Transportation options in a carbon-constrained world: Hybrids, plug-in hybrids, biofuels, fuel cell electric vehicles, and battery electric vehicles

Multiple alternative vehicle and fuel options are being proposed to alleviate the threats of climate change, urban air pollution, and oil dependence caused by the transportation sector. We report here on the results from an extensive computer model developed over the last decade to simulate and compare the societal benefits of deploying various alternative transportation options including hybrid electric vehicles and plug-in hybrids fueled by gasoline, diesel fuel, natural gas, and ethanol, and all-electric vehicles powered by either batteries or fuel cells. These simulations compare the societal benefits over a 100-year time horizon of each vehicle/fuel combination in terms of reduced local air pollution, greenhouse gas pollution, and oil consumption compared to gasoline cars.The model demonstrates that partially electrified vehicles such as hybrids and plug-in hybrids will appreciably cut greenhouse gas pollution and oil consumption, particularly if biofuels such as cellulosic ethanol can displace a large amount of gasoline. But if we are to achieve an 80% reduction in greenhouse gases below 1990 levels, eliminate most oil imports and most urban air pollution, then society must transition to all-electric vehicles powered by some combination of fuel cells and batteries. We cannot achieve our transportation sector goals if most vehicles still rely on internal combustion engines for some of their motive power. We conclude that society must rely on a portfolio of alternative vehicles to achieve our societal objectives, beginning with hybrids, plug-in hybrids, biofuels, and transitioning to all-electric fuel cell and battery electric vehicles over time.