Investigation of Microwave-Assisted Ethanol Pre-Treatment Towards Delignification Efficiency of 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 bio-resources in retrieving the 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 duration against delignification and the total sugars yield. The highest delignification rate was obtained with lowest amount of lignin left in OPEFB sample of 0.57% for samples pre-treated with ethanol, subjected to reaction time of 90 minutes and microwave power of 520 W. Microwave power functions to increase the temperature of the ethanol organic solvent utilized, which in turn helps break the protective lignin layer of OPEFB. On the other hand, the data on surface morphology supports this data finding, where OPEFB samples pre-treated with 55 vol% of solvent subjected to similar microwave duration and power is observed to have higher opened and deepened surface structure, in which higher thermal degradation lead to more lignin being removed in order to expose and extract the total sugars. Therefore, it can be concluded that ethanol pre-treatment in combination with microwave irradiation can serve as a novel integrated method to optimize the delignification process from OPEFB.