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Special Issue "Renewable Energy for Agriculture"

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

Deadline for manuscript submissions: closed (15 May 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Talal Yusaf

Executive Director USQ International and Development; University of Southern Queensland, Toowoomba, Queensland 4350, Australia
Website | E-Mail
Fax: +61 7 4631 2526
Interests: renewable energy; biofuel; bioenergy; water treatment; microalgae; IC engines and emissions; biogas applications; energy recovery

Special Issue Information

Dear Colleagues,

The diminishing supply of conventional energy reserves and the growing environmental concerns have made renewable energy an attractive source for the future. Thus this Special Issue would also address the current and future issues of Renewable Energy in agricultural sectors. We wish to invite researchers in the area of Renewable Energy for Agriculture to submit their contribution to our Special Issue of Renewable Energy for Agricultural sectors. We are interested in articles related to renewable energy resources (solar, wind, biomass, hydraulic, algae, water, hydrogen), bioenergy from agriculture, biomass production and energy recovery in agriculture. Energy is the main input of the agricultural industry and technology.

Prof. Dr. Talal Yusaf
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs).

Keywords

  • solar
  • wind
  • biomass from agriculture
  • hydraulic pumps
  • tractor
  • water pumps
  • harvesting
  • biomass productivity
  • renewable energy policy/issues
  • raw fuel substitution

Published Papers (12 papers)

