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News and Trends
http://www.uiweb.uidaho.edu/bioenergy/EnergyLCAJune2011.pdf Researchers from the University of Idaho and U.S. Department of Agriculture (both in the United States) recently updated the energy life cycle assessment (LCA) of soybean biodiesel under a United States scenario. The first LCA on soybean biodiesel was made in 1998 by the National Renewable Energy Laboratory (NREL). This 2009 update (which utilized 2002 data) has been reported recently in a paper published in the Journal of the American Society of Agricultural and Biological Engineers. Life‐cycle analysis (LCA), within the context of biofuels, is a "cradle‐to‐grave analysis" of the energy and environmental impacts of of a biofuel product, from cultivation of the feedstock to final use as fuel. The goal of biofuel-LCA is usually to assess the sustainability of a particular biodiesel product. One parameter that is used in the assessment of a biofuel in the LCA, is what is known as the "Fossil Energy Ratio" (FER). The FER is defined as the renewable fuel energy output from one unit of fossil energy input for its production. This parameter is reported to be an index of energy renewability. Results showed that the FER of soybean biodiesel in the updated LCA, improved to a value of 4.56, compared to the FER value of 3.2 in the 1998 study. This means that the present technology for soybean biodiesel production has a higher energy renewability compared to the technology used in 1998. The increase in FER was attributed to more energy efficient soybean crushing processes and biodiesel production plants, energy-saving practices adopted by farmers and greater soybean yields from improved crops. Some highlights of the study are: (1) the energy input in soybean agriculture was reduced by 52 per cent, while the energy input in soybean processing was reduced by 58 per cent, (2) The energy input in biodiesel production (by transesterification) was reduced by 33 per cent (per unit volume of biodiesel produced), (4) the overall energy input reduction was 42 per cent for the same amount of biodiesel produced, and (4) the addition of secondary inputs, such as farm machinery and building materials,did not have a significant effect on the fossil energy ratio. Progress in the improvement of energy renewability of soybean biodiesel production was attributed to new production technologies, driven by the increase in demand in soybean biodiesel. Details about the paper can be obtained at the website of the American Society of Agricultural and Biological Engineers (URL Above). Related information on the Basics of Life Cycle Analysis (LCA): http://www.epa.gov/nrmrl/lcaccess/lca101.html
http://aob.oxfordjournals.org/content/early/2011/08/03/aob.mcr175.full?sid=06d16e93-30ae-4841-97c5-17a99e354070 A scientist from the University of Manchester (United Kingdom) showed that the planting of deeply-rooted crops (one meter or longer) can reduce atmospheric carbon (dioxide) levels,while reaping other environmental benefits. According to Professor Douglas Kell, the soil represents a big carbon reservoir, which can take-in twice as much carbon as the atmosphere does. "However,present estimates of the carbon sequestration potential of soils are based more on what is happening now than what might be changed by active agricultural intervention, and tend to concentrate only on the first meter of soil depth". Thus, the cultivation of deeply-rooted crops can maximize the soil's carbon-sequestration capability. In addition to carbon-reduction, other benefits of breeding/cultivating deeply-rooted crops include: (1) improvement of soil structure, (2) improvement in water and nutrient retention, (3) sustainability of plant yields. Professor Kell is reportedly the first to explore the environmental benefits of harnessing deeply-rooted crops for enhancing atmospheric carbon sequestration. He also provided a "carbon calculator that can show the potential benefits of crops burrowed deeply on the ground". The study can stimulate research activities which focus on solutions for climate-change. From a biofuels point of view, the sustainability of a particular bioenergy crop can be enhanced if it can thrive on marginal land, while simultaneously having a root system which extends one meter or more. Professor Kell's paper appears in the journal,Annals of Botany (URL above). Energy Crops and Feedstocks for Biofuels Production
In recent years, algae have been one of the emerging feedstocks for biofuels production, due to the presence of large amounts of potentially useful compounds (embedded within the algae) which can be processed into biofuels. However, little is known about the metabolic processes which drive the production of these useful compounds in algae. A deeper knowledge of the algal metabolism could help in increasing the efficiency of biofuel production from algal harvests. A team of researchers from the University of California (USA),Dana-Farber Cancer Institute (USA), Harvard Medical School (USA), University of Virginia (USA), Harvard University (USA), University of Iceland (Iceland), New York University (UAE) and New York University (USA) recently attempted to reconstruct the metabolic network of an algae for the prediction of its growth rate at a given light source. In their paper, they first presented a genome-scale reconstruction of the central metabolism of a model algae, Chlamydomonas reinhardtii'. This was done in a "bottom-up manner", according to current standards on a pathway-by-pathway basis, drawing biochemical, genomic, and physiological evidence from over 250 publications. Then, they functionally annotated the gene models from the genome-scale reconstruction of the algae. Subsequently, the researchers performed growth simulations using Flux Balance Analysis (i.e. a standard simulation method in the systems biology field with a long history of success) and Flux Variability Analysis. Verification experiments were done by cultivating the model algae at different average photon fluxes and sequencing the transcripts for proof. Finally, spectral bandwidths that effectively drive each photon-utilizing reaction in the reconstructed metabolism network were determined from published experimental activity spectral data, verified and integrated to the prediction to account for different light intensity conditions. The network can offer insights into algal metabolism, which could be useful for improved algal-biofuel production, in terms of better algal strains, and more efficient light source design. The study is published in the journal, Molecular Systems Biology (URL above).
