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News and Trends
Scientists from the University of Minnesota (United States) are working on a bacterial system which can directly convert carbon dioxide and sunlight into "green" hydrocarbon fuel. The study is funded by the Advanced Research Projects Agency-energy (ARPA-e) program (United States Department of Energy, USDOE) and is led by Professor Lawrence Wackett . The scientific team aims to engineer Shewanella bacteria to produce higher levels of hydrocarbons from carbon dioxide. The Science Daily website describes the strategy as follows: "The [University of Minnesota] team is using Synechococcus, a bacterium that fixes carbon dioxide in sunlight and converts CO2 to sugars. Next, they feed the sugars to Shewanella, a bacterium that produces hydrocarbons. This turns CO2, a greenhouse gas produced by combustion of fossil fuel petroleum, into hydrocarbons". One of the project scientists, Janice Frias, tried to study the workings of a protein that can transform fatty acids produced by the bacteria into ketones, which can be cracked to make hydrocarbon fuels. The enzyme (called OleA) is said to normally work together with other enzymes to make hydrocarbons, although the mechanism was unclear. In a paper published in the Journal of Biological Chemistry (related information below), Frias and colleagues presents data supporting a theory of how the mechanism of that olefin biosynthetic pathway works. Related article on the olefin biosynthetic pathway in bacteria (the OleA enzyme) http://www.jbc.org/content/early/2011/01/25/jbc.M110.216127.full.pdf+html.
(complete access to journal article may require subscription or payment) http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V24-525GWR2- Biodiesel fuel is said to be more hygroscopic (i.e. absorbs more water) compared to its counterpart fossil fuel. Since biodiesel is more biodegradable than petroleum diesel, the presence of water may allow undesirable microbial growth. Microbial growth in biodiesel can cause microbial fouling, fuel degradation, increased steel corrosion (in fuel storage tanks), and increased particle loads. Researchers from the Danish Technological Institute (Denmark) investigated microbial growth in incubated biodiesel-blend samples containing contaminated inoculated water. Results of the study showed increased bacterial growth and activity in biodiesel blends compared to neat fossil diesel. The presence of anaerobic microorganisms, notably methanogens, sulfate-reducing bacteria and nitrate reducing bacteria, has been identified after incubation. The proportion of the biodiesel blend also affected anaerobic microbial activity and type of microbial community. A "large shift in the microbial community was observed when the biodiesel blend exceeded 10%–20%. This shift is said to have implications on biofilm corrosiveness, fuel spoiling and other effects which would need further study. The full paper is published in the journal, Bioresource Technology (URL above). Energy Crops and Feedstocks for Biofuels Production
Scientists from the Universidade de São Paulo (Brazil), and Federal Research Institute for Rural Areas, Forestry and Fisheries (Germany) investigated the topochemical distribution of lignin and some aromatic compounds in sugarcane, in an attempt to obtain useful information on the recalcitrance of specific cells. "Recalcitrance" is one property of (lignocellulosic) biomass which make the biomass more difficult for processing into biofuels, particularly during the saccharification process. Saccharification is the breakdown of cellulose polymers in the biomass into simple sugars for ethanol fermentation. Recalcitrance is attributed to lignin compounds in biomass; these molecules wrap around the cellulose polymers and limit cellulose accessibility to enzymatic saccharification. By examining topochemical distribution of lignin compounds in lignocellulosics, strategies might be considered for reducing biomass recalcitrance for improved processing of the biomass to biofuels. The scientists used "cellular ultraviolet (UV) microspectrophotometry (UMSP) to topochemically detect lignin and hydroxycinnamic acids in individual fiber, vessel and parenchyma cell walls of untreated and chlorite-treated sugar cane". Some of the results of their study are: (1) UV measurements of untreated sugarcane fiber cell walls showed absorbance spectra typical of grass lignin; (2) highest levels of lignification were found to be in the cell walls of vessels, followed by fibers and parenchyma; (3) Chlorite treatment of pith cells did not enhance cellulose conversion; but chlorite treatment of the rind cells resulted in the significant removal of hydroxycinnamic acids and lignin, resulting in marked enhancement of cellulose conversion by cellulases. The full results are published in the open access journal, Biotechnology for Biofuels (URL above). Biofuels ProcessingResearchers from the University of Twente (the Netherlands) compared the energy balances for two routes of biodiesel production (the "wet" and "dry" routes) from the microalgae, Chlorella vulgaris. The comparative energy balance would contribute toward a more comprehensive Life Cycle Analysis (LCA) for algal biodiesel production. In the "dry route" the cultivated algae are concentrated, mechanically dewatered, and then thermally dried. The dried algae are cell-disrupted to release the oil, and the oil is converted to biodiesel by reaction called "transesterification". In the wet process, the cultivated algae are concentrated and initially dewatered. Then the wet extraction process (usually involving the use of water under subcritical conditions) is conducted to extract the lipids from the oil. The lipids undergo a process called "hydrotreatment" to produce "green diesel". Results showed that both routes gave "significantly positive" energy balances. The drying process in the dry route consumed large amounts of energy, while in the wet process, it was the wet oil extraction part (involving supercritical fluids) which was most energy consuming. "By applying more efficient dryer/extraction process or coupling waste heat from a nearby power plant to the process, the energy balance can be improved". In the short term, the dry route was found to be "more interesting", because it had a higher FER (fossil energy ratio). However, in the long term, the wet route is said to have "more potential" due to its capability to produce higher-value biofuels. The complete paper is published in the journal, Bioresource Technology (URL above). Related information on the Wet Process for Algal Biodiesel Biofuels Policy and Economics
(complete access to journal article may require subscription or payment) http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V22-51BP6FH-2&_user=9570260&_coverDate=04%2F30%2F2011&_rdoc=2&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info(%23toc%235690%232011%23999649995%233001742%23FLA%23display%23Volume)&_cdi=5690&_sort=d&_docanchor=&_ct=27&_acct=C000061230&_version=1& Researchers from the State University of New York, Kansas State University, and Iowa State University (United States) report the use of a "community case study approach to examine local community perceptions of benefits and burdens of the ethanol industry". Community perceptions of biofuels were explored from community level survey data, as well as individual/focus group interview data in three case study communities in Iowa, Kansas. Among the findings of their study are: (1) communities hosting biofuel ethanol plants "believe that ethanol plants have brought modest economic benefits to their community", (2) areas of concern include increased traffic, water competition, future viability of the ethanol industry, and potentially devastating impacts in their communities if a future decline in the bioethanol industry occurs. The full study is published in the journal, Biomass and Bioenergy (URL above).
(complete access to journal article may require subscription or payment) http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V22-51PR0DJ-2&_user=9570260&_coverDate=04%2F30%2F2011&_rdoc=11&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info(%23toc%235690%232011%23999649995%233001742%23FLA%23display%23Volume)&_cdi=5690&_sort=d&_docanchor=&_ct=27&_acct=C000061230&_version=1&_ Scientists from the University of Illinois at Urbana-Champaign (United States) looked into the use of switchgrass and Miscanthus ("bioenergy grasses") as input material in the co-firing in coal-based power plants in Illinois, and examined some economic/environmental aspects. For the economics aspect, conditions were examined under which cropland would be allocated to bioenergy crops, as well as spatial variability associated with the allocation. For the environmental aspect, they used lifecycle analysis "to examine the potential for bioenergy crops to reduce GHG emissions", accounting for (1) soil carbon sequestered by perennial grasses and (2) carbon emissions displaced by these grasses due to both conversion of land from row crops and co-firing the grasses with coal. Some findings of their study include the following: (1) "conversion of less than 2% of the cropland to bioenergy crops could produce 5.5% of the electricity generated by coal-fired power plants in Illinois and reduce carbon emissions by 11% over the 15-year period", (2) under the previously mentioned scenario (i.e. 2% conversion of cropland to bioenergy crops), the cost of energy from biomass in Illinois would be more than twice as high as that of coal, (3) in order to "induce the production and use of bioenergy for electricity generation, interventions in the form of mandates, government subsidies, or setting a modest price for GHG emissions under a cap-and-trade policy might be needed. The full paper is published in the journal, Biomass and Bioenergy (URL above). |
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