Enhanced rock weathering: Potential UK greenhouse gas removal
This POSTnote outlines the benefits and challenges of using enhanced rock weathering as a GGR approach for addressing emissions from UK hard-to-abate sectors.
DOI: https://doi.org/10.58248/PN726
The UK has committed to reaching Net Zero greenhouse gas (GHG) emissions by 2050. While emissions will be mitigated where possible, the Intergovernmental Panel on Climate Change (IPCC) stated that Greenhouse Gas Removal (GGR) is required to remove final emissions from hard-to-abate sectors. GGR involves removing GHGs, such as CO2, directly from the atmosphere, as opposed to capture from industrial sources.
Rock weathering is a natural process that removes carbon dioxide from the atmosphere, at a rate of ~1100 Mt CO2/year. Enhanced rock weathering (ERW aims) to accelerate this process in order to help address climate change. Fine rock particles are created, increasing the reactive surface area of the rock. This is then spread over land. When the rainwater and rock dust react, the resulting chemical products are released into the soil. Over time, these dissolved products may be taken up by plants, remain in the soil, or be transported to a sink, such as the ocean. Here, the products may react to form a solid carbonate mineral over thousands of years, which is then stable in the ocean for 10,000 years.
Academic studies suggest that ERW has the potential to contribute 6-30 Mt CO2/year removal, and there are several ongoing UK field trials. Several uncertainties remain with ERW, including the rate of CO2 removal, timescales involved, and the efficiency of transport to the ocean, with the potential for some carbon to be re-released. For the highest scale up scenarios, there are challenges for scaling up rock extraction, crushing and transport and there would likely be adverse environmental impacts due to the extent of quarrying required, such as destruction of habitats, noise, water and air pollution. However, ERW has potential benefits for agricultural soils and may increase crop and forestry yields.
Key points
- Enhanced rock weathering (ERW) could be used to remove greenhouse gases from the atmosphere. It involves the spreading of rock dust on land. When rainwater mixes with the dust, the carbon dioxide (CO2) dissolved in the rainwater is converted into minerals that are released into the soil.
- Studies suggest that ERW can also improve soil fertility and increase crop and forestry yields.
- However, there are limited long-term field trials (>5-10 years), either globally or in the UK, to provide evidence that the technique captures carbon on a large scale.
- There is also limited evidence on how different types of rock, soil, climate, and other conditions affect the efficiency of carbon dioxide removal.
- If implemented on a large scale, there are potential risks and environmental impacts. These risks are the subject of research projects.
- Barriers to scaling up rock extraction in the UK include producing large amounts of rock dust through quarrying and crushing, associated greenhouse gas emissions, and potential social and ecological impacts.
- Standardised techniques for measuring and verifying any carbon dioxide removal are yet to be agreed to maintain the integrity of carbon offsets.
- Several commercial operations of ERW occurring globally, including at least one company in the UK.
POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including:
Members of the POST Board*
Dr Grace Andrews, Hourglass Climate
Dr Catherine Bayliss, Environment Agency*
Professor David Beerling, University of Sheffield*
Dr Rob Brown, Bangor University
Dr Frances Buckingham, Department for Energy Security & Net Zero*
Dr Anne Cotton, University of Manchester*
Matthew Davis, Environment Agency
Dr Christiana Dietzen, University of Copenhagen*
Dr Jessica Elias, Natural England
Luke Greicius, Evident Global
Garrett Guard, Evident Global
Dr Kirsty Harrington, Heriot-Watt University
Victoria Harvey, BeZero Carbon
Dr Scott Hawley, Department for Environment, Food & Rural Affairs*
Professor Rachael James, University of Southampton
Gregory Jones, Imperial College London*
Professor Guy Kirk, Cranfield University
Dr Christina Larkin, InPlanet
Dr Jonathan Lindsell, Department for Energy Security & Net Zero*
Dr Mohammad Madankan, Heriot-Watt University
Dr Joseph Mankelow, British Geological Survey
Professor David Manning, Newcastle University*
Dr Jennifer Mills, Cascade Climate
Charles Nicholls, The Carbon Community*
Mark North, Mineral Products Association
Professor Nick Pidgeon, Cardiff University
Theo Platts-Dunn, Evident Global
Professor Noah Planavsky, Yale University
Dr Alan Radbourne, UKCEH*
Professor Phil Renforth, Heriot-Watt
Professor Minik Rosing, University of Copenhagen
Mark Russell, Mineral Products Association
Dr Kate Scott, Department for Energy Security & Net Zero*
Dr Jonathan Scurlock, National Famers’ Union*
Dr Mark Workman, Imperial College London
Dr Julia Woitischek, BeZero Carbon*