Sustainability analysis of copper extraction and processing using LCA methods

The concept of sustainability on the one hand and the extraction and processing of primary resources on the other, at first glance, appear to be in conflict, since the production processes deplete resources that are strictly considered finite. In addition, these processes inevitably disturb the environment. This is especially true in copper production considering this is a metal with a high global demand, currently mined at increasingly low grades. Life Cycle Assessment (LCA) is an established method to assess the sustainability profile of products, processes and systems that has become important in recent years through the establishment of the ISO 14040 series of standards. Although LCA studies on mining and mineral processing systems, including copper, have been carried out since the mid- to late 1990s; these studies are limited to the ore extraction and mineral processing, not considering waste management, which is absent from all LCA based sustainability assessment of metal production systems reported in literature. In addition the low level of detail used in conventional LCA tools (not accounting for emissions at unit process level) lead to oversimplifications and underestimation of the true impacts. In this PhD research an LCA model has been developed to assess the impacts of copper mining and processing, considering the mine, mineral processing and waste disposal facilities life cycles as part of the copper production. The model is designed at unit process level and integrates the mining (open-pit and underground), mineral processing and waste management processes and accounts for emissions to the different environmental compartments (air, water, soil). The life cycle inventory (LCI) models developed are designed using specific activity data at component unit-process level together with emission factors from literature (US EPA, Australian NPI) and engineering calculations or models. The model developed uses mass balance/equilibrium calculations from intermediate products, resource consumption rates or activity levels to estimate life cycle estimates. The model functionality is illustrated using a true Chilean mine case study which was parameterised using mining, mineral processing and waste disposal facilities information for a baseline year when detailed operational data and key variables were recorded. The different LCA impact indicators estimated are carbon footprint (or global warming potential), water footprint, human toxicity, resource depletion and ecotoxicity (USEtox). Different Life Cycle Impact Assessment (LCIA) methods, chosen from the most recent and widely used LCIA methods, are utilised to compare the different methods results. Extensive Sensitivity and Monte Carlo analysis is performed to assess the uncertainty of key parameters. The response of the LCA impact indicator scores to the variation of variables such as the copper ore grade, copper recovery efficiency, average stripping ratio, electricity grid mix, are evaluated and presented.Open Acces