Comparison of science-based and policy-based distance-to-target weighting in life cycle assessment - Using the example of Europe.

Weighting of impacts is frequently applied to enable the prioritization of life cycle assessment (LCA) results for the support of decision making. Most Distance-to-Target (DtT) weighting approaches consider policy targets, whereas potential is seen in the weighting of environmental impacts on a more scientific basis. This study aims at the comparison of science-based (SB) to policy-based (PoB) DtT weighting approaches as well as the application in a comparative case study for the domestic footprint of the European Union. The developed approaches integrated SB targets from ten environmental impact categories into the DtT weighting method of the Ecological Scarcity Method in an effort to derive SB eco-factors. In addition to SB eco-factors based on existing weighting factors for Europe from the literature, weighting factors for the European Union were developed. The application of the eco-factors in the case study showed that the SB approach led to three times higher absolute weighting results in contrast to PoB results. SB weighting was dominated by the impact category climate change with the strictest weighting factors in all approaches considered and a share of 87–92%. For the remaining impact categories, common PoB weighting factors were generally stricter. PoB results showed a more balanced distribution, with shares of 64% for climate change, 10% for photochemical ozone formation, 7% for acidification, and 7% for terrestrial eutrophication. Science-based targets can not replace conventional PoB weighting approaches but should be integrated into the weighting step to provide a more comprehensive view of the environmental performance of product systems. SB weighting results are an additional source of information on environmental sustainability regarding environmental carrying capacity that can broaden the basis for decision making. • Comparison of targets based on science and policy via distance-to-target weighting. • Development of weighting sets for comparative application to EU domestic footprint. • Science-based results are dominated by the impact category climate change. • Lower results in policy-based weighting due to less strict climate policy targets. • Analysis of EU policy regarding effectiveness to stay within carrying capacities. [ABSTRACT FROM AUTHOR]