Life cycle assessment as a design consideration for process development for value recovery from gold mine tailings

With the decline of gold grades of primary resources in many parts of the world, gold recovery from primary resources may become unprofitable. Therefore, the identification of secondary gold resources (such as mine tailings) to prolong the existence of the gold industry has developed growing interest. Life cycle assessment (LCA) was used to design two process flowsheets (cyanide and thiosulphate) for recovering gold from a hypothetical tailings dam scenario in the West Witwatersrand region of South Africa while reducing environmental impacts of processes. The thiosulphate flowsheet reduced environmental impacts for 18 out of 19 impact categories compared to the cyanide flowsheet, apart from the freshwater consumption. The flowsheets proposed reduced sulphide, uranium, and arsenic in mine tailings by 82%, 75% and 94% respectively. Therefore, the solutions presented reduce environmental impacts associated with acid mine drainage, radionuclides and arsenic while producing gold as a value stream. The LCA model and corresponding sensitivity analysis showed that South Africa’s dependency on coal for electricity generation was a major contributor to environmental impacts for both flowsheets and transition to renewable energy can reduce environmental impact of mining operations.