, both straw and manure also have a function in agriculture for soil improvement. Using all the straw and manure will seriously affect the food production. In this paper we first determine the amount of energy that households need for cooking (about 7 GJ per year). Then we estimate the amount of residues that can be obtained from the agricultural system and the amount of energy for cooking that can be derived from this amount when different conversion techniques are used. The amount of residues needed is strongly affected by the technology used. The traditional three stone fires require at least two times as much resource than the more advanced technologies. Up to 4 ha of land or 15 cows are needed to provide enough straw and manure to cook on the traditional three stone fires. When more efficient techniques are used (briquetting, biogas) this can be reduced to 2 ha and six cows. Due to large variation in resource availability between households, about 80% of the households own less than 2 ha and 70% holds less than four cows. This means that even when modern, energy efficient techniques are used the largest share of the population is not able to generate enough energy for cooking from their own land and/or cattle. Most rural households in Sub-Saharan Africa may share similar resource holding characteristics for which the results from the current findings on Ethiopia can be relevant. Full article

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Open AccessReview

Combined Biogas and Bioethanol Production: Opportunities and Challenges for Industrial Application

by Alessandra Cesaro and Vincenzo Belgiorno

Energies 2015, 8(8), 8121-8144; https://doi.org/10.3390/en8088121 - 5 Aug 2015

Cited by 83 | Viewed by 10565

Abstract

In the last decades the increasing energy requirements along with the need to face the consequences of climate change have driven the search for renewable energy sources, in order to replace as much as possible the use of fossil fuels. In this context [...] Read more.

In the last decades the increasing energy requirements along with the need to face the consequences of climate change have driven the search for renewable energy sources, in order to replace as much as possible the use of fossil fuels. In this context biomass has generated great interest as it can be converted into energy via several routes, including fermentation and anaerobic digestion. The former is the most common option to produce ethanol, which has been recognized as one of the leading candidates to substitute a large fraction of the liquid fuels produced from oil. As the economic competitiveness of bioethanol fermentation processes has to be enhanced in order to promote its wider implementation, the most recent trends are directed towards the use of fermentation by-products within anaerobic digestion. The integration of both fermentation and anaerobic digestion, in a biorefinery concept, would allow the production of ethanol along with that of biogas, which can be used to produce heat and electricity, thus improving the overall energy balance. This work aims at reviewing the main studies on the combination of both bioethanol and biogas production processes, in order to highlight the strength and weakness of the integrated treatment for industrial application. Full article

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Open AccessArticle

Release of Extracellular Polymeric Substance and Disintegration of Anaerobic Granular Sludge under Reduced Sulfur Compounds-Rich Conditions

by Takuro Kobayashi, Kai-Qin Xu and Haruyuki Chiku

Energies 2015, 8(8), 7968-7985; https://doi.org/10.3390/en8087968 - 31 Jul 2015

Cited by 34 | Viewed by 6918

Abstract

The effect of reduced form of sulfur compounds on granular sludge was investigated. Significant release of extracellular polymeric substance (EPS) from the granular sludge occurred in the presence of sulfide and methanethiol according to various concentrations. Granular sludge also showed a rapid increase [...] Read more.

The effect of reduced form of sulfur compounds on granular sludge was investigated. Significant release of extracellular polymeric substance (EPS) from the granular sludge occurred in the presence of sulfide and methanethiol according to various concentrations. Granular sludge also showed a rapid increase in turbidity and decrease in diameter in accordance with sulfide concentration during the long-term shaking, suggesting that the strength of the granules was reduced with high-concentration sulfide. A continuous experiment of up-flow anaerobic sludge blanket reactors with different concentrations of sulfide (10, 200, 500 mg-S/L) influence demonstrated that the reactor fed with higher concentration of sulfide allowed more washout of small particle-suspended solid (SS) content and soluble carbohydrate and protein, which were considered as EPS released from biofilm. Finally, the presence of sulfide negatively affected methane production, chemical oxygen demand removal and sludge retention in operational performance. Full article

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Open AccessArticle

Lignin-Furfural Based Adhesives

by Prajakta Dongre, Mark Driscoll, Thomas Amidon and Biljana Bujanovic

Energies 2015, 8(8), 7897-7914; https://doi.org/10.3390/en8087897 - 30 Jul 2015

Cited by 91 | Viewed by 11823

Abstract

Lignin recovered from the hot-water extract of sugar maple (Acer saccharum) is used in this study to synthesize adhesive blends to replace phenol-formaldehyde (PF) resin. Untreated lignin is characterized by lignin content and nuclear magnetic resonance (NMR) analysis. The molecular weight [...] Read more.

Lignin recovered from the hot-water extract of sugar maple (Acer saccharum) is used in this study to synthesize adhesive blends to replace phenol-formaldehyde (PF) resin. Untreated lignin is characterized by lignin content and nuclear magnetic resonance (NMR) analysis. The molecular weight distribution of the lignin and the blends are characterized by size exclusion chromatography (SEC). The effect of pH (0.3, 0.65 and 1), ex situ furfural, and curing conditions on the tensile properties of adhesive reinforced glass fibers is determined and compared to the reinforcement level of commercially available PF resin. The adhesive blend prepared at pH = 0.65 with no added furfural exhibits the highest tensile properties and meets 90% of the PF tensile strength. Full article

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606 KiB

Open AccessReview

Engineering Plant Biomass Lignin Content and Composition for Biofuels and Bioproducts

by Cassie Marie Welker, Vimal Kumar Balasubramanian, Carloalberto Petti, Krishan Mohan Rai, Seth DeBolt and Venugopal Mendu

Energies 2015, 8(8), 7654-7676; https://doi.org/10.3390/en8087654 - 27 Jul 2015

Cited by 154 | Viewed by 22820

Abstract

Lignin is an aromatic biopolymer involved in providing structural support to plant cell walls. Compared to the other cell wall polymers, i.e., cellulose and hemicelluloses, lignin has been considered a hindrance in cellulosic bioethanol production due to the complexity involved in its [...] Read more.

Lignin is an aromatic biopolymer involved in providing structural support to plant cell walls. Compared to the other cell wall polymers, i.e., cellulose and hemicelluloses, lignin has been considered a hindrance in cellulosic bioethanol production due to the complexity involved in its separation from other polymers of various biomass feedstocks. Nevertheless, lignin is a potential source of valuable aromatic chemical compounds and upgradable building blocks. Though the biosynthetic pathway of lignin has been elucidated in great detail, the random nature of the polymerization (free radical coupling) process poses challenges for its depolymerization into valuable bioproducts. The absence of specific methodologies for lignin degradation represents an important opportunity for research and development. This review highlights research development in lignin biosynthesis, lignin genetic engineering and different biological and chemical means of depolymerization used to convert lignin into biofuels and bioproducts. Full article

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Open AccessArticle

Screening and Evaluation of Some Green Algal Strains (Chlorophyceae) Isolated from Freshwater and Soda Lakes for Biofuel Production

by Ramganesh Selvarajan, Tamás Felföldi, Tamás Tauber, Elumalai Sanniyasi, Timothy Sibanda and Memory Tekere

Energies 2015, 8(7), 7502-7521; https://doi.org/10.3390/en8077502 - 22 Jul 2015

Cited by 76 | Viewed by 8863

Abstract

Microalgae are photosynthetic microorganisms that can produce lipids, proteins and carbohydrates in large amounts and within short periods of time and these can be processed into both biofuels and other useful commercial products. Due to this reason microalgae are considered as a potential [...] Read more.

Microalgae are photosynthetic microorganisms that can produce lipids, proteins and carbohydrates in large amounts and within short periods of time and these can be processed into both biofuels and other useful commercial products. Due to this reason microalgae are considered as a potential source of renewable energy; and one of the most important decisions in obtaining oil from microalgae is the choice of species. In this study, the potential of Chlorophyceae species isolated from freshwater and soda lakes in Hungary and Romania (Central Europe) were characterized and evaluated by determining their biomass accumulation, lipid productivity, fatty acid profiles, and biodiesel properties besides protein and carbohydrate productivity. Out of nine strains tested, three accumulated more than 40% dry weight of protein, four accumulated more than 30% dry weight of carbohydrate and the strain Chlorella vulgaris LC8 accumulated high lipid content (42.1% ± 2.6%) with a favorable C16-C18 fatty acid profile (77.4%) as well as suitable biodiesel properties of high cetane number (57.3), low viscosity (4.7 mm²/s), lower iodine number (75.18 g I₂/100 g), relative cloud point (8.8 °C) and negative cold filter plugging point (−6.5 °C). Hence the new strain, Chlorella vulgaris LC8 has potential as a feedstock for the production of excellent quality biodiesel. Full article

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Open AccessArticle

Behavior of Beech Sawdust during Densification into a Solid Biofuel

by Peter Križan, Miloš Matú, Ľubomír Šooš and Juraj Beniak

Energies 2015, 8(7), 6382-6398; https://doi.org/10.3390/en8076382 - 25 Jun 2015

Cited by 51 | Viewed by 7406

Abstract

In solid biofuel manufacture technological and material variables influence the densification process and thus also the final briquette quality. The impact of these technological variables, especially compression pressure and compression temperature, and also of the material parameters (particle size and moisture content) can [...] Read more.

In solid biofuel manufacture technological and material variables influence the densification process and thus also the final briquette quality. The impact of these technological variables, especially compression pressure and compression temperature, and also of the material parameters (particle size and moisture content) can generally be observed during biomass densification in the quality indicators, where the abovementioned variables have a significant influence, especially on the mechanical indicators of quality (briquette density, mechanical durability, etc.). This paper presents the results of experimental research dealing with determining the relationship between the technological and the material variables during densification of beech sawdust. The main goal of the paper is to determine the mutual interaction between compression pressure, compression temperature and material particle size. Research findings were obtained using single-axis densification. The influence of the particle size interacting with compression pressure and compression temperature on the final briquette density was determined. The research findings obtained should prove valuable in briquette production and also in the engineering of densification machines. Full article

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Open AccessArticle

Bio-Refining of Carbohydrate-Rich Food Waste for Biofuels

by Hoang-Tuong Nguyen Hao, Obulisamy Parthiba Karthikeyan and Kirsten Heimann

Energies 2015, 8(7), 6350-6364; https://doi.org/10.3390/en8076350 - 25 Jun 2015

Cited by 32 | Viewed by 11031

Abstract

The global dependence on finite fossil fuel-derived energy is of serious concern given the predicted population increase. Over the past decades, bio-refining of woody biomass has received much attention, but data on food waste refining are sorely lacking, despite annual and global deposition [...] Read more.

The global dependence on finite fossil fuel-derived energy is of serious concern given the predicted population increase. Over the past decades, bio-refining of woody biomass has received much attention, but data on food waste refining are sorely lacking, despite annual and global deposition of 1.3 billion tons in landfills. In addition to negative environmental impacts, this represents a squandering of valuable energy, water and nutrient resources. The potential of carbohydrate-rich food waste (CRFW) for biofuel (by Rhodotorulla glutinis fermentation) and biogas production (by calculating theoretical methane yield) was therefore investigated using a novel integrated bio-refinery approach. In this approach, hydrolyzed CRFW from three different conditions was used for Rhodotorulla glutinis cultivation to produce biolipids, whilst residual solids after hydrolysis were characterized for methane recovery potential via anaerobic digestion. Initially, CRFW was hydrolysed using thermal- (Th), chemical- (Ch) and Th-Ch combined hydrolysis (TCh), with the CRFW-leachate serving as a control (Pcon). Excessive foaming led to the loss of TCh cultures, while day-7 biomass yields were similar (3.4–3.6 g dry weight (DW) L⁻¹) for the remaining treatments. Total fatty acid methyl ester (FAME) content of R. glutinis cultivated on CRFW hydrolysates were relatively low (~6.5%) but quality parameters (i.e., cetane number, density, viscosity and higher heating values) of biomass extracted biodiesel complied with ASTM standards. Despite low theoretical RS-derived methane potential, further research under optimised and scaled conditions will reveal the potential of this approach for the bio-refining of CRFW for energy recovery and value-added co-product production. Full article

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Open AccessArticle

Energy Crop-Based Biogas as Vehicle Fuel—The Impact of Crop Selection on Energy Efficiency and Greenhouse Gas Performance

by Pål Börjesson, Thomas Prade, Mikael Lantz and Lovisa Björnsson

Energies 2015, 8(6), 6033-6058; https://doi.org/10.3390/en8066033 - 18 Jun 2015

Cited by 35 | Viewed by 8314

Abstract

The production of biogas from six agricultural crops was analysed regarding energy efficiency and greenhouse gas (GHG) performance for vehicle fuel from a field-to-tank perspective, with focus on critical parameters and on calculation methods. The energy efficiency varied from 35% to 44%, expressed [...] Read more.

The production of biogas from six agricultural crops was analysed regarding energy efficiency and greenhouse gas (GHG) performance for vehicle fuel from a field-to-tank perspective, with focus on critical parameters and on calculation methods. The energy efficiency varied from 35% to 44%, expressed as primary energy input per energy unit vehicle gas produced. The GHG reduction varied from 70% to 120%, compared with fossil liquid fuels, when the GHG credit of the digestate produced was included through system expansion according to the calculation methodology in the ISO 14044 standard of life cycle assessment. Ley crop-based biogas systems led to the highest GHG reduction, due to the significant soil carbon accumulation, followed by maize, wheat, hemp, triticale and sugar beet. Critical parameters are biogenic nitrous oxide emissions from crop cultivation, for which specific emission factors for digestate are missing today, and methane leakage from biogas production. The GHG benefits were reduced and the interrelation between the crops changed, when the GHG calculations were instead based on the methodology stated in the EU Renewable Energy Directive, where crop contribution to soil carbon accumulation is disregarded. All systems could still reach a 60% GHG reduction, due to the improved agricultural management when digestate replaces mineral fertilisers. Full article

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Open AccessArticle

Oxygen-Containing Fuels from High Acid Water Phase Pyrolysis Bio-Oils by ZSM−5 Catalysis: Kinetic and Mechanism Studies

by Yi Wei, Hanwu Lei, Lei Zhu, Xuesong Zhang, Gayatri Yadavalli, Yupeng Liu and Di Yan

Energies 2015, 8(6), 5898-5915; https://doi.org/10.3390/en8065898 - 17 Jun 2015

Cited by 8 | Viewed by 6859

Abstract

This study developed an upgrading process focusing on acid transformations of water phase pyrolysis bio-oils to esters of oxygen-containing fuels via ZSM−5 catalyst. Temperature was set as a factor with five levels ranging from 60 to 135 °C with reaction time from 1 [...] Read more.

This study developed an upgrading process focusing on acid transformations of water phase pyrolysis bio-oils to esters of oxygen-containing fuels via ZSM−5 catalyst. Temperature was set as a factor with five levels ranging from 60 to 135 °C with reaction time from 1 to 8 h. The results showed that 89% of high acid conversion and over 90% of ester selectivity was obtained from the feedstock via 2 wt % ZSM−5 catalysts in a fixed feedstock to methanol ratio analyzed by HPLC and GC–MS. The upgrading process followed Langmuir–Hinshelwood and reaction constants were calculated to build a practical upgrading model for bio-oil compounds. Thermodynamics of the process showed endothermic properties during the breaking bonds’ reaction on carbonyl of acid while the reaction between the carbon in methanol and electrophile acid intermediate demonstrated exothermic performance. The optimum reaction conditions for the process was at a temperature of 100.1 °C with catalyst loading of 3.98 wt %. Full article

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Open AccessArticle

A Medium-Scale 50 MW_fuel Biomass Gasification Based Bio-SNG Plant: A Developed Gas Cleaning Process

by Ramiar Sadegh-Vaziri, Marko Amovic, Rolf Ljunggren and Klas Engvall

Energies 2015, 8(6), 5287-5302; https://doi.org/10.3390/en8065287 - 3 Jun 2015

Cited by 14 | Viewed by 9681

Abstract

Natural gas is becoming increasingly important as a primary energy source. A suitable replacement for fossil natural gas is bio-SNG, produced by biomass gasification, followed by methanation. A major challenge is efficient gas cleaning processes for removal of sulfur compounds and other impurities. [...] Read more.

Natural gas is becoming increasingly important as a primary energy source. A suitable replacement for fossil natural gas is bio-SNG, produced by biomass gasification, followed by methanation. A major challenge is efficient gas cleaning processes for removal of sulfur compounds and other impurities. The present study focuses on development of a gas cleaning step for a product gas produced in a 50 MW_fuel gasification system. The developed gas cleaning washing process is basically a modification of the Rectisol process. Several different process configurations were evaluated using Aspen plus, including PC-SAFT for the thermodynamic modeling. The developed configuration takes advantage of only one methanol wash column, compared to two columns in a conventional Rectisol process. Results from modeling show the ability of the proposed configuration to remove impurities to a sufficiently low concentrations - almost zero concentration for H₂S, CS₂, HCl, NH₃ and HCN, and approximately 0.01 mg/Nm³ for COS. These levels are acceptable for further upgrading of the gas in a methanation process. Simultaneously, up to 92% of the original CO₂ is preserved in the final cleaned syngas stream. No process integration or economic consideration was performed within the scope of the present study, but will be investigated in future projects to improve the overall process. Full article

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Open AccessArticle

Environmentally Sustainable Biogas? The Key Role of Manure Co-Digestion with Energy Crops

by Alessandro Agostini, Ferdinando Battini, Jacopo Giuntoli, Vincenzo Tabaglio, Monica Padella, David Baxter, Luisa Marelli and Stefano Amaducci

Energies 2015, 8(6), 5234-5265; https://doi.org/10.3390/en8065234 - 3 Jun 2015

Cited by 64 | Viewed by 10165

Abstract

We analysed the environmental impacts of three biogas systems based on dairy manure, sorghum and maize. The geographical scope of the analysis is the Po valley, in Italy. The anaerobic digestion of manure guarantees high GHG (Green House Gases) savings thanks to the [...] Read more.

