Coupling effect of high temperature and thermophilic bacteria indirectly accelerates the humification process of municipal sludge in hyperthermophilic composting

Abstract

Due to its high treatment efficiency and environmental friendliness when used to treat organic waste, hyperthermophilic composting (HC) has attracted extensive attention in recent years. However, it is still unclear how HC accelerates the degradation and humification process of organic matter. This study investigated the effects of high temperature and thermophilic bacteria on the degradation and humification of organic matter during HC. In the process of HC and conventional composting (CC), total organic carbon content decreased by 30.76 mg/g and 18.50 mg/g, while humic acid carbon content increased by 2.26 mg/g and 1.41 mg/g, respectively. These results showed that HC accelerated the humification process by enhancing the degradation of organic matter and the production of humic acid compared to CC. Redundancy analysis revealed that the rapid humification process of HC was related to high temperature and thermophilic bacteria. Thermophilic bacteria accelerated the degradation of organic matter in the high temperature stage, and the degradation products provided sufficient substances for the humification reaction in the low temperature stage, thereby accelerating the humification reaction. In conclusion, the coupling effect of high temperature and thermophilic bacteria indirectly accelerated the humification process. This work contributes to understanding the humification mechanism of HC.