Comparison of acid and alkaline pre-treatment of lignocellulosic materials for biogas production

Abstract

This work deals with the study of a pre-treatment method promoting degradability of lignocellulosic biomass and hence biogas yield therefrom, as this material is challenging to decompose due to its structure. The investigated pre-treatment methods are hydrolysis of the material in NaOH (0.5% and 5%) and H<sub>2</sub>SO<sub>4</sub> (0.5% and 5%) at temperatures of 90–100 °C for 2 h. This work aimed to compare the effects of these pre-treatment methods on the lignocellulosic composition of maize waste (maize stalks, leaves and cobs), rapeseed straw and wheat straw and the biogas yields from its subsequent anaerobic digestion. Pre-treatment by 0.5% NaOH increased the biogas production the most (by 159% for rapeseed straw, 240% for wheat straw and 59% for maize waste) also the degrees of solubilisation was higher, at the same time the proportions of total organic carbon (TOC) in the solid component appear to be sufficiently high, it could be assumed that there has been sufficient disturbance of the material structure. Alkaline methods have proven to be more suitable compared to acid pre-treatment methods, also the use of alkali with a lower concentration has shown to be more efficient, which is more advantageous for use in practice from an environmental and economic point of view.