2007 Volume 86 Issue 7 Pages 462-469
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. The bioethanol has advantages such as low environmental impacts and high octane number. However, its heat of combustion per unit volume is about 70% of that of gasoline. Even an expected cost by a future NREL process is ¥30/kg-ethanol, it is much higher than an assumed production cost of gasoline of ¥25/l (crude oil, $30/bbl). In order to make the production cost of bioethanol competitive to that of gasoline, the bioethanol process should be rationalized. We reported on the rationalization of the refinement process of the bioethanol in the former report and also the rationalization of the fermentation process using corn stover as biomass resource. Herein, we report on the rationalization of the pretreatment process which uses hot water without sulfuric acid. The cost reduction by the rationalization of the pretreatment process is ¥1.5/kg-ethanol. The production cost of bioethanol is decreased by ¥3.5/kg-ethanol by whole process improvements and calculated to be ¥26.3/kg-ethanol.