The seasonal variation of emission of greenhouse gases from a full-scale sewage treatment plant

•Greenhouse gases (CO2, CH4, and N2O) emission from a STP was investigated.•Emission factor and the inventory of total greenhouse gas emission were evaluated.•The effect of water temperature on the CH4 emission was identified.•Measures for reducing greenhouse gas from STP were suggested. The seasonal variety of greenhouse gas (GHGs) emissions and the main emission source in a sewage treatment plant were investigated. The emission coefficient to treated wastewater was 291gCO2m−3. The main source of GHGs was CO2 from the consumption of electricity, nitrous oxide from the sludge incineration process, and methane from the water treatment process. They accounted for 43.4%, 41.7% and 8.3% of the total amount of GHGs emissions, respectively. The amount of methane was plotted as a function of water temperature ranging between 13.3 and 27.3°C. An aeration tank was the main source of methane emission from all the units. Almost all the methane was emitted from the aeration tank, which accounted for 86.4% of the total gaseous methane emission. However, 18.4% of the methane was produced in sewage lines, 15.4% in the primary sedimentation tank, and 60.0% in the aeration tank.