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News and Trends
Researchers from the University of Maine (United States) are reportedly using a new, catalyst-free, and hydrogen-free,thermochemical route for the production of hydrocarbon-like based biofuels from cellulosic biomass. According the University of Maine website news release, the process,known as "thermal deoxygenation (TDO)", can convert biomass residues into a hydrocarbon mixture with boiling points "that encompass those of jet fuel, diesel, and gasoline". Analysis of the product indicated that it could have fuel properties which make it a "drop-in fuel"; this means that the product can be used with little or no refining. In the TDO process, the biomass is first converted to organic acids. Then, the acids are added with calcium hydroxide to form a calcium salt, and the reaction mixture is heated to 450 oC. The process "deoxygenates" (or removes the oxygen) from the biomass, and the resulting product is a dark amber-colored oil with a high energy density (higher fuel heating value) than the original biomass. An interesting feature of the process is that is does not require the use of a catalyst nor hydrogen for the conversion of the material into a hydrocarbon mixture. This can help a great deal to reduce the production cost. According to University of Maine news release, "further refinement to meet emissions standards would be needed in order to use the ‘UMaine oil' in vehicles that drive on public ways, but [senior researcher, Clayton Wheeler] believes the oil can be refined as simply as any other current oil at a standard refinery". Related information: University of Maine video describing the new biofuel production process and research reference
(full access to article may require payment or subscription) Contrary to the assumption that biofuels from forest biomass are carbon-neutral or carbon-negative, an international team of scientists from Oregon State University (United States), University of Leipzig (Germany), Centre d'Etudes Ormes des Merisiers (France) report that biofuel production from US West Coast forests may actually increase carbon dioxide emissions. Using forest inventory data (covering 80 forest types in 19 eco-regions in Oregon, Washington and California), the researchers showed that "fire prevention measures and large-scale bioenergy harvest in US West Coast forests lead to 2% to 14% (46 Teragrams to 405 Teragrams of carbon) higher emissions compared with current management practices over the next 20 years". (One Teragram equals 1 Megatonne). According to the researchers, "If the sink in these ecoregions weakens below its current level by 30 grams to 60 grams carbon per square meter per year) owing to insect infestations, increased fire emissions or reduced primary production, management schemes including bioenergy production may succeed in jointly reducing fire risk and carbon emissions. They concluded that in order to establish how to decrease emissions, forest policy should consider factors which include (1) current forest carbon balance, (2) local forest conditions, and (3) ecosystem sustainability. The full paper is published in the journal, Nature Climate Change (URL above). Energy Crops and Feedstocks for Biofuels Production
In the biofuel-ethanol production process from lignocellulosic biomass, the focus is usually the carbohydrate fractions (cellulose and hemicellulose) of the biomass, which are extracted for further processing into ethanol. The lignin residue is often separated and regarded as a waste stream, because "structural diversity and heterogeneity" of this material can make further processing to biofuels or value-added-chemicals a challenge. In anticipation of future technological developments for the processing of lignin into value-added products, a collaborative team of research scientists from the University of Kentucky and the University of Massachusetts used thermal deconstruction to "identify and examine feedstocks that possess naturally high lignin contents. They performed preliminary experiments to "examine the pyrolytic characteristics of the various feedstocks and to estimate the potential" of these materials for the production of biofuels, bioelectricity or specialty chemicals. "Drupe endocarp"biomass (seen as agricultural wastes from horticultural crops) was identified as a feedstock containing high levels of lignin. The researchers characterized the lignin-derived deconstruction products of endocarp biomass (by pyrolysis coupled to gas chromatography-mass spectrometry) and compared them to switchgrass (a potential feedstock for biofuels production). They found that high-lignin endocarp biomass yielded higher levels of lignin-based pyrolytic products compared to switchgrass; (switchgrass had higher levels of acetic acid and furfural). The results indicated that high-lignin endocarp biomass can be a "source of renewable production of value-added chemicals, like phenol, 2-methoxyphenol, 2-methyl phenol, 2-methoxy-4-methylphenol,and 4-methoxy-2-ethylphenol". The full study is published in the open-access journal, Biotechnology for Biofuels.
