Bin Yang and Charles E. Wyman. Center for Environmental Research and Technology Department of Chemical and Environmental Engineering Bourns College of Engineer, University of California at Riverside, 1084 Columbia Avenue, Riverside, CA 92507
Biological production of cellulosic ethanol from cellulosic biomass presents a particularly promising approach that better fit our transportation infrastructure while providing unparalleled environmental, economic, and strategic benefits due to 1) cellulosic biomass is inexpensive and abundant and provides a unique resource for large scale and low cost solar energy collection and storage and 2) the rapidly evolving tools of biotechnology can radically lower conversions costs and enhance yields. Yet breakdown of the cellulose and hemicellulose in these naturally resistant cellulosic materials to release fermentable sugars is projected to be the most expensive processing step. In addition, the pretreatment step needed to realize high yields has pervasive impacts on all other major operations from choice of feedstock through product recovery and residue processing. Thus, knowledge of how cellulosic biomass responds to pretreatment and following biological processing is vital to successful applications. Furthermore, pretreatment selection is challenging in that it must account for sugar release patterns, solids concentrations, and compatibility with the overall process, feedstock, enzymes, and microorganisms to be applied. A necessary but not sufficient condition is that pretreatment must ensure high overall total sugar yields that are vital to economic viability, and feedstock species, sites, ages, and harvest times can be important considerations in this regard. A key goal now should be to dramatically improve our understanding of pretreatment systems and provide a foundation for substantially reducing costs and accelerating commercial applications.
