Upgrading the performance of high solids feeding anaerobic digestion of chicken manure under extremely high ammonia level

Abstract

Biogas production using high solids feeding anaerobic digestion has several benefits, including higher treatment capacity, lower energy requirements, and reduced volume of digestate. However, when chicken manure is used as a substrate, the process is prone to reactor instability due to ammonia inhibition. This study investigated the performance of three laboratory-scale anaerobic systems fed by chicken manure with total solids (TS) up to 15%, giving rise to total ammonia nitrogen (TAN) concentration of 7.5 g/L. The tolerance of the anaerobic system to ammonia inhibition was evaluated by operating three organic loading rates (OLR) in the range of 1.5–4.5 g-volatile solids (VS)/(L·d). The results showed that methane yield reached 0.33 L/g·VS under an OLR of 1.5 g-VS/(L·d), comparable to conventional wet-type process performance. The total volatile fatty acids (VFAs) were below 0.5 g/L, indicating a highly acceptable performance. The digestive performance deteriorated when the OLR was increased to 4.5 g-VS/(L·d) and highlighted the importance of selecting an appropriate OLR. The result may support the adoption of high solids feeding anaerobic treatment for nitrogen-rich materials.