Exergetic environmental assessment of life cycle emissions for various automobiles and fuels

This paper examines material emissions produced during thirteen fuel life cycles for automobiles, on mass and exergy bases. The masses of fuel life cycle emissions are compared with the chemical exergies of these emissions. For the emissions data used, the chemical exergy results suggest that compressed natural gas use in motor vehicles produces emissions that are the most out of equilibrium with the natural environment, relative to all other fuel life cycle paths considered. It is also shown that diesel use in grid-independent hybrid electric vehicles has the lowest chemical exergies of emissions of all thirteen fuel-vehicle combinations under consideration, suggesting a lower degree of potential environmental impact. The exergy methodology presented for assessing the potential for environmental impact may help in the development and design of transportation technologies that are more environmentally benign than those presently used.