Exergy as a Measure of Resource Use in Life Cycle Assessment and Other Sustainability Assessment Tools

A thermodynamic approach based on exergy use has been suggested as a measure for the use of resources in Life Cycle Assessment and other sustainability assessment methods. It is a relevant approach since it can capture energy resources, as well as metal ores and other materials that have a chemical exergy expressed in the same units. The aim of this paper is to illustrate the use of the thermodynamic approach in case studies and to compare the results with other approaches, and thus contribute to the discussion of how to measure resource use. The two case studies are the recycling of ferrous waste and the production and use of a laptop. The results show that the different methods produce strikingly different results when applied to case studies, which indicates the need to further discuss methods for assessing resource use. The study also demonstrates the feasibility of the thermodynamic approach. It identifies the importance of both energy resources, as well as metals. We argue that the thermodynamic approach is developed from a solid scientific basis and produces results that are relevant for decision-making. The exergy approach captures most resources that are considered important by other methods. Furthermore, the composition of the ores is shown to have an influence on the results. The thermodynamic approach could also be further developed for assessing a broader range of biotic and abiotic resources, including land and water.