Enhanced rock weathering

01Overview and value chain#

Markers EC: REACH | OECD: bioenergy | Regulator: EPA (USA), ADEME (EU), NEA (China)

Enhanced rock weathering spreads finely crushed silicate rock, most often basalt, onto agricultural land, where rainwater and soil carbonic acid accelerate a weathering reaction that would otherwise take geological timescales: the rock’s calcium and magnesium silicates react with dissolved CO2 to form stable bicarbonate, which is either retained in soil porewater or eventually washed to the ocean, where it is sequestered on multi-thousand-year timescales. The same reaction also raises soil pH and releases plant nutrients, giving ERW operators a genuine agronomic pitch to farmers alongside the carbon-removal pitch to corporate buyers — most of this table’s operators run their business as a farmer-partnership model rather than owning land outright. 2025-2026 produced real delivery milestones rather than just pilot announcements: Lithos Carbon issued 5,160 registry-certified tonnes of carbon removal in December 2025, roughly seven times larger than any prior single ERW credit issuance, and InPlanet issued the world’s first independently verified ERW carbon removal credits in December 2024.

The key directions are:

1. Farmer-partnership basalt application: Supplying crushed basalt to working farmland at low or no cost to the farmer, capturing carbon while the farmer captures a free soil amendment.
2. In-field weathering-rate measurement: Soil porewater chemistry sampling and modeling to verify how much CO2 a given application has actually sequestered, since weathering rate depends heavily on rock particle size, soil type, and climate.
3. Upstream mineral supply: Sourcing and milling basalt or other reactive silicate rock at the particle size that maximizes weathering rate without prohibitive energy cost, often via partnership with an existing industrial minerals supplier.
4. Corporate carbon-removal offtake: Structuring multi-year credit-delivery agreements with corporate buyers (Microsoft is the dominant anchor buyer across this table) that fund the field operations years before the CO2 removal is fully verified.

Sectoral value chain#

[Basalt sourcing & milling] ──> [Farmland application] ──> [In-field weathering] ──> [Porewater sampling & MRV]
                                  │
                          (Weathering-rate modeling)
                                  │
                                  ▼
[Corporate offtake buyers] <─── [Credit verification & issuance] <─────┘

Value chain levels#

Cross-cutting technologies of the sector:

• Reactive-surface-area optimization: Milling rock to the particle size that maximizes weathering rate per tonne applied without spending more energy on grinding than the carbon benefit justifies.
• Soil porewater alkalinity measurement: The primary MRV method for verifying how much CO2 an application has actually sequestered, since direct measurement of the weathering reaction itself is impractical at field scale.
• Heavy-metal and trace-element screening: Basalt sources vary in trace heavy-metal content, so responsible operators screen and select sources to avoid soil contamination alongside the carbon benefit.

02US#

The United States hosts the field’s most commercially proven operator, anchored by a farmer-partnership model that has scaled to the largest single verified delivery in the sector’s history.

Largest verified delivery to date, a strategic minerals-supplier tie-up#

• Lithos Carbon: founded in 2022 in San Francisco, spreads basalt across partner farms in North Carolina, Wisconsin, Pennsylvania, Maryland and Michigan, and in December 2025 issued 5,160 registry-certified tonnes of carbon removal — roughly seven times the size of any prior single ERW credit delivery — on top of an earlier Microsoft-funded research partnership.
• Eion: closed a $12 million Series A with Sibelco, the Belgian industrial-minerals group, participating as both a strategic investor and its upstream basalt supplier — a direct commercial link between two of this table’s companies that illustrates how ERW startups are increasingly integrating with existing mining supply chains rather than building their own quarrying operations.

03CN#

No China-headquartered commercial ERW operator was confirmed, despite published research finding the country has some of the most favorable natural conditions for the technology anywhere in the world.