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Research

Open AccessArticle Impacts of the CAP 2014–2020 on the Agroenergy Sector in Tuscany, Italy
Energies 2015, 8(2), 1058-1079; doi:10.3390/en8021058
Received: 26 August 2014 / Revised: 18 November 2014 / Accepted: 20 January 2015 / Published: 2 February 2015
Cited by 3 | PDF Full-text (242 KB) | HTML Full-text | XML Full-text
Abstract
The agricultural sectors’ contribution to the provision of energy is a central issue in Horizon 2020 strategies and has shaped the public and research debates on the future of the bioeconomy. The common agricultural policy (CAP) has been one of the main drivers
[...] Read more.
The agricultural sectors’ contribution to the provision of energy is a central issue in Horizon 2020 strategies and has shaped the public and research debates on the future of the bioeconomy. The common agricultural policy (CAP) has been one of the main drivers of farmers’ behavioural changes and represents the main agricultural policy instrument to address viability of rural areas and maintaining the profitability of the agricultural sector. To contribute to the ongoing policy debate towards CAP reform, this paper will provide an empirical model to simulate the impact of an alternative CAP mechanism on the provision of renewable energy. By applying a dynamic mathematical programming model, the paper tests the impact new policy measures will have on the provision of a second-generation of bio fuel crops that represent a relevant option for Tuscan farmers. Results show that CAP reform positively impacts the supply of energy crops mainly due to the introduction of greening payments, which allows an enlarging of crop diversification. Model results stress also the income stabilisation effects of energy production introduction at farm level, due to reduction of farm exposure to market prices fluctuations. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Opportunities for Energy Crop Production Based on Subfield Scale Distribution of Profitability
Energies 2014, 7(10), 6509-6526; doi:10.3390/en7106509
Received: 14 May 2014 / Revised: 19 September 2014 / Accepted: 29 September 2014 / Published: 13 October 2014
Cited by 9 | PDF Full-text (1795 KB) | HTML Full-text | XML Full-text
Abstract
Incorporation of dedicated herbaceous energy crops into row crop landscapes is a promising means to supply an expanding biofuel industry while benefiting soil and water quality and increasing biodiversity. Despite these positive traits, energy crops remain largely unaccepted due to concerns over their
[...] Read more.
Incorporation of dedicated herbaceous energy crops into row crop landscapes is a promising means to supply an expanding biofuel industry while benefiting soil and water quality and increasing biodiversity. Despite these positive traits, energy crops remain largely unaccepted due to concerns over their practicality and cost of implementation. This paper presents a case study for Hardin County, Iowa, to demonstrate how subfield decision making can be used to target candidate areas for conversion to energy crop production. Estimates of variability in row crop production at a subfield level are used to model the economic performance of corn (Zea mays L.) grain and the environmental impacts of corn stover collection using the Landscape Environmental Analysis Framework (LEAF). The strategy used in the case study integrates switchgrass (Panicum virgatum L.) into subfield landscape positions where corn grain is modeled to return a net economic loss. Results show that switchgrass integration has the potential to increase sustainable biomass production from 48% to 99% (depending on the rigor of conservation practices applied to corn stover collection), while also improving field level profitability of corn. Candidate land area is highly sensitive to grain price (0.18 to 0.26 $·kg−1) and dependent on the acceptable subfield net loss for corn production (ranging from 0 to −1000 $·ha−1) and the ability of switchgrass production to meet or exceed this return. This work presents the case that switchgrass may be economically incorporated into row crop landscapes when management decisions are applied at a subfield scale within field areas modeled to have a negative net profit with current management practices. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle LCA Study of Oleaginous Bioenergy Chains in a Mediterranean Environment
Energies 2014, 7(10), 6258-6281; doi:10.3390/en7106258
Received: 15 May 2014 / Revised: 8 September 2014 / Accepted: 23 September 2014 / Published: 29 September 2014
Cited by 4 | PDF Full-text (867 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports outcomes of life cycle assessments (LCAs) of three different oleaginous bioenergy chains (oilseed rape, Ethiopian mustard and cardoon) under Southern Europe conditions. Accurate data on field practices previously collected during a three-year study at two sites were used. The vegetable
[...] Read more.
This paper reports outcomes of life cycle assessments (LCAs) of three different oleaginous bioenergy chains (oilseed rape, Ethiopian mustard and cardoon) under Southern Europe conditions. Accurate data on field practices previously collected during a three-year study at two sites were used. The vegetable oil produced by oleaginous seeds was used for power generation in medium-speed diesel engines while the crop residues were used in steam power plants. For each bioenergy chain, the environmental impact related to cultivation, transportation of agricultural products and industrial conversion for power generation was evaluated by calculating cumulative energy demand, acidification potential and global warming potential. For all three bioenergy chains, the results of the LCA study show a considerable saving of primary energy (from 70 to 86 GJ·ha−1) and greenhouse gas emissions (from 4.1 to 5.2 t CO2·ha−1) in comparison to power generation from fossil fuels, although the acidification potential of these bioenergy chains may be twice that of conventional power generation. In addition, the study highlights that land use changes due to the cultivation of the abovementioned crops reduce soil organic content and therefore worsen and increase greenhouse gas emissions for all three bioenergy chains. The study also demonstrates that the exploitation of crop residues for energy production greatly contributes to managing environmental impact of the three bioenergy chains. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle The Potential and Utilization of Unused Energy Sources for Large-Scale Horticulture Facility Applications under Korean Climatic Conditions