We analysed the environmental impacts of three biogas systems based on dairy manure, sorghum and maize. The geographical scope of the analysis is the Po valley, in Italy. The anaerobic digestion of manure guarantees high GHG (Green House Gases) savings thanks to the avoided emissions from the traditional storage and management of raw manure as organic fertiliser. GHG emissions for maize and sorghum-based systems, on the other hand, are similar to those of the Italian electricity mix. In crop-based systems, the plants with open-tank storage of digestate emit 50% more GHG than those with gas-tight tanks. In all the environmental impact categories analysed (acidification, particulate matter emissions, and eutrophication), energy crops based systems have much higher impacts than the Italian electricity mix. Maize-based systems cause higher impacts than sorghum, due to more intensive cultivation. Manure-based pathways have always lower impacts than the energy crops based pathways, however, all biogas systems cause much higher impacts than the current Italian electricity mix. We conclude that manure digestion is the most efficient way to reduce GHG emissions; although there are trade-offs with other local environmental impacts. Biogas production from crops; although not providing environmental benefits per se; may be regarded as an option to facilitate the deployment of manure digestion. Full article

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Open AccessArticle

Investigation of Heat Generation from Biomass Fuels

by Naoharu Murasawa and Hiroshi Koseki

Energies 2015, 8(6), 5143-5158; https://doi.org/10.3390/en8065143 - 2 Jun 2015

Cited by 15 | Viewed by 5838

Abstract

New biomass fuels are constantly being developed from renewable resources in an effort to counter global warming and to create a sustainable society based on recycling. Among these, biomass fuels manufactured from waste are prone to microbial fermentation, and are likely to cause [...] Read more.

New biomass fuels are constantly being developed from renewable resources in an effort to counter global warming and to create a sustainable society based on recycling. Among these, biomass fuels manufactured from waste are prone to microbial fermentation, and are likely to cause fires and explosions if safety measures, including sufficient risk assessments and long-term storage, are not considered. In this study, we conducted a series of experiments on several types of newly developed biomass fuels, using combinations of various thermal- and gas-analysers, to identify the risks related to heat- and gas-generation. Since a method for the evaluation of the relative risks of biomass fuels is not yet established in Japan, we also such a method based on our experimental results. The present study found that in cases where safety measures are not thoroughly observed, biomass fuels manufactured from waste materials have a higher possibility of combusting spontaneously at the storage site due to microbial fermentation and heat generation. Full article

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Open AccessArticle

Fast Pyrolysis of Four Lignins from Different Isolation Processes Using Py-GC/MS

by Xiaona Lin, Shujuan Sui, Shun Tan, Charles U. Pittman, Jr., Jianping Sun and Zhijun Zhang

Energies 2015, 8(6), 5107-5121; https://doi.org/10.3390/en8065107 - 1 Jun 2015

Cited by 84 | Viewed by 8854

Abstract

Pyrolysis is a promising approach that is being investigated to convert lignin into higher value products including biofuels and phenolic chemicals. In this study, fast pyrolysis of four types of lignin, including milled Amur linden wood lignin (MWL), enzymatic hydrolysis corn stover lignin [...] Read more.

Pyrolysis is a promising approach that is being investigated to convert lignin into higher value products including biofuels and phenolic chemicals. In this study, fast pyrolysis of four types of lignin, including milled Amur linden wood lignin (MWL), enzymatic hydrolysis corn stover lignin (EHL), wheat straw alkali lignin (AL) and wheat straw sulfonate lignin (SL), were performed using pyrolysis gas-chromatography/mass spectrometry (Py-GC/MS). Thermogravimetric analysis (TGA) showed that the four lignins exhibited widely different thermolysis behaviors. The four lignins had similar functional groups according to the FTIR analysis. Syringyl, guaiacyl and p-hydroxyphenylpropane structural units were broken down during pyrolysis. Fast pyrolysis product distributions from the four lignins depended strongly on the lignin origin and isolation process. Phenols were the most abundant pyrolysis products from MWL, EHL and AL. However, SL produced a large number of furan compounds and sulfur compounds originating from kraft pulping. The effects of pyrolysis temperature and time on the product distributions from corn stover EHL were also studied. At 350 °C, EHL pyrolysis mainly produced acids and alcohols, while phenols became the main products at higher temperature. No obvious influence of pyrolysis time was observed on EHL pyrolysis product distributions. Full article

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Open AccessArticle

Single Cell Oil Producing Yeasts Lipomyces starkeyi and Rhodosporidium toruloides: Selection of Extraction Strategies and Biodiesel Property Prediction

by Nemailla Bonturi, Leonidas Matsakas, Robert Nilsson, Paul Christakopoulos, Everson Alves Miranda, Kris Arvid Berglund and Ulrika Rova

Energies 2015, 8(6), 5040-5052; https://doi.org/10.3390/en8065040 - 28 May 2015

Cited by 62 | Viewed by 10288

Abstract

Single cell oils (SCOs) are considered potential raw material for the production of biodiesel. Rhodosporidium sp. and Lipomyces sp. are good candidates for SCO production. Lipid extractability differs according to yeast species and literature on the most suitable method for each oleaginous yeast [...] Read more.

Single cell oils (SCOs) are considered potential raw material for the production of biodiesel. Rhodosporidium sp. and Lipomyces sp. are good candidates for SCO production. Lipid extractability differs according to yeast species and literature on the most suitable method for each oleaginous yeast species is scarce. This work aimed to investigate the efficiency of the most cited strategies for extracting lipids from intact and pretreated cells of Rhodosporidium toruloides and Lipomyces starkeyi. Lipid extractions were conducted using hexane or combinations of chloroform and methanol. The Folch method resulted in the highest lipid yields for both yeasts (42% for R. toruloides and 48% for L. starkeyi). Also, this method eliminates the cell pretreatment step. The Bligh and Dyer method underestimated the lipid content in the tested strains (25% for R. toruloides and 34% for L. starkeyi). Lipid extractability increased after acid pretreatment for the Pedersen, hexane, and Bligh and Dyer methods. For R. toruloides unexpected fatty acid methyl esters (FAME) composition were found for some lipid extraction strategies tested. Therefore, this work provides useful information for analytical and process development aiming at biodiesel production from the SCO of these two yeast species. Full article

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Open AccessArticle

Techno-Economic Analysis of Bioethanol Production from Lignocellulosic Biomass in China: Dilute-Acid Pretreatment and Enzymatic Hydrolysis of Corn Stover

by Lili Zhao, Xiliang Zhang, Jie Xu, Xunmin Ou, Shiyan Chang and Maorong Wu

Energies 2015, 8(5), 4096-4117; https://doi.org/10.3390/en8054096 - 8 May 2015

Cited by 87 | Viewed by 13394

Abstract

Lignocellulosic biomass-based ethanol is categorized as 2^nd generation bioethanol in the advanced biofuel portfolio. To make sound incentive policy proposals for the Chinese government and to develop guidance for research and development and industrialization of the technology, the paper reports careful techno-economic [...] Read more.

Lignocellulosic biomass-based ethanol is categorized as 2^nd generation bioethanol in the advanced biofuel portfolio. To make sound incentive policy proposals for the Chinese government and to develop guidance for research and development and industrialization of the technology, the paper reports careful techno-economic and sensitivity analyses performed to estimate the current competitiveness of the bioethanol and identify key components which have the greatest impact on its plant-gate price (PGP). Two models were developed for the research, including the Bioethanol PGP Assessment Model (BPAM) and the Feedstock Cost Estimation Model (FCEM). Results show that the PGP of the bioethanol ranges $4.68–$6.05/gal (9,550–12,356 yuan/t). The key components that contribute most to bioethanol PGP include the conversion rate of cellulose to glucose, the ratio of five-carbon sugars converted to ethanol, feedstock cost, and enzyme loading, etc. Lignocellulosic ethanol is currently unable to compete with fossil gasoline, therefore incentive policies are necessary to promote its development. It is suggested that the consumption tax be exempted, the value added tax (VAT) be refunded upon collection, and feed-in tariff for excess electricity (byproduct) be implemented to facilitate the industrialization of the technology. A minimum direct subsidy of $1.20/gal EtOH (2,500 yuan/t EtOH) is also proposed for consideration. Full article

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Open AccessArticle

Comprehensive Characterization of Napier Grass as a Feedstock for Thermochemical Conversion

by Isah Y. Mohammed, Yousif A. Abakr, Feroz K. Kazi, Suzana Yusup, Ibraheem Alshareef and Soh A. Chin

Energies 2015, 8(5), 3403-3417; https://doi.org/10.3390/en8053403 - 24 Apr 2015

Cited by 122 | Viewed by 11186

Abstract

Study on Napier grass leaf (NGL), stem (NGS) and leaf and stem (NGT) was carried out. Proximate, ultimate and structural analyses were evaluated. Functional groups and crystalline components in the biomass were examined. Pyrolysis study was conducted in a thermogravimetric analyzer under nitrogen [...] Read more.

Study on Napier grass leaf (NGL), stem (NGS) and leaf and stem (NGT) was carried out. Proximate, ultimate and structural analyses were evaluated. Functional groups and crystalline components in the biomass were examined. Pyrolysis study was conducted in a thermogravimetric analyzer under nitrogen atmosphere of 20 mL/min at constant heating rate of 10 K/min. The results reveal that Napier grass biomass has high volatile matter, higher heating value, high carbon content and lower ash, nitrogen and sulfur contents. Structural analysis shows that the biomass has considerable cellulose and lignin contents which are good candidates for good quality bio-oil production. From the pyrolysis study, degradation of extractives, hemicellulose, cellulose and lignin occurred at temperature around 478, 543, 600 and above 600 K, respectively. Kinetics of the process was evaluated using reaction order model. New equations that described the process were developed using the kinetic parameters and data compared with experimental data. The results of the models fit well to the experimental data. The proposed models may be a reliable means for describing thermal decomposition of lignocellulosic biomass under nitrogen atmosphere at constant heating rate. Full article

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Open AccessArticle

Life-Cycle Energy and GHG Emissions of Forest Biomass Harvest and Transport for Biofuel Production in Michigan

by Fengli Zhang, Dana M. Johnson and Jinjiang Wang

Energies 2015, 8(4), 3258-3271; https://doi.org/10.3390/en8043258 - 22 Apr 2015

Cited by 42 | Viewed by 9323

Abstract

High dependence on imported oil has increased U.S. strategic vulnerability and prompted more research in the area of renewable energy production. Ethanol production from renewable woody biomass, which could be a substitute for gasoline, has seen increased interest. This study analysed energy use [...] Read more.

High dependence on imported oil has increased U.S. strategic vulnerability and prompted more research in the area of renewable energy production. Ethanol production from renewable woody biomass, which could be a substitute for gasoline, has seen increased interest. This study analysed energy use and greenhouse gas emission impacts on the forest biomass supply chain activities within the State of Michigan. A life-cycle assessment of harvesting and transportation stages was completed utilizing peer-reviewed literature. Results for forest-delivered ethanol were compared with those for petroleum gasoline using data specific to the U.S. The analysis from a woody biomass feedstock supply perspective uncovered that ethanol production is more environmentally friendly (about 62% less greenhouse gas emissions) compared with petroleum based fossil fuel production. Sensitivity analysis was conducted with key inputs associated with harvesting and transportation operations. The results showed that research focused on improving biomass recovery efficiency and truck fuel economy further reduced GHG emissions and energy consumption. Full article

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Open AccessArticle

The Impact of a Mild Sub-Critical Hydrothermal Carbonization Pretreatment on Umbila Wood. A Mass and Energy Balance Perspective

by Carlos Alberto Cuvilas, Efthymios Kantarelis and Weihong Yang

Energies 2015, 8(3), 2165-2175; https://doi.org/10.3390/en8032165 - 19 Mar 2015

Cited by 15 | Viewed by 6556

Abstract

Over the last years, the pretreatment of biomass as a source of energy has become one of the most important steps of biomass conversion. In this work the effect of a mild subcritical hydrothermal carbonization of a tropical woody biomass was studied. Results [...] Read more.

Over the last years, the pretreatment of biomass as a source of energy has become one of the most important steps of biomass conversion. In this work the effect of a mild subcritical hydrothermal carbonization of a tropical woody biomass was studied. Results indicate considerable change in carbon content from 52.78% to 65.1%, reduction of oxygen content from 41.14% to 28.72% and ash slagging and fouling potential. Even though decarboxylation, decarbonylation and dehydration reactions take place, dehydration is the one that prevails. The mass and energy balance was affected by the treatment conditions than the severity of the treatment. Full article

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Open AccessArticle

Impact of Organic Loading Rate on Psychrophilic Anaerobic Digestion of Solid Dairy Manure

by Noori M. Cata Saady and Daniel I. Massé

Energies 2015, 8(3), 1990-2007; https://doi.org/10.3390/en8031990 - 13 Mar 2015

Cited by 9 | Viewed by 7099

Abstract

Increasing the feed total solids to anaerobic digester improves the process economics and decreases the volume of liquid effluent from current wet anaerobic digestion. The objective of this study was to develop a novel psychrophilic (20 °C) anaerobic digestion technology of undiluted cow [...] Read more.

Increasing the feed total solids to anaerobic digester improves the process economics and decreases the volume of liquid effluent from current wet anaerobic digestion. The objective of this study was to develop a novel psychrophilic (20 °C) anaerobic digestion technology of undiluted cow feces (total solids of 11%–16%). Two sets of duplicate laboratory-scale sequence batch bioreactors have been operated at organic loading rates (OLR) of 6.0 to 8.0 g total chemical oxygen demand (TCOD) kg⁻¹ inoculum day⁻¹ (d⁻¹) during 210 days. The results demonstrated that the process is feasible at treatment cycle length (TCL) of 21 days; however, the quality of cow feces rather than the OLR had a direct influence on the specific methane yield (SMY). The SMY ranged between 124.5 ± 1.4 and 227.9 ± 4.8 normalized liter (NL) CH₄ kg⁻¹ volatile solids (VS) fed d⁻¹. Substrate-to-inoculum mass ratio (SIR) was 0.63 ± 0.05, 0.90 ± 0.09, and 1.06 ± 0.07 at OLR of 6.0, 7.0, and 8.0 g TCOD kg⁻¹ inoculum d⁻¹, respectively. No volatile fatty acids (VFAs) accumulation has been observed which indicated that hydrolysis was the rate limiting step and VFAs have been consumed immediately. Bioreactors performance consistency in terms of the level of SMYs, VFAs concentrations at end of the TCL, pH stability and volatile solids reduction indicates a stable and reproducible process during the entire operation. Full article

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Open AccessArticle

Changes in Carbon Electrode Morphology Affect Microbial Fuel Cell Performance with Shewanella oneidensis MR-1

by David V. P. Sanchez, Daniel Jacobs, Kelvin Gregory, Jiyong Huang, Yushi Hu, Radisav Vidic and Minhee Yun

Energies 2015, 8(3), 1817-1829; https://doi.org/10.3390/en8031817 - 4 Mar 2015

Cited by 26 | Viewed by 10311

Abstract

The formation of biofilm-electrodes is crucial for microbial fuel cell current production because optimal performance is often associated with thick biofilms. However, the influence of the electrode structure and morphology on biofilm formation is only beginning to be investigated. This study provides insight [...] Read more.

The formation of biofilm-electrodes is crucial for microbial fuel cell current production because optimal performance is often associated with thick biofilms. However, the influence of the electrode structure and morphology on biofilm formation is only beginning to be investigated. This study provides insight on how changing the electrode morphology affects current production of a pure culture of anode-respiring bacteria. Specifically, an analysis of the effects of carbon fiber electrodes with drastically different morphologies on biofilm formation and anode respiration by a pure culture (Shewanella oneidensis MR-1) were examined. Results showed that carbon nanofiber mats had ~10 fold higher current than plain carbon microfiber paper and that the increase was not due to an increase in electrode surface area, conductivity, or the size of the constituent material. Cyclic voltammograms reveal that electron transfer from the carbon nanofiber mats was biofilm-based suggesting that decreasing the diameter of the constituent carbon material from a few microns to a few hundred nanometers is beneficial for electricity production solely because the electrode surface creates a more relevant mesh for biofilm formation by Shewanella oneidensis MR-1. Full article

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Open AccessArticle

Analysis on Storage Off-Gas Emissions from Woody, Herbaceous, and Torrefied Biomass

by Jaya Shankar Tumuluru, C. Jim Lim, Xiaotao T. Bi, Xingya Kuang, Staffan Melin, Fahimeh Yazdanpanah and Shahab Sokhansanj

Energies 2015, 8(3), 1745-1759; https://doi.org/10.3390/en8031745 - 2 Mar 2015

Cited by 29 | Viewed by 7497

Abstract

Wood chips, torrefied wood chips, ground switchgrass, and wood pellets were tested for off‑gas emissions during storage. Storage canisters with gas‑collection ports were used to conduct experiments at room temperature of 20 °C and in a laboratory oven set at 40 °C. Commercially-produced [...] Read more.

Wood chips, torrefied wood chips, ground switchgrass, and wood pellets were tested for off‑gas emissions during storage. Storage canisters with gas‑collection ports were used to conduct experiments at room temperature of 20 °C and in a laboratory oven set at 40 °C. Commercially-produced wood pellets yielded the highest carbon monoxide (CO) emissions at both 20 and 40 °C (1600 and 13,000 ppmv), whereas torrefied wood chips emitted the lowest of about <200 and <2000 ppmv. Carbon dioxide (CO₂) emissions from wood pellets were 3000 ppmv and 42,000 ppmv, whereas torrefied wood chips registered at about 2000 and 25,000 ppmv, at 20 and 40 °C at the end of 11 days of storage. CO emission factors (milligrams per kilogram of biomass) calculated were lowest for ground switchgrass and torrefied wood chips (2.68 and 4.86 mg/kg) whereas wood pellets had the highest CO of about 10.60 mg/kg, respectively, at 40 °C after 11 days of storage. In the case of CO₂, wood pellets recorded the lowest value of 55.46 mg/kg, whereas switchgrass recorded the highest value of 318.72 mg/kg. This study concludes that CO emission factor is highest for wood pellets, CO₂ is highest for switchgrass and CH₄ is negligible for all feedstocks except for wood pellets, which is about 0.374 mg/kg at the end of 11-day storage at 40 °C. Full article

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Open AccessArticle

Double Distribution Activation Energy Model as Suitable Tool in Explaining Biomass and Coal Pyrolysis Behavior

by Paolo De Filippis, Benedetta De Caprariis, Marco Scarsella and Nicola Verdone

Energies 2015, 8(3), 1730-1744; https://doi.org/10.3390/en8031730 - 2 Mar 2015

Cited by 28 | Viewed by 7124

Abstract

Understanding and modeling of coal and biomass pyrolysis assume particular importance being the first step occurring in both gasification and combustion processes. The complex chemical reaction network occurring in this step leads to a necessary effort in developing a suitable model framework capable [...] Read more.

