Optimizing biogas production through the co-digestion of tannery fleshing, cowdung, and sewage water using response surface methodology

Tannery waste management presents a significant environmental challenge, as improper disposal practices lead to the contamination of land and water bodies. Anaerobic co-digestion has the potential to convert protein-rich tannery fleshing into renewable energy. However, the selection of substrates and its dosing as well as physicochemical properties remain the prime factors for energy production and optimization. Therefore, this study aims to optimize biogas production through the anaerobic co-digestion of tannery fleshing, cowdung, and sewage water using Central Composite Design, inclusive Response Surface Methodology. The impact of temperature (35–45°C), volatile solid (VS) concentration (3500–7000 mg/L), and substrate-to-inoculum ratio (S/I; 1–1.5) in biogas production have been investigated and analyzed using 19 batch experiments. The optimal temperature of 45°C, VS of 6800 mg/L, and S/I of 1.33 have been evaluated producing nearly 6700 mL of biogas (71 % of CH₄) after 35 days. The response surface model shows R² > 99 % with no significant lack-of-fit in predicting the biogas production. These findings may lead to implementing circular bio-economy practices, promoting environmental sustainability, and producing efficient energy.