Study On Characteristics Of Greenhouse Gas Emissions From Aerobic Composting And Anaerobic Digestion Of Municipal Sewage Sludge

With the development of urbanization in China,a large number of urban sewage plants have been built,and the production of municipal sludge has also increased rapidly.Sludge treatment has become an urgent problem to be solved in China.Aerobic composting and anaerobic digestion of sludge are the mainstream technology of sludge stabilization and resource utilization,but greenhouse gases will be produced during aerobic composting and anaerobic digestion of sludge,and emission characteristics data are still relatively lacking.For this reason,this dissertation reveals the emission characteristics of greenhouse gases in aerobic composting and anaerobic digestion through on-site monitoring.Greenhouse gas emission characteristics of four different composting periods were studied during aerobic composting of sewage sludge.The results showed that the higher ambient temperature could accelerate the process of decomposing and decrease the moisture content of the compost;the pH of the compost increased first and then decreased;the total carbon and total nitrogen contents of the compost showed a downward trend;the ammonium nitrogen increased first and then decreased;the higher ambient temperature accelerated the loss of ammonium nitrogen;First increase,the high temperature period decreases,and the cooling period increases rapidly;the nitrite nitrogen shows a cumulative increase trend.And the CO2 emission rates of different cycles in the aerobic composting process were first increased and then decreased,and the CO2 emission rate and the total carbon content and total carbon content were significantly correlated,and the cumulative emission of the four cycles of CO2 was 263,216,92 and 91 g/kg.The emission of CH4 is concentrated in the heating period of compost,and it drops sharply after the high temperature period.There is no obvious emission in the maturity period.The emission rate of CH4 is significantly related to the water content of the heap and the total carbon content,and the cumulative emission of the four cycles is 161.15,400.25,334.46 and 61.57 mg/kg.The emission of N2O is concentrated in the heating period and the maturity period of the compost,and there is a significant negative correlation with the temperature of the heap.The cumulative emission of the four cycles of N2O is 77.84,395.97,329.99 and 210.26 mg/kg.In this dissertation,the characteristics of greenhouse gas emission in the process of sludge traditional anaerobic digestion and advanced anaerobic digestion were studied,and the IPCC calculation method and the CDM clean development mechanism calculation method were used to calculate the carbon emissions of anaerobic digestion.The results showed that the methane yield increased by 36%compared with the traditional anaerobic digestion.The carbon reduction of dry sludge in traditional anaerobic digestion and advanced anaerobic digestion is 0.64 tC02/tDS and 0.46 tC02/tDS respectively.Although advanced anaerobic digestion produces more methane,it will be heated during the hydrolysis process.Digesting large amounts of energy is not conducive to carbon reduction.