Overview
How this pathway works
Natural silicate rock weathering is one of Earth's primary long-term carbon sinks - over millions of years, the slow dissolution of silicate minerals by carbonic acid (CO₂ dissolved in rainwater) produces alkaline bicarbonate ions that are transported by rivers to the ocean and eventually precipitated as calcium or magnesium carbonate minerals, locking CO₂ on geological timescales. Enhanced rock weathering deliberately accelerates this process by orders of magnitude by applying finely crushed silicate rocks to agricultural land, maximising the reactive surface area available for dissolution.
Under TTS v1.0 Annex D, ERW projects earn TTC-R Removal Credits for verified net alkalinity generation attributable to silicate mineral dissolution from the applied rock. The carbon removal pathway is indirect: CO₂ is not physically captured from the atmosphere but is instead drawn down by the ocean or soil system as alkalinity increases absorb atmospheric CO₂ into stable bicarbonate or carbonate form. All credits are TTC-R Removal Credits - there is no fossil displacement component to ERW projects.
Three ERW application types are approved under Annex D. ERW-M01 covers basalt application on cropland with cation flux quantification; ERW-M02 covers silicate rock powder applications (olivine, wollastonite, mixed minerals) on managed land; and ERW-M03 covers coastal and beach weathering in high-energy marine environments. A conservative 10% default deduction applies to all methodologies unless site-specific quantification reduces measured uncertainty below 10% at 90% confidence.
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Class III - Mineral permanence. ERW credits carry Class III Mineral permanence - the highest permanence class in the Teravent system - reflecting the thermodynamic stability of carbonate minerals and dissolved bicarbonate in the ocean on million-year timescales. Once silicate minerals dissolve and produce bicarbonate alkalinity that reaches the ocean, the carbon is effectively permanently removed from the atmosphere. Buffer pool contributions are minimal (2–5%) reflecting this extremely high storage permanence.
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10% conservative deduction. Given inherent uncertainties in field-scale weathering rate quantification, a mandatory 10% conservative deduction applies to all ERW credits before issuance unless the project demonstrates site-specific measurement uncertainty below 10% at 90% confidence using cation flux monitoring or isotopic tracing. The conservative deduction is non-negotiable for geochemical model-based quantification and model-only projects.
Geochemical Mechanism
The weathering
carbon pathway
Understanding the chemical pathway from rock application to atmospheric CO₂ removal is essential for project design, monitoring protocol selection, and credit calculation. The four-stage pathway below describes the primary silicate weathering carbon removal mechanism. All four stages must be accounted for in the project's quantification approach.
Stage 1 · Dissolution
CaSiO₃ + 2CO₂ + H₂O →
Silicate mineral (e.g. wollastonite) dissolves in carbonic acid formed by CO₂ dissolving in soil water. Cations (Ca²⁺, Mg²⁺) and silicic acid released.
Stage 2 · Alkalinity
Ca²⁺ + 2HCO₃⁻
Dissolution consumes CO₂ to form bicarbonate (HCO₃⁻) alkalinity. Net: 2 CO₂ molecules consumed per Ca²⁺ released. Soil alkalinity rises, pH increases.
Stage 3 · Transport
Ca²⁺ + 2HCO₃⁻ → rivers → ocean
Dissolved Ca²⁺ and HCO₃⁻ drain through soil to groundwater and riverine systems, eventually reaching the ocean where alkalinity drives additional atmospheric CO₂ uptake.
Stage 4 · Mineralisation
Ca²⁺ + 2HCO₃⁻ → CaCO₃ + CO₂ + H₂O
Marine organisms and abiotic processes precipitate CaCO₃ from ocean water, locking carbon in carbonate mineral form on geological (million-year) timescales.
⚗️
Net CO₂ removal calculation: The theoretical maximum CO₂ removal per tonne of mineral is calculated from the stoichiometry of the dissolution reaction - for calcium silicates, approximately 1 mol CO₂ removed per mol Ca released; for magnesium silicates (olivine), approximately 2 mol CO₂ per mol Mg. Actual field removal rates are substantially lower due to incomplete dissolution, secondary mineral precipitation, and transport losses. Teravent quantification methods measure the actual net removal, not the theoretical maximum.
Eligible Minerals
Approved silicate rock types
TTS v1.0 Annex D approves a specific list of silicate rock and mineral types for ERW applications. The mineral must be reactive enough to dissolve at agronomically relevant timescales (within years, not centuries) but stable enough that its carbon removal benefit is durable. Carbonate minerals (limestone, dolomite) are explicitly excluded because their liming effect does not consume atmospheric CO₂ in a net sense.