Understanding and modeling of coal and biomass pyrolysis assume particular importance being the first step occurring in both gasification and combustion processes. The complex chemical reaction network occurring in this step leads to a necessary effort in developing a suitable model framework capable of grasping the physics of the phenomenon and allowing a deeper comprehension of the sequence of events. The aim of this work is to show how the intrinsic flexibility of a model based on a double distribution of the activation energy is able to properly describe the two separate steps of primary and secondary pyrolysis, which characterize the thermochemical processing of most of the energetic materials. The model performance was tested by fitting the kinetic parameters from experimental data obtained by thermogravimetric analysis of two materials, which represent very different classes of energy source: a microalgae biomass and a sub-bituminous coal. The model reproduces with high accuracy the pyrolysis behavior of both the materials and adds important information about the relative occurring of the two pyrolysis steps. Full article

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Open AccessArticle

Biohydrogen Fermentation from Sucrose and Piggery Waste with High Levels of Bicarbonate Alkalinity

by Jeongdong Choi and Youngho Ahn

Energies 2015, 8(3), 1716-1729; https://doi.org/10.3390/en8031716 - 2 Mar 2015

Cited by 20 | Viewed by 6280

Abstract

This study examined the influence of biohydrogen fermentation under the high bicarbonate alkalinity (BA) and pH to optimize these critical parameters. When sucrose was used as a substrate, hydrogen was produced over a wide range of pH values (5–9) under no BA supplementation; [...] Read more.

This study examined the influence of biohydrogen fermentation under the high bicarbonate alkalinity (BA) and pH to optimize these critical parameters. When sucrose was used as a substrate, hydrogen was produced over a wide range of pH values (5–9) under no BA supplementation; however, BA affected hydrogen yield significantly under different initial pHs (5–10). The actual effect of high BA using raw piggery waste (pH 8.7 and BA 8.9 g CaCO₃/L) showed no biogas production or propionate/acetate accumulation. The maximum hydrogen production rate (0.32 L H₂/g volatile suspended solids (VSS)-d) was observed at pH 8.95 and 3.18 g CaCO₃/L. BA greater than 4 g CaCO₃/L also triggered lactate-type fermentation, leading to propionate accumulation, butyrate reduction and homoacetogenesis, potentially halting the hydrogen production rate. These results highlight that the substrate with high BA need to amend adequately to maximize hydrogen production. Full article

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Open AccessArticle

Hot Water Pretreatment of Boreal Aspen Woodchips in a Pilot Scale Digester

by Jipeng Yan and Shijie Liu

Energies 2015, 8(2), 1166-1180; https://doi.org/10.3390/en8021166 - 3 Feb 2015

Cited by 13 | Viewed by 6050

Abstract

Hot water extraction of aspen woodchips was treated at about 160 °C for 2 h with a liquor-to-solid ratio of 4.76:1 in a 1.84 m³ batch reactor with external liquor circulation. Both five-carbon and six-carbon sugars are obtained in the extraction liquor. [...] Read more.

Hot water extraction of aspen woodchips was treated at about 160 °C for 2 h with a liquor-to-solid ratio of 4.76:1 in a 1.84 m³ batch reactor with external liquor circulation. Both five-carbon and six-carbon sugars are obtained in the extraction liquor. Xylose and xylooligomers are the main five-carbon sugar in the hot water extract, which reached a maximum concentration of 0.016 mol/L, and 0.018 mol/L, respectively. Minor monosaccharides including galactose, mannose, rhamnose, glucose, and arabinose are also obtained during the hot water extraction. Rhamnose is the main six-carbon sugar in the extraction liquor, which has a maximum concentration of 0.0042 mol/L. The variations of acetyl groups and formic acid are investigated due to their catalytic effect on the extraction reactions. Zeroth-order kinetics models are found to be adequate in describing the dissolved solids, acids, xylose, and xylooligomers. Full article

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Open AccessArticle

Determination of Methane and Carbon Dioxide Formation Rate Constants for Semi-Continuously Fed Anaerobic Digesters

by Jan Moestedt, Jonas Malmborg and Erik Nordell

Energies 2015, 8(1), 645-655; https://doi.org/10.3390/en8010645 - 16 Jan 2015

Cited by 19 | Viewed by 10252

Abstract

To optimize commercial-scale biogas production, it is important to evaluate the performance of each microbial step in the anaerobic process. Hydrolysis and methanogenesis are usually the rate-limiting steps during digestion of organic waste and by-products. By measuring biogas production and methane concentrations on-line [...] Read more.

To optimize commercial-scale biogas production, it is important to evaluate the performance of each microbial step in the anaerobic process. Hydrolysis and methanogenesis are usually the rate-limiting steps during digestion of organic waste and by-products. By measuring biogas production and methane concentrations on-line in a semi-continuously fed reactor, gas kinetics can be evaluated. In this study, the rate constants of the fermentative hydrolysis step (k_c) and the methanogenesis step (k_m) were determined and evaluated in a continuously stirred tank laboratory-scale reactor treating food and slaughterhouse waste and glycerin. A process additive containing Fe²⁺, Co²⁺ and Ni²⁺ was supplied until day 89, after which Ni²⁺ was omitted. The omission resulted in a rapid decline in the methanogenesis rate constant (k_m) to 70% of the level observed when Ni²⁺ was present, while k_c remained unaffected. This suggests that Ni²⁺ mainly affects the methanogenic rather than the hydrolytic microorganisms in the system. However, no effect was initially observed when using conventional process monitoring parameters such as biogas yield and volatile fatty acid concentration. Hence, formation rate constants can reveal additional information on process performance and k_m can be used as a complement to conventional process monitoring tools for semi-continuously fed anaerobic digesters. Full article

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Anaerobic Digestion and Biogas Potential: Simulation of Lab and Industrial-Scale Processes

by Ihsan Hamawand and Craig Baillie

Energies 2015, 8(1), 454-474; https://doi.org/10.3390/en8010454 - 13 Jan 2015

Cited by 31 | Viewed by 10727

Abstract

In this study, a simulation was carried out using BioWin 3.1 to test the capability of the software to predict the biogas potential for two different anaerobic systems. The two scenarios included: (1) a laboratory-scale batch reactor; and (2) an industrial-scale anaerobic continuous [...] Read more.

In this study, a simulation was carried out using BioWin 3.1 to test the capability of the software to predict the biogas potential for two different anaerobic systems. The two scenarios included: (1) a laboratory-scale batch reactor; and (2) an industrial-scale anaerobic continuous lagoon digester. The measured data related to the operating conditions, the reactor design parameters and the chemical properties of influent wastewater were entered into BioWin. A sensitivity analysis was carried out to identify the sensitivity of the most important default parameters in the software’s models. BioWin was then calibrated by matching the predicted data with measured data and used to simulate other parameters that were unmeasured or deemed uncertain. In addition, statistical analyses were carried out using evaluation indices, such as the coefficient of determination (R-squared), the correlation coefficient (r) and its significance (p-value), the general standard deviation (SD) and the Willmott index of agreement, to evaluate the agreement between the software prediction and the measured data. The results have shown that after calibration, BioWin can be used reliably to simulate both small-scale batch reactors and industrial-scale digesters with a mean absolute percentage error (MAPE) of less than 10% and very good values of the indexes. Furthermore, by changing the default parameters in BioWin, which is a way of calibrating the models in the software, as well, this may provide information about the performance of the digester. Furthermore, the results of this study showed there may be an over estimation for biogas generated from industrial-scale digesters. More sophisticated analytical devices may be required for reliable measurements of biogas quality and quantity. Full article

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Open AccessArticle

Comparative Analysis of Milled Wood Lignins (MWLs) Isolated from Sugar Maple (SM) and Hot-Water Extracted Sugar Maple (ESM)

by Mangesh J. Goundalkar, Derek B. Corbett and Biljana M. Bujanovic

Energies 2014, 7(3), 1363-1375; https://doi.org/10.3390/en7031363 - 5 Mar 2014

Cited by 22 | Viewed by 7114

Abstract

To further elucidate the advantageous effects of hot-water extraction (HWE) on delignification, milled wood lignin (MWL) was isolated from sugar maple (SM) and from hot-water extracted sugar maple (ESM). Ball-milled wood was analyzed for particle size distribution (PSD) before and after dioxane:water (DW) [...] Read more.

To further elucidate the advantageous effects of hot-water extraction (HWE) on delignification, milled wood lignin (MWL) was isolated from sugar maple (SM) and from hot-water extracted sugar maple (ESM). Ball-milled wood was analyzed for particle size distribution (PSD) before and after dioxane:water (DW) extraction. The MWL samples were analyzed by analytical and spectral methods. The results indicated that the MWL isolated from SM and ESM was mainly released from the middle lamella (ML) and the secondary wall (SW), respectively. The cleavage of dibenzodioxocin (DB) and spirodienone (SD) lignin substructures during HWE is suggested. The removal of lignin during acetone:water (AW) extraction of hot-water extracted wood indicates that including an additional operation in a hardwood HWE-based biorefinery would be beneficial for processing of wood. Full article

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1045 KiB

Open AccessArticle

Appraising Bioenergy Alternatives in Uganda Using Strengths, Weaknesses, Opportunities and Threats (SWOT)-Analytical Hierarchy Process (AHP) and a Desirability Functions Approach

by Collins Okello, Stefania Pindozzi, Salvatore Faugno and Lorenzo Boccia

Energies 2014, 7(3), 1171-1192; https://doi.org/10.3390/en7031171 - 26 Feb 2014

Cited by 41 | Viewed by 11883

Abstract

Poor access to clean and reliable energy technologies is a major challenge to most developing countries. The decision to introduce new technologies is often faced by low adoption rates or even public opposition. In addition, the data required for effective decision making is [...] Read more.

Poor access to clean and reliable energy technologies is a major challenge to most developing countries. The decision to introduce new technologies is often faced by low adoption rates or even public opposition. In addition, the data required for effective decision making is often inadequate or even lacking, thus constraining the planning process. In this study, a methodology for participatory appraisal of technologies, integrating desirability functions to the strengths, weaknesses, opportunities and threats (SWOT)-analytical hierarchy process (AHP) methodology was developed. Application of the methodology was illustrated with an example for participatory appraisal of four bioenergy technologies in Uganda. Results showed that the methodology is effective in evaluating stakeholder preferences for bioenergy technologies. It showed a high potential to be used to identify and rate factors that stakeholders take into consideration when selecting bioenergy systems. The method could be used as a tool for technology screening, or reaching consensus in a participatory setup in a transparent manner. Full article

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642 KiB

Open AccessReview

A Review of Thermal Co-Conversion of Coal and Biomass/Waste

by Aime Hilaire Tchapda and Sarma V. Pisupati

Energies 2014, 7(3), 1098-1148; https://doi.org/10.3390/en7031098 - 25 Feb 2014

Cited by 178 | Viewed by 14290

Abstract

Biomass is relatively cleaner than coal and is the only renewable carbon resource that can be directly converted into fuel. Biomass can significantly contribute to the world’s energy needs if harnessed sustainably. However, there are also problems associated with the thermal conversion of [...] Read more.

Biomass is relatively cleaner than coal and is the only renewable carbon resource that can be directly converted into fuel. Biomass can significantly contribute to the world’s energy needs if harnessed sustainably. However, there are also problems associated with the thermal conversion of biomass. This paper investigates and discusses issues associated with the thermal conversion of coal and biomass as a blend. Most notable topics reviewed are slagging and fouling caused by the relatively reactive alkali and alkaline earth compounds (K₂O, Na₂O and CaO) found in biomass ash. The alkali and alkaline earth metals (AAEM) present and dispersed in biomass fuels induce catalytic activity during co-conversion with coal. The catalytic activity is most noticeable when blended with high rank coals. The synergy during co-conversion is still controversial although it has been theorized that biomass acts like a hydrogen donor in liquefaction. Published literature also shows that coal and biomass exhibit different mechanisms, depending on the operating conditions, for the formation of nitrogen (N) and sulfur species. Utilization aspects of fly ash from blending coal and biomass are discussed. Recommendations are made on pretreatment options to increase the energy density of biomass fuels through pelletization, torrefaction and flash pyrolysis to reduce transportation costs. Full article

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606 KiB

Open AccessArticle

Impact of Hot-Water Extraction on Acetone-Water Oxygen Delignification of Paulownia Spp. and Lignin Recovery

by Chen Gong and Biljana M. Bujanovic

Energies 2014, 7(2), 857-873; https://doi.org/10.3390/en7020857 - 19 Feb 2014

Cited by 24 | Viewed by 8093

Abstract

A hardwood-based biorefinery process starting with hot-water extraction (HWE) is recommended in order to remove most of the hemicelluloses/xylans before further processing. HWE may be followed by delignification in acetone/water in the presence of oxygen (AWO) for the production of cellulose and lignin. [...] Read more.

A hardwood-based biorefinery process starting with hot-water extraction (HWE) is recommended in order to remove most of the hemicelluloses/xylans before further processing. HWE may be followed by delignification in acetone/water in the presence of oxygen (AWO) for the production of cellulose and lignin. In this study, the HWE-AWO sequence was evaluated for its effectiveness at removing lignin from the fast-growing species Paulownia tomentosa (PT) and Paulownia elongata (PE), in comparison with the reference species, sugar maple (Acer saccharum, SM). HWE might lead to a remarkable increase in lignin accessibility, and as a result, a greater AWO delignification degree was observed for extracted PT, PE, and SM than for unextracted ones. Organosolv lignin was recovered from the spent liquor of AWO delignification of PT with/without prior HWE and characterized to evaluate the benefits of HWE on the lignin structure and purity. The lignin recovered from the spent liquor of HWE-AWO sequence is of higher purity and lighter color than that recovered from the AWO spent liquor. These properties along with low sulfur content are desirable for lignin high-value applications. Full article

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341 KiB

Open AccessArticle

Fractionation for Biodiesel Purification Using Supercritical Carbon Dioxide

by Chao-Yi Wei, Tzou-Chi Huang, Zer-Ran Yu, Be-Jen Wang and Ho-Hsien Chen

Energies 2014, 7(2), 824-833; https://doi.org/10.3390/en7020824 - 19 Feb 2014

Cited by 7 | Viewed by 8175

Abstract

In recent years, biodegradable and alternative biodiesel has attracted increased attention worldwide. Producing biodiesel from biomass involves critical separation and purification technology. Conventional technologies such as gravitational settling, decantation, filtration, water washing, acid washing, organic solvent washing and absorbent applications are inefficient, less [...] Read more.

In recent years, biodegradable and alternative biodiesel has attracted increased attention worldwide. Producing biodiesel from biomass involves critical separation and purification technology. Conventional technologies such as gravitational settling, decantation, filtration, water washing, acid washing, organic solvent washing and absorbent applications are inefficient, less cost effective and environmentally less friendly. In this study supercritical carbon dioxide (SC-CO₂) with few steps and a low environmental impact, was used for biodiesel fractionation from impure fatty acid methyl ester (FAME) solution mixes. The method is suitable for application in a variety of biodiesel production processes requiring subsequent stages of purification. The fractionation and purification was carried out using continuous SC-CO₂ fractionation equipment, consisting of three columns filled with stainless steel fragments. A 41.85% FAME content solution mix was used as the raw material in this study. Variables were a temperature range of 40–70 °C, pressure range of 10–30 MPa, SC-CO₂ flow rate range of 7–21 mL/min and a retention time range of 30–90 min. The Taguchi method was used to identify optimal operating conditions. The results show that a separated FAME content of 99.94% was verified by GC-FID under optimal fractionation conditions, which are a temperature of 40 °C of, a pressure level of 30MPa and a flow rate of 7 mL/min of SC-CO₂for a retention time of 90 min. Full article

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Open AccessArticle

Availability of Biomass Residues for Co-Firing in Peninsular Malaysia: Implications for Cost and GHG Emissions in the Electricity Sector

by W. Michael Grifﬁn, Jeremy Michalek, H. Scott Matthews and Mohd Nor Azman Hassan

Energies 2014, 7(2), 804-823; https://doi.org/10.3390/en7020804 - 18 Feb 2014

Cited by 46 | Viewed by 9556

Abstract

Fossil fuels comprise 93% of Malaysia’s electricity generation and account for 36% of the country’s 2010 Greenhouse Gas (GHG) emissions. The government has targeted the installation of 330 MW of biomass electricity generation capacity by 2015 to avoid 1.3 Mt of CO₂ [...] Read more.

Fossil fuels comprise 93% of Malaysia’s electricity generation and account for 36% of the country’s 2010 Greenhouse Gas (GHG) emissions. The government has targeted the installation of 330 MW of biomass electricity generation capacity by 2015 to avoid 1.3 Mt of CO₂ emissions annually and offset some emissions due to increased coal use. One biomass option is to co-fire with coal, which can result in reduced GHG emissions, coal use, and costs of electricity. A linear optimization cost model was developed using seven types of biomass residues for Peninsular Malaysia. Results suggest that about 12 Mt/year of residues are available annually, of which oil-palm residues contribute 77%, and rice and logging residues comprise 17%. While minimizing the cost of biomass and biomass residue transport, co-firing at four existing coal plants in Peninsular Malaysia could meet the 330 MW biomass electricity target and reduce costs by about $24 million per year compared to coal use alone and reduces GHG emissions by 1.9 Mt of CO₂. Maximizing emissions reduction for biomass co-firing results in 17 Mt of CO₂ reductions at a cost of $23/t of CO₂reduced. Full article

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835 KiB

Open AccessArticle

The Influence of Loading Rate and Variable Temperatures on Microbial Communities in Anaerobic Digesters

by Richard J. Ciotola, Jay F. Martin, Abigail Tamkin, Juan M. Castańo, James Rosenblum, Michael S. Bisesi and Jiyoung Lee

Energies 2014, 7(2), 785-803; https://doi.org/10.3390/en7020785 - 18 Feb 2014

Cited by 20 | Viewed by 6907

Abstract

The relationship between seasonal temperatures, organic loading rate (OLR) and the structure of archaeal communities in anaerobic digesters was investigated. Previous studies have often assessed archaeal community structure at fixed temperatures and constant OLRs, or at variable temperatures not characteristic of temperate climates. [...] Read more.

