RELEASING DIVALENT CATIONS TO SEQUESTER CARBON ON LAND AND SEA

Lead Research Organisation: Cardiff University
Department Name: School of Earth and Ocean Sciences

Abstract

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 1.5oC 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.

Publications

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Gore S (2018) The potential environmental response to increasing ocean alkalinity for negative emissions in Mitigation and Adaptation Strategies for Global Change

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Renforth P (2021) The role of soils in the regulation of ocean acidification. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

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Renforth P (2019) Specialty Grand Challenge: Negative Emission Technologies in Frontiers in Climate

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Type Of Art Film/Video/Animation 
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URL https://www.climatexchange.org.uk/media/3749/greenhouse-gas-removal-technologies.pdf
 
Description CUROP Summer Student Bursary
Amount £3,000 (GBP)
Organisation Cardiff University 
Sector Academic/University
Country United Kingdom
Start 06/2018 
End 09/2018
 
Description FUTURES Research Fair 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Presentation of a set of activities by research team around ocean acidification and ocean alkalinity at Futures Research Fair in Bristol - 28 Sept 18
Year(s) Of Engagement Activity 2018
 
Description Interview with press - BBC Online 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Interview quotes taken for piece by Matt McGrath "'Nature-based' greenhouse gas removal to limit UK climate change".
Year(s) Of Engagement Activity 2018
URL https://www.bbc.com/news/science-environment-45486864
 
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Form Of Engagement Activity A magazine, newsletter or online publication
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Year(s) Of Engagement Activity 2018
URL https://www.carbonbrief.org/negative-emissions-scientists-meet-sweden-first-international-conference
 
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Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
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Results and Impact Quotes taken for environment piece by Josh Gabbatiss "Future technology 'cannot rescue' mankind from climate change, say experts" associated with the publication of the EASAC report on negative emissions.
Year(s) Of Engagement Activity 2018
URL https://www.independent.co.uk/environment/future-technology-cannot-rescue-mankind-climate-change-glo...
 
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Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
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URL https://www.independent.co.uk/environment/forests-uk-climate-change-greenhouse-gas-removal-co2-royal...
 
Description Interview with press - The Chemical Engineer 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Quotes taken for a piece by Amanda Doyle "Paris Agreement targets can't be reached with negative emission technologies" associated with the release of the EASAC's report on negative emission technologies
Year(s) Of Engagement Activity 2018
URL https://www.thechemicalengineer.com/news/paris-agreement-targets-can-t-be-reached-with-negative-emis...
 
Description Presentation - Engineering Geologists Special Interest Group 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
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Form Of Engagement Activity Participation in an activity, workshop or similar
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Year(s) Of Engagement Activity 2020
 
Description Webinar: Governance of Research on Geoengineering in the CBD Context 
Form Of Engagement Activity A talk or presentation
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