Primary - ERW-M01
Basalt
Ca/Mg-rich volcanic rock · ~50% SiO₂
Most widely available and studied ERW feedstock. Moderate dissolution rate. Good Ca²⁺ and Mg²⁺ release. Broad co-benefit profile. Suitable for tropical and subtropical agricultural soils.
Primary - ERW-M02
Olivine
(Mg,Fe)₂SiO₄ · High Mg content
Highest theoretical CDR potential per tonne. Rapid dissolution rate in warm humid conditions. Concerns about Ni and Cr trace metal release must be assessed per Teravent Heavy Metal Protocol HMP-01.
High reactivity - ERW-M02
Wollastonite
CaSiO₃ · Pure calcium silicate
Fastest dissolution rate of all approved ERW minerals. High Ca²⁺ release with strong soil pH amelioration. Limited global supply compared to basalt. Most suitable for temperate and boreal soils.
Supplementary - ERW-M02
Dunite
>90% olivine · Ultramafic rock
Near-pure olivine rock. Very high CDR potential with same trace metal considerations as pure olivine. Used where dunite quarry waste is locally available as low-cost feedstock.
Supplementary - ERW-M02
Mixed Silicates
Anorthosite, gabbro, phonolite
Mixed silicate rock types approved where site-specific mineralogical characterisation is provided and dissolution kinetics are validated against field measurements at the project site.
Marine - ERW-M03
Coastal Olivine/Basalt
High-energy beach application
Crushed olivine or basalt applied to coastal beaches and high-energy shoreline environments where wave action provides mechanical abrasion accelerating dissolution beyond land-based rates.
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Carbonate minerals are excluded. Limestone (CaCO₃), dolomite (CaMg(CO₃)₂), and agricultural lime products are explicitly excluded from ERW eligibility under TTS Annex D. Carbonate mineral liming releases CO₂ during dissolution (the reverse of the silicate reaction) and does not drive net atmospheric CO₂ removal. Projects using agricultural lime cannot claim ERW credits - they may claim separate soil pH co-benefits but no carbon removal benefit.
Governing Standard
TTS v1.0 - Annex D
This pathway is governed exclusively by the Teravent Technology Carbon Standard (TTS v1.0). All requirements - quantification method selection, cation flux monitoring, isotopic tracing, geochemical model calibration, and credit issuance - are defined within TTS v1.0 and Annex D.
TCR›
TTS v1.0›
Annex D - Enhanced Rock Weathering›
ERW-M01 through ERW-M03
M02
TRL-based common practice test (auto-pass ≤TRL 7) · Financial additionality via full-project IRR · Quarrying and transport costs confirmed as carbon-revenue dependent
M03
Three approved quantification approaches: (1) cation flux monitoring, (2) Sr/Li isotopic tracing, (3) geochemical model calibrated with 12+ months field data · 10% conservative deduction
M04
Class III Mineral permanence · Buffer pool 2–5% · No storage site monitoring required - permanence is thermodynamically assured once bicarbonate reaches ocean
M05
Heavy metal risk assessment mandatory per HMP-01 - Ni, Cr, As, Pb, Cd, Hg · Soil Health+ and Food Security+ co-benefit labels frequently applicable
M03
Rock application mass and mineralogical characterisation (XRF) mandatory - reactive mineral fraction and reactive surface area quantified at quarry or field sample annually
M03
Secondary mineral precipitation deduction required - Ca/Mg lost to secondary carbonate or silicate mineral formation in soil does not contribute to atmospheric CDR and must be deducted
Teravent Technology Credit (Removal) - Serial Format (TTS Annex D)
TCR
–
TTS
–
R
–
ERW
–
IN
–
00412
–
2025
–
000001
Methodologies Accepted
Three approved application variants
TTS v1.0 Annex D approves three ERW application types. The methodology code determines the application environment, eligible rock types, and applicable quantification approach. All three share the same three quantification methods and the 10% conservative default deduction, but differ in their monitoring requirements - particularly for coastal applications (ERW-M03), which face greater ocean chemistry attribution challenges.
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Quantification approach must be declared at registration. Projects must declare their primary quantification approach - cation flux, isotopic tracing, or geochemical model - in the PDD before validation. Switching quantification approaches after validation requires a material project design amendment and TSA approval. Where a geochemical model is used, the model must be independently validated against site-specific field data from a minimum of 12 months of cation flux or isotopic measurements before the model-based quantification is accepted for credit issuance.
