ABSTRACT
Biomass promises to be an efficient and environmentally sound raw material for producing fuels and commodity chemicals in the future. Lignocellulosic biomass, an abundant resource, provides a potentially cheap feedstock to convert to fuel ethanol and other chemicals. The important process factors in cost reduction are seed requirement, feed solids concentration, ethanol yield and volumetric productivity in cellulosic conversion, and ethanol tolerance of microorganisms. New process schemes for improving the base-case technology should be investigated in parallel with ongoing base-case process improvement. Co-fermentation of cellulose and xylose to ethanol represents the simplest new configuration for inclusion in the base-case technology. The fermentor design employed currently in the base-case process is the conventional continuous stirred-tank reactor. Novel reactor configurations such as the fluidized bed using either free or immobilized cells could enhance the efficiency of ethanol production. In a fluidized-bed reactor, the catalyst particles are suspended and agitated by the upward flow of fluid.
