Life cycle value assessment (LCVA) comparison of conventional gasoline and reformulated gasoline

摘要

Fuel choices are being made today by consumers, industry and government. One such choice is whether to use reformulated gasoline to replace regular unleaded gasoline. A second choice involves the source of crude oil, with synthetic crude oil from tar sands currently expanding its share of the Canadian supply. Decision makers usually work with the direct economic consequences of their fuel choice. However, they generally lack the knowledge to measure environmental aspects of different fuel systems. This paper uses Life Cycle Value Assessment (LCVA) to demonstrate how the life cycle environmental aspects can be compared for alternative fuel choices. LCVA is an engineering decision-making tool which provides a framework for the decision maker to consider the key economic and environmental impacts for the entire life cycle of alternative products or process systems. This paper presents an LCVA case-study comparing conventional gasoline and reformulated gasoline as produced from energy resources in Alberta, Canada. A fifteen percent MTBE-blended gasoline is compared to regular unleaded gasoline using data from publicly accessible sources. In addition, this paper compares conventional crude oil to tar sands synthetic crude as hydrocarbon sources for the two gasoline fuels. The study concludes that the only significant advantage of MTBE-blended gasoline over regular unleaded gasoline is a reduction of hazardous air pollutants at the combustion stage. Considering the entire life cycle, there is no significant difference between the fuels in ground-level ozone precursors while MTBE-blended gasoline is at a slight disadvantage with respect to acid rain precursors, greenhouse gases and particulate matter emissions. Comparing energy sources, fuel produced from tar sands crude produces substantially more acid rain precursors and greenhouse gases in the upstream processes. However, in the context of the overall fuel system, the increase is relatively small (less than 5% in best case). One aspect of the sensitivity analysis compared various approaches to reducing environmental impact. This showed that reducing vehicle fuel consumption would reduce environmental impact more than comparable improvements in emission rates at the various steps of the process.