Emission Inventory Of The Greenhouse Pollutants From Motor Vehicles In China And Its Control Potential Analysis

In recent years, China’s auto industry has been going through a skyrocketing development. The production and sales of motor vehicles in China have been ranking top one in the world for the latest five consecutive years. Vehicular emissions become a major source of urban and regional air pollution in China, and it is one of the fastest growing areas in greenhouse gas emissions. In China, most of the studies of vehicular greenhouse pollutant emissions have been focusing on CO2and black carbon, so there are few investigations on the emission factors or inventory of CH4, N2O and HFC-134a, which are also important greenhouse gases. Because of the absence of reliable data and technical support, it is difficult for the government to control the vehicular emissions of greenhouse gases and black carbon.In this study,106vehicles, including light-duty vehicles, motorcycles and heavy-duty vehicles, were tested on the chassis dynamometer and real road. With a broad literature investigation and a field survey in more than10typical cities in China, the activity data and emission characteristics of motor vehicles were obtained. Based on the work above, it has been developed the national-level emission inventory in year2010of CO2, CH4, N2O, HFC-134a and black carbon for motor vehicles in China. And the control potential of the vehicular greenhouse pollutant emissions in year2020has been further analyzed, in order to provide technical support for decision-makers to control the emissions.Based on the work above, the main conclusions and recommendations were given below,(1) The test results show that CO2emission factors of light-duty vehicles are between132g/km and286g/km, and the CO2emissions of natural gas powered vehicles are significantly lower, about22.31%in average, than those of gasoline vehicles. The CO2emission factors of heavy-duty vehicles range from376g/km to1246g/km, affected greatly by engine power and vehicle load, and the CO2emission factors of city buses are generally much higher than those of heavy-duty trucks because the buses are mostly operated at low-speed driving mode. CH4emission factors of light-duty gasoline vehicles range from0.017g/km to0.064g/km, while the average CH4emission factors of natural gas powered taxies are as high as1.11g/km, and the CH4emission factors of motorcycles are0.029～0.054g/km. N2O emission factors of light-duty gasoline vehicles range from0.008g/km to0.076g/km, and those of motorcycles fall in the range of0.014g/km-0.025g/km. The N2O emission factors of diesel trucks are very low, the maximum of which is only about0.014g/km. For heavy-duty diesel vehicles, black carbon account for39.36%of the total PM2.5mass in the exhaust emissions, and the emission factors are0.11～1.32g/km. In comparison, black carbon account for only9.40%of the total PM2.5mass in the exhaust emissions of gasoline vehicles, and the emission factor are0.002～0.033g/km. Because of the limited vehicle samples, it is recommended that more vehicles need to be tested in the future, to better represent the average emissions of the whole fleet.(2) In2010, the greenhouse pollutant (CO2, CH4, N2O, HFC-134a and black carbon) emissions of motor vehicles in China are6.78×18t,25.13×104t,6.02×104t,1.18×104t and9.78×104t, respectively, and7.83×108t CO2eq. in total. CO2and black carbon emissions account for86.50%and8.49%of the total vehicular greenhouse pollutant emissions (in terms of CO2eq.), so CO2and black carbon are the key pollutants for emission reduction. The contribution of non-CO2greenhouse gases (CH4, N2O and HFC-134a) to the total vehicular greenhouse pollutant emissions is5.01%, in which N2O and HFC-134a are more significant, sharing2.38%and1.95, and CH4has the smallest share of0.67%only. Analysis of the emission contributions by each type of motor vehicles reveals that, the two largest contributors of CO2emission are heavy-duty diesel vehicles and light-duty gasoline vehicles, and their emission reduction are generally implemented by improving the energy efficiency of power system and using low carbon fuels. For black carbon emissions, heavy-duty diesel vehicles should be the key type of vehicles to control. For non-CO2greenhouse gases, light-duty gasoline vehicles and natural gas powered taxis should be the key types of vehicles to control CH4emissions, and the emission reduction of natural gas powered taxis will be more efficient; additionally, light-duty gasoline vehicles should be the priority to control N2O emissions, and light-duty passenger cars are the main fleet to control HFC-134a emissions.(3) Under the baseline scenario, the greenhouse pollutant (CO2, CH4, N2O, HFC-134a and black carbon) emissions of motor vehicles in China are9.03×108t,39.31×104t (i.e., 825.43×104t C02eq.),7.47×104t (i.e.,2314.60×104t C02eq),3.23×104t (i.e.,4915.41×104t CO2eq) and5.07×104t (i.e.,3.45×104t CO2eq), respectively, in2020. Based on the baseline scenario, four emission control scenarios are designed including the implementation of tightened emission standards, using alternative fuels (natural gas), refrigerant recovery and refrigerant replacement. The implementation of more stringent emission standards promises a biggest emission reduction, by cutting13.16%of the total greenhouse pollutant emissions, which is about1.23x10t CO2. It is followed by the HFC-134a refrigerant replacement (by HFO-1234yf), which could bring an emission reduction of about2.06%. And using alternative fuels (Scheme1in2020) could reduce the emissions by about1.00%, but causing an increase of CH4emissions. Compared with the three emission control scenarios given above, there is no significant emission reduction by the refrigerant recovery, which could cut only0.45%of the total emissions.