Releasing divalent cations to sequester carbon on land and sea

Lead Research Organisation: University of Southampton
Department Name: School of Ocean and Earth Science


The natural response of the carbon cycle to the warming induced by increased atmospheric CO2 features two negative feedbacks that remove CO2 from the atmosphere. One, caused by the greater acidity of the oceans, is for carbonate minerals to be dissolved, which causes an increase in the ability of seawater to contain carbon (as the bicarbonate ion). The other is for warmer conditions to increase the rate at which silicate minerals dissolve, with the products either precipitated as carbonate minerals, or flowing to the oceans. This silicate weathering also removes CO2 from the atmosphere.

Intentional acceleration of these two weathering feedbacks is a potential approach to remove the CO2 added to the atmosphere by burning of fossil fuels, and therefore alleviate extreme climate change. Such an approach is challenging, however, because to be useful at a significant scale (i.e. 1-10 GtC pa removal), requires a dramatic increase in weathering relative to natural rates. Whether such accelerated weathering is a feasible route to remove significant atmospheric CO2 is unknown. This proposal will address this unknown, and provide a comprehensive assessment of the feasibility of CO2 removal by accelerated weathering, including consideration of the technical, economic, environmental, and societal aspects of the approach.

The core of our work will be a life-cycle assessment of the enhanced-weathering approaches that might lead to 1-10Gt removal of CO2 per year. This modelling will start from the availability of minerals for weathering, paying particular but not exclusive attention to waste materials from industries such as mining. It will consider how the weathering of these minerals might be enhanced, either through treatment in mining waste piles or, in collaboration with project partners, by addition to soils. It will also consider the fate of the weathered materials, either as carbonate on land or in the sea, or as alkalinity in the sea. It will assess the economic cost of such approaches, the energy requirements, the environmental damage they would cause, and the societal limitations on such approaches (e.g. social acceptability, political, legal, governance).

In some key areas, understanding is not yet sufficient to allow this life-cycle assessment. We will address these gaps in knowledge by five specific pieces of research. These will:
1. Characterise how much waste material is available for enhanced weathering, including its location, its grain size, and its chemistry and mineralogy. This is critical information to underpin the life-cycle assessment.
2. Measure how quickly typical minerals weather and how this weathering rate changes with temperature and, particularly, through addition of microbes that are known to cause accelerated weathering of silicates.
3. Assess how best to scale up weathering to the 1-10GtC pa level. This will be done by both modelling of possible engineered approached to weathering, and by experiments on piles of silicate and carbonate minerals (each of 10 cubic meters), in which the conditions are altered and responses measured.
4. Assess the response of the ocean to increased alkalinity resulting from enhanced weathering. If more carbonate is produced in the ocean, it reduces the effectiveness of enhanced weathering; we will measure the rates of both inorganic and biological carbonate formation and their impact in the C cycle globally.
5. Consider how society will response to possible scenarios for accelerated weathering, and whether this may limit such an approach. Will enhanced weathering be socially acceptable? Will there be the political will to pursue it? Are their legal or governance barriers?

Information from these five "research components" will provide critical information for the life-cycle assessment, and thereby allow the overall potential and challenge of enhanced weathering CO2 removal to be fully assessed.

Planned Impact

This project brings together a trans-disciplinary team to determine the efficacy of enhanced weathering and ocean alkalinity enhancement for greenhouse gas removal, as well as its technical and socio-economic feasibility, its wider governance, ethical and societal issues, and environmental impact. The project is expected to benefit a range of communities, in different ways and over different timescales:

1. Government policymakers: who are tasked to achieve the goal of keeping global temperatures to 1.5 oC above preindustrial level. In support of this task, this project will provide a comprehensive assessment of the quantity of CO2 that could be removed due to enhanced weathering and ocean alkalinity enhancement, and over what timescale. The project will also provide predictions for CO2 uptake for a range of different technologies and technological approaches.

2. Industry, who are committed to reducing levels of greenhouse gas emissions and to developing techniques to manage atmospheric CO2. In this project we will work directly with the mining industry and provide a comprehensive assessment of how they could turn their 'waste' products into a commodity for CO2 reduction thereby reducing the carbon footprint of their activities. Managing levels of CO2 in this way will require industrial capabilities on a large scale that represents an opportunity to develop new income streams to the UK economy.

3. Intergovernmental Panel on Climate Change: Our research on the efficacy of enhanced weathering and ocean alkalinity enhancement is expected to feed in to the 6th IPCC Assessment Report which will have a strong focus on climate change mitigation strategies.

4. Civil Society: Global warming is a global issue that will significantly impact the lives of our children and grandchildren. Civil society is keenly interested in science that works to mitigate these impacts, but is rightly concerned that geoengineering approaches may have unintended consequences that do more harm than good. This project will undertake research to assess the potential costs and benefits of enhanced weathering and ocean alkalinity enhancement approaches. Communicating the results of this work, to both NGOs and the wider public, will be critical for driving this approach to full-scale deployment.


