Harnessing Lignocellulosic Pretreatment Waste Streams for Direct In-situ Biogas Upgrading

Recovering the underutilized hemicellulose fraction from lignocellulosic biomass pretreatment is crucial for ensuring the long-term sustainability of biorefinery operations. This study evaluates the feasibility of producing high-grade biomethane from the hydrolyzed hemicellulose fraction using a novel in-situ H2-assisted biogas upgrading approach. Selective hemicellulose depolymerisation of aspen poplar was performed using dilute acid - microwave hydrothermal treatment (DA-MHT), yielding an acidic xylose-acetate-rich feedstock suitable for anaerobic digestion (AD). To enhance biogas quality, an external ceramic membrane contactor was integrated with the AD, achieving up to 98% CH4 purity. Microbial analysis found enriched communities capable of metabolising lignocellulosic matter which contributed to a stable reactor performance.