Biogas production from water lilies, food waste, and sludge: substrate characterization and process performance

Abstract The potential of water lilies, food waste, and sludge as substrates for biogas production through anaerobic digestion was investigated. We thoroughly characterized these substrates and found that water lilies had a pH of 6.4, total solids (TS) of 18.42%, volatile solids (VS) of 81.46%, and a moisture content of 87%. Food waste exhibited a pH of 7.6, TS at 27.23%, VS at 90.6%, and a moisture content of 75%. Sludge had a pH of 6.5, TS of 6%, VS of 60%, and a moisture content of 95%. Biogas production exhibited variations among the reactors. Reactor 1 reached a cumulative production of 2,527 mL, while Reactor 4 achieved 3,404 mL, with different lag phases. Reactor 4 displayed the highest biogas yield at 262 mL/g VS. Post-digestion tests confirmed efficient digestion, with volatile fatty acids ranging from 140 to 300 mg/L acetic acid and alkalinity levels between 800 and 1,500 mg CaCO3/L. Our study estimated a significant methane content, with the potential to produce 94.32 L of methane from 1 kg of TS.