Fuel-cycle energy and emissions effects of tripled fuel-economy vehicles

Estimates of the full fuel-cycle energy and emissions effects of light-duty vehicles with tripled fuel economy (3X vehicles) as currently being developed by the Partnership for a New Generation of Vehicles are presented. Seven engine and fuel combinations were analyzed: reformulated gasoline, methanol, and ethanol in spark-ignition, direct-injection engines; low-sulfur diesel and dimethyl ether in compression-ignition, direct-injection engines; and hydrogen and methanol in fuel-cell vehicles. Results were obtained for two market share scenarios. Under the higher of the two scenarios, the fuel-efficiency gain by 3X vehicles translated directly into reductions in total energy demand, petroleum demand, and carbon dioxide emissions. The combination of fuel substitution and fuel efficiency resulted in substantial reductions in emissions of nitrogen oxide, carbon monoxide, volatile organic compounds, sulfur oxide, and particulate matter smaller than 10 microns (PM10) for most of the engine-fuel combinations examined. The key exceptions were diesel- and ethanol-fueled vehicles, for which PM10 emissions increased.