Suppression of ammonia inhibition in anaerobic digestion of high nitrogen concentrated feedstock with continuous pH control by acid addition

抄録

Anaerobic digestion of high-nitrogen wastes is inhibited by the presence of ammonia. We investigated a method to alleviate this inhibition by reducing free ammonia through pH control in the digester. The pH was reduced to a level lower than usual by adding acid. The results showed that the pH 6.8 could be controlled, without compromising methane production. Furthermore, low pH control enables operating the system under high nitrogen concentrations, up to a total ammonia nitrogen of 10,000 mg L⁻¹, while keeping a free ammonia at 100 mg L⁻¹ or less. This method can contribute to producing liquid fertilizers with high nitrogen concentration derived from highly nitrogenous wastes, and can be used as substitutes for both biomass energy and chemical fertilizers.