Air quality and climate co-benefits estimation for vehicle fuel switching in Ho Chi Minh City

Transportation is identified as one of the major sources causing air pollution in Ho Chi Minh City (HCMC). International Vehicle Emission Model was used to conduct emission inventory of taxis and motorcycles in HCMC in 2014 and project the total emission in 2020. CO2 equivalent of nine air pollutants including climate forcers was generated from the model. To estimate emissions from different vehicle types, Global Positioning System (GPS) and technical activities surveys were carried. Emission factors (EFs) of taxi and motorbike, as well as the reduction of CO2 equivalent of fuel switching scenarios, were figured out. Results showed that the annual emission of taxis and motorcycles of HCMC in 2020 for CO, NOx, SO2, CO2, N2O, CH4 were 0.539; 1.417; 0.047; 1.597; 0.064; 0.109; 0.014; 0.046 and 4.213; 1.329; 0.124; 0.696; 0.510; 2.035; 1.653; 5.370 Mt/year, respectively. The potentiality of air quality and climate co-benefits was determined by using Global Warming Potential (GWP) and EFs of emission species. Fuel switching would bring noticeable benefits, in CO2 equivalent. If 50% of taxis and motorcycles in HCMC switched from traditional fuels to compressed natural gas (CNG) (Scenario 1) and liquefied petroleum gas (LPG) (Scenario 2), the total emission of nine selected pollutants for both taxi and MC fleets would reduce in Scenario 1 more than Scenario 2. Switching to CNG would also bring more climate benefits than those of switching to LPG as it reduced 16% and 57% of climate forcers in CO2 eq. Between taxi and motorcycle fleet, emission from motorcycles was higher than those from taxis.