BIOCHEMICAL-ENGINEERING ANALYSIS OF CRITICAL PROCESS FACTORS IN THE BIOMASS-TO-ETHANOL TECHNOLOGY

Ethanol from cellulosic biomass is a promising renewable liquid transp ortation fuel. Applied research in the area of biomass conversion to e thanol in the last 20 years has answered most of the major challenges on the road to commercialization but, as with any new technology, ther e is still room for performance improvement. A verified mathematical m odel was used to examine the most critical biochemical engineering asp ects of ethanol production in this study. Extensive simulations of the simultaneous saccharification and fermentation (SSF) of cellulose wer e conducted to identify the effects of operating conditions, pretreatm ent effectiveness, microorganism parameters, and enzyme characteristic s on ethanol production. The results clearly show that the biomass-enz yme interaction plays a dominant role in determining the performance o f SSF in batch and continuous operating modes. In particular, the dige stibility of the substrate (as a result of pretreatment) and the cellu lase enzyme dosage, specific activity, and composition had a profound effect on ethanol yield. This investigation verified the conclusion th at R&D emphasis should be placed on developing more effective pretreat ment methods and producing cellulase preparations of high specific act ivity (low cost per enzyme unit) to realize gains fi om any developmen t of advanced hexose/pentose-fermenting organisms.