The relationship between seasonal temperatures, organic loading rate (OLR) and the structure of archaeal communities in anaerobic digesters was investigated. Previous studies have often assessed archaeal community structure at fixed temperatures and constant OLRs, or at variable temperatures not characteristic of temperate climates. The goal of this study was to determine the maximum OLR that would maintain a balanced microbial ecosystem during operation in a variable temperature range expected in a temperate climate (27–10 °C). Four-liter laboratory digesters were operated in a semi-continuous mode using dairy cow manure as the feedstock. At OLRs of 1.8 and 0.8 kg VS/m³·day the digesters soured (pH < 6.5) as a result of a decrease in temperature. The structure of the archaeal community in the sour digesters became increasingly similar to the manure feedstock with gains in the relative abundance of hydrogenotrophic methanogens. At an OLR of 0.3 kg VS/m³·day the digesters did not sour, but the archaeal community was primarily hydrogenotrophic methanogens. Recommendations for operating an ambient temperature digester year round in a temperate climate are to reduce the OLR to at least 0.3 kg VS/m³·day in colder temperatures to prevent a shift to the microbial community associated with the sour digesters. Full article

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Graphical abstract

434 KiB

Open AccessArticle

Effects of Organic Loading Rate on the Performance of a Pressurized Anaerobic Filter in Two-Phase Anaerobic Digestion

by Yuling Chen, Benjamin Rößler, Simon Zielonka, Anna-Maria Wonneberger and Andreas Lemmer

Energies 2014, 7(2), 736-750; https://doi.org/10.3390/en7020736 - 13 Feb 2014

Cited by 44 | Viewed by 8802

Abstract

The effect of organic loading rate (OLR) on a pressurized anaerobic filter was studied in a laboratory two-phase anaerobic digestion system. The anaerobic filter was operated successively at two working pressures (9 bar and 1.5 bar). The OLR_(COD) for each pressure was [...] Read more.

The effect of organic loading rate (OLR) on a pressurized anaerobic filter was studied in a laboratory two-phase anaerobic digestion system. The anaerobic filter was operated successively at two working pressures (9 bar and 1.5 bar). The OLR_(COD) for each pressure was increased from 5 to 17.5 kg·m⁻³·day⁻¹. The best performance of the reactor at 9 bar was observed at OLR_(COD) of 12.5 kg·m⁻³·day⁻¹ and hydraulic retention time (HRT) of 1.8 day, with specific biogas productivity (SBP) of 5.3 L·L⁻¹·day⁻¹ and COD degradation grade of 90.6%. At higher OLRs and shorter HRTs, the process became unstable. In contrast, there was no indication of digester failure during the experiments at 1.5 bar. The SBP peaked at OLR_(COD) of 17.5 kg·m⁻³·day⁻¹ with 8.2 L·L⁻¹·day⁻¹, where COD degradation grade was 90.4%. The biogas collected from the reactor at 9 bar and 1.5 bar contained approximately 74.5% CH₄ and 66.2% CH₄, respectively, regardless of OLR variation. At OLR_(COD) of 5–12.5 kg·m⁻³·day⁻¹, the reactor at 9 bar had the same specific methane yield as at 1.5 bar, which was in the range of 0.31–0.32 L_N·g⁻¹COD. Raising the working pressure in the reactor resulted in an increase of methane content of the produced biogas. However, the low pH value (approximately 6.5) inside the reactor, induced by high CO₂ partial pressure seemed to limit the reactor performance at high OLRs and short HRT. Full article

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Open AccessArticle

Nanofibrillated Cellulose (NFC): A High-Value Co-Product that Improves the Economics of Cellulosic Ethanol Production

by Qiong Song, William T. Winter, Biljana M. Bujanovic and Thomas E. Amidon

Energies 2014, 7(2), 607-618; https://doi.org/10.3390/en7020607 - 7 Feb 2014

Cited by 44 | Viewed by 10483

Abstract

Cellulosic ethanol is a sustainable alternative to petroleum as a transportation fuel, which could be made biologically from agricultural and forestry residues, municipal waste, or herbaceous and woody crops. Instead of putting efforts on steps overcoming the natural resistance of plants to biological [...] Read more.

Cellulosic ethanol is a sustainable alternative to petroleum as a transportation fuel, which could be made biologically from agricultural and forestry residues, municipal waste, or herbaceous and woody crops. Instead of putting efforts on steps overcoming the natural resistance of plants to biological breakdown, our study proposes a unique pathway to improve the outcome of the process by co-producing high-value nanofibrillated cellulose (NFC), offering a new economic leverage for cellulosic ethanol to compete with fossil fuels in the near future. In this study, glucose has been produced by commercial enzymes while the residual solids are converted into NFC via sonification. Here, we report the morphology of fibers changed through the process and yield of glucose in the enzymatic hydrolysis step. Full article

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1647 KiB

Open AccessArticle

Emission Characteristics of a CI Engine Running with a Range of Biodiesel Feedstocks

by Belachew Tesfa, Fengshou Gu, Rakesh Mishra and Andrew Ball

Energies 2014, 7(1), 334-350; https://doi.org/10.3390/en7010334 - 16 Jan 2014

Cited by 61 | Viewed by 8485

Abstract

Currently, alternative fuels are being investigated in detail for application in compression ignition (CI) engines resulting in exciting potential opportunities to increase energy security and reduce gas emissions. Biodiesel is one of the alternative fuels which is renewable and environmentally friendly and can [...] Read more.

Currently, alternative fuels are being investigated in detail for application in compression ignition (CI) engines resulting in exciting potential opportunities to increase energy security and reduce gas emissions. Biodiesel is one of the alternative fuels which is renewable and environmentally friendly and can be used in diesel engines with little or no modifications. The objective of this study is to investigate the effects of biodiesel types and biodiesel fraction on the emission characteristics of a CI engine. The experimental work was carried out on a four-cylinder, four-stroke, direct injection (DI) and turbocharged diesel engine by using biodiesel made from waste oil, rapeseed oil, corn oil and comparing them to normal diesel. The fuels used in the analyses are B10, B20, B50, B100 and neat diesel. The engine was operated over a range of engine speeds. Based on the measured parameters, detailed analyses were carried out on major regulated emissions such as NO_x, CO, CO₂, and THC. It has been seen that the biodiesel types (sources) do not result in any significant differences in emissions. The results also clearly indicate that the engine running with biodiesel and blends have higher NO_x emission by up to 20%. However, the emissions of the CI engine running on neat biodiesel (B100) were reduced by up to 15%, 40% and 30% for CO, CO₂and THC emissions respectively, as compared to diesel fuel at various operating conditions. Full article

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691 KiB

Open AccessArticle

An Experimental and Numerical Investigation of Fluidized Bed Gasification of Solid Waste

by Sharmina Begum, Mohammad G. Rasul, Delwar Akbar and David Cork

Energies 2014, 7(1), 43-61; https://doi.org/10.3390/en7010043 - 24 Dec 2013

Cited by 36 | Viewed by 13454

Abstract

Gasification is a thermo-chemical process to convert carbon-based products such as biomass and coal into a gas mixture known as synthetic gas or syngas. Various types of gasification methods exist, and fluidized bed gasification is one of them which is considered more efficient [...] Read more.

Gasification is a thermo-chemical process to convert carbon-based products such as biomass and coal into a gas mixture known as synthetic gas or syngas. Various types of gasification methods exist, and fluidized bed gasification is one of them which is considered more efficient than others as fuel is fluidized in oxygen, steam or air. This paper presents an experimental and numerical investigation of fluidized bed gasification of solid waste (SW) (wood). The experimental measurement of syngas composition was done using a pilot scale gasifier. A numerical model was developed using Advanced System for Process ENgineering (Aspen) Plus software. Several Aspen Plus reactor blocks were used along with user defined FORTRAN and Excel code. The model was validated with experimental results. The study found very similar performance between simulation and experimental results, with a maximum variation of 3%. The validated model was used to study the effect of air-fuel and steam-fuel ratio on syngas composition. The model will be useful to predict the various operating parameters of a pilot scale SW gasification plant, such as temperature, pressure, air-fuel ratio and steam-fuel ratio. Therefore, the model can assist researchers, professionals and industries to identify optimized conditions for SW gasification. Full article

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337 KiB

Open AccessArticle

Product Yields and Characteristics of Corncob Waste under Various Torrefaction Atmospheres

by Jau-Jang Lu and Wei-Hsin Chen

Energies 2014, 7(1), 13-27; https://doi.org/10.3390/en7010013 - 20 Dec 2013

Cited by 47 | Viewed by 8224

Abstract

Biomass is a promising energy source due to its abundant, carbon-fixing, and carbon-neutral properties. Torrefaction can be employed to improve the properties of biomass in an oxygen-free or nitrogen atmosphere. This study investigates the product yields and the solid product characteristics from corncob [...] Read more.

Biomass is a promising energy source due to its abundant, carbon-fixing, and carbon-neutral properties. Torrefaction can be employed to improve the properties of biomass in an oxygen-free or nitrogen atmosphere. This study investigates the product yields and the solid product characteristics from corncob waste torrefaction at the temperatures of 250 °C and 300 °C for 1 h. Nitrogen, carbon dioxide, and a gas mixture of air and carbon dioxide are employed as the carrier gases. The solid product characteristics approach those of coal at the higher temperature, regardless of what the carrier gases are. The fixed carbon, higher heating value, and solid and energy yields using carbon dioxide as a carrier gas at 300 °C are close to those using nitrogen. The product safety and storage properties before and after torrefaction are revealed by the measurements of ignition temperature and hygroscopicity. A higher torrefaction temperature leads to a higher ignition temperature of treated biomass, except using the mixture of air and carbon dioxide as the carrier gas. Carbon dioxide is a better carrier gas than nitrogen for biomass torrefaction, from the storage and transportation points of view. Full article

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967 KiB

Open AccessArticle

Evaluation of Biofuel Cells with Hemoglobin as Cathodic Electrocatalysts for Hydrogen Peroxide Reduction on Bare Indium-Tin-Oxide Electrodes

by Yusuke Ayato and Naoki Matsuda

Energies 2014, 7(1), 1-12; https://doi.org/10.3390/en7010001 - 20 Dec 2013

Cited by 3 | Viewed by 7714

Abstract

A biofuel cell (BFC) cathode has been developed based on direct electron transfer (DET) of hemoglobin (Hb) molecules with an indium-tin-oxide (ITO) electrode and their electrocatalysis for reduction of hydrogen peroxide (H₂O₂). In this study, the ITO-coated glass plates [...] Read more.

A biofuel cell (BFC) cathode has been developed based on direct electron transfer (DET) of hemoglobin (Hb) molecules with an indium-tin-oxide (ITO) electrode and their electrocatalysis for reduction of hydrogen peroxide (H₂O₂). In this study, the ITO-coated glass plates or porous glasses were prepared by using a chemical vapor deposition (CVD) method and examined the electrochemical characteristics of the formed ITO in pH 7.4 of phosphate buffered saline (PBS) solutions containing and not containing Hb. In half-cell measurements, the reduction current of H₂O₂ due to the electrocatalytic activity of Hb increased with decreasing electrode potential from around 0.1 V versus Ag|AgCl|KCl(satd.) in the PBS solution. The practical open-circuit voltage (OCV) on BFCs utilizing H₂O₂ reduction at the Hb-ITO cathode with a hydrogen (H₂) oxidation anode at a platinum (Pt) electrode was expected to be at least 0.74 V from the theoretical H₂ oxidation potential of −0.64 V versus Ag|AgCl|KCl(satd.) in pH 7.4. The assembled single cell using the ITO-coated glass plate showed the OCV of 0.72 V and the maximum power density of 3.1 µW cm⁻². The maximum power per single cell was recorded at 21.5 µW by using the ITO-coated porous glass. Full article

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Graphical abstract

487 KiB

Open AccessArticle

Performance Analysis of an Integrated Fixed Bed Gasifier Model for Different Biomass Feedstocks

by Sharmina Begum, Mohammad G. Rasul, Delwar Akbar and Naveed Ramzan

Energies 2013, 6(12), 6508-6524; https://doi.org/10.3390/en6126508 - 16 Dec 2013

Cited by 78 | Viewed by 10082

Abstract

Energy recovery from biomass by gasification technology has attracted significant interest because it satisfies a key requirement of environmental sustainability by producing near zero emissions. Though it is not a new technology, studies on its integrated process simulation and analysis are limited, in [...] Read more.

Energy recovery from biomass by gasification technology has attracted significant interest because it satisfies a key requirement of environmental sustainability by producing near zero emissions. Though it is not a new technology, studies on its integrated process simulation and analysis are limited, in particular for municipal solid waste (MSW) gasification. This paper develops an integrated fixed bed gasifier model of biomass gasification using the Advanced System for Process ENngineering (Aspen) Plus software for its performance analysis. A computational model was developed on the basis of Gibbs free energy minimization. The model is validated with experimental data of MSW and food waste gasification available in the literature. A reasonable agreement between measured and predicted syngas composition was found. Using the validated model, the effects of operating conditions, namely air-fuel ratio and gasifier temperature, on syngas production are studied. Performance analyses have been done for four different feedstocks, namely wood, coffee bean husks, green wastes and MSWs. The ultimate and proximate analysis data for each feedstock was used for model development. It was found that operating parameters have a significant influence on syngas composition. An air-fuel ratio of 0.3 and gasifier temperature of 700 °C provides optimum performance for a fixed bed gasifier for MSWs, wood wastes, green wastes and coffee bean husks. The developed model can be useful for gasification of other biomasses (e.g., food wastes, rice husks, poultry wastes and sugarcane bagasse) to predict the syngas composition. Therefore, the study provides an integrated gasification model which can be used for different biomass feedstocks. Full article

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771 KiB

Open AccessArticle

Rapid Biogas Production by Compact Multi-Layer Membrane Bioreactor: Efficiency of Synthetic Polymeric Membranes

by Supansa Youngsukkasem, Hamidreza Barghi, Sudip K. Rakshit and Mohammad J. Taherzadeh

Energies 2013, 6(12), 6211-6224; https://doi.org/10.3390/en6126211 - 28 Nov 2013

Cited by 18 | Viewed by 7309

Abstract

Entrapment of methane-producing microorganisms between semi-permeable synthetic membranes in a multi-layer membrane bioreactor (MMBR) was studied and compared to the digestion capacity of a free-cell digester, using a hydraulic retention time of one day and organic loading rates (OLR) of 3.08, 6.16, and [...] Read more.

Entrapment of methane-producing microorganisms between semi-permeable synthetic membranes in a multi-layer membrane bioreactor (MMBR) was studied and compared to the digestion capacity of a free-cell digester, using a hydraulic retention time of one day and organic loading rates (OLR) of 3.08, 6.16, and 8.16 g COD/L·day. The reactor was designed to retain bacterial cells with uprising plug flow through a narrow tunnel between membrane layers, in order to acquire maximal mass transfer in a compact bioreactor. Membranes of hydrophobic polyamide 46 (PA) and hydroxyethylated polyamide 46 (HPA) as well as a commercial membrane of polyvinylidene fluoride (PVDF) were examined. While the bacteria in the free-cell digester were washed out, the membrane bioreactor succeeded in retaining them. Cross-flow of the liquid through the membrane surface and diffusion of the substrate through the membranes, using no extra driving force, allowed the bacteria to receive nutrients and to produce biogas. However, the choice of membrane type was crucial. Synthesized hydrophobic PA membrane was not effective for this purpose, producing 50–121 mL biogas/day, while developed HPA membrane and the reference PVDF were able to transfer the nutrients and metabolites while retaining the cells, producing 1102–1633 and 1016–1960 mL biogas/day, respectively. Full article

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1730 KiB

Open AccessArticle

Co-Combustion of Animal Waste in a Commercial Waste-to-Energy BFB Boiler

by Farzad Moradian, Anita Pettersson, Solvie Herstad Svärd and Tobias Richards

Energies 2013, 6(12), 6170-6187; https://doi.org/10.3390/en6126170 - 27 Nov 2013

Cited by 16 | Viewed by 7895

Abstract

Co-combustion of animal waste, in waste-to-energy boilers, is considered a method to produce both heat and power and to dispose of possibly infected animal wastes. This research conducted full-scale combustion tests to identify the impact of changed fuel composition on a fluidized-bed boiler. [...] Read more.

Co-combustion of animal waste, in waste-to-energy boilers, is considered a method to produce both heat and power and to dispose of possibly infected animal wastes. This research conducted full-scale combustion tests to identify the impact of changed fuel composition on a fluidized-bed boiler. The impact was characterized by analyzing the deposit formation rate, deposit composition, ash composition, and emissions. Two combustion tests, denoted the reference case and animal waste case, were performed based on different fuel mixes. In the reference case, a normal solid waste fuel mix was combusted in the boiler, containing sorted industry and household waste. In the animal waste case, 20 wt% animal waste was added to the reference fuel mix. The collected samples, comprising sampling probe deposits, fuel mixes, bed ash, return sand, boiler ash, cyclone ash and filter ash, were analyzed using chemical fractionation, SEM-EDX and XRD. The results indicate decreased deposit formation due to animal waste co-combustion. SEM-EDX and chemical fractionation identified higher concentrations of P, Ca, S, and Cl in the bed materials in the animal waste case. Moreover, the risk of bed agglomeration was lower in the animal waste case and also a decreased rate of NO_x and SO₂ emissions were observed. Full article

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701 KiB

Open AccessArticle

Biomass Fuel and Combustion Conditions Selection in a Fixed Bed Combustor

by María E. Arce, Ángeles Saavedra, José L. Míguez, Enrique Granada and Antón Cacabelos

Energies 2013, 6(11), 5973-5989; https://doi.org/10.3390/en6115973 - 18 Nov 2013

Cited by 29 | Viewed by 6384

Abstract

The biomass market has experienced an increase in development, leading to research and development efforts that are focused on determining optimal biofuel combustion conditions. Biomass combustion is a complex process that involves divergent parameters and thus requires the use of advanced analysis methods. [...] Read more.

