http://www.technologyreview.com/read_article.aspx?ch=specialsections&sc=emerging08&id=20240&a=

Although ethanol for transport biofuel applications is still largely produced using “first generation biofuel feedstocks” (such as corn, and sugarcane), many see “cellulose ethanol”, or ethanol from cellulosic biomass (a “second generation” biofuel crop) as the bioethanol of the future. Many studies have shown that cellulose ethanol has a better net energy yield and a better GHG (greenhouse gas) balance compared to corn ethanol. However, cellulose ethanol production technology (via the biochemical route) still has some hurdles that limit cost-effective applications on a large scale such as the identification of effective cellulases. Cellulases are enzymes which break down the cellulose into simple sugars that can be fermented into ethanol. Frances Arnold, a scientist from the California Institute of Technology (Caltech), in the United States, aims to develop new cost effective cellulases, by using a tool called, “directed evolution”. This tool is described as a method of protein engineering that “harnesses Darwinian selection to evolve proteins or RNA with desirable properties not found in nature” (wikipedia.org). It may involve creating variations of the gene that codes for cellulases, inserting the mutated cellulase genes into a microorganism, and then screening it for a particular/desired characteristic..

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http://www.sciencedaily.com/releases/2008/03/080320182932.htm
http://www.public.iastate.edu/~nscentral/news/2008/mar/syngas.shtml

Researchers from the Iowa State University (ISU), in the United States, are developing a themochemical catalytic process which can produce ethanol from plant biomass. The thermochemical route is an alternative to the biochemical route (i.e., via fermentation) for ethanol production. The research, which is funded by a grant from the U.S. Departments of Agriculture and Energy, is headed by Victor Lin, ISU professor of chemistry. In their process, the plant biomass (like corn stalks or grasses) is heated at 900 ^oF in the absence of oxygen (“fast pyrolysis) to produce a “bio-oil”. The”bio-oil” is then heated in a gasifier at 1100 ^oF to 1500 ^oF to produce “synthesis gas” ( a mixture containing carbon monoxide, hydrogen, carbon dioxide, and short chain hydrocarbon chains). Finally, the hydrogen and carbon monoxide in the synthesis gas are combined in a reactor, containing a metal catalyst embedded in solid nanosphere particles. The technology is said to solve some problems related to selectivity and control of the reaction..

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http://www.biofpr.com/view/MTAzNzUzL0pBLzUxL251bGw=/journalArticleDetail.html

The production of cellulose-ethanol from lignocellulosic biomass usually takes four main processing steps: (1) “Pretreatment”, where the cellulose fibers are liberated from the tough “lignin wrapping” in the plant biomass, (2) “Saccharification”, where the liberated cellulose fibers are broken into simple sugars, (3) “Fermentation”, where microorganisms (usually yeasts) convert the simple sugars into ethanol, and (4) “Distillation”, the thermal separation of high purity ethanol from the fermentation broth. A recent review paper by Bin Yang and Charles Wyman (in the journal “Biofuels, Bioproducts and Biorefining”) mentions that the pretreatment step is “projected to be the single, most expensive processing step, representing about 20% of the total cost”. The use of chemical agents is said to “offer the high yields and low costs vital to economic success”. The review paper lists the following chemical pretreatments as the “most promising”: dilute acid, sulfur dioxide, near-neutral pH control, ammonia expansion, aqueous ammonia, and lime, with significant differences among the sugar-release patterns”. There is a need to improve knowledge of pretreatment systems to “substantially reduce costs and to accelerate commercial applications”..