Greenhouse gas emissions in a microbial fuel cell-assisted composting system: Microbial insights into bacterial structures and genetic functions.

Greenhouse gas emissions, including methane (CH), carbon dioxide (CO), and nitrous oxide (NO), have significant environmental impacts during the composting process. Herein, a microbial fuel cell (MFC)-assisted composting system was employed to investigate the emission profiles of these gases. CH and CO emissions were peaked during the temperature-heating phase, while NO emission showed maximum levels during the temperature-heating and maturation phases. Compared to the control (without MFC), MFC increased the abundance of Proteobacteria, Bacteroidota, and Gemmatimonadota in the composting mixtures, thereby enhancing the degradation of aromatic components, polymers, and lignin. Additionally, MFC increased pmoA abundance during the thermophilic phase while decreasing (nirS + nirK)/nosZ ratio after the temperature-heating phase. Consequently, cumulative emissions of CH, CO, and NO increased by 28 %, 18 % and 110 %, respectively, in the MFC-assisted composting system. These findings provide valuable insights into the microbial mechanisms driving gas emissions, and offer effective strategies for optimizing composting processes to mitigate greenhouse effects.