Spatially explicit characterization of acidifying and eutrophying air pollution in life-cycle assessment

Simple models are often used to assess the potential impact of acidifying and eutrophying substances released during the life cycle of products. As fate, background depositions, and ecosystem sensitivity are not included in these models, environmental life-cycle assessment of products (LCA) may produce incorrect results for these impact categories. This paper outlines the spatially explicit regional air pollution information and simulation model (RAINS-LCA), which was developed for the calculation of acidification and terrestrial eutrophication potentials of ammonia (NH₃) and nitrogen oxide (NO_x) air emissions and acidification potentials for sulfur dioxide (SO₂) air emissions for Europe and a number of European regions, taking fate, background depositions and effects into account. Two impact definitions are explored in the calculations: 1) the marginal change in the hazard index of all ecosystems in Europe and 2) the marginal change in the hazard index of ecosystems in Europe where the critical load is actually exceeded. The inclusion of fate, background depositions, and ecosystem sensitivity results in a different ranking of substances compared to simpler model outcomes. In the context of acidification, emissions of nitrogen compounds are regarded as about a factor 2 less important relative to sulfur compounds. Furthermore, using RAINS-LCA as opposed to simpler models, it was found that region-specific differences in terrestrial eutrophication and acidification potentials range up to 1.5 and 3.5 orders of magnitude, respectively. By means of scenario analysis, it was also shown that "only above critical load" terrestrial eutrophication and acidification potentials for the years 1995 and 2010 differ up to 0.6 order and 1 order of magnitude, respectively. These results imply that it is important to use region-specific and time-specific acidification and terrestrial eutrophication potentials, if it is expected that life-cycle emissions of acidifying and eutrophying air pollutants are predominantly situated in a few (European) regions and within a specific year. Further improvements in RAINS-LCA may be established by including source-receptor matrices of the Northern Hemisphere instead of Europe and using the probability of species occurrence as a basis for the effect assessment.