January 4, 2011
BY USDA-ARS
Chemical engineer Nasib Qureshi at the Agricultural Research Service’s National Center for Agricultural Utilization Research in Peoria, Ill., has been leading a research team that says barley straw could be a viable feedstock for biobutanol.
Butanol burns cleaner than ethanol, can be transported in existing pipelines, is less corrosive and less prone to water contamination, and packs more energy per gallon than ethanol, according to Qureshi and his research teammates, Badak Saha, Bruce Dien, Ronald Hector and Michael Cotta.
Like other biomass feedstocks, barley straw must be physically broken down and then hydrolyzed with enzymes to release both its five-carbon and six-carbon plant sugars for fermentation into fuel.
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After pretreating and hydrolyzing the barley straw, the team used the bacterium Clostridium beijerinckii P260 to ferment the plant sugars that were released. However, the butanol production rate was only around 0.1 gram of butanol per liter per hour, a very low yield that probably resulted from the development of “inhibitors,” which are substances that can form during pretreatment and suppress yields.
The team then diluted the pretreated and hydrolyzed barley straw with distilled water and added lime to the mixture, which reduced its acidity. Butanol fermentation rates rose to 0.39 grams per liter per hour, which was nearly four times that of undiluted barley straw feedstock that had not been treated with lime. It also exceeded butanol yields the scientists obtained from a control feedstock that only contained the six-carbon sugar glucose.
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These findings suggest that producing butanol by using barley straw could someday be a cost-effective alternative to using more expensive crop byproducts as feedstocks to produce ethanol or butanol.
ARS is the chief scientific research agency of the USDA, and the results from this research support the USDA priority of developing new sources of bioenergy.
For more information, contact Nasib Qureshi, USDA-ARS Bioenergy Research Unit at Nasib.qureshi@ars.usda.gov.