http://www.purdue.edu/newsroom/research/2011/111020MeilanPoplar.html The news service website of Purdue University (Indiana,United States) announced that a research team led by Associate Professor Rick Meilan of the Department of Forestry and Natural Resources began a five-year research project on assessing the viability of poplar tree species as a biofuel feedstock for ethanol production. Poplar trees (trees belonging to the genus Populus) are already used for energy; the wood from these trees are burned in electricity-generating plants. They have been identified poplars as a potential biofuel feedstocks in the forest biomass category due to the following reasons:
The Purdue University news website mentions that the Purdue study will be looking into 69 poplar tree varieties of poplar species and how they would perform under (1) different soil and climatic conditions, (2) disease and insect pressure, and (3) fertilization and watering regimes. Associate professor Meilan and researcher Patrick T. Murphy will also be looking into planting/harvesting issues. An example is a strategy to modify conventional farm machinery for harvesting operations,so that farmers will not be required to make large investments in new equipment. The research hopes to "help propel the fledgling cellulosic industry" in the country. Biofuels Processing
Cellulose is the principal carbohydrate in lignocellulosic biomass which can be enzymatically broken down (i.e., "hydrolysed"or "saccharified") to simple sugars that are necessary for biofuel-ethanol fermentation. In order for the cellulose to be effectively broken down by (cellulolytic or "cellulose") enzymes, it has to undergo a pretreatment step. The purpose of pretreatment is usually (1) to remove the tough lignin wrapping surrounding the cellulose molecules, and (2) to reduce cellulose-crystallinity. Removal of lignin from the cellulose molecules exposes the cellulose to more effective attack by cellulolytic enzymes. The reduction cellulose-crystalline structure into a more amorphous form, is also reported to facilitate enzymatic saccharification. Treatments such as alkali or ammonia treatments are said to be effective in reducing cellulose crystallinity. Researchers from the National Renewable Energy Laboratory (NREL) (United States) investigated the effects of sodium hydroxide and liquid ammonia treatments on the cellulose-crystalline structure,and the ease of enzymatic digestibility of the treated cellulose for the production of sugars for ethanol fermentation. They found that alkali and ammonia treatments in combination with low or high temperatures, resulted in the formation of different forms of crystalline cellulose ("allomorphs"), and these forms have varied degrees of enzymatic digestibility. For example, treatment at a low temperature (25°C) resulted in a less crystalline product, whereas treatment at higher temperatures (130°C or 140°C) resulted in a more crystalline product. "Treatment of cellulose I with aqueous sodium hydroxide (16.5 percent by weight) resulted in formation of cellulose II, but also produced a much less crystalline cellulose". The chemical treatments were found to produce different allomorphs of cellulose, which in turn affected its crystallinity and enzymatic digestibility. The full paper is published in the open access journal, Biotechnology for Biofuels. Biofuels Policy and Economics
The United States National Academy of Sciences(US-NAS) recently published a report, entitled, "Renewable Fuel Standard: Potential Economic and Environmental Effects of U.S. Biofuel Policy". The report was made on the request of the United States Congress to assess the economic and environmental benefits/concerns related to achieving the targets of the Renewable Fuels Standard (RFS). The RFS was enacted by the U.S. Congress in 2005 as part of the Energy Policy Act, and was amended in the 2007 Energy Independence and Security Act (EISA). The purpose of the RFS was to "encourage the production and consumption of biofuels in the United States". The amended RF Sunder the 2007 EISA is sometimes referred to as "RFS 2". There are four categories for the total renewable fuel requirement under the RFS 2:
Among the key findings mentioned in the report are:
Details on how to access the NAS report can be obtained from the website of the National Academy of Sciences (URL above). |
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