ERW-M01 applies finely crushed basalt rock - milled to a particle size distribution typically below 2 mm median diameter for maximum reactive surface area - to managed cropland at agronomically determined application rates. Basalt is the most widely researched and deployed ERW feedstock, with multi-year field trials in India, the UK, the US, and Brazil providing the evidence base for quantification model calibration. The calcium and magnesium cations released during dissolution raise soil pH, supplying plant-available nutrients and reducing the need for conventional agricultural lime - providing a direct, verifiable agricultural co-benefit alongside the carbon removal benefit. Application rates range from 1 to 50 tonnes per hectare depending on soil baseline pH, crop type, and desired liming effect.
Rock Type
Basalt (Ca/Mg silicate)
Particle Size
<2 mm median - XRF mineralogy required
Application Rate
1–50 t/ha (agronomic design)
Credit Type
TTC-R Removal Credit
Conservative Deduction
10% default · Reducible with measurement data
Co-benefit
Soil pH amelioration · Ca/Mg nutrient supply
Key Monitoring Indicators
- Rock application mass per field (tonnes/ha) - GPS-tracked field application records per delivery and spread event
- Rock mineralogy - XRF analysis per quarry batch confirming reactive mineral fraction (Ca-silicate, Mg-silicate content)
- Particle size distribution - laser diffraction or sieve analysis per batch; reactive surface area calculation per BET method annually
- Soil drainage cation flux (Ca²⁺, Mg²⁺, Si) - lysimeter or tile drain water sampling at permanent stations, minimum monthly during growing season
- Soil pH at permanent monitoring plots - annually at 0–15 cm and 15–30 cm depth at baseline and each monitoring event
- Secondary mineral precipitation assessment - soil carbonate and secondary silicate mineral formation quantified by XRD analysis annually to determine deduction from gross cation flux
- Trace metal monitoring (Ni, Cr) in soil and crops per HMP-01 - annually for first 5 years; every 3 years thereafter
- Crop yield data - annual records per field for Food Security+ co-benefit label qualification
ERW-M02 covers silicate rock powders beyond basalt - specifically olivine (forsterite/fayalite), wollastonite, dunite, and TSA-approved mixed silicate formulations. These materials often have higher theoretical CDR potential per tonne than basalt but require more careful agronomic and environmental management. Olivine and dunite applications must comply with the Teravent Heavy Metal Protocol HMP-01 for nickel and chromium because ultramafic rocks can contain elevated Ni and Cr concentrations that may enter soil, crops, and drainage water at elevated application rates. Wollastonite carries the highest dissolution rate and lowest trace metal risk of the approved ERW-M02 minerals, making it particularly suitable for temperate agricultural systems where rapid liming response is needed.
Rock Types
Olivine, wollastonite, dunite, mixed silicates
Trace Metal Protocol
HMP-01 mandatory for olivine/dunite
Conservative Deduction
10% default · Reducible with measurement
Mineralogy Verification
XRF + XRD per batch - reactive fraction confirmed
Credit Type
TTC-R Removal Credit
Wollastonite Advantage
Fastest dissolution - strong liming co-benefit
Key Monitoring Indicators
- Rock application mass and mineralogical batch analysis (XRF + XRD) - reactive mineral fraction, trace metal content per delivery
- Cation flux monitoring (Ca²⁺, Mg²⁺, Si, Sr isotopes) at drainage lysimeters or tile drains - minimum monthly during growing season
- Strontium or lithium isotopic tracing (⁸⁷Sr/⁸⁶Sr or δ⁷Li) at minimum 4 drainage sampling events per year - distinguishes rock-derived alkalinity from soil background and biological cycling
- Soil Ni, Cr, Co, As concentrations - HMP-01 mandatory for olivine/dunite: annual soil sampling at 0–30 cm for first 5 application years; crop tissue Ni/Cr where edible crops are grown
- Secondary mineral precipitation (secondary carbonate and silicate) - XRD analysis of soil samples annually to quantify Ca/Mg lost to non-CDR mineral phases
- Soil pH trajectory at permanent plots - confirms dissolution progression and liming co-benefit
- Drainage water pH, alkalinity (TA), Ca²⁺, Mg²⁺ - confirms net alkalinity export at field scale
ERW-M03 applies crushed silicate minerals to beaches, coastlines, and nearshore environments where wave action provides mechanical abrasion that dramatically accelerates mineral dissolution compared to terrestrial soil application. The constant wetting and mechanical energy of high-energy coastal environments can increase dissolution rates by 10–100× compared to agricultural ERW. Dissolved alkalinity enters the ocean directly rather than via terrestrial drainage, where it drives additional atmospheric CO₂ uptake through ocean carbonate chemistry equilibria. This methodology sits at the boundary between land-based ERW and ocean alkalinity enhancement - ocean chemistry attribution monitoring requirements from TTS Annex K (OAE) apply to coastal deployments alongside the land-based rock application monitoring requirements of ERW.
