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    Enhanced rock weathering

    Also known as enhanced weathering, EW, terrestrial enhanced weathering

    Enhanced weathering speeds up the natural reaction between certain rocks and CO2 by spreading crushed rock, usually silicate rock such as basalt, on farmland; the reaction takes months to centuries.[1] A four-year US Corn Belt trial reported both CO2 removal and higher crop yields, but verified removals in 2025 were tiny because real-world measurement remains the field's main problem.[2][3][4]

    Editor reviewedUpdated Climate science and carbon removalEnergy and climateScience
    Key facts

    What it is

    Rocks such as basalt slowly react with CO2 as they weather. Enhanced weathering grinds the rock and spreads it, mostly on agricultural land where acidic soils speed up the reactions and existing supply chains can distribute the material.[1] It is classed as a “novel” carbon dioxide removal method alongside biochar and direct air capture.[5]

    Evidence from the field

    The most cited field study is a replicated trial on an experimental farm in the US Corn Belt from 2016 to 2020. Applying 50 tonnes of crushed basalt per hectare each autumn gave a conservative cumulative removal of 10.5 ± 3.8 tonnes of CO2 per hectare, and maize and soybean yields rose 12–16%.[2] The same study found no significant increase in trace metals in the grain or in soil exchangeable pools compared with control plots, a common concern with spreading basalt.[6]

    First verified credits and buyers

    Verified tonnes are still counted in the hundreds per project. In January 2025 the registry Isometric issued 235.53 credits to InPlanet, which it called the first independently verified enhanced weathering credits, for delivery to the payments company Adyen.[7] In November 2025 it issued Alt Carbon’s first 221 credits, from waste basalt spread on farms in Darjeeling, India, for the shipping line Mitsui O.S.K. Lines.[8] In 2026 Microsoft signed a 36,920-tonne deal with Alt Carbon, one of only a few purchases after it was reported to be pausing.[9] The buyers’ coalition frontier-carbon-removal says its members signed the first commercial enhanced weathering deals.[10]

    Commercial activity grew in 2024 and 2025, with companies spreading tens of thousands of tonnes of basalt in India and Brazil.[3] Yet the State of CDR report counted only about 0.0038 million tonnes of verifiable removal in 2025, using a revised method that includes only publicly documented values.[3] Because the reaction proceeds over months to centuries, rock spread now keeps removing CO2 in later years.[1]

    Potential

    Estimates of technical potential on farmland range from 0.2 to 2 billion tonnes of CO2 a year, and sustainable potential may be limited to 0.7 billion tonnes.[11] Higher estimates exist for more reactive but rarer rocks, which the State of CDR report calls likely unattainable.[11] Frontier’s estimate of about 1–2 billion tonnes a year at $75–200 per tonne gives a sense of the physical scale. One billion tonnes would mean crushing around four billion tonnes of rock and spreading it on roughly 28% of global cropland.[12]

    The measurement problem

    Measurement, reporting and verification (MRV) is the core challenge. Global estimates typically extrapolate from lab data, while field rates are slower and fall over time, and carbon can be lost downstream in soils and groundwater.[4] Readiness assessments range from TRL 3–4 in conservative estimates to 8–9 in supplier estimates, a spread that reflects this uncertainty.[1] The State of CDR report lists measurement of enhanced weathering among the main unresolved quality issues for novel removal.[13] Scaling makes the tension sharper. Frontier argues that reaching gigaton scale would require moving from direct soil measurements to modelled quantification “without sacrificing rigor”.[12] Yet the State of CDR report warns that estimates extrapolated from lab data run ahead of the slower rates seen in the field.[4]

    Where it fits

    Enhanced weathering shares its chemistry with ocean alkalinity enhancement, which adds alkalinity to seawater instead of soil; see ocean-carbon-dioxide-removal.[14] Its claimed co-benefits for crop yields set it apart from engineered methods such as direct-air-capture.[2]

    Questions readers ask

    Does enhanced weathering work?

    Field evidence is growing. A 2016–2020 Corn Belt trial reported cumulative removal of 10.5 ± 3.8 tonnes of CO2 per hectare, but confirming net removal with real-world monitoring remains challenging.[2][4]

    Does it help farmers?

    In the Corn Belt trial, maize and soybean yields rose 12–16% with basalt applications.[2]

    How much CO2 could it remove?

    Estimates of technical potential on farmland range from 0.2 to 2 billion tonnes a year, with sustainable potential possibly limited to 0.7 billion tonnes.[11]

    Why are verified removals so small?

    The reaction is slow and hard to measure. Verifiable removals were about 0.0038 million tonnes in 2025 under a stricter counting method, even though much more rock has been spread.[3][1]

    Has anyone sold verified enhanced weathering credits?

    Yes, in small numbers. Isometric issued the first independently verified enhanced weathering credits, 235.53 tonnes for InPlanet, in January 2025, and 221 credits for Alt Carbon's Darjeeling project in November 2025.[7][8]

    Sources

    Each numbered claim is a statement we checked against the sources listed with it. Status shows how well established it is.