The biomass market has experienced an increase in development, leading to research and development efforts that are focused on determining optimal biofuel combustion conditions. Biomass combustion is a complex process that involves divergent parameters and thus requires the use of advanced analysis methods. This study proposes combining grey relational analysis (GRA) and error propagation theory (EPT) to select a biofuel and its optimal combustion conditions. This research will study three biofuels that are currently used in a region of South Europe (Spain), and the most important variables that affect combustion are the ignition front propagation speed and the highest temperature that is reached at the fixed bed combustor. The results demonstrate that a combination of both theories for the analysis of solid-state thermochemical phenomena enables a fast and simple way of choosing the best configuration for each fuel. Full article

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417 KiB

Open AccessArticle

Corn Stover and Wheat Straw Combustion in a 176-kW Boiler Adapted for Round Bales

by René Morissette, Philippe Savoie and Joey Villeneuve

Energies 2013, 6(11), 5760-5774; https://doi.org/10.3390/en6115760 - 4 Nov 2013

Cited by 9 | Viewed by 7618

Abstract

Combustion trials were conducted with corn stover (CS) and wheat straw (WS) round bales in a 176-kW boiler (model Farm 2000). Hot water (80 °C) stored in a 30,000-L water tank was transferred to a turkey barn through a plate exchanger. Gross calorific [...] Read more.

Combustion trials were conducted with corn stover (CS) and wheat straw (WS) round bales in a 176-kW boiler (model Farm 2000). Hot water (80 °C) stored in a 30,000-L water tank was transferred to a turkey barn through a plate exchanger. Gross calorific value measured in the laboratory was 17.0 and 18.9 MJ/kg DM (dry matter) for CS and WS, respectively. Twelve bales of CS (1974 kg DM total, moisture content of 13.6%) were burned over a 52-h period and produced 9.2% ash. Average emissions of CO, NO_x and SO₂ were 2725, 9.8 and 2.1 mg/m³, respectively. Thermal efficiency was 40.8%. For WS, six bales (940 kg DM total, MC of 15%) were burned over a 28-h period and produced 2.6% ash. Average emissions of CO, NO_x and SO₂ were 2210, 40.4 and 3.7 mg/m³, respectively. Thermal efficiency was 68.0%. A validation combustion trial performed a year later with 90 CS bales confirmed good heating performance and the potential to lower ash content (6.2% average). Full article

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507 KiB

Open AccessArticle

Biogas Production from Thin Stillage on an Industrial Scale—Experience and Optimisation

by Jan Moestedt, Sören Nilsson Påledal, Anna Schnürer and Erik Nordell

Energies 2013, 6(11), 5642-5655; https://doi.org/10.3390/en6115642 - 29 Oct 2013

Cited by 38 | Viewed by 13862

Abstract

With the increasing demand for renewable energy and sustainable waste treatment, biogas production is expanding. Approximately four billion litres of bio-ethanol are produced annually for vehicle fuel in Europe, resulting in the production of large amounts of stillage residues. This stillage is energy-rich [...] Read more.

With the increasing demand for renewable energy and sustainable waste treatment, biogas production is expanding. Approximately four billion litres of bio-ethanol are produced annually for vehicle fuel in Europe, resulting in the production of large amounts of stillage residues. This stillage is energy-rich and can be used for biogas production, but is a challenging substrate due to its high levels of nitrogen and sulphate. At the full-scale biogas production plant in Norrköping, Sweden (Svensk Biogas i Linköping AB), thin grain stillage is used as a biogas substrate. This paper describes the plant operation and strategies that have been implemented to digest thin stillage successfully. High ammonia concentrations in the digester have resulted in syntrophic acetate oxidation (SAO) becoming the major pathway for acetate degradation. Therefore, a long hydraulic retention time (HRT) (40–60 days) is used to allow the syntrophic acetate-oxidising bacteria time to grow. The high sulphate levels in thin stillage result in high levels of hydrogen sulphide following degradation of protein and the activity of sulphate-reducing bacteria (SRB), the presence of which has been confirmed by quantitative polymerase chain reaction (qPCR) analysis. To optimise biogas production and maintain a stable process, the substrate is diluted with tap water and co-digested with grain residues and glycerine to keep the ammonium nitrogen (NH₄-N) concentration below 6 g L⁻¹. Combined addition of iron, hydrochloric acid and cobalt successfully precipitates sulphides, reduces ammonia toxicity and supplies microorganisms with trace element. Mesophilic temperature (38 °C) is employed to further avoid ammonia toxicity. Together, these measures and doubling the digester volume have made it possible to increase annual biogas production from 27.7 TJ to 69.1 TJ. Full article

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Open AccessArticle

Decision Support for the Construction of Farm-Scale Biogas Digesters in Developing Countries with Cold Seasons

by Charlotte Rennuit and Sven Gjedde Sommer

Energies 2013, 6(10), 5314-5332; https://doi.org/10.3390/en6105314 - 18 Oct 2013

Cited by 14 | Viewed by 8658

Abstract

Biogas production is a clean renewable energy source that can improve lives in developing countries. However, winter temperatures in some areas are too low to enable enough biogas production in small unheated digesters to meet the energy requirements of households. Low-cost, high yield [...] Read more.

Biogas production is a clean renewable energy source that can improve lives in developing countries. However, winter temperatures in some areas are too low to enable enough biogas production in small unheated digesters to meet the energy requirements of households. Low-cost, high yield reactors adapted to the local climate are needed in those situations. A decision-support model was developed to assist in the design of biogas reactors capable of meeting households’ year-round energy needs. Monthly biogas production relative to household energy needs was calculated for the scenario of suburban Hanoi, Vietnam. Calculations included pig number, slurry (manure water mixture) dilution, retention time and biogas/solar heating. Although using biogas to heat the digester increased biogas production, it did not lead to an energy surplus, particularly with the 1:9 slurry dilution rate commonly used on pig farms. However, at a 1:3 slurry dilution, the use of solar heating to provide 90% and biogas 10% of the heat required to heat the digester to 35 °C improved the biogas production by 50% compared to psychrophilic production. The energy needs of an average five-person family throughout the year required 17 fattening pigs. This model can establish the best solution for producing sufficient energy throughout the year. Full article

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640 KiB

Open AccessArticle

Building Agro-Energy Supply Chains in the Basilicata Region: Technical and Economic Evaluation of Interchangeability between Fossil and Renewable Energy Sources

by Severino Romano, Mario Cozzi, Francesco Di Napoli and Mauro Viccaro

Energies 2013, 6(10), 5259-5282; https://doi.org/10.3390/en6105259 - 15 Oct 2013

Cited by 18 | Viewed by 7127

Abstract

In this study, we present a model for the implementation of agro-energy chains based on the actual availability of forest biomass and the real demand for energy (heat) in the area of the Basilicata region, Italy. The demand for energy has been estimated [...] Read more.

In this study, we present a model for the implementation of agro-energy chains based on the actual availability of forest biomass and the real demand for energy (heat) in the area of the Basilicata region, Italy. The demand for energy has been estimated by drawing on the database of the Ministry of Economic Development or by calculating the Annual Energy Requirement (AER) index, while for the estimate of the available forest biomass, reference was made to the public forest lands managed according to forestry management plans. The collected data were cross-checked with a view to detecting the technical and economic feasibility of district heating systems. The technical evaluation has mainly focused on the energetic and plant aspects, while the economic assessment was directed to defining the cost effectiveness criteria [Net Present Value (NPV), Internal Rate of Return (IRR), Payback Period] that can measure the profitability of the investment. In the economic evaluation we also included the national public incentives, designed to encourage the production of energy from renewable sources in compliance with the international agreements signed by Italy for the reduction of greenhouse gases (GHGs). Full article

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Open AccessArticle

Microbial Community Response to Seasonal Temperature Variation in a Small-Scale Anaerobic Digester

by Richard J. Ciotola, Jay F. Martin, Juan M. Castańo, Jiyoung Lee and Frederick Michel

Energies 2013, 6(10), 5182-5199; https://doi.org/10.3390/en6105182 - 14 Oct 2013

Cited by 18 | Viewed by 6575

Abstract

The Bacterial and Archaeal communities in a 1.14 m³ ambient temperature anaerobic digester treating dairy cow manure were investigated using terminal restriction fragment length polymorphisms (T-RFLP) and direct sequencing of the cloned polymerase chain reaction (PCR) products. Results indicate shifts in the [...] Read more.

The Bacterial and Archaeal communities in a 1.14 m³ ambient temperature anaerobic digester treating dairy cow manure were investigated using terminal restriction fragment length polymorphisms (T-RFLP) and direct sequencing of the cloned polymerase chain reaction (PCR) products. Results indicate shifts in the structure of the both the Archaeal and Bacterial communities coincided with digester re-inoculation as well as temperature and loading rate changes. Following re-inoculation of the sour digester, the predominant Archaea shifted from Methanobrevibacter to Methanosarcina, which was the most abundant Archaea in the inoculum. Methonosarcina was replaced by Methanosaeta after the resumption of digester loading in the summer of 2010. Methanosaeta began to decline in abundance as the digester temperature cooled in the fall of 2010 while Methanobrevibacter increased in abundance. The microbial community rate of change was variable during the study period, with the most rapid changes occurring after re-inoculation. Full article

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263 KiB

Open AccessArticle

Effects of Biodiesel Blend on Marine Fuel Characteristics for Marine Vessels

by Cherng-Yuan Lin

Energies 2013, 6(9), 4945-4955; https://doi.org/10.3390/en6094945 - 24 Sep 2013

Cited by 25 | Viewed by 6988

Abstract

Biodiesel produced from vegetable oils, animal fats and algae oil is a renewable, environmentally friendly and clean alternative fuel that reduces pollutants and greenhouse gas emissions in marine applications. This study investigates the influence of biodiesel blend on the characteristics of residual and [...] Read more.

Biodiesel produced from vegetable oils, animal fats and algae oil is a renewable, environmentally friendly and clean alternative fuel that reduces pollutants and greenhouse gas emissions in marine applications. This study investigates the influence of biodiesel blend on the characteristics of residual and distillate marine fuels. Adequate correlation equations are applied to calculate the fuel properties of the blended marine fuels with biodiesel. Residual marine fuel RMA has inferior fuel characteristics compared with distillate marine fuel DMA and biodiesel. The flash point of marine fuel RMA could be increased by 20% if blended with 20 vol% biodiesel. The sulfur content of residual marine fuel could meet the requirement of the 2008 MARPOL Annex VI Amendment by blending it with 23.0 vol% biodiesel. In addition, the kinematic viscosity of residual marine fuel could be reduced by 12.9% and the carbon residue by 23.6% if 20 vol% and 25 vol% biodiesel are used, respectively. Residual marine fuel blended with 20 vol% biodiesel decreases its lower heating value by 1.9%. Moreover, the fuel properties of residual marine fuel are found to improve more significantly with biodiesel blending than those of distillate marine fuel. Full article

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566 KiB

Open AccessReview

Microbial Conversion of Waste Glycerol from Biodiesel Production into Value-Added Products

by Cheng Li, Keaton L. Lesnik and Hong Liu

Energies 2013, 6(9), 4739-4768; https://doi.org/10.3390/en6094739 - 10 Sep 2013

Cited by 81 | Viewed by 14812

Abstract

Biodiesel has gained a significant amount of attention over the past decade as an environmentally friendly fuel that is capable of being utilized by a conventional diesel engine. However, the biodiesel production process generates glycerol-containing waste streams which have become a disposal issue [...] Read more.

Biodiesel has gained a significant amount of attention over the past decade as an environmentally friendly fuel that is capable of being utilized by a conventional diesel engine. However, the biodiesel production process generates glycerol-containing waste streams which have become a disposal issue for biodiesel plants and generated a surplus of glycerol. A value-added opportunity is needed in order to compensate for disposal-associated costs. Microbial conversions from glycerol to valuable chemicals performed by various bacteria, yeast, fungi, and microalgae are discussed in this review paper, as well as the possibility of extending these conversions to microbial electrochemical technologies. Full article

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Open AccessArticle

Catalytic Conversion of Bio-Oil to Oxygen-Containing Fuels by Acid-Catalyzed Reaction with Olefins and Alcohols over Silica Sulfuric Acid

by Zhijun Zhang, Shujuan Sui, Fengqiang Wang, Qingwen Wang and Charles U. Pittman, Jr.

Energies 2013, 6(9), 4531-4550; https://doi.org/10.3390/en6094531 - 2 Sep 2013

Cited by 20 | Viewed by 8488

Abstract

Crude bio-oil from pine chip fast pyrolysis was upgraded with olefins (1-octene, cyclohexene, 1,7-octadiene, and 2,4,4-trimethylpentene) plus 1-butanol (iso-butanol, t-butanol and ethanol) at 120 °C using a silica sulfuric acid (SSA) catalyst that possesses a good catalytic activity and stability. [...] Read more.

Crude bio-oil from pine chip fast pyrolysis was upgraded with olefins (1-octene, cyclohexene, 1,7-octadiene, and 2,4,4-trimethylpentene) plus 1-butanol (iso-butanol, t-butanol and ethanol) at 120 °C using a silica sulfuric acid (SSA) catalyst that possesses a good catalytic activity and stability. Gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (¹H-NMR) analysis showed that upgrading sharply increased ester content and decreased the amounts of levoglucosan, phenols, polyhydric alcohols and carboxylic acids. Upgrading lowered acidity (pH value rose from 2.5 to >3.5), removed the unpleasant odor and increased hydrocarbon solubility. Water content dramatically decreased from 37.2% to about 7.0% and the heating value increased from 12.6 MJ·kg⁻¹ to about 31.9 MJ·kg⁻¹. This work has proved that bio-oil upgrading with a primary olefin plus 1-butanol is a feasible route where all the original heating value of the bio-oil plus the added olefin and alcohol are present in the resulting fuel. Full article

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Open AccessArticle

Effect of Mixing Driven by Siphon Flow: Parallel Experiments Using the Anaerobic Reactors with Different Mixing Modes

by Takuro Kobayashi, Ya-Peng Wu, Kai-Qin Xu and Yu-You Li

Energies 2013, 6(8), 4207-4222; https://doi.org/10.3390/en6084207 - 19 Aug 2013

Cited by 15 | Viewed by 7208

Abstract

The effect of mixing by siphon flow on anaerobic digestion, sludge distribution and microbial community were examined in parallel experiments using a siphon-mixed reactor (SMR), an unmixed reactor (UMR) and a continuously mixed reactor (CMR). The SMR performed well without the accumulation of [...] Read more.

The effect of mixing by siphon flow on anaerobic digestion, sludge distribution and microbial community were examined in parallel experiments using a siphon-mixed reactor (SMR), an unmixed reactor (UMR) and a continuously mixed reactor (CMR). The SMR performed well without the accumulation of fatty acids under COD loading rates varying from 3 to 18 kg/m³/day, while the UMR was totally acidified when the loading rate increased to 10 kg/m³/day. The methane yield of the SMR was at least 10% higher than that of the UMR, and comparable to that of the CMR. Furthermore, the SMR was found to markedly improve the dispersion of solids and reduce deposit formation compared to the UMR. Besides, during stable operation, the fatty acids level in the effluent of the SMR and UMR was lower than that in the CMR, and the archaeal community structure of the SMR was similar to that of the UMR. Full article

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Open AccessArticle

A Two-Stage Continuous Fermentation System for Conversion of Syngas into Ethanol

by Hanno Richter, Michael E. Martin and Largus T. Angenent

Energies 2013, 6(8), 3987-4000; https://doi.org/10.3390/en6083987 - 7 Aug 2013

Cited by 136 | Viewed by 14442

Abstract

We have established a two-stage continuous fermentation process for production of ethanol from synthesis gas (syngas) with Clostridium ljungdahlii. The system consists of a 1-L continuously stirred tank reactor as a growth stage and a 4-L bubble column equipped with a cell [...] Read more.

We have established a two-stage continuous fermentation process for production of ethanol from synthesis gas (syngas) with Clostridium ljungdahlii. The system consists of a 1-L continuously stirred tank reactor as a growth stage and a 4-L bubble column equipped with a cell recycle module as an ethanol production stage. Operating conditions in both stages were optimized for the respective purpose (growth in stage one and alcohol formation in stage two). The system was fed with an artificial syngas mixture, mimicking the composition of syngas derived from lignocellulosic biomass (60% CO, 35% H₂, and 5% CO₂). Gas recycling was used to increase the contact area and retention time of gas in the liquid phase, improving mass transfer and metabolic rates. In stage two, the biocatalyst was maintained at high cell densities of up to 10 g DW/L. Ethanol was continuously produced at concentrations of up to 450 mM (2.1%) and ethanol production rates of up to 0.37 g/(L·h). Foam control was essential to maintain reactor stability. A stoichiometric evaluation of the optimized process revealed that the recovery of carbon and hydrogen from the provided carbon monoxide and hydrogen in the produced ethanol was 28% and 74%, respectively. Full article

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Open AccessArticle

Effects of Biomass Feedstocks and Gasification Conditions on the Physiochemical Properties of Char

by Kezhen Qian, Ajay Kumar, Krushna Patil, Danielle Bellmer, Donghai Wang, Wenqiao Yuan and Raymond L. Huhnke

Energies 2013, 6(8), 3972-3986; https://doi.org/10.3390/en6083972 - 6 Aug 2013

Cited by 174 | Viewed by 10787

Abstract

Char is a low-value byproduct of biomass gasification and pyrolysis with many potential applications, such as soil amendment and the synthesis of activated carbon and carbon-based catalysts. Considering these high-value applications, char could provide economic benefits to a biorefinery utilizing gasification or pyrolysis [...] Read more.