Environment
High-energy beach or coastal shoreline
Rock Type
Crushed olivine or basalt
Conservative Deduction
10% default (mandatory - no waiver available)
Ocean Monitoring
TA/DIC paired sampling required (per Annex K)
Marine Ecology
Annual marine ecology survey mandatory
Trace Metal Risk
HMP-01 + marine sediment sampling
Key Monitoring Indicators
- Rock application mass and XRF mineralogy per deployment - GPS-recorded placement coordinates
- Residual rock mass on beach - annual photogrammetric survey to assess mechanical abrasion loss and remaining reactive material
- Nearshore seawater total alkalinity (TA) and dissolved inorganic carbon (DIC) at treatment and paired control sites - minimum 6 sampling events per year
- Strontium isotopic tracing (⁸⁷Sr/⁸⁶Sr) in nearshore water - to distinguish rock-derived alkalinity from background marine chemistry
- Marine sediment Ni, Cr, Fe concentrations - HMP-01 marine adaptation: sediment sampling at application zone and 500m buffer quarterly in first 2 years
- Benthic and intertidal ecology survey - annual independent marine ecologist survey of invertebrate communities, seagrass, macroalgae in application zone
- Beach sediment grain size and carbonate content - annual survey to track dissolution progress and beach geomorphology impacts
Quantification Methods
Three approved approaches
for measuring CDR
TTS v1.0 Annex D provides three approved quantification approaches for measuring the net CO₂ removal attributable to ERW. All three can reduce the 10% conservative deduction if site-specific uncertainty falls below 10% at 90% confidence. The choice of approach determines the monitoring infrastructure required and the level of field data investment needed before first credit issuance.
APPROACH 1 - PREFERRED
Cation Flux Monitoring
Measures the increase in dissolved Ca²⁺, Mg²⁺, and Si ions in soil drainage water relative to a non-amended control. Net cation flux from the amended plot minus the control plot represents the mineral dissolution rate. CO₂ removal is calculated from cation stoichiometry per approved dissolution equations.
Monitoring: Lysimeters or tile drains · Min. monthly sampling · ICP-MS laboratory analysis
Typical uncertainty: 8–15% · Can reduce conservative deduction below 10%
APPROACH 2 - HIGH CONFIDENCE
Strontium / Lithium Isotopic Tracing
Uses the distinct isotopic signature of the applied rock (⁸⁷Sr/⁸⁶Sr ratio or δ⁷Li) to fingerprint rock-derived alkalinity in drainage water, soil solution, and groundwater. Provides highly specific attribution of dissolution to the ERW rock rather than background soil mineral weathering or biological cycling.
Monitoring: Isotopic analysis of rock + drainage water · Min. 4×/yr · Specialist isotope geochemistry lab
Typical uncertainty: 5–10% · Strongest approach for reducing conservative deduction
APPROACH 3 - REQUIRES CALIBRATION
Calibrated Geochemical Model
Uses a process-based geochemical model (WITCH, SAFE, or TSA-approved equivalent) calibrated with site-specific data - climate, soil type, mineralogy, hydrology - to estimate dissolution rates and net CDR. Model must be calibrated against minimum 12 months of field cation flux or isotopic data before being accepted for credit issuance.
Monitoring: 12+ months field calibration data required · Annual recalibration if climate or management changes
Typical uncertainty: 15–35% · Conservative deduction waiver not available for model-only projects
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Secondary mineral precipitation deduction: Not all Ca²⁺ and Mg²⁺ released from dissolving silicates contributes to atmospheric CO₂ removal. A fraction precipitates as secondary calcite, dolomite, or secondary silicate minerals in the soil - re-releasing CO₂ rather than removing it. This fraction must be measured by annual XRD analysis of soil samples and deducted from gross cation flux before calculating net CDR. Typical secondary precipitation deductions range from 5–25% depending on soil pH and calcium carbonate saturation index, and are in addition to the 10% conservative deduction where both apply.
