Two stage pretreatment of empty fruit bunches (EFB) with acetic acid and aqueous ammonia for the enzymatic hydrolysis

Oil palm empty fruit bunches (EFB) are the main waste products of the palm oil processing industry. Every year 14.9 and 37.7 million tons of EFB are produced in Malaysia and worldwide, respectively. Since the bunches are rich in cellulose and hemicellulose that are not easily digested, they are considered to be one of the most abundant lignocellulosic feedstocks available for the production of biofuels. Pretreatment is necessary for reducing the hemicellulose and lignin contents in EFB for effective bioethanol fermentation. Several studies have evaluated the effects of some pretreatment processes, such as alkaline pretreatment, aqueous ammonia soaking pretreatment, and sequential pretreatment with dilute acid and then alkali on enzymatic digestibility of EFB. However, to obtain high glucose yield in the enzymatic hydrolysis stage and minimizing the sugar loss by decomposition process, an effective pretreatment process still needs to be investigated to fulfill the biorefinery of EFB. In this study, The sequencial two stage process with combination of CH₃COOH and NH₄OH was performed to increase the fraction of cellulose per unit raw EFB. The pretreatment procedure consisted of a CH₃COOH treatment as the first step to extract hemicellulose fraction and then NH₄OH treatment as a second step to eliminate lignin from EFB. Unique process above mentioned has been evaluated on reducing non-fermentable components, but also on enhancing enzymatic hydrolysis due to changed compositional structure in EFB.