Enhancing microstructural and biomethane yield of Xyris capensis using combined oxidative and nanoparticle additive pretreatment methods

Abstract

Renewable energy production from lignocellulose materials is a significant interest of modern research because it can assist in reducing the global challenges of climate preservation and energy demand. Lignocellulose materials are recalcitrant and are not easy to digest during anaerobic digestion, and this necessitated their pretreatment before anaerobic digestion for effective and efficient use of the feedstock. Therefore, this study investigated the effect of oxidative, nanoparticle additive, and combined pretreatment on the microstructural arrangement and biomethane yield of Xyris capensis, an economical feedstock that is readily available. Xyris capensis was pretreated with the oxidizing agent at varying conditions of H2O2: H2SO4 using 100: 0%, 95: 5%, 85: 15%, and 75: 25%. The effects of the pretreatment on the microstructure, crystallinity, and functional groups of the substrate were investigated. Pretreated and untreated substrates were digested as mono pretreatment and in combination with 20 mg/L Fe3O4 (< 50 nm) nanoparticles at mesophilic temperature to study the influence of pretreatment on biomethane yield. Results from structural analyses showed that the pretreatment conditions have a varying degree of effect on the microstructural arrangement. The optimum biomethane yield of 212.18 mL CH4/gVSadded, representing 48% improvement, was recorded for a single pretreatment. For the combined pretreatment method, the highest biomethane yield of 278.59 mL CH4/gVSadded, which represents a 95% increase, was observed. Therefore, combined oxidative pretreatment and Fe3O4 nanoparticle additive could be a promising approach to debase the recalcitrant properties of lignocellulose feedstock microstructure to enhance the biomethane yield. This technique can improve energy recovery from lignocellulose materials, assist in decarbonization of the environment, and can be examined on a commercial scale.