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(82-01) Life cycle indicators, a comparison of aggregation methods. Hunkeler, David*,1, Rebitzer, Gerald1, 1 Swiss Federal Institute of Technology, Lausanne, Switzerland ABSTRACT- The presentation of indicators and the credibility of the underlying aggregation methods are of crucial importance for the acceptance of LCA results within the LCM toolbox. Results of LCIAs can be aggregated by several different methods, the advantages and disadvantages of which will be discussed herein, using recent case studies. One option involves the, often non-transparent and subjective, weighting of impact categories. Here, significant value choices are inherently involved, with all the pros and cons associated with them. Alternatively, the potential impacts themselves can be converted into financial equivalents, yielding a matrix of values for various impact categories as, for example, Euros per unit of GWP. The resulting values can then be calculated and aggregated easily for the specific case. However, with this option one has to cope with the challenges of monetarizing (potential) environmental impacts, which itself is a whole controversially discussed discipline in economics. Another methodological approach which has been proposed is the application of a double-normalized indicator which scales life cycle assessments with life cycle costs. The E2-Vector and the Return on Environment concepts are examples of the latter. It is shown that aggregated double normalized metrics offer advantages if the overall environmental burden is dominated by a limited number of impact categories. In contrast, when a larger number of impact categories contribute to the total environmental assessment, then a series of specific indicators, such as the Euros per unit of GWP or ODP, or weighting procedures, if accepted by the stakeholders, are better means by which to compare alternatives in LCA. Other options in this case include panel methods for specific cases. It will be shown that benchmarking via the aforementioned double-normalized techniques can be quite good, permitting the comparison, or possibly even validation of new studies with existing data. Furthermore, the normalization methods permit the estimation of life cycle costs from impact assessment data, and vice versa, with a reasonable preliminary precision. Key words: aggregated LCA results, indicators, Return on Environment, normalization |