GHG Accounting
What must be
measured and deducted
ERW projects have a relatively simple GHG accounting boundary compared to BECCS or CCUS. The primary benefit is the net alkalinity generated by silicate dissolution (measured as CO₂-equivalent removal). The primary emission sources are quarrying, crushing, and transport of rock. All must be assessed in the lifecycle GHG analysis per TLP v1.0 to confirm net-negative carbon balance.
Required - Primary Benefit
Net Alkalinity Generation (CDR)
Verified net CDR from silicate mineral dissolution, quantified via cation flux, isotopic tracing, or calibrated geochemical model. Expressed as tCO₂e removed after secondary precipitation deduction and conservative deduction. This is the sole source of TTC-R credit generation for ERW projects.
Required - Deduct
Quarrying & Crushing Emissions
GHG from rock extraction at the quarry (blasting, heavy machinery), primary and secondary crushing (grinding mills), and drying where required. Typically the largest single GHG source in the ERW supply chain - quantified from energy consumption records and TSA-approved emission factors per TLP v1.0.
Required - Deduct
Transport Emissions
GHG from road, rail, or ship transport of crushed rock from quarry to project site. Transport distance and mode must be documented. This is a significant emission source for ERW projects - transport emissions alone can negate CDR benefits at distances exceeding 500 km by road for basalt, or 200 km for olivine (higher CDR per tonne offsets longer transport distances).
Required - Deduct
Field Application Emissions
GHG from farm machinery used to spread rock powder on fields - tractor and spreader fuel consumption. Typically minor (1–5% of gross CDR benefit) but must be included. Where application machinery is electrically powered, the grid emission factor at the time of operation is applied per TLP v1.0.
Where material
N₂O Soil Emission Change
Where ERW significantly raises soil pH, N₂O emissions from agricultural soils may decrease because nitrification and denitrification rates are pH-sensitive. Where independently measured and significant, this secondary N₂O benefit may be credited as a minor additional benefit. Not required for most projects but may contribute 5–15% to total GHG benefit in highly acid soils.
Excluded
CO₂ from Carbonate Impurities
Where the rock feedstock contains carbonate mineral impurities (e.g. calcite veins in basalt), the CO₂ released during dissolution of these impurities must be measured and excluded from the gross CDR benefit. XRD mineralogy must quantify the carbonate fraction per batch. Carbonate impurities above 3% of mineral mass trigger an additional CO₂ release deduction in the credit calculation.
MRV Confidence
Measurement, reporting
& verification
ERW has a distinctive MRV profile - rock application and permanence confidence are very high (the rock is applied and the carbon removal is thermodynamically permanent once dissolved), while weathering rate measurement at field scale remains the frontier challenge. Field-scale weathering quantification uncertainty is the primary reason for the 10% conservative deduction and the ongoing investment in isotopic tracing and lysimeter monitoring infrastructure across the ERW research community.
Rock Application Quantification (mass & mineralogy)Very High
Permanence Confidence (mineral thermodynamics)Very High
Cation Flux Field MeasurementMedium–High
Isotopic Tracing AttributionHigh
Additionality ClarityVery High
Secondary Precipitation Deduction AccuracyMedium
🔬 Field Monitoring Standard - TTS Module 3 · ERW
All ERW-M01 and ERW-M02 projects must install a minimum of one lysimeter or tile drain monitoring station per 25 ha of project area, distributed across soil type strata. Water samples must be collected at minimum monthly frequency during the active growing season (when dissolution rates are highest) and at minimum quarterly during dormant seasons. ICP-MS analysis for Ca²⁺, Mg²⁺, K⁺, Na⁺, Si, Sr, and alkalinity is required per sample. All laboratory analyses must be conducted by an ISO/IEC 17025 accredited facility. For isotopic tracing approaches, rock feedstock ⁸⁷Sr/⁸⁶Sr reference measurement must be conducted at least once per quarry batch. Full data sets, laboratory QA/QC records, and field measurement logs must be archived and available for VVB audit for the project lifetime plus 10 years.
Additionality
Demonstrating additionality
ERW additionality is among the strongest of any Teravent Technology pathway. No farmer or land manager applies crushed basalt or olivine without an economic incentive - the costs of quarrying, crushing, and transporting rock powder significantly exceed any agronomic benefit alone at current rock powder prices. Three-test additionality is required but is almost always straightforwardly satisfied.
