Anaerobic Digestion of Poultry Droppings in Semi-Continuous Mode and Effect of Their Co-Digestion with Physico-Chemical Sludge on Methane Yield

Abstract

Poultry waste is rich in organic matter, which allows its treatment by the process of anaerobic digestion (AD) to reinforce economic and environmental green strategies. The aim of this study is to assess the technical feasibility of poultry waste AD in semi-continuous mode and to intensify methane production by co-digestion with physico-chemical sludge, i.e., the product of the primary treatment of wastewater after the slaughtering process. First, the AD of poultry droppings is conducted in a continuous stirred anaerobic digester (CSAD) at 37 °C. A volume of 0.791 and 0.623 Nm3·Nm−3 reactor·days−1 of biogas and methane, respectively, were produced during the entire process stabilization period. Biochemical characterization of the substrate and the final digestate show high reduction rates of the biochemical fractions, which corroborates with methane yield. In addition, the co-digestion of poultry droppings with two different ratios of physico-chemical sludge (20% and 40% added sludge considering the amount of volatile solids) shows an increase in methane production versus droppings alone, with a higher increase of 54% with a sludge ratio of 40%. Altogether, these promising results were obtained in stable processes, highlighting the pertinence of our study.