Country-dependent characterisation factors for acidification in Europe - A critical evaluation

Goal, Scope and Background. Country-dependent characterisation factors for acidification have been derived for use in life cycle assessments to describe the effect on ecosystem protection of a change in national emissions. They have recently also been used in support of European air pollution abatement policies and related cost benefit analyses. We demonstrate that the characterisation factors as calculated to date are unstable due to being derived from the non-smooth and highly varying part of the underlying emission-impact functions. The purpose of this paper is to discuss the currently available characterisation factors and to propose a modification that makes use of the full range of the underlying functions. Method. The characterisation factors derived in this paper are based on updates of data used to support European air pollution agreements under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP) and the European Commission. The focus in this paper is on the analysis of characterisation factors for acidification. The analysis of characterisation factors for terrestrial eutrophication from nitrogen compounds is a simple extension of the methods described here. The analysis is conducted for 25 European nations, i.e. for 23 EU countries plus Norway and Switzerland; Cyprus and Malta are excluded due to lack of data on critical loads. Results and Conclusions. We show that a linear model which is calibrated to emission changes of -50% is generally more reliable than characterisation factors which are based on emission changes of plus or minus 10%. Application of these characterisation factors are justified for emission reductions up to 30% in total European emissions, compared to 2000. This is within the range of currently agreed upon emission reductions in 2010 relative to 2000. Therefore, characterisation factors can be used in LCA as well as for the support of the revision of existing European air pollution agreements.