Life Cycle Inventories of Conventional and Alternative Automobile Fuel/Propulsion Systems:Summary and Conclusions

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. The improved fuel economy and lower emissions of hybrid and fuel cell vehicles do not justify their higher costs. We conclude that neither fuel availability nor environmental emissions need prevent personal transportation vehicles from dominating urban transportation over the next two decades.