Optimization of Energy and Material Balances in Small-Scale Bioethanol Production System

We have proposed the “local fuel” system which achieves a reasonable regional energy system based on local production of fuels for local consumption. As an example we developed a bioethanol production system from locally available unused lingocellulosic biomass (e.g., rice straw). Because most of the local biomass utilization systems are operated within limited areas, the scale of the processes cannot be so large. It is important to optimize the energy and material balances in the system, so that the system runs sustainably even in a small-scale. This presentation deals with the design and demonstration of a small-scale bioethanol production system equipped with a biomass boiler. The fuel of this biomass boiler was also locally available biomass (e.g., rice husk) and charcoal/ash was produced as well as the energy (steam). The material and energy balances in the ethanol production process such as pretreatment, saccharification and fermentation, and the biomass boiler such as gasification, combustion and heat exchange, were analyzed. As a result, the operation condition was optimized to achieve a sustainable local fuel production away from the dependence of fossil energy.