USEtox relevance as an impact indicator for automotive fuels. Application on diesel fuel, gasoline and hard coal electricity
Purpose In order to provide more sustainable fuels and address the depletion of oil as a feedstock, the automotive industry must adapt to a growing market share of alternative fuels. The environmental impacts of the automotive industry to date would suggest that these alternatives will be more environmentally friendly than petroleum-based fuels. This is nonetheless an assumption that cannot be confirmed without a systematic life cycle assessment (LCA). This article explores the feasibility of USEtox to provide information needed for automotive-fuel LCA. Materials and methods USEtox is tested on three energy pathways: gasoline, diesel fuel and hard coal electricity. The studied emissions are mainly volatile organic compounds (VOCs) and heavy metals. USEtox being dependent on the physicochemical and toxic properties of the studied species, a speciation of all VOCs emitted was performed. Moreover, since USEtox allows a distinction between rural and urban emissions, a geographical information system was developed in order to distinguish these emissions. Finally, because crude oil comes from various countries, characterization factors have been calculated for new regional compartments. Results and discussion Human health issues are caused by aldehydes and heavy metals while ecotoxicity is caused by polycyclic aromatic hydrocarbons, aldehydes and heavy metals. For organic compounds, a clear distinction is observed between urban and rural emissions while inorganic mechanisms are independent of this distinction. Among the three energy pathways, urban diesel is the more impacting. Conclusions USEtox can be used for the assessment of automotive fuels, though it only addresses specific aspects of human health and ecotoxicity. The LCA practitioner must keep in mind that USEtox has to be used in conjunction with other indicators, such as ReCiPe or CML, to comprehensively cover the toxic and ecotoxic impacts of fuels. The level of analysis is dependent on the accuracy of the inventory, aldehydes and PAH playing a crucial role. Inorganic impacts are highly uncertain, contrary to organic compounds. The distinction between rural and urban emissions allows a better assessment of internal combustion engine-powered cars compared with electric and hybrid cars, which is especially useful for the automotive industry now that these technologies are clearly being developed.