Potential Impacts of Compressed Natural Gas in the Vehicular Fleet of Mexico City

Abstract

One of the control measures to decrease urban air pollution in Mexico City is the introduction of compressed natural gas in gasoline-powered vehicles. In this study, an in-use vehicular fleet, representative of Mexico City's total vehicle population, was selected and converted to use natural gas. A comparison of emission factors for total hydrocarbons, CO, and NOx were obtained from the gasoline- and gas-powered vehicles using the Federal Test Procedure (FTP-75). Average emissions reductions from private cars and taxis, the most numerous fleet type, were 88% for CO, 91% for non-methane hydrocarbons, and 40% NOx. However, there is a 13% emissions increase in total hydrocarbons (that is, including methane). Speciated hydrocarbon data were used to estimate the potential of the emissions to form ozone and to predict the impact of fuel changes on air quality. In average, emissions from natural gas-converted vehicles were 2.3 times less reactive to form ozone than those from same vehicle fleet when gasoline-pow...