Optimization of Biomethane Yield of Xyris capensis Grass Using Oxidative Pretreatment

Biogas production from lignocellulose feedstocks has become an acceptable energy source globally due to their availability and economy. Lignocellulose materials have a complex arrangement that hinders digestion during the process. Therefore, applying the pretreatment process to lower the recalcitrant properties is required to utilize the full potential of the feedstock. This study, therefore, examines the influence of the oxidative pretreatment on the microstructural arrangement and biomethane yield of Xyris capensis. Piranha solution was prepared using H₂O₂ and H₂SO₄ at 100, 95:5, 85:15, and 75:25% of H₂O₂:H₂SO₄, respectively, and Xyris capensis grass was soaked in the prepared solution. The pretreated and untreated feedstocks were examined under the scanning electron microscope (SEM) to study the effect of the pretreatment on the microstructural arrangement. The effect of the pretreatment on biomethane yield was investigated during anaerobic digestion in a laboratory-scale batch digester at a mesophilic temperature (37 °C). The SEM analysis shows that the oxidative pretreatment method significantly affects the substrate’s microstructure, and the pretreatment’s severity depends on the percentage of H₂SO₄ added. A biomethane yield of 174.41, 188.61, 192.23, 207.51, and 139.71 mL CH₄/g VS_added was observed, and the yield was increased by between 24.84 and 48.52% compared to the untreated substrate. Therefore, applying oxidative pretreatment using low-cost H₂O₂ is a clear method of improving the biomethane yield of lignocellulose feedstocks.