Synergistic effects of anaerobic digestion for diverse feedstocks: A holistic study on feedstock properties, process efficiency, biogas yield, and economic viability

Abstract

This research evaluates the anaerobic digestion potential of three distinct waste streams – sewage sludge, fruit and vegetable waste, and aquatic weeds – in independent batch systems, analyzing the feedstock characteristics, process efficiency indicators, and biogas generation potential over 56 days. Among these, fruit and vegetable waste feedstock produced the best results in terms of water displacement (685 mL), reducing volatile solids (VS) by 32.33 %, and chemical oxygen demand (COD) removal by 52.51 %, followed by sewage sludge and aquatic weed. Normalized biogas yield generated from fruit and vegetable waste digester reached 0.5814 m³ CH₄/kg VS, outperforming sewage sludge (0.4577 m³ CH₄/kg VS) and aquatic weed digester (0.4531 m³ CH₄/kg VS). Pearson's correlation analysis revealed a strong positive relationship between VS reduction and biogas yield in fruit and vegetable waste digester (r = 0.75). Digestate analysis confirmed suitability as a bio-fertilizer based on NPK content and heavy metal concentrations, meeting Fertilizer Control Order (1985) and CPCB standards. The economic analysis identified fruit and vegetable waste as the most viable feedstock, with the highest net profit (₹14,329.54) and the shortest discounted payback period (2.33 batches). This study's holistic approach of integrating experimental, statistical and economic assessment contributes to optimizing waste-to-energy strategies and circular economy initiatives by offering a structured framework for enhancing biogas production and anaerobic digestion process efficiency.