Strong theoretical potential, no confirmed commercial operator#

• Published life-cycle-assessment research on basalt-based ERW in China estimates nationwide deployment could sequester on the order of 0.2 gigatonnes of CO2 by 2100 using coarser rock particles, or up to 0.5 gigatonnes by 2060 using finer particles — reflecting China’s large basalt reserves and extensive agricultural land base.
• That research remains academic and techno-economic rather than commercial: no China-headquartered company was confirmed operating a farmer-partnership or credit-issuance ERW business comparable to Lithos Carbon, UNDO or the other operators in this table.

04EU#

Europe’s strongest entry is a UK operator with the sector’s largest single corporate offtake commitment, backed by an established industrial-minerals supplier that has become a strategic investor across the category.

Largest corporate offtake to date, minerals-industry convergence#

• UNDO: signed a deal with Microsoft to deliver 15,000 tonnes of CO2 removal via ERW, spreading a combined 65,000 tonnes of crushed silicate rock — 40,000 tonnes of basalt across the UK and 25,000 tonnes of wollastonite across Canada — making it, by rock tonnage, one of the largest ERW field operations announced to date.
• Sibelco: the Belgium-headquartered global minerals group has set science-based Scope 3 emissions targets covering its own supply chain and, separately, has taken a strategic-investor and upstream-supplier position in Eion’s carbon-removal business, positioning an established industrial minerals major as infrastructure for the ERW sector rather than a standalone carbon-removal operator in its own right.

05Leading companies and research institutes#

06Tech stack and innovations#

The stack centers on making the natural weathering reaction fast enough, and its progress measurable enough, to sell as a financeable carbon removal product rather than a geological curiosity.

1. Particle-Size Engineering:
   • Finer milling increases the reactive surface area that drives weathering rate, but grinding energy cost rises sharply below a certain particle size, so operators optimize for the size that maximizes net carbon benefit rather than raw weathering speed.
2. Porewater MRV Methodology:
   • Since the weathering reaction itself cannot be directly observed at scale, operators sample soil porewater alkalinity and cation concentrations over multiple growing seasons and model actual sequestration against controls, the methodology InPlanet’s independently verified credits relied on.
3. Feedstock Sourcing Integration:
   • Basalt is frequently a byproduct or co-product of existing quarrying operations, which is why minerals majors like Sibelco are becoming strategic partners and investors rather than remaining outside the ERW value chain.

07Value chains and production pipelines#

Industrial pipeline of farmer-partnership ERW (Verified Credit Issuance)#

┌───────────────────────────┐      ┌───────────────────────────┐
│ 1. Basalt sourcing        │ ───> │ 2. Milling to target       │
│                            │      │    particle size            │
└───────────────────────────┘      └───────────────────────────┘
                                                 │
                                                 ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 4. Multi-season porewater │ <─── │ 3. Farmland spreading      │
│    sampling                │      │                            │
└───────────────────────────┘      └───────────────────────────┘
              │
              ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 5. Weathering-rate         │ ───> │ 6. Registry verification & │
│    modeling                │      │    credit issuance         │
└───────────────────────────┘      └───────────────────────────┘

Stage 1: Basalt sourcing

Basalt is quarried directly or, increasingly, sourced as a byproduct from an established minerals supplier’s existing quarrying operations.

Stage 2: Milling to target particle size

The rock is crushed and milled to a particle size calibrated to maximize reactive surface area without exceeding the energy budget the carbon-removal economics can support.

Stage 3: Farmland spreading

Milled rock is spread onto partner farmland using standard agricultural spreading equipment, integrated into the farm’s normal operating calendar.

Stage 4: Multi-season porewater sampling

Field teams collect soil porewater samples across multiple growing seasons, tracking alkalinity and cation concentrations that indicate how much weathering has actually occurred.

Stage 5: Weathering-rate modeling

Sampled data is fed into geochemical models that translate porewater chemistry into an estimated tonnage of CO2 sequestered, accounting for local soil type, rainfall and rock particle size.

Stage 6: Registry verification and credit issuance

An independent carbon-credit registry reviews the MRV dataset and methodology before issuing certified carbon removal credits, which are then delivered against corporate offtake agreements like those Lithos Carbon, UNDO and InPlanet have signed with Microsoft.