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Description The global mining industry produces huge volumes of finely ground tailings that have a large potential for removing atmospheric carbon dioxide and converting it to stable hydrogen carbonate ions or carbonate minerals. Our works has shown that mafic and ultramafic rock-hosted mining operations and high tonnage Cu-hosting deposits have the potential to capture approximately 1.2 to 4.8 Gt CO2 annually, equivalent of up to ~97% of the industry's direct emissions. However, as dissolution rates of many minerals are relatively slow, we estimate that only a fraction (~6-17%) of this potential may be realised by mid-century. New approaches to accelerate mineral dissolution, such as improved tailings management practices and enhancing the CO2 content of the reacting fluid, are urgently required.
Exploitation Route Mining industry is using this information to develop its strategy for achieving net zero emissions.
Sectors Chemicals,Construction,Environment

Description Base Metal Leaching with Carbonic Acid Testing
Amount £196,957 (GBP)
Organisation Anglo American PLC 
Department Anglo American Platinum
Sector Private
Country South Africa
Start 03/2022 
End 09/2022
Description INSPIRE CDT
Amount £5,000,000 (GBP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 08/2021 
End 03/2025
Description Collaboration with Anglo American 
Organisation Anglo American PLC
Department Anglo American Platinum
Country South Africa 
Sector Private 
PI Contribution We are exploring the potential of mine waste material from Anglo's Mogalakwena PGE mine to capture carbon dioxide.
Collaborator Contribution Anglo have provided access to the Mogalakwena PGE mine, the biggest of this type on the world, to sample mine waste material. Their chief geologist and chief geochemist accompanied us and guided us throughout our 4-day visit. They have provided us with background documentation, and historic production records. They have provided us with samples of mine tailings, country rock, ore, core material, waste waters, and slag. They have allowed is to access all parts of the mine, including the mine itself, the smelter and processing plans, and the core store.
Impact We have determined the reactivity of mine tailings from various Anglo mine sites for sequestration of atmospheric carbon dioxide. We have recently received funding from Anglo to continue this work and are also exploring applying mine tailings to Anglo-owned forests for enhanced rock weathering.
Start Year 2018
Description Collabroation with De Beers (lead PI Dr Evelyn Mervine) 
Organisation De Beers Group
Country United Kingdom 
Sector Private 
PI Contribution We are providing information on the CO2 sequestration potential of mine waste materials.
Collaborator Contribution Provision of mine waste material and information on the quantities, mineralogy and location of mine waster materials. Provision of a field site to conduct field experiments on mine waster material, including logistical support.
Impact So far, we have received material on which we can conduct laboratory experiments.
Start Year 2017
Description Leverhulme Centre for Climate Change Mitigation 
Organisation University of Sheffield
Country United Kingdom 
Sector Academic/University 
PI Contribution Through this partnership we are investigating the benefits of applying waste silicate minerals to agricultural crops, in terms of drawdown of carbon dioxide (enhanced weathering) as well as crop yields and nutritional benefits. We are working directly with LC3M to quantify weathering rates in various agricultural settings.
Collaborator Contribution Our Partners are funding our work within their project, and they are working with us to model the efficacy of this technique for greenhouse gas removal at the global scale.
Impact Various papers in press, these will be updated as they become available. Collaboration involves geochemists, biologists, engineers, economists and social scientists.
Start Year 2018
Description 39 Ways to Save the Planet 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Our work on Enhanced Rock Weathering featured as one of '39 Ways to Save the Planet', a BBC broadcast/podcast series and book by broadcaster Tom Heep. Episode was called 'Magical Rockdust' Tom also toured the country to promote the book, and the book's forward is by Arnold Schwarzenegger (ISBN: 9781473532793). Rachael James was interviewed for the episode and features in the book. The series has reached an audience of >10 million worldwide and we have had interest in applying rockdust from farmers, start-up companies and other entrepreneurs.
Year(s) Of Engagement Activity 2021
Description Presentation at De Beers Mineral Carbonation Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Workshop led by De Beers in Johannesburg, South Africa, to bring together the mining industry, government officials and NGOs, and academics, to assess the potential of mine waste material for sequestering atmospheric carbon dioxide. As a result, we are now working with various organisations in South Africa to quantify historic and current production of mine waste that will feed in to government policy for achieving greenhouse gas reduction targets.
Year(s) Of Engagement Activity 2018
Description Royal Geographical Society Presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Live streamed presentation followed by Q&A session as part of the Royal Geographic Society seminar series on Greenhouse Gas Removal. Over 200 people watched the presentation live; subsequent viewings >400. Around 50 people attended the Q&A session- this was by invite only. Provked numerous follow-up enquiries from the public, industry and policy makers.
Year(s) Of Engagement Activity 2020
Description Sabah Climate Change International Conference 2021 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact The conference, held in Sabah Malaysia, bought together officials from government, private sector, research, civil society and indigenous organisations, youth and community groups in Sabah to:
1. Create awareness on the impacts of climate change.
2. Share knowledge and experiences on the awareness approaches and initiatives that strengthen resilience to climate change at global and local scales.
3. Facilitate networking and enhance cooperation amongst a broad base of stakeholder groups and promote public participation in both the climate change and conservation agendas.
4. Provide a platform for youths to participate and raise voices on climate change action.
The Conference sparked much discussion from the various parties, and interest in work that we are doing on enhanced rock weathering in the region.
Year(s) Of Engagement Activity 2021