Mitigation of ammonia inhibition in continuous operation of anaerobic digestion by addition of biochar

Abstract

Anaerobic digestion is an energy production system in which organic wastes such as livestock manure and food waste are decomposed by anaerobic microbial metabolism and converted to methane. One of the challenges of anaerobic digestion is ammonia inhibition. Ammonia inhibition is a phenomenon in which the accumulation of ammonia generated during fermentation inhibits the bacteria, resulting in reduced fermentation performance. Co-digestion, ammonia stripping, and acclimation of microorganisms to ammonia have been considered as methods to deal with ammonia inhibition, but their low operability is a disadvantage. Therefore, we examined the use of additives as a simpler solution. It has been reported that the use of electron-transferring substances as additives can alleviate ammonia inhibition by promoting metabolic reactions in microorganisms. In this study, biochar was added in a continuous mesophilic anaerobic digestion test under high ammonia concentration conditions, and the effect of biochar on fermentation performance, including methane yield and volatile fatty acid concentration, was evaluated.