Abstract
Biomass is a carbon neutral material and the development of processes for the use of the bioethanol is accelerating worldwide as the demand for its use as an alternate transportation fuel increases. The bioethanol has various advantages in the fuel performances of the environmental and the octane number, etc. But the amount of heat of combustion for each unit volume is about 70% of gasoline, the price of bioethanol is necessary to be less than 70% of the gasoline with competitive for gasoline. It is assumed a current gasoline refinery cost is about Y40/L (crude oil, $50/bbl). The ethanol production cost is preferable to be less than Y20/ kg to be competitive to gasoline cost. Then the rationalization of the bioethanol process is necessary. The examination of the use of the lignocellulosic biomass with the possibility of cheap and a large amount of supply as a raw material biomass and the rationalization in the process are necessary. We reported on the rationalization process in the refinement process of the bioethanol by the former report. Herein, the design of a high speed fermentation process which uses recombinant Coryneform type bacteria transformed by a recombinant DNA technology for the cost reduction is reported. A high speed fermentation of 30kg-ethanolm-3·h-1 was assumed by the application of a high bacteria concentration of 30wt% (wet base). The produc-tion cost including both fixed and variable cost of the newly designed process was evaluated at an annual production rate of 206, 000t-ethanol. The resulting cost was compared with the production cost using a future NREL (National Renewable Energy Laboratory) process. The high speed fermentation process, whose reten-tion time was 1.7h, required smaller volume of fermentators than those for NREL process by 5%. This reduced the investment cost by Y0.3/kg-ethanol compared to that of NREL process. The variable cost of the new process could be reduced by Y1.1/kg-ethanol. Further research work to attain the above cost reduction is for the confirmation of high bacteria concentration fermentation with low nutrient dose.