Energies 2014, 7(8), 4781-4801; doi:10.3390/en7084781
Received: 7 May 2014 / Revised: 12 June 2014 / Accepted: 16 July 2014 / Published: 24 July 2014
Cited by 8 | PDF Full-text (1282 KB) | HTML Full-text | XML Full-text
Abstract
As the use of fossil fuel has increased, not only in construction, but also in agriculture due to the drastic industrial development in recent times, the problems of heating costs and global warming are getting worse. Therefore, introduction of more reliable and environmentally-friendly
[...] Read more.
As the use of fossil fuel has increased, not only in construction, but also in agriculture due to the drastic industrial development in recent times, the problems of heating costs and global warming are getting worse. Therefore, introduction of more reliable and environmentally-friendly alternative energy sources has become urgent and the same trend is found in large-scale horticulture facilities. In this study, among many alternative energy sources, we investigated the reserves and the potential of various different unused energy sources which have infinite potential, but are nowadays wasted due to limitations in their utilization. In addition, we utilized available unused energy as a heat source for a heat pump in a large-scale horticulture facility and analyzed its feasibility through EnergyPlus simulation modeling. Accordingly, the discharge flow rate from the Fan Coil Unit (FCU) in the horticulture facility, the discharge air temperature, and the return temperature were analyzed. The performance and heat consumption of each heat source were compared with those of conventional boilers. The result showed that the power load of the heat pump was decreased and thus the heat efficiency was increased as the temperature of the heat source was increased. Among the analyzed heat sources, power plant waste heat which had the highest heat source temperature consumed the least electric energy and showed the highest efficiency. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Influence of Chemical Blends on Palm Oil Methyl Esters’ Cold Flow Properties and Fuel Characteristics
Energies 2014, 7(7), 4364-4380; doi:10.3390/en7074364
Received: 25 February 2014 / Revised: 28 June 2014 / Accepted: 2 July 2014 / Published: 8 July 2014
Cited by 11 | PDF Full-text (716 KB) | HTML Full-text | XML Full-text
Abstract
Alternative fuels, like biodiesel, are being utilized as a renewable energy source and an effective substitute for the continuously depleting supply of mineral diesel as they have similar combustion characteristics. However, the use of pure biodiesel as a fuel for diesel engines is
[...] Read more.
Alternative fuels, like biodiesel, are being utilized as a renewable energy source and an effective substitute for the continuously depleting supply of mineral diesel as they have similar combustion characteristics. However, the use of pure biodiesel as a fuel for diesel engines is currently limited due to problems relating to fuel properties and its relatively poor cold flow characteristics. Therefore, the most acceptable option for improving the properties of biodiesel is the use of a fuel additive. In the present study, the properties of palm oil methyl esters with increasing additive content were investigated after addition of ethanol, butanol and diethyl ether. The results revealed varying improvement in acid value, density, viscosity, pour point and cloud point, accompanied by a slight decrease in energy content with an increasing additive ratio. The viscosity reductions at 5% additive were 12%, 7%, 16.5% for ethanol, butanol and diethyl ether, respectively, and the maximum reduction in pour point was 5 °C at 5% diethyl ether blend. Engine test results revealed a noticeable improvement in engine brake power and specific fuel consumption compared to palm oil biodiesel and the best performance was obtained with diethyl ether. All the biodiesel-additive blend samples meet the requirements of ASTM D6751 biodiesel fuel standards for the measured properties. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Effect of Aqueous Ammonia Soaking on the Methane Yield and Composition of Digested Manure Fibers Applying Different Ammonia Concentrations and Treatment Durations
Energies 2014, 7(7), 4157-4168; doi:10.3390/en7074157
Received: 12 May 2014 / Revised: 19 June 2014 / Accepted: 20 June 2014 / Published: 30 June 2014
Cited by 3 | PDF Full-text (474 KB) | HTML Full-text | XML Full-text
Abstract
The continuously increasing demand for renewable energy sources renders anaerobic digestion one of the most promising technologies for renewable energy production. Due to the animal production intensification, manure is being used as the primary feedstock for most biogas plants. Thus, their economical profitable
[...] Read more.
The continuously increasing demand for renewable energy sources renders anaerobic digestion one of the most promising technologies for renewable energy production. Due to the animal production intensification, manure is being used as the primary feedstock for most biogas plants. Thus, their economical profitable operation relies on increasing the methane yield from manure, and especially of its solid fraction which is not so easily degradable. In the present study, aqueous ammonia soaking (AAS) at six different concentrations in ammonia (5%, 10%, 15%, 20%, 25% and 32%) and for 1, 3 and 5 days at 22 °C was applied on digested fibers separated from the effluent of a manure-fed, full-scale anaerobic digester. A methane yield increase from 76% to 104% was achieved during the first series of experiments, while the difference in reagent concentration did not considerably affect the methane yield. It was shown that the optimal duration was three days for both 5% and 25% w/w reagent concentrations in ammonia tested. Carbohydrates and phosphorus content remained unaffected, while a slight decrease in Klason lignin and non-soluble organic nitrogen content was observed after AAS. It is concluded that AAS is a very promising treatment resulting to an overall increase of the methane yield of digested manure fibers from 76% to 265% depending on the conditions and the batch of digested fibers used (an even higher increase of 190%–265% was achieved during the 2nd series of experiments, where different AAS durations were tested, compared to the 1st series were different ammonia concentrations were applied). Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Investigation of Process Variables in the Densification of Corn Stover Briquettes
