While significant reductions in greenhouse gas emissions are essential for managing the climate crisis, it is now recognised that the Paris Agreement goal of limiting the increase in global temperature to less than 2 °C above pre-industrial levels cannot be achieved without active removal of carbon dioxide (CO2) from the atmosphere. Weathering is a natural geological process whereby atmospheric CO2 dissolved in rainwater attacks rocks and soils, converting the CO2 into stable hydrogen carbonate ions (alkalinity) that are either captured in the ocean or precipitate as carbonate minerals (carbon mineralisation). By speeding up the weathering process, for example, by distribution of ground rock to improve soils, this technique could capture enough atmospheric CO2 to meet Paris Agreement targets .
As many metals are profitably mined at very low concentrations, most processed mine material is effectively ‘waste’ ground rock that is stockpiled in dumps and tailings ponds. The aim of this project is to determine whether this rock waste could be repurposed for CO2 removal by enhanced weathering. Critically, as demand for metals and mineral resources grows as we transition to green energy, this project will determine whether implementation of CO2 removal schemes at mine sites could offset or even eliminate their carbon emissions .
The project will establish the potential of mine wastes for removal of atmospheric CO2 by conducting laboratory-based and field-scale experiments of CO2-mineral reactivity under different environmental conditions (e.g., temperature, rainfall, CO2 concentration, rock mineralogy). The student will characterize mine wastes for their chemistry, mineralogy and grain size distribution and establish their CO2 removal potential. They will conduct CO2-waste reaction experiments under different environmental conditions and explore the potential for scale-up in larger field experiments. The student will be trained in state-of-the-art geochemical techniques, including high precision analyses of alkalinity, elemental concentrations and stable and radiogenic isotopes, necessary for proper quantification of CO2 removal. The project will also assess the potential effects of mine waste weathering and carbonate precipitation on soil and water quality. The student will undertake fieldwork at mine sites in the UK, South Africa and Ghana, supported by our industrial partners, to collect samples for their study.
The student will join a team of researchers in Southampton exploring enhanced rock weathering and mineral carbonation as CO2 removal strategies, and they will work closely with our collaborators in the Leverhulme Centre for Climate Change Mitigation (www.lc3m.org) on wider aspects of these technologies including their social acceptability.
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre Southampton. Specific training will include:
- Sampling of mine waste materials at mine sites.
- Characterisation of the geochemistry, mineralogy, petrology and reactivity of mine waste materials.
- The determination of trace element concentrations and isotopic ratios by inductively coupled plasma mass spectrometry (ICP-MS), thermal ionization mass spectrometry (TIMS) and multi-collector (MC) ICP-MS.
- Use of geochemical models such as PHREEQC and CO2SYS to constrain changes in aqueous geochemistry, mineral saturation states and CO2 drawdown.
 Beerling D.J., Kantzas E., Lomas, M.R., Wade, P., Eufrasio, R.M., Renforth, P., Sarkar, B., Andrews, M.G., James, R.H., Pearce, C.R., Mercure, J.F., Pollitt, H., Holden, P.B., Edwards, N.R., Khanna, M., Koh, L., Quegan, S., Pidgeon, N.F., Janssens, I.A., Hansen, J., and Banwart, S.A. 2020. Potential for large-scale CO2 removal via enhanced rock weathering with croplands. Nature v583, p242-248.
 Bullock L.A., James R.H., Matter J., Renforth P., and Teagle D.A.H. (2021) Global carbon dioxide removal potential of waste materials from metal and diamond mining. Frontiers in Climate 3:694175, doi: 10.3389/fclim.2021.694175