The conversion of organic nitrogen by functional bacteria determines the end-result of ammonia in compost

The conversion of organic nitrogen determines the quality of composting and its environmental impact, but its underlying microbial mechanism is unclear. Hence, in static composting reactors with forced ventilation, vegetable waste, straw and pig manure were used as raw materials to simulate the composting for 33 days with or without adding 9% biochar. In composting, amino acid and amino sugar nitrogen were most easily converted to ammonium and hydrolysable unknown nitrogen was synthesized from ammonium. The aprA and chiA-related bacteria converted amino acid nitrogen to ammonium, and ammonium to hydrolysable unknown nitrogen, while amoA and HAO-related bacteria converted amine and amino sugar nitrogen to ammonium. Additionally, soluble microbial byproduct-like materials (62.4%) significantly affect organic nitrogen transformation, and could reduce ammonia emission by increasing ammoxidation rates. Thus, whether or not adsorbent substances are added, microorganisms affect the production of ammonia by controlling the conversion of organic nitrogen.