The preceding chapter described the major components of plant biomass – cellulose, hemicelluloses, and lignin – and their natural pathways of biodegradation. Many view the sugars locked up in cellulose and the hemicelluloses as an immense storehouse of renewable feedstocks for the fermentative production of fuel alcohol. This chapter begins with a discussion of the conversion of such sugars to ethanol and ends with an assessment of the future impact of fermentation alcohol as a fuel.

In microbiology, fermentation is defined as a metabolic process leading to the generation of ATP and in which degradation products of organic compounds serve as hydrogen donors as well as hydrogen acceptors. Oxygen is not a reactant in fermentation processes. In the words of Louis Pasteur, “[l]a fermentation est la vie sans l'air” – fermentation is life without air. The long history of brewing and wine making has produced highly refined technologies for large-scale fermentation and for the recovery of ethanol.