Four economies of sustainable automotive transportation

Life cycle analysis for automotive transportation, commonly known as well-to-wheels (WTW) analysis, has traditionally focused on greenhouse gas (GHG) emissions and primary energy consumption. Clearly, economizing on the use of primary energy sources and the amount of GHG emissions associated with automotive transportation are important sustainability metrics. Other important metrics are water usage and cost of vehicle operation. Thus, we propose the evaluation of four economies in WTW analysis: primary energy consumption, GHG emissions, water usage, and cost of vehicle operation. No scenario is likely to simultaneously minimize all four metrics, suggesting the identification of a single figure of merit that encompasses all four economies of transportation fuels. We employed a normalization scheme that allowed calculation of a single composite score for each scenario called the CWEG (Cost-Water-Energy-GHG) score. Automotive transportation scenarios evaluated in this paper include a variety of fossil and renewable primary energy sources; several energy carriers as transportation fuels; and three distinct vehicle platforms including internal combustion engines, battery electric vehicles, and fuel cell electric vehicles. Compressed natural gas scored highest, with CWEG scores of 71-74 out of a possible score of 100, well above the next highest score, which was 45 for conventional diesel hybrid electric vehicles. Fuel cell vehicles running on hydrogen generated using power from the US electric grid had the lowest CWEG scores, ranging from 13 to 15. (C) 2011 Society of Chemical Industry and John Wiley & Sons, Ltd