Effect of Alkali Pretreatment on Lignocellulosic Waste Biomass for Biogas Production

Converting lignocellulosic waste biomass into biogas is a multi-step process; the rate limiting reaction is lignin removal. The objective of the current study was to evaluate alkali treatment for lignin removal and potential of biogas yield of pretreated waste biomass compared to untreated one. Three alkali reagents at various dosages: NaOH (1,2,3, and 5%), KOH (1,2,3, and 5%), and Ca(OH)(2) (0.5%) were tested at three different heating processes, water bath, autoclave and short time microwave. NaOH with short time microwave heating process had the highest delignification of 70-86% compares to other alkalies and heating processes. However, an opposite effect of high alkali dosage was observed on holocellulose. The highest cumulative biogas of 560 mL/gVS was obtained from 2% NaOH pretreated wheat straw, which was 2-times higher than the cumulative biogas produced from the same untreated substrates. In the present study, 2% NaOH alkali and microwave heating are determined optimum for lignin removal from waste biomass and enhancement in biogas production.