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

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.