Energies 2014, 7(6), 4019-4032; doi:10.3390/en7064019
Received: 27 March 2014 / Revised: 6 June 2014 / Accepted: 17 June 2014 / Published: 24 June 2014
Cited by 2 | PDF Full-text (1237 KB) | HTML Full-text | XML Full-text
Abstract
The bulk density of raw corn stover is a major limitation to its large-scale viability as a biomass feedstock. Raw corn stover has a bulk density of 50 kg/m3, which creates significant transportation costs and limits the optimization of transport logistics.
[...] Read more.
The bulk density of raw corn stover is a major limitation to its large-scale viability as a biomass feedstock. Raw corn stover has a bulk density of 50 kg/m3, which creates significant transportation costs and limits the optimization of transport logistics. Producing a densified corn stover product during harvest would reduce harvest and transportation costs, resulting in viable pathways for the use of corn stover as a biomass feedstock. This research investigated the effect of different process variables (compression pressure, moisture content, particle size, and material composition) on a densification method that produces briquettes from raw corn stover. A customized bench-scale densification system was designed to evaluate different corn stover inputs. Quality briquette production was possible using non-reduced particle sizes and low compression pressures achievable in a continuous in-field production system. At optimized bench settings, corn stover was densified to a dry bulk density of 190 kg/m3. Corn stover with a moisture content above 25%wb was not suitable for this method of bulk densification, and greater cob content had a positive effect on product quality. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Batch Growth of Chlorella Vulgaris CCALA 896 versus Semi-Continuous Regimen for Enhancing Oil-Rich Biomass Productivity
Energies 2014, 7(6), 3840-3857; doi:10.3390/en7063840
Received: 10 March 2014 / Revised: 7 May 2014 / Accepted: 11 June 2014 / Published: 19 June 2014
Cited by 4 | PDF Full-text (1090 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study was to induce lipid accumulation in Chlorella cells by creating stressful growth conditions. Chlorella vulgaris CCALA 896 was grown under various batch growth modes in basal and modified BG-11 and Kolkwitz culture broths, using a continuous light regimen
[...] Read more.
The aim of this study was to induce lipid accumulation in Chlorella cells by creating stressful growth conditions. Chlorella vulgaris CCALA 896 was grown under various batch growth modes in basal and modified BG-11 and Kolkwitz culture broths, using a continuous light regimen of 150 µE/m2/s, at 30 °C. In order to perform the experiments, two indoor photobioreactor shapes were used: a cylindrical glass photobioreactor (CGPBR) with a working volume of 350 mL, and a flat glass photobioreactor (FGPBR) with a working volume of 550 mL. Stress-eliciting conditions, such as nitrogen and phosphorous starvation, were imposed in order to induce lipid accumulation. The results demonstrated that more than 56% of the lipids can be accumulated in Chlorella biomass grown under two-phase batch growth conditions. The highest biomass productivity of 0.30 g/L/d was obtained at the highest nominal dilution rate (0.167 day−1) during a semi-continuous regimen, using a modified Kolkwitz medium. During the pH-stress cycles, the amount of lipids did not increase significantly and a flocculation of Chlorella cells was noted. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Statistical Diagnosis of the Best Weibull Methods for Wind Power Assessment for Agricultural Applications
Energies 2014, 7(5), 3056-3085; doi:10.3390/en7053056
Received: 20 February 2014 / Revised: 22 April 2014 / Accepted: 23 April 2014 / Published: 2 May 2014
Cited by 15 | PDF Full-text (588 KB) | HTML Full-text | XML Full-text
Abstract
The best Weibull distribution methods for the assessment of wind energy potential at different altitudes in desired locations are statistically diagnosed in this study. Seven different methods, namely graphical method (GM), method of moments (MOM), standard deviation method (STDM), maximum likelihood method (MLM),
[...] Read more.
The best Weibull distribution methods for the assessment of wind energy potential at different altitudes in desired locations are statistically diagnosed in this study. Seven different methods, namely graphical method (GM), method of moments (MOM), standard deviation method (STDM), maximum likelihood method (MLM), power density method (PDM), modified maximum likelihood method (MMLM) and equivalent energy method (EEM) were used to estimate the Weibull parameters and six statistical tools, namely relative percentage of error, root mean square error (RMSE), mean percentage of error, mean absolute percentage of error, chi-square error and analysis of variance were used to precisely rank the methods. The statistical fittings of the measured and calculated wind speed data are assessed for justifying the performance of the methods. The capacity factor and total energy generated by a small model wind turbine is calculated by numerical integration using Trapezoidal sums and Simpson’s rules. The results show that MOM and MLM are the most efficient methods for determining the value of k and c to fit Weibull distribution curves. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Biofuels from the Fresh Water Microalgae Chlorella vulgaris (FWM-CV) for Diesel Engines
Energies 2014, 7(3), 1829-1851; doi:10.3390/en7031829