Char is a low-value byproduct of biomass gasification and pyrolysis with many potential applications, such as soil amendment and the synthesis of activated carbon and carbon-based catalysts. Considering these high-value applications, char could provide economic benefits to a biorefinery utilizing gasification or pyrolysis technologies. However, the properties of char depend heavily on biomass feedstock, gasifier design and operating conditions. This paper reports the effects of biomass type (switchgrass, sorghum straw and red cedar) and equivalence ratio (0.20, 0.25 and 0.28), i.e., the ratio of air supply relative to the air that is required for stoichiometric combustion of biomass, on the physiochemical properties of char derived from gasification. Results show that the Brunauer-Emmett-Teller (BET) surface areas of most of the char were 1–10 m²/g and increased as the equivalence ratio increased. Char moisture and fixed carbon contents decreased while ash content increased as equivalence ratio increased. The corresponding Fourier Transform Infrared spectra showed that the surface functional groups of char differed between biomass types but remained similar with change in equivalence ratio. Full article

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Open AccessArticle

Biofuel that Keeps Glycerol as Monoglyceride by 1,3-Selective Ethanolysis with Pig Pancreatic Lipase Covalently Immobilized on AlPO₄ Support

by Carlos Luna, Enrique Sancho, Diego Luna, Verónica Caballero, Juan Calero, Alejandro Posadillo, Cristóbal Verdugo, Felipa M. Bautista and Antonio A. Romero

Energies 2013, 6(8), 3879-3900; https://doi.org/10.3390/en6083879 - 30 Jul 2013

Cited by 27 | Viewed by 7995

Abstract

By using pig pancreatic lipase (EC 3.1.1.3 or PPL) as a biocatalyst, covalently immobilized on amorphous AlPO₄ support, a new second generation biodiesel was obtained in the transesterification reaction of sunflower oil with ethanol. The resulting biofuel is composed of fatty acid [...] Read more.

By using pig pancreatic lipase (EC 3.1.1.3 or PPL) as a biocatalyst, covalently immobilized on amorphous AlPO₄ support, a new second generation biodiesel was obtained in the transesterification reaction of sunflower oil with ethanol. The resulting biofuel is composed of fatty acid ethyl esters and monoglycerides (FAEE/MG) blended in a 2:1 molar ratio. This novel product, which integrates glycerol as monoacylglycerols (MG) into the biofuels composition, has similar physicochemical properties as conventional biodiesel and also avoids the removal step of the by-product by washing of the biodiesel with water. Immobilization of PPL was achieved by covalent attachment of the ε-amino group of the lysine residues of PPL with the aldehyde groups of p-hydroxybenzaldehyde linked on a hybrid organic-inorganic functionalized AlPO₄ surface. With this procedure, the PPL biocatalyst was strongly fixed to the inorganic support surface (94.3%). Nevertheless, the efficiency of the immobilized enzyme was relatively lower compared to that of the free PPL, but it showed a remarkable stability as well as a great capacity of reutilization (25 reuses) without a significant loss of its initial catalytic activity. Therefore, this enzymatic method allows the production of a biodiesel which integrates the glycerol, allows a more efficient fabrication method and minimizes the waste production as compared to the conventional alkali-catalyzed process. Full article

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Open AccessArticle

Catalytic Steam Reforming of Toluene as a Model Compound of Biomass Gasification Tar Using Ni-CeO₂/SBA-15 Catalysts

by Jun Tao, Leiqiang Zhao, Changqing Dong, Qiang Lu, Xiaoze Du and Erik Dahlquist

Energies 2013, 6(7), 3284-3296; https://doi.org/10.3390/en6073284 - 4 Jul 2013

Cited by 70 | Viewed by 9433

Abstract

Nickel supported on SBA-15 doped with CeO₂ catalysts (Ni-CeO₂/SBA-15) was prepared, and used for steam reforming of toluene which was selected as a model compound of biomass gasification tar. A fixed-bed lab-scale set was designed and employed to evaluate the [...] Read more.

Nickel supported on SBA-15 doped with CeO₂ catalysts (Ni-CeO₂/SBA-15) was prepared, and used for steam reforming of toluene which was selected as a model compound of biomass gasification tar. A fixed-bed lab-scale set was designed and employed to evaluate the catalytic performances of the Ni-CeO₂/SBA-15 catalysts. Experiments were performed to reveal the effects of several factors on the toluene conversion and product gas composition, including the reaction temperature, steam/carbon (S/C) ratio, and CeO₂ loading content. Moreover, the catalysts were subjected to analysis of their carbon contents after the steam reforming experiments, as well as to test the catalytic stability over a long experimental period. The results indicated that the Ni-CeO₂/SBA-15 catalysts exhibited promising capabilities on the toluene conversion, anti-coke deposition and catalytic stability. The toluene conversion reached as high as 98.9% at steam reforming temperature of 850 °C and S/C ratio of 3 using the Ni-CeO₂(3wt%)/SBA-15 catalyst. Negligible coke formation was detected on the used catalyst. The gaseous products mainly consisted of H₂ and CO, together with a little CO₂ and CH₄. Full article

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Open AccessArticle

Hydrogen-Rich Gas Production by Sorption Enhanced Steam Reforming of Woodgas Containing TAR over a Commercial Ni Catalyst and Calcined Dolomite as CO₂ Sorbent

by Mario Sisinni, Andrea Di Carlo, Enrico Bocci, Andrea Micangeli and Vincenzo Naso

Energies 2013, 6(7), 3167-3181; https://doi.org/10.3390/en6073167 - 1 Jul 2013

Cited by 43 | Viewed by 9149

Abstract

The aim of this work was the evaluation of the catalytic steam reforming of a gaseous fuel obtained by steam biomass gasification to convert topping atmosphere residue (TAR) and CH₄ and to produce pure H₂ by means of a CO₂ [...] Read more.

The aim of this work was the evaluation of the catalytic steam reforming of a gaseous fuel obtained by steam biomass gasification to convert topping atmosphere residue (TAR) and CH₄ and to produce pure H₂ by means of a CO₂ sorbent. This experimental work deals with the demonstration of the practical feasibility of such concepts, using a real woodgas obtained from fluidized bed steam gasification of hazelnut shells. This study evaluates the use of a commercial Ni catalyst and calcined dolomite (CaO/MgO). The bed material simultaneously acts as reforming catalyst and CO₂ sorbent. The experimental investigations have been carried out in a fixed bed micro-reactor rig using a slipstream from the gasifier to evaluate gas cleaning and upgrading options. The reforming/sorption tests were carried out at 650 °C while regeneration of the sorbent was carried out at 850 °C in a nitrogen environment. Both combinations of catalyst and sorbent are very effective in TAR and CH₄ removal, with conversions near 100%, while the simultaneous CO₂ sorption effectively enhances the water gas shift reaction producing a gas with a hydrogen volume fraction of over 90%. Multicycle tests of reforming/CO₂capture and regeneration were performed to verify the stability of the catalysts and sorbents to remove TAR and capture CO₂ during the duty cycle. Full article

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Open AccessArticle

The Effect of Effluent Recirculation in a Semi-Continuous Two-Stage Anaerobic Digestion System

by Solmaz Aslanzadeh, Karthik Rajendran, Azam Jeihanipour and Mohammad J. Taherzadeh

Energies 2013, 6(6), 2966-2981; https://doi.org/10.3390/en6062966 - 17 Jun 2013

Cited by 38 | Viewed by 8924

Abstract

The effect of recirculation in increasing organic loading rate (OLR) and decreasing hydraulic retention time (HRT) in a semi-continuous two-stage anaerobic digestion system using stirred tank reactor (CSTR) and an upflow anaerobic sludge bed (UASB) was evaluated. Two-parallel processes were in operation for [...] Read more.

The effect of recirculation in increasing organic loading rate (OLR) and decreasing hydraulic retention time (HRT) in a semi-continuous two-stage anaerobic digestion system using stirred tank reactor (CSTR) and an upflow anaerobic sludge bed (UASB) was evaluated. Two-parallel processes were in operation for 100 days, one with recirculation (closed system) and the other without recirculation (open system). For this purpose, two structurally different carbohydrate-based substrates were used; starch and cotton. The digestion of starch and cotton in the closed system resulted in production of 91% and 80% of the theoretical methane yield during the first 60 days. In contrast, in the open system the methane yield was decreased to 82% and 56% of the theoretical value, for starch and cotton, respectively. The OLR could successfully be increased to 4 gVS/L/day for cotton and 10 gVS/L/day for starch. It is concluded that the recirculation supports the microorganisms for effective hydrolysis of polyhydrocarbons in CSTR and to preserve the nutrients in the system at higher OLRs, thereby improving the overall performance and stability of the process. Full article

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2012

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864 KiB

Open AccessReview

Biofuels Production through Biomass Pyrolysis —A Technological Review

by Mohammad I. Jahirul, Mohammad G. Rasul, Ashfaque Ahmed Chowdhury and Nanjappa Ashwath

Energies 2012, 5(12), 4952-5001; https://doi.org/10.3390/en5124952 - 23 Nov 2012

Cited by 1061 | Viewed by 53479

Abstract

There has been an enormous amount of research in recent years in the area of thermo-chemical conversion of biomass into bio-fuels (bio-oil, bio-char and bio-gas) through pyrolysis technology due to its several socio-economic advantages as well as the fact it is an efficient [...] Read more.

There has been an enormous amount of research in recent years in the area of thermo-chemical conversion of biomass into bio-fuels (bio-oil, bio-char and bio-gas) through pyrolysis technology due to its several socio-economic advantages as well as the fact it is an efficient conversion method compared to other thermo-chemical conversion technologies. However, this technology is not yet fully developed with respect to its commercial applications. In this study, more than two hundred publications are reviewed, discussed and summarized, with the emphasis being placed on the current status of pyrolysis technology and its potential for commercial applications for bio-fuel production. Aspects of pyrolysis technology such as pyrolysis principles, biomass sources and characteristics, types of pyrolysis, pyrolysis reactor design, pyrolysis products and their characteristics and economics of bio-fuel production are presented. It is found from this study that conversion of biomass to bio-fuel has to overcome challenges such as understanding the trade-off between the size of the pyrolysis plant and feedstock, improvement of the reliability of pyrolysis reactors and processes to become viable for commercial applications. Further study is required to achieve a better understanding of the economics of biomass pyrolysis for bio-fuel production, as well as resolving issues related to the capabilities of this technology in practical application. Full article

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Open AccessArticle

A Novel Miniature Culture System to Screen CO₂-Sequestering Microalgae

by Wei Han, Chunying Li, Xiaoling Miao and Guangxin Yu

Energies 2012, 5(11), 4372-4389; https://doi.org/10.3390/en5114372 - 1 Nov 2012

Cited by 18 | Viewed by 7322

Abstract

In this study, a novel 96-well microplate swivel system (M96SS) was built for high-throughput screening of microalgal strains for CO₂ fixation. Cell growth under different CO₂ supply conditions (0.2, 0.4, 0.8, and 1.2 gL⁻¹d⁻¹), residual nitrate, [...] Read more.

In this study, a novel 96-well microplate swivel system (M96SS) was built for high-throughput screening of microalgal strains for CO₂ fixation. Cell growth under different CO₂ supply conditions (0.2, 0.4, 0.8, and 1.2 gL⁻¹d⁻¹), residual nitrate, and pH value of Chlorella sp. SJTU-3, Chlorella pyrenoidosa SJTU-2, and Scenedesmus obliquus SJTU-3 were examined in the M96SS and traditional flask cultures. The dynamic data showed there was a good agreement between the systems. Two critical problems in miniature culture systems (intra-well mixing and evaporation loss) were improved by sealed vertical mixing of the M96SS. A sample screen of six microalgal species (Chlorella sp. SJTU-3, Chlorella pyrenoidosa SJTU-2, Selenastrum capricornutum, Scenedesmus obliquus SJTU-3, Chlamydomonas sajao, Dunaliella primolecta) was carried out in flasks and the M96SS. Chlamydomonas sajao appeared to be a robust performer (highest cell density: 1.437 g L⁻¹) in anaerobic pond water with 0.8, and 1.2 gL⁻¹d⁻¹ CO₂. The reliability and efficiency of the M96SS were verified through a comparison of traditional flask culture, M96SS, Lukavský’s system, and a microplate shaker. Full article

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Open AccessArticle

Some Chemical Compositional Changes in Miscanthus and White Oak Sawdust Samples during Torrefaction

by Jaya Shankar Tumuluru, Richard D. Boardman, Christopher T. Wright and J. Richard Hess

Energies 2012, 5(10), 3928-3947; https://doi.org/10.3390/en5103928 - 16 Oct 2012

Cited by 29 | Viewed by 8391

Abstract

Torrefaction tests on miscanthus and white oak sawdust were conducted in a bubbling sand bed reactor to see the effect of temperature and residence time on the chemical composition. Process conditions for miscanthus and white oak sawdust were 250–350 °C for 30–120 min [...] Read more.

Torrefaction tests on miscanthus and white oak sawdust were conducted in a bubbling sand bed reactor to see the effect of temperature and residence time on the chemical composition. Process conditions for miscanthus and white oak sawdust were 250–350 °C for 30–120 min and 220–270 °C for 30 min, respectively. Torrefaction of miscanthus at 250 °C and a residence time of 30 min resulted in a significant decrease in moisture—about 82.68%—but the other components—hydrogen, nitrogen, sulfur, and volatiles—changed only marginally. Increasing torrefaction temperatures to 350 °C with a residence time of 120 min further reduced the moisture content to 0.54%, with a significant decrease in the hydrogen, nitrogen, and volatiles by 58.29%, 14.28%, and 70.45%, respectively. Regression equations developed for the moisture, hydrogen, nitrogen, and volatile content of the samples with respect to torrefaction temperature and time have adequately described the changes in chemical composition based on R² values of >0.82. Surface plots based on the regression equation indicate that torrefaction temperatures of 280–350 °C with residence times of 30–120 min can help reduce moisture, nitrogen, and volatile content from 1.13% to 0.6%, 0.27% to 0.23%, and 79% to 23%, with respect to initial values. Trends of chemical compositional changes in white oak sawdust are similar to miscanthus. Torrefaction temperatures of 270 °C and a 30 min residence time reduced the moisture, volatiles, hydrogen, and nitrogen content by about 79%, 17.88%, 20%, and 5.88%, respectively, whereas the carbon content increased by about 3.5%. Full article

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Open AccessArticle

Study of Pea Accessions for Development of an Oilseed Pea

by Ehsan Khodapanahi, Mark Lefsrud, Valerie Orsat, Jaswinder Singh and Tom D. Warkentin

Energies 2012, 5(10), 3788-3802; https://doi.org/10.3390/en5103788 - 27 Sep 2012

Cited by 11 | Viewed by 6908

Abstract

Global interest in stable energy resources coupled with growing demand for bio-oils in various conventional and arising industries has renewed the importance of vegetable oil production. To address this global interest, oilseed production has been increased in recent decades by different approaches, such [...] Read more.

Global interest in stable energy resources coupled with growing demand for bio-oils in various conventional and arising industries has renewed the importance of vegetable oil production. To address this global interest, oilseed production has been increased in recent decades by different approaches, such as extending the cultivation area of oil crops, or breeding and growing genetically modified plants. In this study, pea (Pisum sativum L.) accessions were screened for lipid content using a rapid extraction method. This method quantifies lipid concentration in pea seeds and was developed by assessing and comparing the results of existing extraction methods used for canola and soybean, the top two Canadian oilseeds. Seeds of 151 field pea accessions were grown to maturity in 2009 and 2010 at McGill University (Quebec, Canada). Overall, lipid concentration in pea seeds ranged from 0.9 to 5.0%. Among several seed characteristics, only seed shape (wrinkled verses round) had a significant effect on the total lipid production in the seeds. Peas are a valuable source of protein and starch, but the lipid concentration in their seeds has been undervalued. This research supports the idea of developing a novel dual-purpose oilseed pea that emulates the protein and oil production in soybean seeds while being conveniently adapted to a colder climate. Full article

537 KiB

Open AccessReview

Biotechnological Utilization with a Focus on Anaerobic Treatment of Cheese Whey: Current Status and Prospects

by Aspasia A. Chatzipaschali and Anastassios G. Stamatis

Energies 2012, 5(9), 3492-3525; https://doi.org/10.3390/en5093492 - 10 Sep 2012

Cited by 102 | Viewed by 13460

Abstract

Cheese whey utilization is of major concern nowadays. Its high organic matter content, in combination with the high volumes produced and limited treatment options make cheese whey a serious environmental problem. However, the potential production of biogas (methane), hydrogen or other marketable products [...] Read more.

Cheese whey utilization is of major concern nowadays. Its high organic matter content, in combination with the high volumes produced and limited treatment options make cheese whey a serious environmental problem. However, the potential production of biogas (methane), hydrogen or other marketable products with a simultaneous high COD reduction through appropriate treatment proves that cheese whey must be considered as an energy resource rather than a pollutant. The presence of biodegradable components in the cheese whey coupled with the advantages of anaerobic digestion processes over other treatment methods makes anaerobic digestion an attractive and suitable treatment option. This paper intends to review the most representative applications of anaerobic treatment of cheese whey currently being exploited and under research. Moreover, an effort has been made to categorize the common characteristics of the various research efforts and find a comparative basis, as far as their results are concerned. In addition, a number of dairy industries already using such anaerobic digestion systems are presented. Full article

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3014 KiB

Open AccessArticle

Energy from Agricultural and Animal Farming Residues: Potential at a Local Scale

by Giulia Fiorese and Giorgio Guariso

Energies 2012, 5(9), 3198-3217; https://doi.org/10.3390/en5093198 - 28 Aug 2012

Cited by 9 | Viewed by 6947

Abstract

Animal wastes from high-density farming have severe impacts on the nitrogen cycle. According to current regulations, the disposal of manure on cropland is constrained by nitrogen content in the agricultural soils. On the contrary, anaerobic digestion (AD) of these wastes can produce energy [...] Read more.

