Multiple Issues Surrounding the Feasibility of LCA Impact Assessment, 1997 Nonwovens Conference Proceedings

The presentation evaluates the overall feasibility of life-cycle impact assessment to yield accurate, useful results. The evaluation raises feasibility issues based on (1) inherent scalar issues, e.g., spatial and temporal discontinuities, between LCA and environmental processes; (2) differences between LCA threshold and dose-response assumptions and actual environmental processes; (3) extensive use of subjective judgment and opinion to create impact categories, equivalency models, and scores; and (4) the current lack of development of systems to indicate whether real and relevant differences can be identified by LCA. Several of these issues originate in procedures and calculations that are fundamental to life-cycle inventory: data collection and aggregation across multiple system operations, allocation rules for emissions and resources, and data normalization to a study functional unit. These operations remove spatial, temporal, and other considerations, resulting in significant interpretive limitations for impact assessment. In addition, although often presented as a technical or scientific process, extensive subjective judgments are used throughout impact assessment. Some of these judgments compromise or conflict with scientific knowledge, e.g., when independent processes or compounds are placed into common categories and aggregated. There is a significant range in the mixture of these scalar issues, process assumptions, and subjective judgments among impact categories. For example, the most useful results may be for global, long lived processes with known mechanisms. Problematic areas involve transient or local processes, those measured by biological parameters, e.g., biodiversity habitat and toxicity, and those involving independent mechanisms. As a result, one cannot quantify or predict actual environmental impacts using LCA. Current practices can generate a hazard estimate that may be useful to guide pollution prevention and resource conservation strategies. The evaluation helps to identity and track these issues to improve user understanding of the LCA impact assessment. The evaluation also points to needed future methodological development to deal with these uncertainties and to conduct more disciplined and useful comparisons using impact assessment.