(619am) Hydrothermal Pretreatment of Rice Husk with Biodiesel Waste As the Reaction Medium

Agricultural waste is becoming more popular as cellulosic biomass for bioethanol production because it is not competing with human food supply. Rice is the largest agriculture product of Japan including in the small district in Oasa, Kita Hiroshima, Hiroshima Prefecture. As the consequence, rice husk is produced annually in large amount in this region. Rice husk is mostly remains unutilized and it contains cellulose. Therefore, it has the potential to be converted into bioethanol. Hydrothermal process is known as environmental friendly pretreatment technique to convert cellulosic biomass into various products including bioethanol since it is using hot compressed water solely as the medium. However, studies shown that catalyst addition improve the yield of products. Alkali catalyst like sodium hydroxide is often used in hydrothermal pretreatment since it is low cost chemical and easily obtained. Nonetheless, the reduction of catalyst cost will be beneficial to make bioethanol more economically competitive. Interestingly, in district of Oasa, Kita Hiroshima Japan, biodiesel has been produced from vegetable cooking oil waste and being utilized for diesel engine vehicles. This biodiesel production generates biodiesel waste that has very high pH (alkaline) and treatment is required to neutralized it before discarding it into the environment. In this research, the possibility of using the alkali characteristic in biodiesel waste to replace commercial alkali catalyst for hydrothermal pretreatment of rice husk is studied. The study was conducted using autoclave reactor made from stainless steel. The experiments were carried out at reaction temperatures of 150, 200 and 250 °C, reaction times of 30 min, and the biodiesel waste addition varied 0, 10, 20, 50 % v/v. To measure the effectiveness of pretreatment, enzymatic hydrolysis was employed after pretreatment to obtain glucose yield. The effect of biodiesel waste addition on rice husk conversion to glucose by hydrothermal pretreatment at various temperature was elaborated.