Life cycle environmental impact assessments and comparisons of alternative fuels for clean vehicles

In this study, a comparative life cycle assessment of internal combustion engine-based vehicles fueled by various fuels, ranging from hydrogen to gasoline, is conducted in addition to electric and hybrid electric vehicles. Three types of vehicles are considered, namely; internal combustion engine vehicles using gasoline, diesel, liquefied petroleum gas, methanol, compressed natural gas, hydrogen and ammonia; hybrid electric vehicles using 50% gasoline and 50% electricity; and electric only vehicles for comprehensive comparison and environmental impact assessment. The processes are analyzed from raw material extraction to vehicle disposal using process-based life cycle assessment methodology. In order to reflect the sustainability of the vehicles, seven different environmental impact categories are considered: abiotic depletion, acidification, eutrophication, global warming, human toxicity, ozone layer depletion and terrestrial ecotoxicity. The primary energy resources are selected based on currently utilized options to indicate the actual performances of the vehicles. The results show that electric and plug-in hybrid electric vehicles result in higher human toxicity, terrestrial ecotoxicity and acidification values because of manufacturing and maintenance phases. In contrast, hydrogen vehicles yield the most environmentally benign option because of high energy density and low fuel consumption during operation.