Bacterial agents affected bacterial community structure to mitigate greenhouse gas emissions during sewage sludge composting

•Impact of bacterial agents and bamboo biochar on sewage sludge composting were investigated.•The addition of B1 and C reduced CH4 emission and decreased C and N losses.•B1 was more effective to reduce GHG emissions than B2.•Bacterial agents and bamboo biochar affected the microbial structure.•Temperature, pH, and TKN were the main factors that affect the microbial dynamics. The present work studied the influence of bacterial agents (B1, B2) and bamboo biochar (BB) on greenhouse gas emissions and bacterial community during the sewage sludge composting. Results showed that compared with CK, the total methane emissions ofC, B1, B1C, B2, and B2C treatments declined by 16.4%, 25.2%, 45.4%, 7.8%, and 44.4%, respectively. The total N2O emissions ofC and B1C treatments declined by 5.1% and 3.7% while B1, B2, and B2C treatments increased the total N2O emissions by 6.7%, 21.6%, and 10.4%, respectively. These results illustrated that the addition of BB is conducive for reducing greenhouse gas emissions while different bacterial agents have various effects. According to pearson correlation analysis, N2O emissions and Acidimicrobiia, Alphaproteobacteria, Gammaproteobacteria, and Tepidiformia have strong negative correlation while positive correlation with Bacilli and Clostridia. Methane emissions have a strong negative correlation with Actinobacteria. CO2 emissions have a strong positive correlation with Bacilli.