Anaerobic digestion of poultry droppings for biogas production: a pilot study of renewable energy technology in the agricultural sector

Abstract

Proper management of agricultural waste is challenging due to diverse sources, high production volumes, seasonal fluctuations, limited technical knowledge, and insufficient funding. These challenges often lead to soil degradation, environmental pollution, and adverse effects on ecosystems and human health. This study aims to investigate biogas production from poultry droppings using Continuous Stirred Tank Reactor (CSTR) Anaerobic Digestion (AD) technology to promote green energy use and as a sustainable solution for agricultural waste management. Dried poultry manure samples were collected from two poultry farms in Lafia city and from their manure disposal sources. The samples were thoroughly stirred to ensure homogeneity and digested at a mesophilic temperature of 28.0 °C. With an initial solid concentration of 20.0%, the manure was diluted with water at 1:2 ratio to produce an input slurry containing 12.0% total volatile solids by weight. The experiment was conducted from July 20 to September 10, 2025. Parameters including pH, alkalinity, temperature, and biogas flow rate were monitored daily. Chemical and physical analyses of total solids, total volatile solids, and chemical oxygen demand were conducted during startup using three biological replicates (n = 3), with results expressed using statistical tool of mean ± standard error. Volatile fatty acids and alkalinity were measured using the distillation method. Due to reduced ambient temperatures during the rainy month of August, a solar water heating system was integrated to stabilize digester temperature and evaluate the influence of solar energy on anaerobic fermentation. Volatile fatty acid concentrations increased during early digestion due to hydrolysis, acidogenesis, and acetogenesis. Biogas production began after 29 days, indicating methanogenesis. The digester produced an average of 0.3 L day⁻¹, with a cumulative yield of 4.5 L. Solar heating increased average temperature by 35% and biogas production by 85% on sunny days compared with rainy days. Anaerobic digestion of poultry droppings using CSTR technology is effective for bioenergy recovery and sustainable waste management. The process supports circular economy principles by converting waste into renewable energy. Further research on co-substrates and economic optimization is recommended to enhance biogas production and support Sustainable Development Goal 7.