Upgraded Seawater-Alkaline Pre-Treatment of Lignocellulosic Biomass for Bio-Methane Production

The presence of lignin in lignocellulosic biomass leads to a protective barrier that prevents plant cell destruction by fungi and bacteria for conversion to bio-methane gas. Therefore, the aim of this study was to evaluate the effects of upgraded seawater with NaOH, NaCO2 and palm kernel ash (PKA) to produce the best alkaline solution in order to convert lignin and increase the fermentable sugars content in oil palm empty fruit bunch (OPEFB). In this study, alkaline pretreatment of EFB is carried out at room temperature using different concentration of alkaline solution which are 5%, 10%, 15% and 20% w/v of chemical (NaOH, Na2CO3 and PKA) and seawater for 48 hours. OPEFB in a size of 0.5 - 1.0 mm was soaked into the NaOH and Na2CO3 solution for 48 hours at room temperature. The surface morphology analysis of lignocellulosic biomass after pre-treatment were done by using scanning electron microscopic (SEM). Analysis of delignification using Kappa Number showed that the highest percentage of delignification were 86.6%, 69.8% and 58.8% by using concentration of 5% NaOH, 15% Na2CO3 and 20% PKSA, respectively. Morphological change on OPEFB was found when silica was cracks and creating a pore during pre-treatment. This significant increase in reducing sugar yields due to removal of silica and lignin. The results of FTIR showed lignocellulose were removed effectively from EFB fiber. This observation also supported FTIR and SEM analysis that showed significant changes in lignin structure throughout the pre-treatment process. Interestingly, with respect to all factors, upgraded seawater with NaOH demonstrated the highest delignification and fermentable sugar production.