Optimizing biogas production from poultry manure and cocoa pod husks co-digestion: implications for circular bioeconomy and decentralized energy systems in West Africa

Introduction: Rapid population growth and agro-industrial expansion in West Africa are intensifying organic waste accumulation and energy insecurity, necessitating scalable waste-to-energy strategies. Methods: Batch biogas potential assessment assays were conducted using the ANKOM system under mesophilic (37°C) and thermophilic (55°C) conditions at C/N ratios of 20, 25, 30, and 35 using poultry manure (PM) and cocoa pod husk (CPH). Results: Under mesophilic mono-digestion, PM and CPH yielded 210.73 ± 27.12 and 244.65 ± 8.48 mL/g VS, respectively. Co-digestion significantly improved performance, with maximum cumulative biogas production of 348.65 ± 10.44 mL/g VS at C/N 25 under mesophilic conditions, corresponding to increases of approximately 65% and 42% compared with PM and CPH mono-digestion, respectively. Statistical analysis confirmed a significant effect of C/N ratio (p < 0.001) and a significant interaction between C/N ratio and temperature (p = 0.031). Discussion: Maintaining a balanced C/N ratio (25-30) under mesophilic conditions provides a technically robust and energy-efficient pathway for decentralized biogas systems. These findings support low-input anaerobic digestion strategies for circular bioeconomy development and sustainable energy access in West Africa.