Prioritizing impacts: the second stage of life cycle assessment

The first stage of life cycle assessment, inventory analysis, may be complex in practice but is conceptually straightforward. The second stage, impact assessment, is much more conceptually difficult, because it ultimately involves making choices among different impacts on the environment. Several techniques for impact assessment of specific products have been proposed; none has yet seen general use. This paper presents and discusses some of the product ranking systems in use, analyzes their favorable and unfavorable characteristics, and suggests steps that can assist engineers in life cycle analyses even while techniques for relative ranking of environmental impacts remain under development