Life cycle assessment of the desulfurisation flotation process to prevent acid rock drainage: A base metal case study

摘要

The long-term generation of acid rock drainage (ARD) from sulfide-bearing mine waste is a major environmental liability for the mining sector. Previous studies have demonstrated that these ARD risks can be effectively avoided, and resource recovery simultaneously improved, through the pre-disposal removal of sulfide minerals, by means of flotation, which may, however, involve the use of eco-toxic reagents. This study uses life cycle assessment to evaluate the environmental consequences of incorporating a desulfurisation flotation unit for the pre-disposal treatment of a base metal sulfide tailings wastestream. The desulfurisation flotation process is shown to result in a significant decrease in human and eco-toxicity impacts, but an increase in GHG emissions and global warming potential, in comparison to conventional tailings disposal. Desulfurisation flotation also offers the opportunity for improved recovery of valuable resources, such as water, residual metals and sulfur. An expanded system boundary would, however, be required to capture the environmental benefits of upstream and downstream utilisation of recovered resources. The study also highlighted the deficiencies of current LCIA tools, in terms of their ability to adequately assess the environmental impacts associated with solid mineral wastes.