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Special Issue "Biomass and Biofuels 2012"

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (30 May 2012)

Special Issue Editor

Guest Editor
Prof. Dr. Thomas E. Amidon (Website)

Department of Paper and Bioprocess Engineering, College of Environmental Science and Forestry, State University of New York, 1 Forestry Drive, Syracuse, NY 13210, USA
Interests: biorefineries; biofuels; bioenergy; bio-based materials and chemicals; nanocellulose; pulp and paper; pellets; forest and biomass resources; process development; novel bio-based products; cell wall deconstruction; hot water extraction; cellulosic bioproducts; improved fiber based products; biomass productivity

Special Issue Information

Dear Colleagues,

We would like to see articles in the intellectual space from raw materials (any form of biomass), to extraction and separation into components, to conversion of intermediates into final products. The products do not have to be biofuels if the products are renewable in origin and substitute for fossil fuel derived products. Engineering work applicable to any of the component operations are also appreciated. We would also be interested in articles showing that more sophistication in product development could lead to greater returns.  An example here might be furfural production from xylose as a more valuable product than fermentation of xylose to ethanol as well as showing that this might be an energetically preferable way to produce furfural.

Prof. Dr. Thomas E. Amidon
Guest Editor

Keywords

  • biomass
  • biofuels
  • biorefinery
  • extraction
  • component separation
  • conversion
  • novel biobased products
  • biorefinery engineering
  • biomass and biorefinery policy
  • fossil fuel substitution

Related Special Issue

Published Papers (20 papers)

