...Both President Barack Obama and his predecessor in the White House have identified production of ethanol from cellulosic materials such as switchgrass and wood as vital to overcoming the U.S. “addiction†to oil. In recent years, California also adopted several bold new initiatives, including: (1) AB32, The Global Warming Solutions Act of 2006, which caps greenhouse-gas emissions at 1990 levels by 2020, (2) an executive order establishing the first Low Carbon Fuel Standard and calling for a reduction in the carbon intensity of passenger-vehicle fuels by at least 10% by 2020, and (3) an historic agreement with Arizona, New Mexico, Oregon and Washington to reduce greenhouse-gas emissions through a market-based approach. Meeting these targets will be challenging for a state with a transportation fuels market that dwarfs that of other states. Transportation fuels account for about 40% of California's total energy use; the state is the largest transportation fuels market in the country. Additionally, about 40% of California's greenhouse-gas emissions come from transportation, a higher fraction than the country as a whole.
At present, cellulosic biomass is the only environmentally sustainable resource for producing liquid transportation fuels to meet these goals. California has large quantities of agricultural residues, forest thinnings and residues, and municipal waste. The California Biomass Collaborative estimates that the state produces about 24.2 million dry tons of cellulosic biomass annually, with enough of this available for the sustainable production of fuels displacing about 1.1 billion gallons of gasoline each year ( http://biomass.ucdavis.edu ).
Cellulosic biomass composition
Cellulosic biomass has three major components: hemicellulose, cellulose and lignin. Hemicellulose is an amorphous, branched polymer that is usually composed primarily of five sugars (arabinose, galactose, glucose, mannose and xylose); it typically comprises about 15% to 30% of cellulosic biomass. Cellulose is a large, linear polymer of glucose molecules typically joined together in a highly crystalline structure due to hydrogen bonding between parallel chains; it typically comprises about 35% to 50% of cellulosic biomass. Lignin is a complex phenyl-propane polymer that often comprises about 15% to 30% of cellulosic biomass. Although lignin cannot be converted into fermentable sugars, this component has high value as a boiler fuel and could also be useful as a raw material for making aromatic compounds such as benzene and toluene.