Animal wastes from high-density farming have severe impacts on the nitrogen cycle. According to current regulations, the disposal of manure on cropland is constrained by nitrogen content in the agricultural soils. On the contrary, anaerobic digestion (AD) of these wastes can produce energy and a digestate, which is easier to handle than manure and can be applied for agronomic uses. When herbaceous crops are co-digested with manure to increase the efficiency of biogas production, the nitrogen content in the digestate further increases, unless these larger plants are equipped with nitrogen stripping technologies. We propose a model to compare larger (cooperative) and smaller (single parcel) AD conversion plants. The whole process is modeled: from the collection of manures, to the cultivation of energy crops, to the disposal of the digestate. The model maximizes the energy produced on the basis of available biomass, road network, local heat demand and local availability of land for digestate disposal. Results are the optimal size and location of the plants, their technology and collection basins. The environmental performances of such plants are also evaluated. The study has been applied to the province of Forlì-Cesena, an Italian district where animal farming is particularly relevant. Full article

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353 KiB

Open AccessArticle

Optimization of Nitrogen and Metal Ions Supplementation for Very High Gravity Bioethanol Fermentation from Sweet Sorghum Juice Using an Orthogonal Array Design

by Orawan Deesuth, Pattana Laopaiboon, Prasit Jaisil and Lakkana Laopaiboon

Energies 2012, 5(9), 3178-3197; https://doi.org/10.3390/en5093178 - 24 Aug 2012

Cited by 46 | Viewed by 7699

Abstract

Optimization of four parameters, i.e., zinc (Zn²⁺), magnesium (Mg²⁺), manganese (Mn²⁺) and yeast extract for bioethanol production from sweet sorghum juice by Saccharomyces cerevisiae NP 01 under very high gravity (VHG, 270 g·L⁻¹ of total [...] Read more.

Optimization of four parameters, i.e., zinc (Zn²⁺), magnesium (Mg²⁺), manganese (Mn²⁺) and yeast extract for bioethanol production from sweet sorghum juice by Saccharomyces cerevisiae NP 01 under very high gravity (VHG, 270 g·L⁻¹ of total sugar) conditions was performed using an L₉ (3⁴) orthogonal array design. The fermentation was carried out at 30 °C in 500-mL air-locked Erlenmeyer flasks at the agitation rate of 100 rpm and the initial yeast cell concentration in the juice was approximately 5 × 10⁷ cells·mL⁻¹. The results showed that the order of influence was yeast extract > Mn²⁺ > Zn²⁺ > Mg²⁺ and the optimum nutrient concentrations for the ethanol fermentation were Zn²⁺, 0.01; Mg²⁺, 0.05; Mn²⁺, 0.04; and yeast extract, 9 g·L⁻¹. The verification experiments under the optimum condition clearly indicated that the metals and nitrogen supplementation improved ethanol production efficiency under the VHG fermentation conditions. The ethanol concentration (P), yield (Y_p/s) and productivity (Q_p) were 120.58 ± 0.26 g·L⁻¹, 0.49 ± 0.01 and 2.51 ± 0.01 g·L⁻¹·h⁻¹, respectively, while in the control treatment (without nutrient supplement) P, Y_p/sand Q_p were only 93.45 ± 0.45 g·L⁻¹, 0.49 ± 0.00 and 1.30 ± 0.01 g·L⁻¹·h⁻¹, respectively. Full article

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677 KiB

Open AccessArticle

Research on the Gas Reburning in a Circulating Fluidized Bed (CFB) System Integrated with Biomass Gasification

by Xiaoying Hu, Tao Wang, Zhihui Dong, Hanfei Zhang and Changqing Dong

Energies 2012, 5(9), 3167-3177; https://doi.org/10.3390/en5093167 - 24 Aug 2012

Cited by 7 | Viewed by 6307

Abstract

N₂O emissions from coal fired fluidized-bed combustion are approximately 30–360 mg/Nm³, much higher than that from pulverized coal combustion (less than 30 mg/Nm³). One approach to reduce the N₂O is to reburn the biomass gasification [...] Read more.

N₂O emissions from coal fired fluidized-bed combustion are approximately 30–360 mg/Nm³, much higher than that from pulverized coal combustion (less than 30 mg/Nm³). One approach to reduce the N₂O is to reburn the biomass gasification gas in the coal-fired fluidized bed. In this paper, the effects of gasified biomass reburning on the integrated boiler system were investigated by both simulation and experimental methods. The simulation as well as experimental results revealed that the increase of the reburning ratio would decrease the theoretical air volume and boiler efficiency, while it would increase the fuel gas volume, combustion and exhuast gas temperature. The experimental results also indicated that the N₂O removal could reach as high as 99% when the heat ratio of biomass gas to coal is 10.5%. Full article

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286 KiB

Open AccessArticle

A Complementary Biodiesel Blend from Soapnut Oil and Free Fatty Acids

by Yi-Hung Chen, Ting-Cheng Tang, Tsung-Han Chiang, Bo-Yu Huang, Ching-Yuan Chang, Pen-Chi Chiang, Je-Lueng Shie, Matthias Franzreb and Lu-Yen Chen

Energies 2012, 5(8), 3137-3148; https://doi.org/10.3390/en5083137 - 17 Aug 2012

Cited by 18 | Viewed by 6988

Abstract

Blends of biodiesels produced from soapnut oil and high-oleic free fatty acids (FFAs), which are potential non-edible oil feedstocks, were investigated with respect to their fuel properties. The soapnut oil methyl esters (SNME) had satisfactory fuel properties with the exception of its high [...] Read more.

Blends of biodiesels produced from soapnut oil and high-oleic free fatty acids (FFAs), which are potential non-edible oil feedstocks, were investigated with respect to their fuel properties. The soapnut oil methyl esters (SNME) had satisfactory fuel properties with the exception of its high cold filter plugging point. In contrast, the biodiesel from the FFAs had favorable fuel properties such as a low cold filter plugging point of −6 °C; however, it exhibits poor oxidation stability with an induction period (IP) of 0.2 h. The complementary blend of the SNME and the FFA-based biodiesel at various weight ratios was studied to improve the fuel properties. As a result, the biodiesel blend at a weight ratio of 70:30 can successfully meet all the biodiesel specifications, except the marginal oxidation stability. Furthermore, the effectiveness of N,N’-di-sec-butyl-p-phenylenediamine at the concentration between 100 and 500 ppm on the improvement in the oxidation stability of the biodiesel blend was examined. The relationship between the IP values associated with the consumption of antioxidants in the biodiesel blends was described by first-order reaction rate kinetics. In addition, the natural logarithm of IP (ln IP) at various concentrations of antioxidant presented a linear relation with the test temperature. The IP at ambient temperature can be predicted based on the extrapolation of the temperature dependence relation. Full article

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272 KiB

Open AccessArticle

The Long-Term Prospects of Biofuels in the EU-15 Countries

by Amela Ajanovic, Gerfried Jungmeier, Martin Beermann and Reinhard Haas

Energies 2012, 5(8), 3110-3125; https://doi.org/10.3390/en5083110 - 17 Aug 2012

Cited by 1 | Viewed by 6607

Abstract

The core objective of this paper is to analyze the energy and CO₂ reduction potentials as well as the market prospects of biofuels in EU-15 in a dynamic framework till 2050. The most important result of this analysis is that 2nd generation [...] Read more.

The core objective of this paper is to analyze the energy and CO₂ reduction potentials as well as the market prospects of biofuels in EU-15 in a dynamic framework till 2050. The most important result of this analysis is that 2nd generation biofuels might become economically competitive between 2020 and 2030, yet this can only be achieved if the following preconditions are fulfilled: (1) achievement of significant learning effects leading to considerably lower plant costs; (2) significant improvement of conversion efficiency from feedstock to fuel leading to lower feedstock costs and better ecological performance; (3) increases in conventional diesel and gasoline prices, e.g., due to CO₂ based taxes. Full article

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465 KiB

Open AccessArticle

Gamma Irradiation Induced Degradation of Orange Peels

by Raymundo Sánchez Orozco, Patricia Balderas Hernández, Nelly Flores Ramírez, Gabriela Roa Morales, Jaime Saucedo Luna and Agustín Jaime Castro Montoya

Energies 2012, 5(8), 3051-3063; https://doi.org/10.3390/en5083051 - 14 Aug 2012

Cited by 36 | Viewed by 10772

Abstract

In this study, gamma irradiation induced degradation of orange peels (OP) was investigated. The lignocellulosic biomass degradation was carried out at doses of 0 (control), 600, 1800 and 3500 kGy using a Co-60 gamma radiation source. The samples were tested for total and [...] Read more.

In this study, gamma irradiation induced degradation of orange peels (OP) was investigated. The lignocellulosic biomass degradation was carried out at doses of 0 (control), 600, 1800 and 3500 kGy using a Co-60 gamma radiation source. The samples were tested for total and reducing sugars. The concentrations of total sugars ranged from 0.530 g∙g⁻¹ in control sample to 0.382 g∙g⁻¹ of dry weight in the sample which received the highest radiation dose. The reducing sugars content varying from 0.018 to 0.184 g∙g⁻¹ of dry weight with the largest rise occurring in the sample irradiated at 3500 kGy. The concentrations of sucrose, glucose and fructose were determined. The changes generated in physico-chemical properties were determined by Fourier Transform Infrared Spectroscopy (FTIR) and termogravimetric analysis (TG-DTG). The results show that OP was affected, but not significantly, which suggests that lignocellulose and sugars profiles were partially degraded after gamma irradiation. Full article

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321 KiB

Open AccessArticle

Continuous Fermentation of Clostridium tyrobutyricum with Partial Cell Recycle as a Long-Term Strategy for Butyric Acid Production

by Jianjun Du, Amy McGraw, Nicole Lorenz, Robert R. Beitle, Edgar C. Clausen and Jamie A. Hestekin

Energies 2012, 5(8), 2835-2848; https://doi.org/10.3390/en5082835 - 2 Aug 2012

Cited by 30 | Viewed by 10358

Abstract

In making alternative fuels from biomass feedstocks, the production of butyric acid is a key intermediate in the two-step production of butanol. The fermentation of glucose via Clostridium tyrobutyricum to butyric acid produces undesirable byproducts, including lactic acid and acetic acid, which significantly [...] Read more.

In making alternative fuels from biomass feedstocks, the production of butyric acid is a key intermediate in the two-step production of butanol. The fermentation of glucose via Clostridium tyrobutyricum to butyric acid produces undesirable byproducts, including lactic acid and acetic acid, which significantly affect the butyric acid yield and productivity. This paper focuses on the production of butyric acid using Clostridium tyrobutyricum in a partial cell recycle mode to improve fermenter yield and productivity. Experiments with fermentation in batch, continuous culture and continuous culture with partial cell recycle by ultrafiltration were conducted. The results show that a continuous fermentation can be sustained for more than 120 days, which is the first reported long-term production of butyric acid in a continuous operation. Further, the results also show that partial cell recycle via membrane ultrafiltration has a great influence on the selectivity and productivity of butyric acid, with an increase in selectivity from ≈9% to 95% butyric acid with productivities as high as 1.13 g/Lh. Continuous fermentation with low dilution rate and high cell recycle ratio has been found to be desirable for optimum productivity and selectivity toward butyric acid and a comprehensive model explaining this phenomenon is given. Full article

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224 KiB

Open AccessArticle

Deacidification of Pistacia chinensis Oil as a Promising Non-Edible Feedstock for Biodiesel Production in China

by Shenjun Qin, Yuzhuang Sun, Changlin Shi, Leqin He, Yuan Meng and Xiaohui Ren

Energies 2012, 5(8), 2759-2770; https://doi.org/10.3390/en5082759 - 31 Jul 2012

Cited by 17 | Viewed by 7174

Abstract

Pistacia chinensis seed oil is proposed as a promising non-edible feedstock for biodiesel production. Different extraction methods were tested and compared to obtain crude oil from the seed of Pistacia chinensis, along with various deacidification measures of refined oil. The biodiesel was [...] Read more.

Pistacia chinensis seed oil is proposed as a promising non-edible feedstock for biodiesel production. Different extraction methods were tested and compared to obtain crude oil from the seed of Pistacia chinensis, along with various deacidification measures of refined oil. The biodiesel was produced through catalysis of sodium hydroxide (NaOH) and potassium hydroxide (KOH). The results showed that the acid value of Pistacia chinensis oil was successfully reduced to 0.23 mg KOH/g when it was extracted using ethanol. Consequently, the biodiesel product gave a high yield beyond 96.0%. The transesteriﬁcation catalysed by KOH was also more complete. Fourier transform infrared (FTIR) spectroscopy was used to monitor the transesterification reaction. Analyses by gas chromatography-mass spectrometry (GC-MS) and gas chromatography with a flame ionisation detector (GC-FID) certified that the Pistacia chinensis biodiesel mainly consisted of C₁₈ fatty acid methyl esters (81.07%) with a high percentage of methyl oleate. Furthermore, the measured fuel properties of the biodiesel met the required standards for fuel use. In conclusion, the Pistacia chinensis biodiesel is a qualified and feasible substitute for fossil diesel. Full article

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370 KiB

Open AccessArticle

Fuel Characteristics of Biodiesel Produced from a High-Acid Oil from Soybean Soapstock by Supercritical-Methanol Transesterification

by Cherng-Yuan Lin and Yi-Wei Lin

Energies 2012, 5(7), 2370-2380; https://doi.org/10.3390/en5072370 - 9 Jul 2012

Cited by 66 | Viewed by 8866

Abstract

A supercritical methanol transesterification method was applied to produce biodiesel from the high-acid oil of soybean soapstock. The fuel properties of biodiesel produced with various molar ratios of methanol to raw oil were analyzed and compared in this experimental study. Oleic acid (C18:1), [...] Read more.

A supercritical methanol transesterification method was applied to produce biodiesel from the high-acid oil of soybean soapstock. The fuel properties of biodiesel produced with various molar ratios of methanol to raw oil were analyzed and compared in this experimental study. Oleic acid (C18:1), linoleic acid (C18:2), and palmitic acid (C16:0) were the three main compounds in the high-acid oil-biodiesel. The saturated fatty acid content of the high-acid oil increased significantly due to the supercritical-methanol transesterification reaction. The fuel characteristics of the resulting high-acid oil, including the specific gravity and kinematic viscosity, were also greatly improved. The saturated fatty acid content of the biodiesel produced from the high-acid oil was higher than that of biodiesel from waste cooking oil produced by the subcritical transesterification using a strongly alkaline catalyst. The high-acid oil-biodiesel that was produced with a molar ratio of methanol to raw oil of 42 had the best fuel properties, including a higher distillation temperature and cetane index and a lower kinematic viscosity and water content, among the biodiesels with different molar ratios. Full article

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498 KiB

Open AccessArticle

Evaluating the Marginal Land Resources Suitable for Developing Pistacia chinensis-Based Biodiesel in China

by Lu Lu, Dong Jiang, Dafang Zhuang and Yaohuan Huang

Energies 2012, 5(7), 2165-2177; https://doi.org/10.3390/en5072165 - 29 Jun 2012

Cited by 33 | Viewed by 8102

Abstract

Bio-energy from energy plants is expected to play an increasing role in the future energy system, with benefits in terms of reducing greenhouse gas emissions and improving energy security. Pistacia chinensis is believed to be one of the most promising non-food input for [...] Read more.

Bio-energy from energy plants is expected to play an increasing role in the future energy system, with benefits in terms of reducing greenhouse gas emissions and improving energy security. Pistacia chinensis is believed to be one of the most promising non-food input for biodiesel production. This study focused on the marginal land availability for developing Pistacia chinensis-based bioenergy in China. The spatial distribution, quality and total amount of marginal land resources suitable for cultivating Pistacia chinensis were identified with multiple datasets (natural habitat, remote sensing-derived land use, meteorological and soil data) and geoinformatic techniques. The results indicate that the area of marginal land exploitable for Pistacia chinensis plantations in China is 19.90 million hectares, which may produce approximately 56.85 million tons of biodiesel each year. The spatial variation of both marginal land resources and biodiesel potential are also presented. The results can be useful for national and regional bio-energy planning. Full article

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574 KiB

Open AccessArticle

Evaluation of Net Energy Obtainable from Combustion of Stabilised Olive Mill By-Products

by Antonio Messineo, Roberto Volpe and Francesco Asdrubali

Energies 2012, 5(5), 1384-1397; https://doi.org/10.3390/en5051384 - 11 May 2012

Cited by 34 | Viewed by 6583

Abstract

This work is aimed at calculating the energy content of the residues from olive oil production. Olive pulp, olive husk and sludge (a mixture of olive pulp and husk) have been analyzed separately. Olive Mill Effluents (OME) are normally a problem for olive [...] Read more.

This work is aimed at calculating the energy content of the residues from olive oil production. Olive pulp, olive husk and sludge (a mixture of olive pulp and husk) have been analyzed separately. Olive Mill Effluents (OME) are normally a problem for olive mill farms, yet they may be used as feedstock for biomass-fuelled power plants. Nonetheless, OMEs are characterized by a relatively high humidity content and are produced only during the olive season. Thus, OME need a stabilization process to be employed as a solid biofuel throughout the year. The analyses conducted attempt an evaluation of the energy consumption of a three-stage stabilization process: drying, milling and pelletising. The net electrical energy available from OME is then calculated as a difference between gross energy available and energy consumed for stabilization. The gross available electrical energy was calculated based on direct energy conversion of the stabilized feedstock on a small scale direct combustion and Organic Rankine Cycle (ORC) turbine. Results show that OME are suitable for energy production. Approximately 4500 kJ/kg of net electrical energy may be obtained out of olive sludge or olive pulp, while olive husk shows a potential gross energy of 3400 kJ/kg. Full article

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346 KiB

Open AccessArticle

Repeated-Batch Ethanol Production from Sweet Sorghum Juice by Saccharomyces cerevisiae Immobilized on Sweet Sorghum Stalks

by Pongthep Ariyajaroenwong, Pattana Laopaiboon, Prasit Jaisil and Lakkana Laopaiboon

Energies 2012, 5(4), 1215-1228; https://doi.org/10.3390/en5041215 - 23 Apr 2012

Cited by 45 | Viewed by 7723

Abstract

Sweet sorghum stalks were used as a low cost carrier for immobilization of Saccharomyces cerevisiae NP 01 to produce ethanol from sweet sorghum juice. The effects on ethanol production of carrier size (6 × 6 × 6 to 20 × 20 × 20 [...] Read more.

