Catalogue of South African mine tailings for geochemical carbon dioxide removal purposes

Abstract

South Africa has the potential to be a global leader in implementing strategies targeting geochemical carbon dioxide removal (CDR) using mine tailings, utilising methods for alkalinity production and mineral carbonation. This is due to the hundreds of millions of tonnes of geochemically and mineralogically suitable tailings produced annually from diamond, PGM, chrome, nickel, phosphate, copper, talc and magnesite mines, exploiting mafic and ultramafic rocks. This approach may offer an additional route towards emissions offsets and reduction targets for South Africa. Here, a catalogue of tailings has been developed to highlight overall national CDR potential, drawing attention to site opportunities for pilot schemes. It has been calculated, using bulk geochemistry and shrinking core modelling, that South Africa has an average 1.1-1.7 MtCO2 removal capacity per year across all suitable sites, while an additional 11-17 MtCO2 could be removed through weathering historic tailings. The total CDR that could be achieved over the 2030-2100 period, considering all annually produced tailings available to weather, is 79-119 MtCO2. The capacity may be higher if mines of limited production information are considered, and pre- 2017 tailings production amounts, abandoned stockpiles, and other industrial by-products are included. Diamond mines hold the highest geochemical CDR capacities, along with high tailings producers in Phalaborwa, Nkomati and Mogalakwena metal mines. There are incentives for academia, industry and policymakers to revise the geochemical CDR potential of mine sites in the years to come, and for other countries to catalogue their own suitable tailings and geochemical CDR potential capacities for future Mt-scale opportunities.