Study of washing method of oil palm empty fruit bunch-treated with alkali explosion in lignocellulosic bioethanol production

Abstract

The conventional process of lignocellulosic bioethanol production includes four steps: pretreatment, hydrolysis, fermentation, and purification. Pretreatment is the crucial way to enhance cellulose purity and remove lignin as well as other impurities compounds in biomass. Alkaline explosion is one of the most used pretreatment methods but pulp-produced is still in base condition. This pulp is not suitable as a substrate for enzymatic hydrolysis that needed a pH of 4.5-5.5. Therefore, pulp washing is required for separating pulp with black liquor and obtaining neutral pH pulp before going to hydrolysis. This study explored the washing method of oil palm empty fruit bunch (EFB)-treated with alkaline explosion in bioethanol production. The washing method using freshwater, acid solution, and a combination of freshwater and acid solution was investigated. As a result, the washing used freshwater needed the highest of water and wash cycles. The washing method using acid solution could obtain neutral pulp in two cycles wash step or more, thus, requiring higher acid consumption. The washing with combination method provided neutral pulp with fewer wash cycles, water, and acid. This method also provided the highest glucose and ethanol concentration. Therefore, the combination washing method is considered more efficient, economical, and environmentally for EFB pulp washing in bioethanol production.