# UNDO Enhanced Rock Weathering by UNDO

Canonical page: https://technooptimist.io/agriculture/undo-rock-weathering
Frontier: [Agriculture](https://technooptimist.io/agriculture.md) · Field: Soil carbon & rock weathering · Company: [UNDO](https://technooptimist.io/companies/undo.md)
Stage: Deploy (4 of 5: Research → Proto → Pilot → Deploy → Scaling)
Updated: last update 2025-09-24, facts checked 2026-10-11
Goal: Remove CO2 from the air permanently and cheaply by speeding up natural rock weathering on farmland. Nature already removes about a billion tonnes a year this way; spreading crushed rock makes it happen far faster.
Status: Rock spread on 444 farms across 61,000 acres in the UK and Canada; corporate offtakes growing.

## Milestones

| Status | Milestone | Date | Slip |
| --- | --- | --- | --- |
| Done | First Microsoft deal: 5,000 t of CO2 | 2023 |   |
| Done | Microsoft follow-on: 15,000 t (UK basalt, Canadian wollastonite) | Sep 2024 |   |
| Done | Barclays deal: 6,538 t on 10,000 acres in Ontario | Sep 2025 |   |

## Most important updates

- **24 Sep 2025**: Barclays makes its first carbon removal purchase: 6,538 tonnes from UNDO's rock weathering in Ontario. Barclays agreed to buy 6,538 tonnes of permanent CO2 removal from UNDO, which will spread crushed silicate rock across 10,000 acres of farmland in Ontario, Canada. ([our story](https://technooptimist.io/stories/barclays-makes-its-first-carbon-removal-purchase-6-538-tonnes-from-undo-6150b96c.md) · [original source](https://www.esgdive.com/news/barclays-turns-to-enhanced-rock-weathering-for-first-carbon-removal-deal-undo/802500/))
- **26 Sep 2024**: Microsoft expands its deal with UNDO to remove 15,000 tonnes of CO2 by rock weathering in the UK and Canada. Microsoft signed a follow-on agreement with UNDO to permanently remove 15,000 tonnes of CO2, using crushed basalt on UK farmland and wollastonite in rural Canada. ([our story](https://technooptimist.io/stories/microsoft-expands-its-deal-with-undo-to-remove-15-000-tonnes-of-co2-by-4102619c.md) · [original source](https://bettersociety.net/Microsoft-partnership-aims-to-remove-15000-tonnes-of-CO2-from-the-atmosphere.php))

## Current obstacles

- **Measuring removal on real farms**: Removal must be inferred from rock, soil and water data over years; methods are still being refined with academic partners.
- **Transport emissions**: Hauling heavy rock emits CO2; UNDO tracks trucks by GPS and subtracts it, so long hauls cut net removal.

## Physics limits

- **Weathering speed is set by nature**: How fast rock dissolves depends on rainfall, temperature, soil chemistry and grain size. Cool, dry fields weather slowly, so credits for removal accrue over years, not at spreading.
- **A lot of rock per tonne of CO2**: Several tonnes of rock are needed per tonne of CO2 removed, so crushing and trucking costs and emissions decide where the method makes sense.

## How it works

### Spread: Crushed rock on fields

Finely crushed basalt (UK) or wollastonite (Ontario) is spread on farmland, much like farmers spread lime.

### Weather: Rain turns CO2 into bicarbonate

Rain absorbs CO2 and forms a weak acid that dissolves the rock, converting the CO2 into dissolved bicarbonate.

### Store: Carried to the ocean

Bicarbonate drains through soils and rivers to the sea, where carbon stays for tens of thousands of years or more.

### Soil: Minerals for crops

The rock releases calcium, magnesium and potassium and can raise soil pH; trials with Newcastle University saw yield gains.

## Spec sheet

| Spec | UNDO Enhanced Rock Weathering | Provenance |
| --- | --- | --- |
| Rock spread to date | 358,340 t | reported |
| Area spread | 61,310 acres | reported |
| Farms | 444 | reported |
| CO2 removal expected | 78,835 t | reported |
| Carbon efficiency, basalt | ~95% (after operating emissions) | reported |
| Carbon efficiency, wollastonite | ~90% | reported |

Provenance: reported = stated by the company; estimated = our estimate; sample = a sample figure.

## About UNDO

London company that spreads crushed basalt and wollastonite on farmland in the UK and Canada so rain slowly turns CO2 into dissolved bicarbonate, and sells the carbon removal to buyers such as Microsoft.

- 358,000 t of rock spread on 444 farms; 78,800 t of CO2 removal expected (company figures).
- Buyers include Microsoft (15,000 t deal, 2024) and Barclays (6,538 t, 2025).
- Uses basalt in the UK and Canadian wollastonite in Ontario.

- Founded: 2022
- Headquarters: GB
- Status: private
- Website: https://un-do.com
- Partners, customers, investors: Microsoft (customer); Barclays (customer)

Company page: https://technooptimist.io/companies/undo.md

## Related programs

Everything in Agriculture: https://technooptimist.io/agriculture.md

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