Methods för Describing and Characterising Resource Depletion in the Context of Life-Cycle Assessment

There are three major categoroies of impacts that should be consnidered in an impact assessment in connection with LCA: Eesource depletion, Human health and ecological impacts. Each of these can be further divided into specific impact categories. There are today several methods available for describing and characterising depletion of energy and material resources. They are based on different defintions of the problem and will give different results. In this report a review of suggested methods are presented. Furthermore, a new approach (in the context of LCA) based on the concept of exergy is outlined and discussed. Exergy is the amount of energy that can be transformed into work and is connected with the concept of entrophy. When materials and energy sources are used, low-entropy matter.energy is converted into high-entropy matter-energy. Consumption of resources can therefore be described as produciton of entropy or cosnpumtion of exergy. It can be claimed that exergy is an ultimate limiting resource. Every material resource has an associated energy cost, so every potantially limiting resuorce is limiting in part because its exergy costs are too high. Given sufficient amounts of exergy, a society can divert exergy, within present technical range of possiblities, to the acqusition or mobilisation of essentially whatever material that is in short supply. Results ffrom exergy calcualtion of some mnerals are included