Biomass is a carbon neutral material and the development of processes for the use of the bioethanol is being accelerated worldwidely, as its demand for an alternate transportation fuel is increasing. In order to make the production cost of bioethanol competitive to that of gasoline, the bioethanol process should be rationalized. We reported on rationalized process using corn stover as biomass resources. The production cost of bioethanol was decreased by 3.5¥/kg-ethanol by whole process improvements and calculated to be ¥26.3/kg-ethanol. Here, the results of rationalized process design and cost estimation of ethanol using cassava pulp instead of corn stover as biomass resource are reported. Cassava pulp is cheaper than corn stover based on unit ethanol production, however its composition is characterized as low cellulose and hemicellulose, and high starch and water contents compared to those of corn stover. The rationalized process was proposed under the consideration of those complex characteristics of cassava pulp. The production cost of bioethanol could be decreased to ¥22.2/kg-ethanol due to the rationalization in the pretreatment process and the saccharification process. The cost reduction of about ¥8/kg-ethanol or 26% compared to by the future NREL process was obtained.
