ABSTRACT
This chapter aims to assess the status of R&D in the cellulose-to-ethanol conversion field and presents issues of critical importance to the scale-up and commercialization of the technology. The cellulose conversion factors of major importance, such as the effect of substrate and enzyme loading on ethanol productivity, the most efficient mode of operation, the effect of feedstock composition, and the pretreatment effectiveness, can be systematically evaluated to improve the overall biomass-to-ethanol technology. Lignocellulosic biomass consists primarily of cellulose, hemicellulose, and lignin. Cellulose is usually the major biomass component, typically in the 40%-50% range on a dry basis. To increase the digestibility of cellulose, cellulosic biomass is pretreated mechanically or chemically before it is exposed to cellulases. Mechanical pretreatment methods include hammer milling, ball milling, and roll milling to increase the substrate's surface area and reactivity. Separate hydrolysis and fermentation (SHF) uses separate process steps to first enzymatically hydrolyze cellulose to glucose and then ferment glucose to ethanol.
