Optimization of Biomethane Yield of Xyris capensis Grass Using Oxidative Pretreatment

Abstract

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 VSadded 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.

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“…The optimum daily biomethane released was recorded between days 6 and 11 for pretreated substrates, whereas the optimum daily biomethane yield from untreated substrates was recorded on day 16. This result further established the previous findings that pretreatment methods influence the daily biomethane yield of lignocellulose feedstocks (Olatunji and Madyira, 2023d). This indicates that DES pretreatment significantly affects the daily biomethane yield and reduces the retention time of the process.…”