How Many Environmental Impact Indicators Are Needed in the Evaluation of Product Life Cycles?

TLDR

Numerous LCIA indicators exist, but using hundreds simultaneously is infeasible, necessitating a nonredundant key set that represents overall environmental impact. The study aimed to identify such a nonredundant set based on mutual correlations among indicators. Principal Component Analysis combined with an optimization algorithm was applied to 135 indicators for 976 ecoinvent products to select an optimal subset. Four principal components explained 92 % of variance, and a minimal set of six indicators—climate change, ozone depletion, acidification/eutrophication, terrestrial ecotoxicity, marine ecotoxicity, and land use—also captured 92 %, outperforming the 84 % explained by the four common resource footprints.

Abstract

Numerous indicators are currently available for environmental impact assessments, especially in the field of Life Cycle Impact Assessment (LCIA). Because decision-making on the basis of hundreds of indicators simultaneously is unfeasible, a nonredundant key set of indicators representative of the overall environmental impact is needed. We aimed to find such a nonredundant set of indicators based on their mutual correlations. We have used Principal Component Analysis (PCA) in combination with an optimization algorithm to find an optimal set of indicators out of 135 impact indicators calculated for 976 products from the ecoinvent database. The first four principal components covered 92% of the variance in product rankings, showing the potential for indicator reduction. The same amount of variance (92%) could be covered by a minimal set of six indicators, related to climate change, ozone depletion, the combined effects of acidification and eutrophication, terrestrial ecotoxicity, marine ecotoxicity, and land use. In comparison, four commonly used resource footprints (energy, water, land, materials) together accounted for 84% of the variance in product rankings. We conclude that the plethora of environmental indicators can be reduced to a small key set, representing the major part of the variation in environmental impacts between product life cycles.