BIOGAS PRODUCTION FROM RICE-STRAW BY SOLID-STATE ANAEROBIC DIGESTION
Abstract
This study investigated the potential of rice straw as a feedstock for biogas production using solidstate anaerobic digestion (SS-AD) under varying substrate-to-inoculum ratios. The rice straw exhibited a high volatile solids content (83.2%), with significant cellulose (41.6%) and hemicellulose (25.7%) concentrations, indicating its suitability for biogas production. Three reactors with substrateto-inoculum ratios of 1:1, 2:1, and 3:1 were assessed over a 30-day retention period. The reactor with a 2:1 ratio (R2) produced the highest cumulative biogas yield (310 mL/g volatile solids) and the highest methane content (58%), with the lowest CO₂ content (39.5%), making it the most efficient configuration. Peak biogas production occurred within the first 20 days for all reactors, aligning with rapid hydrolysis and methanogenesis phases. Reactor R2 also achieved the highest volatile solids removal efficiency (77.5%), demonstrating superior substrate digestion compared to R1 (69.5%) and R3 (63.2%). These results highlight the importance of optimizing the substrate-to-inoculum ratio to maximize biogas yield and methane content. The findings are consistent with previous studies on anaerobic digestion of lignocellulosic biomass and suggest that rice straw is a promising renewable feedstock for sustainable energy production. Future work could explore pretreatment methods to enhance the biodegradability of lignin-rich substrates.
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