Environmental news No. 80 2005 – Spatial differentiation in LCA impact assessment

Spatial differentiation in LCA impact assessment

Summary

This Guideline presents the recommendations on characterisation from the Danish LCA Methodology Development and Consensus Creation Project 1997-2003. New characterisation factors and accompanying normalisation references have been developed for each of the non-global impact categories:

acidification
terrestrial eutrophication
photochemical ozone exposure of plants
photochemical ozone exposure of human beings
aquatic eutrophication
human toxicity via air exposure
ecotoxicity

For the global impact categories global warming and stratospheric ozone depletion, the characterisation factors are updated with the latest recommendations from IPCC and WMO/UNEP. The new methodology is referred to as the EDIP2003 life cycle impact assessment methodology.

Compared to the EDIP97 methodology, the models underlying the EDIP2003 characterisation factors take a larger part of the causality chain into account for all the non-global impact categories. The EDIP2003 factors thus include the modelling of the dispersion of the substance and the subsequent exposure increase. For a number of impact categories, the modelling also includes the background exposure and vulnerability of the target systems to allow assessment of the exceedance of thresholds. Therefore, the environmental relevance of the calculated impacts is higher – they are expected to be in better agreement with the actual environmental effects from the substances that are observed, and they are easier and more certain to interpret in terms of environmental damage.

The EDIP2003 factors have been developed in a site-dependent and a site-generic form. The site-generic form disregards spatial variation in dispersion and distribution of the substance and exposure of the target systems like the EDIP97 methodology, but the results are in the same metrics as the site-dependent EDIP2003 results and can hence be added to these. In the site-dependent form of EDIP2003, the characterisation factors are spatially resolved at the level of countries allowing the differences in impact from an emission when released in different countries to be a part of characterisation. For most of the impact categories, the potential spatially determined variation is very large.

The relevance of spatial differentiation depends on the goal of the study. For many applications of LCA, the impact assessment should give the best prediction of the environmental impacts that are caused by the emissions from the product system, and this is obtained through reduction of the spatially determined variation. There are, however, applications of LCA, where the information provided through inclusion of spatial differentiation >may not be relevant to the goal of the study. This can be the case for preparation of environmental product declarations and ecolabel criteria.

The Guideline recommends that the EDIP2003 characterisation methodology be used as an alternative to EDIP97 for performing site-generic characterisation (i.e. disregarding spatial information). For the non-global impact categories, the environmental relevance of the site-generic EDIP2003 impact potentials is higher, and they provide the option to quantify and reduce the spatial variation not taken into account.

Further, the Guideline recommends that the EDIP2003 site-dependent factors can be used to identify the main sources of spatially determined variation for the non-global impact categories and to reduce the variation to the desired level according to the goal of the study.

EDIP97 can of course still be used if a new LCA should be compared with prior results based on EDIP97 methodology and factors.