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Enhanced rock weathering

United Kingdom and Canada · $609.82USD per tonne

Contributions to this project immediately pay for the spreading of silicate rock, which starts removing carbon immediately. However, it will take years for the rock to fully absorb carbon. Only once the process is fully complete, the carbon removals will be verified, validated, and added to our subscribers’ total tonnes of CO₂.

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For millions of years, carbon dioxide (CO₂) has combined with rainwater to form carbonic acid. When this dilute acid falls on mountains, forests and grassland, CO₂ interacts with the rocks and soil, mineralizes and is safely stored in carbonate form. However, natural rock weathering takes hundreds of thousands of years, and there really is no time to wait.

UNDO, the company behind this project, enhances and accelerates this process by spreading crushed silicate rock on farmland. In Canada, this project primarily uses crushed wollastonite, a calcium silicate mineral. This increases the surface area of the rock and gives it immediate contact with the carbonic acid from the rainwater.

UNDO is scaling operations over time by expanding rock supply, local spreading capacity, and measurement techniques to unlock over 1 billion tonnes of community-led carbon dioxide removal (CDR) by 2050.

Crushed silicate rock such as Wollastonite is spread on farmland around the project's sites to accelerate rock weathering and sequester carbon. Photo by UNDO.

How does it work?

1. UNDO sources crushed silicate rock from mining and quarry partners.

2. UNDO spreads the rock on farmland sourced through their agricultural partnerships.

3. When rainwater reacts with carbon dioxide, a weak carbonic acid is formed.

4. When this carbonic acid comes into contact with the silicate minerals in the rock, the pH increases, resulting in the production of solid bicarbonate ions.

5. With the carbon now stabilized in dissolved form, bicarbonate and associated ions travel from the soil to the earth’s waterways, before finally entering our oceans.

What is enhanced weathering?

Why this project?

UNDO’s only revenue stream is from carbon removals purchased by customers. Without this funding, the rock would remain at source sites rather than being transported and applied to farmland at enhanced weathering rates.

As part of UNDO’s LCA, the (very limited) CO₂ uptake in this counterfactual situation is calculated based on the estimated exposed surface area and deducted from UNDO’s CO₂ calculations to account for this potential CO₂ impact.

Along with strong additionality, UNDO supports a wide variety of co-benefits, including:

1. Agriculture: As weathering of silicate rock occurs, nutrients and minerals are released into the soil. UNDO’s agricultural partners are already seeing a positive impact in trials, including yield improvements reported as high as 20.5% on spring oats. UNDO is carrying out agronomic trials with universities in the United Kingdom, Canada, United States, and Australia to present empirical evidence across a range of over 10 crop types.

2. Biodiversity: As the weathering process occurs, the dissolved calcium and bicarbonate ions formed from the carbonic acid travel downstream through the water systems, eventually ending up in the sea, where the added alkalinity can help to counter ocean acidification, reducing the associated impact on coral reefs and fisheries.

3. Social: UNDO’s operational model focuses on empowering local operational teams to deliver operations within agricultural communities. Its work helps to drive money back into these communities that are adversely affected by climate change.

Where is the project located?

UNDO operates this project in Canada, with the United Kingdom serving as a science hub for research and measurement.

Who is behind this project?

UNDO is the company behind this project, with field operations in Ontario, Canada, and a science hub in the United Kingdom. In 2025, UNDO was named one of four global winners of the $100 million XPRIZE Carbon Dioxide Removal (CDR) competition, signed its third deal with Microsoft and became Barclays first-ever CDR purchase.

UNDO’s research program includes collaborations with the University of Guelph (including its Simcoe Research Station), Yale, the University of Washington, University College London, and Newcastle University.

Here, the team is collecting soil data at a project site. The project is operated on large plots of land with heavy rainfall, perfect for an enhanced weathering project. Photo by UNDO.

How is the money spent?

The project cost per tonne of CO₂ sequestered includes costs for rock supply, haulage and spreading, plus monitoring and third-party verification. We'll update this page when we receive a more detailed cost breakdown.

Crushed silicate rock (wollastonite) ready for application on agricultural land as part of the project’s enhanced rock weathering operations. Photo by UNDO.

Verification

UNDO’s Monitoring, Reporting, and Verification (MRV) approach is designed to be both scalable and conservative. Carbon removal is quantified using empirical measurements from monitoring sites, including soil and porewater sampling, supported by modelling that is calibrated with local data such as soil properties, climate conditions, and feedstock characteristics. This combination helps UNDO estimate carbon removal across operational areas while keeping results anchored to real-world measurements. Reported removals account for lifecycle emissions and potential downstream losses, supporting a more complete net carbon removal estimate for verification.

Preparing soil samples for lab analysis, helping track weathering and carbon removal signals over time. Photo by UNDO.

✅ Carbon credit insured

Wren partners with Kita, a Lloyd’s Coverholder, to protect subscribers' carbon credit pre-purchases and ensure the promised impact of this project.