Evaluation and life cycle assessment of a poultry litter anaerobic digester with nutrient capture

This study evaluated a farm-scale (400 m3) anaerobic digestion (AD) system processing 11.2 tons/month of poultry litter (PL) with liquid recirculation and creation of three solid fertilizer products. An average CH4 production of 112 L CH4/kg volatile solids (VS) was achieved during the 22-month monitoring period, which rose to 222 L CH4/kg VS (949 m3 CH4/month) over time. The average TKN and TP captured from solid separation were 36.1 % and 56.4 %, respectively, with additional nutrients (12.9 % TKN and 23.3 % TP) captured from the filter press prior to liquid recirculation. The life cycle assessment (LCA) showed that if 3× more PL was processed in the AD system and the biogas was used in a combined heat and power (CHP) generator, the climate change impact would be 722 % lower and the eutrophication potential would be 510 % lower than the ‘Baseline Scenario’ of transporting unprocessed PL 40 km away for field application.