Microscopic and Biochemical Analysis to Better Understand the Impact of Alkaline Pretreatments on Lignocellulosic Biomass

Abstract

Due to an increased demand for more sustainable energy sources, Anaerobic Digestion (AD) of solid organic wastes such as biomass and energy crops have been gaining attention. In this study, varieties of sorghum and miscanthus were chosen as lignocellulosic biomass to be used for biodigestion because of their promising features for energy production in the context of a French initiative called Biomass for the Future (BFF). In the process of AD, organic material such as cellulose is broken down, but in lignocellulosic substrates, lignin acts as an inhibitor for this process. Pretreatments can be applied to the substrate in order to break down lignin and expose cellulose before the digestion. In this study, alkali pretreatments were applied using CaO and NaOH at 10% of concentration according to the sample’s Dry Mass value in different temperatures (26 and 55⁰C) to evaluate its efficiency, quantifying both the removal of lignin and the availability of cellulose. Pretreatments were evaluated from 0,5 to 144 hours. Staining with FASGA and Phloroglucinol HCl solution were performed and a kinetics study was made. Phloroglucinol-HCl staining showed that temperature has a positive correlation with lignin removal. The most effective pretreatments on both sorghum and miscanthus samples was pretreatment using NaOH at 55⁰C.