    1. [1]

      Enhanced weathering spreads crushed rock, usually silicate rock on farmland, to speed natural reactions that take up CO2; the reactions take months to centuries, and readiness estimates range from TRL 3–4 (conservative) to 8–9 (suppliers). Most applications use farmland, where acidic soils speed up reactions and existing supply chains can distribute the rock. confirmedas of 2026-06-01

    2. [2]

      A four-year (2016–2020) replicated field trial on a US Corn Belt farm applying 50 tonnes of crushed basalt per hectare each year found cumulative CO2 removal of 10.5 ± 3.8 tonnes per hectare and maize and soybean yield gains of 12–16%. confirmedas of 2024-02-22

    3. [3]

      Verifiable enhanced weathering removals totalled about 0.0038 million tonnes of CO2 in 2025 under a stricter counting method, even as companies spread tens of thousands of tonnes of basalt in India and Brazil. confirmedas of 2026-06-01

    4. [4]

      Global enhanced weathering estimates typically extrapolate from lab data, while field rates are slower and decline over time, carbon can be lost downstream in soils and groundwater, and confirming net removal with real-world monitoring is challenging. confirmedas of 2026-06-01

    5. [5]

      The State of CDR report splits removal into "conventional" methods, largely forests and soils, and "novel" methods such as biochar, enhanced weathering and direct air carbon capture and storage. confirmedas of 2026-06-01

    6. [6]

      The Corn Belt enhanced weathering trial found no significant increase in trace metals in maize or soybean grain or in soil exchangeable pools compared with controls. confirmedas of 2024-02-22

    7. [7]

      In January 2025 Isometric said it had issued 235.53 enhanced weathering removal credits to InPlanet, the first independently verified enhanced weathering credits, for delivery to Adyen. confirmedas of 2025-01-06

    8. [8]

      In November 2025 Isometric issued Alt Carbon's first 221 enhanced weathering credits, from a project spreading waste basalt powder on farms in Darjeeling, India, for delivery to Mitsui O.S.K. Lines. confirmedas of 2025-11-17

    9. [9]

      In August 2026 Microsoft signed a deal with Crew Carbon for up to 23,602 removal units from wastewater alkalinity enhancement, its third removal deal since reports that it was adjusting the pace of purchases, after BioCirc (650,000 tonnes) and enhanced weathering firm Alt Carbon (36,920 tonnes); DatacenterDynamics said its purchasing cadence had dropped significantly in 2026. reportedas of 2026-08-05

    10. [10]

      Frontier says its buyers signed the first commercial deals in enhanced rock weathering, inland water and ocean alkalinity enhancement, biomass injection and waste-to-energy with carbon capture, and that it has assessed more than 500 companies. confirmedas of 2026-06-17

    11. [11]

      Estimates of enhanced weathering technical potential on farmland range from 0.2 to 2 billion tonnes of CO2 a year, with sustainable potential possibly limited to 0.7 billion tonnes; much higher estimates for rarer, more reactive rocks are described as likely unattainable. confirmedas of 2026-06-01

    12. [12]

      Frontier estimates enhanced rock weathering could reach about 1–2 billion tonnes a year at $75–200 per tonne; 1 billion tonnes would mean crushing about four billion tonnes of rock and spreading it on roughly 28% of global cropland, and would require moving from direct soil measurements to modelled quantification. confirmedas of 2026-06-17· interpretation

    13. [13]

      The State of CDR report lists open problems for novel CDR quality, including sustainable biomass sourcing for BECCS and biochar, permanence of storage, measurement of enhanced weathering and ocean alkalinity enhancement, and lifecycle emissions of energy-intensive DACCS. confirmedas of 2026-06-01

    14. [14]

      In ocean alkalinity enhancement, alkalinity is added to seawater and the resulting uptake of atmospheric CO2 happens gradually over broad areas of ocean surface, so quantification relies mainly on ocean modelling. confirmedas of 2026-06-01

    15. [15]

      BECCS is an umbrella term for technologies that turn biomass into energy and capture and geologically store the CO2; bioethanol with CCS is commercial (TRL 9) while biomass combustion with CCS is at demonstration stage (TRL 7). confirmedas of 2026-06-01

    16. [16]

      Solid-sorbent and mineral-looping direct air capture are commercially deployed (TRL 9), liquid-solvent systems are at pilot scale (TRL 6–7), and electrochemical regeneration is earlier (TRL 4–6); all are energy intensive. confirmedas of 2026-06-01

    Revision history (2)
    1. Page created.
    2. Refresh: added the first verified credits, Microsoft's 2026 Alt Carbon deal, Frontier's scale estimate and the Corn Belt trial's trace-metal finding; re-verified the PNAS excerpt via Europe PMC.

    Created Oct 10, 2026. Last reviewed by an editor on Oct 10, 2026. Next scheduled review: Jan 10, 2027.

    Cite this page

    "Enhanced rock weathering." ContentLora, updated Oct 10, 2026. https://contentlora.com/wiki/enhanced-rock-weathering

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    Ocean-based carbon … Ocean counterpartBECCS Alternative methodDirect air capture Alternative method
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