Pilot-scale anaerobic digester for enhanced biogas production from poultry manure using a solar water heating system

A pilot-scale (0.5 m³) anaerobic digester was constructed in a small Palestinian poultry farm. The farm, located in Beit Ur Al Foqa village of Ramallah district, with a total area of 140 m² and accommodating about 1800 birds every 50 days produces annually about 6.57 tonnes (18 kg/day). The digester was filled with poultry manure and operated to obtain design parameters for a farm-scale biogas plant. The digester contained 20% of poultry manure co-digested with seed materials (70% cow manure and 10% anaerobic sludge) and mixed with the water in (1:1 ratio) to create dry digestion conditions (20% TS). Operated for one year, the feeding sequence of the anaerobic digester was once a day with a loading capacity of the daily produced manure in the farm. A low-cost solar water heating system was installed to enhance the biogas production in the digester under mesophilic process conditions. Poultry manure proved a suitable substrate for the installed biogas digester with total solids: 20%, and C:N ratio: 32:1. Total biogas production was 39.95 m³, and the methane content ranged between 46% and 68%. As substitute to natural gas, the biogas generated (788 MJ) was used for farm heating purposes during the study period. The fresh anaerobically digested slurry showed a nutrient rich fertilizer (NPK ratio of 2:3:3). Sun-drying of digested slurry increased pathogens removal (F. streptococcus) up to 3 log₁₀. Anaerobic digestion of poultry manure constitutes a bio-resource for both energy and nutrients. It is therefore an environmentally sound technology with zero waste emissions.