Life cycle impact assessment methods for estimating the impacts of dissipative flows of metals

Abstract

The dissipation of metals leads to potential environmental impacts, usually evaluated for product systems with life cycle assessment. Dissipative flows of metals become inaccessible for future users, going against the common goal of a more circular economy. Therefore, they should be addressed in life cycle impact assessment (LCIA) in the area of protection “Natural Resources.” However, life cycle inventory databases provide limited information on dissipation as they only track emissions to the environment as elementary flows. Therefore, we propose two LCIA methods capturing the expected dissipation patterns of metals after extraction, based on dynamic material flow analysis data. The methods are applied to resource elementary flows in life cycle inventories. The lost potential service time method provides precautionary indications on the lost service due to dissipation over different time horizons. The average dissipation rate method distinguishes between the conservation potentials of different metals. Metals that are relatively well conserved, including major metals such as iron and aluminum, have low characterization factors (CFs). Those with poor process yields, including many companion and high-tech metals such as gallium and tellurium, have high CFs. A comparative study between the developed CFs, along with those of the Abiotic Depletion Potential and Environmental Dissipation Potential methods, show that dissipation trends do not consistently match those of the depletion and environmental dissipation potentials. The proposed methods may thus be complementary to other methods when assessing the impacts of resource use on the area of protection Natural Resources when pursuing an increased material circularity.