Efficient biogas production from food waste utilizing Ag@ZnONPs catalyst and inoculum immobilization within anaerobic digestion reactors

Food waste presents a major opportunity for bioenergy production. Anaerobic digestion (AD) is effective but limited by low biogas yields. This study enhances biogas and biomethane generation by immobilizing anaerobic sludge (AS) within a polyvinyl alcohol/chitosan (PVA/Ch) cryogel matrix and incorporating silver doped zinc oxide nanoparticles (Ag@ZnONPs) as a catalyst. The highest biogas and biomethane production were achieved in R4-(FW+cryogel+NPs) at 534 mL/gVS and 252 mL/gVS, respectively, showing a 56.6% increase in biogas yield compared to R1-(FW). The methane content improved from 40.64% (R1) to 60.15% (R4), while substrate degradation efficiency also increased, with total solids (TS) reduction reaching 66.34% and volatile solids (VS) reduction at 74.8% in R4. The synergistic effect of cryogel and nanoparticles (NPs) enhanced microbial retention, improved substrate biodegradability, and stabilized the digestion process. These findings demonstrate the potential of advanced AD techniques for efficient waste-to-energy conversion and sustainable waste management.