Plant Residues and Energy Crops: Biotechnology offers the promise of dramatically increasing ethanol production using cellulose, the most abundant biological material on earth, and other polysaccharides (hemicellulose). Residue including postharvest corn plants (stover) and timber residues could be used, as well as such specialized high-biomass "energy" crops as domesticated poplar trees and switchgrass. Biochemical conversion of cellulosic biomass to ethanol for transportation fuel currently involves three basic steps: (1) Pretreatments to increase the accessibility of cellulose to enzymes and solubilize hemicellulose sugars; (2) Hydrolysis with special enzyme preparations to break down cellulose to sugars; and (3) Fermentation to ethanol. Making cellulosic biomass conversion to ethanol more economical and practical will require a science base for molecular redesign of numerous enzymes, biochemical pathways, and full cellular systems.
[Some images taken from "Genomics:GTL Transforming Cellulosic Biomass," U.S. Department of Energy Office of Science and Office of Energy Efficiency and Renewable Energy, June 2006, genomicscience.energy.gov/biofuels/ and U.S. DOE. 2006. "Breaking the Biological Barriers to Cellulosic Ethanol: A Joint Research Agenda," DOE/SC/EE-0095, U.S. Department of Energy Office of Science and Office of Energy Efficiency and Renewable Energy, genomicscience.energy.gov/biofuels/.]
Credit or Source: Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science. science.energy.gov/ber/
US DOE. May 2007. Biofuels Primer Placemat: From Biomass to Cellulosic Ethanol and Understanding Biomass: Plant Cell Walls, US Department of Energy Office of Science. (website)