Correlation analysis of life cycle impact assessment indicators measuring resource use

Even though the necessity of a sustainable use of natural resources is widely accepted, there is neither consensus on how “resource use” is clearly defined nor how it should be measured. Depending on the definition, it can comprise raw material consumption only or the consumption and pollution of natural resources. Consequently, lots of indicators can be applied, and the result of a life cycle assessment study aiming to quantify resource use seems to depend on the selection of impact categories. Therefore, this paper aims at analyzing life cycle impact assessment results obtained by means of several indicators to check if different indexes lead to similar results and if the number of indicators can be reduced.

Life cycle impact assessment results of 100 materials from the GaBi and ecoinvent databases were compiled using the GaBi 4.3 software. The results obtained by different resource- and emission-oriented as well as single-score indicators were compared by means of correlation analysis to check for potential dependencies between indicators.

The analyses revealed large differences regarding the correlations between indicators. While no significant correlations were found between emission-oriented indexes (R ² = 0.40–0.62), strong linear regressions were identified between indicators assessing raw material consumption (R ² = 0.65–0.98). This can be explained by the facts that all indicator results are dominated by the consumption of fossil fuels and that characterization models of correlating indexes rely on net calorific values when computing characterization factors for fossil energy carriers. In material groups that consist of energy carriers themselves, like monomers and polymers, significant linear regressions were identified between all resource-oriented indicators (R ² = 0.78–1.00).

Depending on the definition, different life cycle impact assessment indicators can be used for measuring resource use. Following the broader definition, a wide range of impacts has to be evaluated as no significant correlations between indexes assessing resource consumption and pollution were identified. In contrast, since strong linear regressions were revealed among some resource-oriented indicators, the number of indexes can be reduced when defining resource use in a conventional sense.