Hyperthermophilic composting reduces nitrogen loss via inhibiting ammonifiers and enhancing nitrogenous humic substance formation

Abstract Composting is an efficient and economic approach used to convert organic waste into organic fertilizers. However, the substantial nitrogen loss during the composting process is one of the major disadvantages of conventional thermophilic composting ( c TC). Here, we demonstrated for the first time that hyperthermophilic composting ( h TC) was able to mitigate nitrogen loss by 40.9% compared to c TC after 44 days of composting in a full-scale plant. Results demonstrate a decrease in NH 3 volatilization (52.4%), together with an inhibitory effect on protease (19.4–87.5%) and urease (9.1–75.2%) enzyme activities and the ammonification rate (5.2–80.1%) for h TC. Additionally, this study found that h TC could accelerate the humification process, thereby enhancing the formation of the recalcitrant nitrogen reservoir (mainly in the form of nitrogenous humic substances) and reducing the substrate for ammonification reactions. These findings suggest that h TC can significantly reduce nitrogen loss and provide insights into the role of humic substances in nitrogen retention in composting systems.