Environment & Ecology

September 26, 2011

Corn1 300x235 Environment & EcologyDid you know that…

…sugars for ethanol fermentation can be obtained from cellulose. Until recently, however, the cost of the cellulase enzymes capable of hydrolyzing cellulose has been prohibitive. The Canadian firm Iogen brought the first cellulose-based ethanol plant on-stream in 2004. Its primary consumer so far has been the Canadian government, which, along with the United State Department of Energy, has invested heavily in the commercialization of cellulosic ethanol. Deployment of this technology could turn a number of cellulose-containing agricultural by-products, such as corncobs, straw, and sawdust, into renewable energy resources. Other enzyme companies are developing genetically engineered fungi that produce large volumes of cellulase, xylanase, and hemicellulase enzymes. These would convert agricultural residues such as corn stover, wheat straw, and sugar cane bagasse and energy crops such as swithcglass into fermentable sugars.
Cellulose-bearing materials typically also contain other polisaccarides, including hemicellulose. When undergoing hydrolysis, hemicellulose decomposes into mostly five-carbon sugars such as xylose. S. cerevisiae, the yeast most commonly used for ethanol production, cannot metabolize xylose. Other yeasts and bacteria are under investigation to ferment xylose and other pentoses into ethanol.
On January 14, 2008, General Motors announced a partnership with Coskata, Inc. The goal is to produce cellulosic ethanol cheaply, with an eventual goal of US$1 per U.S. gallon ($0.30/L) for the fuel. The partnership plans to begin producing the fuel in large quantity by the end of 2008. In June 2009, this goal is still ahead of the firm. By 2011 a full-scale plant will come on line, capable of producing 50 to 100 million gallons of ethanol a year.

EthanolChemicalFormula 150x150 Environment & Ecology

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