(complete access to journal article may require payment or subscription) The "food-versus-fuel"debate is one of main considerations when selecting a bioenergy crop as a feedstock for biofuel production. In order to avoid the use of productive agricultural land (which must be prioritized for food production), marginal lands are eyed for biofuel crop plantations, using "robust"bioenergy crops that can withstand stressful growth conditions. However,the use of marginal lands for large scale bioenergy crop plantations could pose new problems for farmers, specially on the aspect of pest control. Bioenergy crops could reportedly serve as refuge for pests. In order to prepare for anticipated pest problems that could arise in such situations, researchers from the Centre for Environmental Stress and Adaptation Research (CESAR), University of Melbourne (Australia) reviewed the possible pest management challenges that could be encountered in the cultivation of bioenergy crops in marginal lands. Some of the problems discussed by the researchers in their paper are the biodiversity loss associated with intensification of agriculture in marginal lands, the enhancement of pest numbers, the breakage of links of pests with its natural enemies and the chemical impact of pest control. Some of the highlights of the review are: (1) Pests will attack biofuel crops despite claims that they might be immune from pests, (2) Landscape heterogeneity provides ecosystem services, including pest suppression, (3) Less toxic pesticides enhance sustainable pest control, and (4) Distribution modeling and related crop pests predict potential pest pressures. The paper is published in the journal, Current Opinion in Environmental Sustainability (URL above). Biofuels Processing
(complete access to journal article may require payment or subscription) Researchers from the Technical University of Denmark recently attempted to compare different operating scenarios in the production of bioethanol using mathematical models. Production processes, like bioethanol production, could be operated in different operating scenarios, such as fed-batch or continuous processes.Selection of the appropriate operating condition can be a challenge because of the many different factors that affect production performance. The researchers used a model-based simulation framework for the comparison of three bioethanol production scenarios: (1) fed-batch, (2) continuous, and (3) continuous with recycle configuration. The framework consists of two main parts: (1) the collection, analysis and identification of promising mathematical models for pre-treatment, enzymatic hydrolysis and co-fermentation, and (2) the design, simulation and comparison of the different integrated hydrolysis and co-fermentation operational scenarios. From their simulation, the researchers found that among the three scenarios, the simultaneous saccharification and co-fermentation (SSCF) process,operated in a continuous mode with recycling (of the SSCF reactor effluent) was the best in terms of ethanol yield, having a value of 0.18 kilogram ethanol per kilogram dry-biomass. The paper is published in the journal, Bioresource Technology (URL above).
(complete access to journal article may require payment or subscription) In biodiesel production, plant oils are usually reacted with an alcohol (commonly,methanol) to produce a mixture of compounds known as methyl esters (the "biodiesel" product). The reaction (which is called "transesterification") is usually catalyzed by a base, such as sodium hydroxide. Because base-catalysts can reduce the biodiesel yield due to side-reactions, scientists are exploring alternative catalyst-materials. Alternative catalysts for the transesterification reaction in biofuel production are enzymes, such as those that belong to the family of lipases (triglyceride hydrolases). Lipases are said to be efficient and selective for the transesterification reaction. However, the cost and possible instability make enzymes unfavorable for industrial biodiesel production applications. A team of French researchers from French National Center for Scientific Research (CNRS), the Institute for Molecular Sciences (France) and the Laboratory of Condensed Matter Chemistry (France) report a way to overcome the above-mentioned problems. They employed monolithic biohybrid foams to confine the enzymes for a relatively long period of time (approximately 2 months). Confinement in the biohybrid foams allowed good accessibility and enhanced mass transport, resulting in a high biodiesel yield. The long term stability of the enzymes make the process attractive for commercial applications. The researchers then devised a method for the in-situ production of the new biocatalyst in the reactor itself; thus, allowing uninterrupted, continuous, unidirectional flow industrial production of this biofuel. The biodiesel yields from this novel method were the best achieved so far and it met all the current energy and environmental requirements and standards. According to the researchers, the next step in the research is the solvent-free conversion of triesters, aimed at minimizing waste production by curbing the use of solvent sand metals in chemical transformation processes. The full study is published in the journal, Energy and Environmental Science (URL above). Biofuels Policy and Economics
(complete access to journal article may require payment or subscription) Issues on energy security and climate change have prompted the shift of energy sources from fossil energy to bio-based energy. However, effects of this shift in new energy sources have not been fully understood, specially on the effect of bio-based energy on engine performance and emission.A team of researchers from Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, USA and College of Engineering, Nanjing Agricultural University, China attempted to provide a whole picture of the effect of the use of biodiesel on the performance and emissions on current diesel engines by using a compilation of previous studies. In their paper, the engine performance was gauged based on three factors: (1) power performance, (2) economic performance and (3) durability. The emissions,on the other hand, where evaluated based on (1) emitted particulate matter(PM), (3) oxides of nitrogen (NOx), (3) carbon monoxide (CO), (4) hydrocarbons(HC), (5) carbon dioxide (CO2) and (6) non-regulated emissions. Some highlights of the study are: (1) the power performance of a biodiesel-fueled engine is lower due its lower heating value, (2) an increase in fuel consumption resulted from the lower power performance, (3) the use of biodiesel favors reduced carbon deposits and reduced wear of the key engine parts, (4) PM, CO, HC, CO2 emissions for biodiesel are significantly reduced while NOx and non-regulated emissions were observed to increase, (5) the blends of biodiesel with small content by volume could replace diesel in order to help in controlling air pollution and easing the pressure on scarce resources to a great extent without significantly sacrificing engine power and economy. The paper is published in the journal, Renewable and Sustainable Energy Reviews (URL above). |
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