Estimation of Bioethanol Production Cost from Rice Straw by On-site Enzyme Production

Abstract

Production of bioethanol by the conversion of lignocellulosic material such as rice straw, based on enzyme hydrolysis and yeast fermentation has attracted much interest in recent years. Furthermore, the on-site production of cellulase enzyme is an important strategy for the development of commercial ethanol production. The cost-effectiveness analysis of bioethanol production from rice straw was analyzed in various scenarios of on-site cellulase enzyme production and cellulase enzyme purchase, assuming 15 JPY/kg rice straw cost and 15,000 kL/year facility size. Bioethanol production cost by on-site cellulase enzyme production was estimated at 177 JPY/L-ethanol. The equivalent enzyme cost suitable for the same ethanol production cost was 938 JPY/10⁶ FPU. The analysis showed that decreasing aeration from 1.0 to 0.5 VVM reduced the cost of bioethanol production to 171 JPY/L-ethanol and increasing cellulase productivity from 10.5 FPU/100 mg rice straw to 21.0 FPU/100 mg rice straw reduced the cost of bioethanol production to 147 JPY/L-ethanol. Therefore, bioethanol production cost was greatly affected by the enzyme productivity.