Sweet sorghum stalks were used as a low cost carrier for immobilization of Saccharomyces cerevisiae NP 01 to produce ethanol from sweet sorghum juice. The effects on ethanol production of carrier size (6 × 6 × 6 to 20 × 20 × 20 mm³) and initial cell concentrations (5 × 10⁷ to 2 × 10⁸ cells mL⁻¹) for cell immobilization were investigated. The ethanol production medium was the juice containing 230 g L⁻¹ of total sugar without nutrient supplementation. The fermentations were carried out under static conditions in 500-mL air-locked Erlenmeyer flasks at 30 °C. The results showed that the optimum size of sorghum stalk pieces for repeated-batch ethanol production was 6 × 6 × 6 mm³, while the optimum initial cell concentration for the immobilization was 1.0 × 10⁸ cells mL⁻¹. The immobilized yeast under these conditions could be used for at least eight successive batches without any losses of ethanol production efficiencies. The average ethanol concentration, productivity and yield of the eight successive batches were 99.28 ± 3.53 g L⁻¹, 1.36 ± 0.05 g L⁻¹ h⁻¹ and 0.47 ± 0.03 g g⁻¹, respectively. Full article

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648 KiB

Open AccessArticle

The Effects of Particle Size, Different Corn Stover Components, and Gas Residence Time on Torrefaction of Corn Stover

by Dorde Medic, Matthew Darr, Ajay Shah and Sarah Rahn

Energies 2012, 5(4), 1199-1214; https://doi.org/10.3390/en5041199 - 23 Apr 2012

Cited by 55 | Viewed by 10779

Abstract

Large scale biofuel production will be possible only if significant quantities of biomass feedstock can be stored, transported, and processed in an economic and sustainable manner. Torrefaction has the potential to significantly reduce the cost of transportation, storage, and downstream processing through the [...] Read more.

Large scale biofuel production will be possible only if significant quantities of biomass feedstock can be stored, transported, and processed in an economic and sustainable manner. Torrefaction has the potential to significantly reduce the cost of transportation, storage, and downstream processing through the improvement of physical and chemical characteristics of biomass. The main objective of this study was to investigate the effects of particle size, plant components, and gas residence time on the production of torrefied corn (Zea mays) stover. Different particle sizes included 0.85 mm and 20 mm. Different stover components included ground corn stover, whole corn stalk, stalk shell and pith, and corn cob shell. Three different purge gas residence times were employed to assess the effects of interaction of volatiles and torrefied biomass. Elemental analyses were performed on all of the samples, and the data obtained was used to estimate the energy contents and energy yields of different torrefied biomass samples. Particle density, elemental composition, and fiber composition of raw biomass fractions were also determined. Stalk pith torrefied at 280 °C and stalk shell torrefied at 250 °C had highest and lowest dry matter loss, of about 44% and 13%, respectively. Stalk pith torrefied at 250 °C had lowest energy density of about 18–18.5 MJ/kg, while cob shell torrefied at 280 °C had the highest energy density of about 21.5 MJ/kg. The lowest energy yield, at 59%, was recorded for stalk pith torrefied at 280 °C, whereas cob and stalk shell torrefied at 250 °C had highest energy yield at 85%. These differences were a consequence of the differences in particle densities, hemicellulose quantities, and chemical properties of the original biomass samples. Gas residence time did not have a significant effect on the aforementioned parameters. Full article

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443 KiB

Open AccessArticle

Supercritical Transesterification of Palm Oil and Hydrated Ethanol in a Fixed Bed Reactor with a CaO/Al₂O₃ Catalyst

by Ruengwit Sawangkeaw, Pornicha Tejvirat, Chawalit Ngamcharassrivichai and Somkiat Ngamprasertsith

Energies 2012, 5(4), 1062-1080; https://doi.org/10.3390/en5041062 - 19 Apr 2012

Cited by 18 | Viewed by 7853

Abstract

Biodiesel production from palm oil and hydrated ethanol in a fixed bed reactor using CaO/Al₂O₃ as the catalyst was investigated and optimized using response surface methodology. The investigated parameters were temperature, pressure, ethanol/palm oil molar ratio, residence time and total [...] Read more.

Biodiesel production from palm oil and hydrated ethanol in a fixed bed reactor using CaO/Al₂O₃ as the catalyst was investigated and optimized using response surface methodology. The investigated parameters were temperature, pressure, ethanol/palm oil molar ratio, residence time and total mass flow rate. The approach was divided into two parts, a preliminary study using broad scale changes over a reasonable range of the above operating parameters and then, using this data to select a narrower range, a finer scale study to optimize the selected narrower operating parameters from the preliminary study. The resultant biodiesel obtained under the optimal conditions (285 °C, 20 MPa, 30:1 ethanol/oil molar ratio, 2 g/min flow rate and 4.85 min residence time) was measured for 11 fuel properties following the International Biodiesel Standard (EN14214), and was found to comply with this International Standard. Moreover, ZnO/Al₂O₃ and La₂O₃/Al₂O₃ catalysts were tested for their activity and stability. Although the La₂O₃/Al₂O₃ catalyst had a slightly higher initial activity than that of CaO/Al₂O₃, it is some 800-fold more expensive. Therefore, the CaO/Al₂O₃ catalyst has a greater industrial potential than La₂O₃/Al₂O₃, when comparing together the technical and economic benefits. Full article

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2153 KiB

Open AccessArticle

Lubrication Properties of Bio-Oil and Its Emulsions with Diesel Oil

by Qiang Lu, Zhi-Bo Zhang, Hang-Tao Liao, Xiao-Chu Yang and Chang-Qing Dong

Energies 2012, 5(3), 741-751; https://doi.org/10.3390/en5030741 - 14 Mar 2012

Cited by 24 | Viewed by 8003

Abstract

Bio-oil from fast pyrolysis of biomass is a low-grade liquid fuel, which can be upgraded through the emulsification with diesel oil. In this study, we prepared two rice husk bio-oil samples with different solid char contents and three bio-oil/diesel-oil emulsion samples with the [...] Read more.

Bio-oil from fast pyrolysis of biomass is a low-grade liquid fuel, which can be upgraded through the emulsification with diesel oil. In this study, we prepared two rice husk bio-oil samples with different solid char contents and three bio-oil/diesel-oil emulsion samples with the bio-oil content of 10 wt%, 30 wt% and 50 wt%, respectively. The lubrication properties of these oil samples were evaluated by a four-ball tester. The morphologies of the worn ball surface were observed by scanning electron microscope (SEM). The chemical states of the elements on the worn surface and non-worn surface were analyzed by X-ray photoelectron spectroscope (XPS). The results showed that the bio-oil possessed better extreme-pressure, anti-wear and friction-reducing properties than the commercial diesel oil (number zero). The solid char particles in the bio-oil could improve its lubrication performance. Moreover, the lubrication ability of the emulsions would be enhanced with the increasing of the bio-oil content in the emulsions. Full article

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2011

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258 KiB

Open AccessArticle

Experimental Research on Heterogeneous N₂O Decomposition with Ash and Biomass Gasification Gas

by Junjiao Zhang, Yongping Yang, Xiaoying Hu, Changqing Dong, Qiang Lu and Wu Qin

Energies 2011, 4(11), 2027-2037; https://doi.org/10.3390/en4112027 - 21 Nov 2011

Cited by 7 | Viewed by 7046

Abstract

In this paper, the promoting effects of ash and biomass gas reburning on N₂O decomposition were investigated based on a fluidized bed reactor, with the assessment of the influence of O₂ on N₂O decomposition with circulating ashes. Experimental [...] Read more.

In this paper, the promoting effects of ash and biomass gas reburning on N₂O decomposition were investigated based on a fluidized bed reactor, with the assessment of the influence of O₂ on N₂O decomposition with circulating ashes. Experimental results show that different metal oxides contained in ash play distinct roles in the process of N₂O decomposition with biomass gas reburning. Compared with other components in ash, CaO is proven to be very active and has the greatest promoting impact on N₂O decomposition. It is also found that O₂, even in small amounts, can weaken the promoting effect of ash on N₂O decomposition by using biomass gas reburning. Full article

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181 KiB

Open AccessArticle

Outdoor Storage Characteristics of Single-Pass Large Square Corn Stover Bales in Iowa

by Ajay Shah, Matthew J. Darr, Keith Webster and Christopher Hoffman

Energies 2011, 4(10), 1687-1695; https://doi.org/10.3390/en4101687 - 21 Oct 2011

Cited by 34 | Viewed by 6678

Abstract

Year-round operation of biorefineries can be possible only if the continuous flow of cellulosic biomass is guaranteed. If corn (Zea mays) stover is the primary cellulosic biomass, it is essential to recognize that this feedstock has a short annual harvest window [...] Read more.

Year-round operation of biorefineries can be possible only if the continuous flow of cellulosic biomass is guaranteed. If corn (Zea mays) stover is the primary cellulosic biomass, it is essential to recognize that this feedstock has a short annual harvest window (≤1–2 months) and therefore cost effective storage techniques that preserve feedstock quality must be identified. This study evaluated two outdoor and one indoor storage strategies for corn stover bales in Iowa. High- and low-moisture stover bales were prepared in the fall of 2009, and stored either outdoors with two different types of cover (tarp and breathable film) or within a building for 3 or 9 months. Dry matter loss (DML), changes in moisture and biomass compositions (fiber and ultimate analyses) were determined. DML for bales stored outdoor with tarp and breathable film covers were in the ranges of 5–11 and 14–17%, respectively. More than half of the total DML occurred early during the storage. There were measurable differences in carbon, hydrogen, nitrogen, sulfur, oxygen, cellulose, hemi-cellulose and acid detergent lignin for the different storage treatments, but the changes were small and within a narrow range. For the bale storage treatments investigated, cellulose content increased by as much as 4%s from an initial level of ~41%, hemicellulose content changed by −2 to 1% from ~34%, and acid detergent lignin contents increased by as much as 3% from an initial value of ~5%. Tarp covered bales stored the best in this study, but other methods, such as tube-wrapping, and economics need further investigation. Full article

386 KiB

Open AccessReview

Available Resources for Algal Biofuel Development in China

by Shuhao Huo, Renjie Dong, Zhongming Wang, Changle Pang, Zhenhong Yuan, Shunni Zhu and Li Chen

Energies 2011, 4(9), 1321-1335; https://doi.org/10.3390/en4091321 - 31 Aug 2011

Cited by 22 | Viewed by 11672

Abstract

Microalgal biofuel research in China has made noticeable progress, and algae cultivation for biofuel production is considered to be an important contribution to Greenhouse Gas (GHG) mitigation and energy security. In this paper, the algal biofuel potentiality in China was reviewed from the [...] Read more.

Microalgal biofuel research in China has made noticeable progress, and algae cultivation for biofuel production is considered to be an important contribution to Greenhouse Gas (GHG) mitigation and energy security. In this paper, the algal biofuel potentiality in China was reviewed from the points of view of algal biodiversity, algal culture collection, GHGs (especially CO₂) mitigation, and the availability of the required sunlight, wastewater and land resources. The cultivation of microalgae utilizing power plants gas with large amounts of CO₂ and wastewaters from urban households, industry and animal husbandry are suitable for large scale production in China. Land is hardly a limitation for algae cultivation. Full article

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892 KiB

Open AccessArticle

Removal and Conversion of Tar in Syngas from Woody Biomass Gasification for Power Utilization Using Catalytic Hydrocracking

by Jiu Huang, Klaus Gerhard Schmidt and Zhengfu Bian

Energies 2011, 4(8), 1163-1177; https://doi.org/10.3390/en4081163 - 12 Aug 2011

Cited by 37 | Viewed by 9364

Abstract

Biomass gasification has yet to obtain industrial acceptance. The high residual tar concentrations in syngas prevent any ambitious utilization. In this paper a novel gas purification technology based on catalytic hydrocracking is introduced, whereby most of the tarry components can be converted and [...] Read more.

Biomass gasification has yet to obtain industrial acceptance. The high residual tar concentrations in syngas prevent any ambitious utilization. In this paper a novel gas purification technology based on catalytic hydrocracking is introduced, whereby most of the tarry components can be converted and removed. Pilot scale experiments were carried out with an updraft gasifier. The hydrocracking catalyst was palladium (Pd). The results show the dominant role of temperature and flow rate. At a constant flow rate of 20 Nm³/h and temperatures of 500 °C, 600 °C and 700 °C the tar conversion rates reached 44.9%, 78.1% and 92.3%, respectively. These results could be increased up to 98.6% and 99.3% by using an operating temperature of 700 °C and lower flow rates of 15 Nm³/h and 10 Nm³/h. The syngas quality after the purification process at 700 °C/10 Nm³/h is acceptable for inner combustion (IC) gas engine utilization. Full article

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286 KiB

Open AccessArticle

Combustion of Corn Stover Bales in a Small 146-kW Boiler

by René Morissette, Philippe Savoie and Joey Villeneuve

Energies 2011, 4(7), 1102-1111; https://doi.org/10.3390/en4071102 - 22 Jul 2011

Cited by 27 | Viewed by 9563

Abstract

Spring harvested corn stover was used for direct combustion in a 146 kW dual chamber boiler designed for wood logs. Stover had a very low moisture content (6.83 ± 0.17%), a gross calorific value (GCV) of 18.57 MJ/kg of dry matter (±0.32 MJ/kg [...] Read more.

Spring harvested corn stover was used for direct combustion in a 146 kW dual chamber boiler designed for wood logs. Stover had a very low moisture content (6.83 ± 0.17%), a gross calorific value (GCV) of 18.57 MJ/kg of dry matter (±0.32 MJ/kg DM) and an ash content of 5.88% (±1.15%). Small stover bales (8.83 ± 0.90 kg) were placed manually in the upper combustion chamber at a rate of 10.5 to 12.8 kg/h over a 24-h period, with three replications, and compared to a control wood combustion trial (12.1 kg/h during 24 h). The overall heat transfer efficiency for stover was lower than for wood (57% vs. 77%). Stover bales produced on average 7.5% ash which included about 2% of unburned residues while wood produced 1.7% ash. CO gas emissions averaged 1324 mg/m³ for stover (118 mg/m³ for wood). The corn stover showed a good calorific potential, but it would have to be densified and the boiler should be modified to improve airflow, completeness of combustion and handling of the large amount of ash formed. Full article

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312 KiB

Open AccessCommunication

Time to Substitute Wood Bioenergy for Nuclear Power in Japan

by Nophea Sasaki, Toshiaki Owari and Francis E. Putz

Energies 2011, 4(7), 1051-1057; https://doi.org/10.3390/en4071051 - 6 Jul 2011

Cited by 8 | Viewed by 10069

Abstract

Damage to the Fukushima Nuclear Power Plant by the recent earthquake and tsunami that hit northern Japan should stimulate consideration of alternative sources of energy. In particular, if managed appropriately, the 25.1 million ha of Japanese forests could be an important source of [...] Read more.

Damage to the Fukushima Nuclear Power Plant by the recent earthquake and tsunami that hit northern Japan should stimulate consideration of alternative sources of energy. In particular, if managed appropriately, the 25.1 million ha of Japanese forests could be an important source of wood biomass for bioenergy production. Here, we discuss policy incentives for substituting wood bioenergy for nuclear power, thereby creating a safer society while better managing the forest resources in Japan. Full article

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559 KiB

Open AccessReview

Environmental Impacts and Costs of Hydrotreated Vegetable Oils, Transesterified Lipids and Woody BTL—A Review

by Kathrin Sunde, Andreas Brekke and Birger Solberg

Energies 2011, 4(6), 845-877; https://doi.org/10.3390/en4060845 - 25 May 2011

Cited by 58 | Viewed by 15972

Abstract

This article reviews and compares assessments of three biodiesel fuels: (1) transesterified lipids, (2) hydrotreated vegetable oils (HVO), and (3) woody biomass-to-liquid (BTL) Fischer-Tropsch diesel and selected feedstock options. The article attempts to rank the environmental performance and costs of fuel and feedstock [...] Read more.

This article reviews and compares assessments of three biodiesel fuels: (1) transesterified lipids, (2) hydrotreated vegetable oils (HVO), and (3) woody biomass-to-liquid (BTL) Fischer-Tropsch diesel and selected feedstock options. The article attempts to rank the environmental performance and costs of fuel and feedstock combinations. Due to inter-study differences in goal and study assumptions, the ranking was mostly qualitative and intra-study results are emphasized. Results indicate that HVO made from wastes or by-products such as tall oil, tallow or used cooking oil outperform transesterified lipids and BTL from woody material, both with respect to environmental life cycle impacts and costs. These feedstock options are, however, of limited availability, and to produce larger volumes of biofuels other raw materials must also be used. BTL from woody biomass seems promising with good environmental performance and the ability not to compete with food production. Production of biofuels from agricultural feedstock sources requires much energy and leads to considerable emissions due to agrochemical inputs. Thus, such biodiesel fuels are ranked lowest in this comparison. Production of feedstock is the most important life cycle stage. Avoiding detrimental land use changes and maintaining good agricultural or forestry management practices are the main challenges to ensure that biofuels can be a sustainable option for the future transport sector. Full article

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276 KiB

Open AccessArticle

Selective Preparation of Furfural from Xylose over Sulfonic Acid Functionalized Mesoporous Sba-15 Materials

by Xuejun Shi, Yulong Wu, Huaifeng Yi, Guo Rui, Panpan Li, Mingde Yang and Gehua Wang

Energies 2011, 4(4), 669-684; https://doi.org/10.3390/en4040669 - 20 Apr 2011

Cited by 101 | Viewed by 11234

Abstract

Sulfonic acid functionalized mesoporous SBA-15 materials were prepared using the co-condensation and grafting methods, respectively, and their catalytic performance in the dehydration of xylose to furfural was examined. SBA-15-SO₃H(C) prepared by the co-condensation method showed 92–95% xylose conversion and 74% furfural [...] Read more.

Sulfonic acid functionalized mesoporous SBA-15 materials were prepared using the co-condensation and grafting methods, respectively, and their catalytic performance in the dehydration of xylose to furfural was examined. SBA-15-SO₃H(C) prepared by the co-condensation method showed 92–95% xylose conversion and 74% furfural selectivity, and 68–70% furfural yield under the given reaction conditions. The deactivation and regeneration of the SBA-15-SO₃H(C) catalyst for the dehydration of xylose was also investigated. The results indicate that the used and regeneration catalysts retained the SBA-15 mesoporous structure, and the S content of SBA-15-SO₃H(C) almost did not change. The deactivation of the catalysts is proposed to be associated with the accumulation of byproducts, which is caused by the loss reaction of furfural. After regeneration by H₂O₂, the catalytic activity of the catalyst almost recovered. Full article

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