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We compare the life cycle inventories of near–term fuel–propulsion technologies. We analyze fossil fuels (conventional and reformulated gasolines, low sulfur diesel, and compressed natural gas (CNG)), ethanol from biomass, and electricity, together with internal combustion engines (port and direct injection, spark and compression ignited) and electric vehicles (battery–powered, hybrid electric, and fuel cell). The fuel economy and emissions of conventional internal combustion engines powered by gasoline continue to improve. Unless emissions of pollutants and greenhouse gases (GHG) are stringently regulated or gasoline prices more than double, gasoline powered internal combustion engines will continue to dominate the light duty fleet. Two appealing alternative fuels are CNG and biomass ethanol. CNG cars have low emissions, including GHG and the fuel is less expensive than gasoline. Biomass ethanol can be renewable and have no net carbon dioxide (CO2) emissions.

We compare two methods for life cycle analysis: the conventional SETAC-EPA approach and Economic Input-Output Life Cycle Analysis (EIO-LCA). The methods are compared for steel versus plastic fuel tank systems and for the entire life cycle of an automobile, from materials extraction to end of life. The EIO-LCA method gives comparable results for the data common to the two methods. EIO-LCA gives more detailed data, specifies the economy wide implications, and is much quicker and less expensive to implement.