Enhanced biogas production from lignocellulosic biomass via integrated Fenton and plasma treatment

Despite its potential as a sustainable energy source, the direct bioenergy conversion of plant-based lignocellulosic biomass in anaerobic digestion (AD) is hindered by its recalcitrant structure, which is attributed to its high lignin content. This study proposes a novel integrated pretreatment that combines Fenton and microbubble plasma technology to enhance biomethane production from maize biomass. The approach disrupts the complex lignocellulosic structure by harnessing the synergistic oxidative effects of Fenton and plasma-generated radicals, facilitated by enhanced mass transfer of plasma-generated reactive oxygen and nitrogen species through microbubble plasma technology. Pretreatments were carried out across varying molar ratios of Fenton reagents (1:25, 1:50, and 1:75) and plasma treatment durations (30, 60, and 90 min). The optimal conditions, 1:25 M reagent ratio and 30 min microbubble-plasma exposure, achieved a 32 % improvement in delignification compared to untreated maize. ATR-FTIR analyses confirmed structural and chemical alterations that improved substrate accessibility. As a result, biomethane yields increased by 26 % in batch tests (348 N mL/g VS) and by 16 % under continuous tests (119 N mL/g VS) in comparison to the untreated biomass. This combined pretreatment approach enhances AD efficiency, as evidenced by improved biomethane yields and process stability. Energy input-output analysis showed that integrated pretreatment required ∼1.67 MJ/kg biomass, while biomethane production yielded a positive fourfold net energy gain. These findings demonstrate that synergistic integration of Fenton and plasma technologies is a promising approach to valorise lignocellulosic biomass and advance circular bioeconomy goals, including waste-to-energy conversion, renewable energy production, resource recovery, and environmental resilience.