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

• LCA is used to model environmental implications of a tailings desulfurisation flotation process.
• The process results in reduced aqueous emissions, waste burden and water losses.
• Opportunities exist for recovery of valuable minerals.
• Climate change, fossil-fuel depletion and acidification impacts are increased.
• The deficiencies of current LCIA models and input data quality are highlighted.

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.This study uses life cycle assessment to evaluate the broader 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 toxicity, eco-toxicity, urban land occupation and natural land transformation impacts, but an increase in climate change, fossil fuel depletion and terrestrial acidification impacts. 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 life cycle impact assessment tools, in terms of their ability to adequately assess the environmental impacts associated with solid mineral wastes. These deficiencies and shortcomings will be the subject of further studies.