Normalization and weighting. The forgotten theme in LCA

To draw the right conclusions based on environmental indicators can be a challenging task due to the consideration of a broad variety of environmental impacts that show diverging results. Many LCA practitioners seek help in interpreting diverging results in different impact catego­ries by applying single score LCIA methods. But the ISO standards do not support weighting for publishing comparative LCA. Nevertheless, the increasing need for unequivocal results lead to the development of single score impact assessment method.

This DF focuses on the present state of normalization and weighting in LCA. The statements in ISO 14040 are taken as one of the baselines, e.g. concerning internal and external normaliza­tion and hints on interpretation. The ongoing developments for the technical specification on this theme (ISO/TS 14074) are covered. Approaches broadening this view in ISO will be pre­sented as well.

An overview on present schemes such as the ILCD recommendations for LCIA and further deve­lopments within the EU Product Environmental Footprint (PEF) initiative will be provided. An­other key question will be: How useful is the concept of the carrying capacity or the plane­tary boundaries for aggregating indicator scores?

A discussion of different weighting methods should shed more light on the uncertainties and differences of various approaches (e.g. transparency, complete­ness, applicability). The forum should launch further discussion about these issues to initiate also a revision of standards like ISO 14040/44/74 to better reflect the current state of the art.

In summary, the DF aims at a critical discussion and review of currently available methods for normalization and weighting to promote a better understanding of the complex topic and con­troversial debate in the scientific community. How ISO standards on weighting, normalization and grouping can be implemented in the future are identified. Research needs are formulated to foster progress in this field of LCA application.

This forum aims to provide a fertile ground for discussion between LCA researchers, practition­ers and other people interested in the interpretation and development of normalization and weighting methods.