Investigation of Microwave Irradiation and Ethanol Pre-Treatment toward Bioproducts Fractionation from Oil Palm Empty Fruit Bunch

Abstract

Lignocellulosic biomass (LCB), such as the oil palm empty fruit bunches (OPEFB), has emerged as one of the sustainable alternative renewable bioresources in retrieving valuable bioproducts, such as lignin, cellulose, and hemicellulose. The natural recalcitrance of LCB by the disarray of lignin is overcome through the combinative application of organosolv pre-treatment followed by microwave irradiation, which helps to break down LCB into its respective components. This physicochemical treatment process was conducted to evaluate the effect of ethanol solvent, microwave power, and microwave duration against delignification and the total sugar yield. The highest delignification rate was achieved, and the optimum level of total sugars was obtained, with the smallest amount of lignin left in the OPEFB sample at 0.57% and total sugars at 87.8 mg/L, respectively. This was observed for the OPEFB samples pre-treated with 55 vol% of ethanol subjected to a reaction time of 90 min and a microwave power of 520 W. Microwave irradiation functions were used to increase the temperature of the ethanol organic solvent, which in turn helped to break the protective lignin layer of OPEFB. On the other hand, the surface morphology supported this finding, where OPEFB samples pre-treated with 55 vol% of solvent subjected to similar microwave duration and power were observed to have higher opened and deepened surface structures. Consequently, higher thermal degradation can lead to more lignin being removed in order to expose and extract the total sugars. Therefore, it can be concluded that organosolv pre-treatment in combination with microwave irradiation can serve as a novel integrated method to optimize the total sugar yield synthesized from OPEFB.