Received: 19 February 2014 / Revised: 11 March 2014 / Accepted: 18 March 2014 / Published: 24 March 2014
Cited by 17 | PDF Full-text (1243 KB) | HTML Full-text | XML Full-text
Abstract
This work aims to investigate biofuels for diesel engines produced on a lab-scale from the fresh water microalgae Chlorella vulgaris (FWM-CV). The impact of growing conditions on the properties of biodiesel produced from FWM-CV was evaluated. The properties of FWM-CV biodiesel were found
[...] Read more.
This work aims to investigate biofuels for diesel engines produced on a lab-scale from the fresh water microalgae Chlorella vulgaris (FWM-CV). The impact of growing conditions on the properties of biodiesel produced from FWM-CV was evaluated. The properties of FWM-CV biodiesel were found to be within the ASTM standards for biodiesel. Due to the limited amount of biodiesel produced on the lab-scale, the biomass of dry cells of FWM-CV was used to yield emulsified water fuel. The preparation of emulsion fuel with and without FWM-CV cells was conducted using ultrasound to overcome the problems of large size microalgae colonies and to form homogenized emulsions. The emulsified water fuels, prepared using ultrasound, were found to be stable and the size of FWM-CV colonies were effectively reduced to pass through the engine nozzle safely. Engine tests at 3670 rpm were conducted using three fuels: cottonseed biodiesel CS-B100, emulsified cottonseed biodiesel water fuel, water and emulsifier (CS-E20) and emulsified water containing FWM-CV cells CS-ME20. The results showed that the brake specific fuel consumption (BSFC) was increased by about 41% when the engine was fueled with emulsified water fuels compared to CS-B100. The engine power, exhaust gas temperature, NOx and CO2 were significantly lower than that produced by CS-B100. The CS-ME20 produced higher power than CS-E20 due to the heating value improvement as a result of adding FWM-CV cells to the fuel. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle Characterization of Biochar from Switchgrass Carbonization
Energies 2014, 7(2), 548-567; doi:10.3390/en7020548
Received: 17 November 2013 / Revised: 24 December 2013 / Accepted: 14 January 2014 / Published: 24 January 2014
Cited by 21 | PDF Full-text (683 KB) | HTML Full-text | XML Full-text
Abstract
Switchgrass is a high yielding, low-input intensive, native perennial grass that has been promoted as a major second-generation bioenergy crop. Raw switchgrass is not a readily acceptable feedstock in existing power plants that were built to accommodate coal and peat. The objective of
[...] Read more.
Switchgrass is a high yielding, low-input intensive, native perennial grass that has been promoted as a major second-generation bioenergy crop. Raw switchgrass is not a readily acceptable feedstock in existing power plants that were built to accommodate coal and peat. The objective of this research was to elucidate some of the characteristics of switchgrass biochar produced via carbonization and to explore its potential use as a solid fuel. Samples were carbonized in a batch reactor under reactor temperatures of 300, 350 and 400 °C for 1, 2 and 3 h residence times. Biochar mass yield and volatile solids decreased from 82.6% to 35.2% and from 72.1% to 43.9%, respectively, by increasing carbonization temperatures from 300 °C to 400 °C and residence times from 1 h to 3 h. Conversely, biochar heating value (HV) and fixed carbon content increased from 17.6 MJ kg−1 to 21.9 MJ kg−1 and from 22.5% to 44.9%, respectively, under the same conditions. A biomass discoloration index (BDI) was created to quantify changes in biochar colors as affected by the two tested parameters. The maximum BDI of 77% was achieved at a carbonization temperature of 400 °C and a residence time of 3 h. The use of this index could be expanded to quantify biochar characteristics as affected by thermochemical treatments. Carbonized biochar could be considered a high quality solid fuel based on its energy content. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)
Open AccessArticle How Efficient are Agitators in Biogas Digesters? Determination of the Efficiency of Submersible Motor Mixers and Incline Agitators by Measuring Nutrient Distribution in Full-Scale Agricultural Biogas Digesters
Energies 2013, 6(12), 6255-6273; doi:10.3390/en6126255
Received: 19 September 2013 / Revised: 13 November 2013 / Accepted: 19 November 2013 / Published: 2 December 2013
Cited by 8 | PDF Full-text (748 KB) | HTML Full-text | XML Full-text
Abstract
The goal of this work was to evaluate the efficiency of two different agitation systems by measuring the nutrient distribution in a digester fed with renewable energy crops and animal manure. The study was carried out at the practical research biogas plant of
[...] Read more.
The goal of this work was to evaluate the efficiency of two different agitation systems by measuring the nutrient distribution in a digester fed with renewable energy crops and animal manure. The study was carried out at the practical research biogas plant of Hohenheim University. A unique probe sampling system has been developed that allows probe sampling from the top of the concrete roof into different parts and heights of the digester. The samples were then analyzed in the laboratory for natural fatty acids concentrations. Three different agitation setups were chosen for evaluation at continuous stirring and feeding procedures. The results showed that the analysis approach for agitator optimization through direct measurement of the nutrients distribution in the digester is promising. The type of the agitators and the agitation regime showed significant differences on local concentrations of organic acids, which are not correlated to the dry matter content. Simultaneous measurements on electric energy consumption of the different agitator types verify that by using the slow-moving incline agitator with large propeller diameters in favor of the fast-moving submersible mixer with smaller propeller diameters, the savings potential rises up to 70% by maintaining the mixing quality. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)

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