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Research

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Open AccessArticle A Novel Miniature Culture System to Screen CO2-Sequestering Microalgae
Energies 2012, 5(11), 4372-4389; doi:10.3390/en5114372
Received: 1 September 2012 / Revised: 23 October 2012 / Accepted: 23 October 2012 / Published: 1 November 2012
Cited by 5 | PDF Full-text (627 KB) | HTML Full-text | XML Full-text
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 g L−1 d−1), residual [...] 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 g L−1 d−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 g L−1 d−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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Some Chemical Compositional Changes in Miscanthus and White Oak Sawdust Samples during Torrefaction
Energies 2012, 5(10), 3928-3947; doi:10.3390/en5103928
Received: 13 July 2012 / Accepted: 19 September 2012 / Published: 16 October 2012
Cited by 6 | PDF Full-text (1137 KB) | HTML Full-text | XML Full-text
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 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Study of Pea Accessions for Development of an Oilseed Pea
Energies 2012, 5(10), 3788-3802; doi:10.3390/en5103788
Received: 25 August 2012 / Revised: 7 September 2012 / Accepted: 14 September 2012 / Published: 27 September 2012
Cited by 3 | PDF Full-text (247 KB) | HTML Full-text | XML Full-text
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, [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Energy from Agricultural and Animal Farming Residues: Potential at a Local Scale
Energies 2012, 5(9), 3198-3217; doi:10.3390/en5093198
Received: 31 May 2012 / Revised: 11 August 2012 / Accepted: 16 August 2012 / Published: 28 August 2012
Cited by 5 | PDF Full-text (3014 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
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Open AccessArticle Research on the Gas Reburning in a Circulating Fluidized Bed (CFB) System Integrated with Biomass Gasification
Energies 2012, 5(9), 3167-3177; doi:10.3390/en5093167
Received: 12 June 2012 / Revised: 24 July 2012 / Accepted: 3 August 2012 / Published: 24 August 2012
Cited by 1 | PDF Full-text (677 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Optimization of Nitrogen and Metal Ions Supplementation for Very High Gravity Bioethanol Fermentation from Sweet Sorghum Juice Using an Orthogonal Array Design
Energies 2012, 5(9), 3178-3197; doi:10.3390/en5093178
Received: 25 June 2012 / Revised: 1 August 2012 / Accepted: 17 August 2012 / Published: 24 August 2012
Cited by 8 | PDF Full-text (353 KB) | HTML Full-text | XML Full-text
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 (Yp/s) and productivity (Qp) 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, Yp/s and Qp 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
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Open AccessArticle The Long-Term Prospects of Biofuels in the EU-15 Countries
Energies 2012, 5(8), 3110-3125; doi:10.3390/en5083110
Received: 18 June 2012 / Revised: 9 August 2012 / Accepted: 13 August 2012 / Published: 17 August 2012
PDF Full-text (272 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle A Complementary Biodiesel Blend from Soapnut Oil and Free Fatty Acids
Energies 2012, 5(8), 3137-3148; doi:10.3390/en5083137
Received: 29 June 2012 / Revised: 24 July 2012 / Accepted: 16 August 2012 / Published: 17 August 2012
Cited by 2 | PDF Full-text (286 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Gamma Irradiation Induced Degradation of Orange Peels
Energies 2012, 5(8), 3051-3063; doi:10.3390/en5083051
Received: 8 June 2012 / Revised: 21 July 2012 / Accepted: 1 August 2012 / Published: 14 August 2012
Cited by 6 | PDF Full-text (465 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Continuous Fermentation of Clostridium tyrobutyricum with Partial Cell Recycle as a Long-Term Strategy for Butyric Acid Production
Energies 2012, 5(8), 2835-2848; doi:10.3390/en5082835
Received: 6 June 2012 / Revised: 16 July 2012 / Accepted: 26 July 2012 / Published: 2 August 2012
Cited by 11 | PDF Full-text (321 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Deacidification of Pistacia chinensis Oil as a Promising Non-Edible Feedstock for Biodiesel Production in China
Energies 2012, 5(8), 2759-2770; doi:10.3390/en5082759
Received: 1 March 2012 / Revised: 29 June 2012 / Accepted: 20 July 2012 / Published: 31 July 2012
Cited by 4 | PDF Full-text (224 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Fuel Characteristics of Biodiesel Produced from a High-Acid Oil from Soybean Soapstock by Supercritical-Methanol Transesterification
Energies 2012, 5(7), 2370-2380; doi:10.3390/en5072370
Received: 29 May 2012 / Revised: 19 June 2012 / Accepted: 29 June 2012 / Published: 9 July 2012
Cited by 6 | PDF Full-text (370 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Evaluating the Marginal Land Resources Suitable for Developing Pistacia chinensis-Based Biodiesel in China
Energies 2012, 5(7), 2165-2177; doi:10.3390/en5072165
Received: 29 April 2012 / Revised: 14 June 2012 / Accepted: 26 June 2012 / Published: 29 June 2012
Cited by 11 | PDF Full-text (498 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Evaluation of Net Energy Obtainable from Combustion of Stabilised Olive Mill By-Products
Energies 2012, 5(5), 1384-1397; doi:10.3390/en5051384
Received: 22 March 2012 / Revised: 23 April 2012 / Accepted: 10 May 2012 / Published: 11 May 2012
Cited by 15 | PDF Full-text (574 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
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Open AccessArticle The Effects of Particle Size, Different Corn Stover Components, and Gas Residence Time on Torrefaction of Corn Stover
Energies 2012, 5(4), 1199-1214; doi:10.3390/en5041199
Received: 20 February 2012 / Revised: 31 March 2012 / Accepted: 17 April 2012 / Published: 23 April 2012
Cited by 20 | PDF Full-text (648 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Repeated-Batch Ethanol Production from Sweet Sorghum Juice by Saccharomyces cerevisiae Immobilized on Sweet Sorghum Stalks
Energies 2012, 5(4), 1215-1228; doi:10.3390/en5041215
Received: 4 January 2012 / Revised: 5 April 2012 / Accepted: 12 April 2012 / Published: 23 April 2012
Cited by 13 | PDF Full-text (346 KB) | HTML Full-text | XML Full-text
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 × [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessArticle Supercritical Transesterification of Palm Oil and Hydrated Ethanol in a Fixed Bed Reactor with a CaO/Al2O3 Catalyst
Energies 2012, 5(4), 1062-1080; doi:10.3390/en5041062
Received: 11 January 2012 / Revised: 2 April 2012 / Accepted: 6 April 2012 / Published: 19 April 2012
Cited by 3 | PDF Full-text (443 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
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Open AccessArticle Lubrication Properties of Bio-Oil and Its Emulsions with Diesel Oil
Energies 2012, 5(3), 741-751; doi:10.3390/en5030741
Received: 23 January 2012 / Revised: 4 March 2012 / Accepted: 6 March 2012 / Published: 14 March 2012
Cited by 5 | PDF Full-text (2153 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)

Review

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Open AccessReview Biofuels Production through Biomass Pyrolysis —A Technological Review
Energies 2012, 5(12), 4952-5001; doi:10.3390/en5124952
Received: 10 October 2012 / Revised: 13 November 2012 / Accepted: 14 November 2012 / Published: 23 November 2012
Cited by 77 | PDF Full-text (864 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)
Open AccessReview Biotechnological Utilization with a Focus on Anaerobic Treatment of Cheese Whey: Current Status and Prospects
Energies 2012, 5(9), 3492-3525; doi:10.3390/en5093492
Received: 30 May 2012 / Revised: 9 August 2012 / Accepted: 5 September 2012 / Published: 10 September 2012
Cited by 12 | PDF Full-text (537 KB) | HTML Full-text | XML Full-text
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 [...] 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
(This article belongs to the Special Issue Biomass and Biofuels 2012)

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