1
Regulatory Surplus Test
ERW is not mandated by any environmental regulation, agricultural policy, or carbon pricing mechanism in any current jurisdiction. No national or regional policy requires farmers to apply silicate rock powders. Agricultural lime requirements (where they exist as best practice guidance) use carbonate minerals, not the silicate minerals eligible under ERW. Projects that substitute eligible ERW silicates for mandated carbonate lime applications must demonstrate that the silicate application goes beyond the mandated liming requirement in terms of quantity, type, and carbon benefit. This regulatory surplus analysis is straightforward in all geographies where Teravent ERW projects are currently operating.
2
Financial Additionality Test
Carbon revenue must be the primary economic driver of the rock powder application. A cost-benefit analysis must demonstrate that the cost of sourcing, crushing, transporting, and applying the silicate rock powder - including the monitoring and verification costs - exceeds the agronomic value of the liming and nutrient co-benefits without carbon revenue. At current market prices for crushed basalt or olivine delivered to farm gates in most geographies, this test is met: silicate rock powders cost $50–250/tonne delivered, while their agronomic benefit (liming and nutrient supply) is worth only $10–60/tonne equivalent in conventional lime and fertiliser terms. Carbon revenue bridges this gap.
3
TRL-Based Common Practice Test
ERW with carbon accounting is at TRL 6–8 in most deployment contexts - commercial-scale ERW with quantified carbon removal is not common practice in any agricultural geography. The TRL ≤7 automatic common practice test pass applies to all first-generation commercial ERW projects. For projects deploying basalt application in geographies with established quarrying and farming infrastructure, a TRL 8–9 assessment may be required, but the common practice threshold (<20% voluntary farmer adoption) is not approached in any current market. The common practice test is universally satisfied for ERW in the current market environment.
Leakage Assessment
Leakage types & deductions
Supply Chain Emissions
Quarrying & Transport GHG
The primary leakage-equivalent consideration for ERW is the lifecycle GHG emissions from rock extraction, processing, and transport - these are assessed in the LCA rather than as a separate leakage deduction. Projects must demonstrate net-negative lifecycle GHG balance. Transport distance is the most critical variable - projects beyond 500 km road transport should carefully assess whether net CDR remains positive at their scale.
Assessed in LCA per TLP v1.0 · Not a separate deduction · Net-negativity must be demonstrated
Market Leakage
Conventional Lime Displacement
Where ERW projects displace agricultural lime (CaCO₃) from farm inputs, the CO₂ released during carbonate lime dissolution that would have occurred under the baseline scenario must be credited as avoided emission - but carbonate lime releases CO₂ on dissolution, so displacement of lime by silicate minerals represents a net additional benefit. This is quantified as a secondary benefit where documented farm lime application records are available.
Secondary benefit - lime displacement quantified separately as avoided CO₂ emission where documented
Downstream Attribution
Ocean CDR Attribution (ERW-M03)
For coastal applications (ERW-M03), attribution of ocean CO₂ uptake to the added alkalinity - rather than to natural ocean chemistry variability - is the primary MRV challenge. Paired treatment and control site monitoring with strontium isotopic tracing is required. Where ocean attribution cannot be confirmed within quantification uncertainty, coastal ERW projects fall back to the conservative terrestrial cation flux approach.
ERW-M03 only · Ocean attribution uncertainty captured in 10% conservative deduction
Secondary Precipitation
In-Soil Carbonate Formation
Ca²⁺ and Mg²⁺ released by silicate dissolution that precipitates as secondary calcite or dolomite in the soil does not contribute to atmospheric CO₂ removal - the CO₂ consumed in dissolution is re-released on precipitation. This is assessed by XRD analysis of soil samples and deducted from gross cation flux. Typical deductions range from 5–25%, making this the single most important quantification correction for ERW projects on calcareous soils.
Mandatory deduction · Annual XRD soil analysis · Typically 5–25% of gross cation flux
Permanence
Why ERW credits carry
geological permanence
ERW permanence is fundamentally different from biological carbon storage (forests, soils) or even physical geological storage (injected CO₂). Once silicate minerals have dissolved and produced dissolved bicarbonate that reaches the ocean, the carbon is effectively irreversibly removed from the atmosphere on human-relevant timescales. The chemical pathway to atmospheric re-release - ocean acidification reversing the bicarbonate equilibrium - operates on geological timescales of millions of years under current ocean chemistry.
| Methodology |
Permanence Class |
Buffer Pool Rate |
Permanence Basis |
Re-release Risk |
| ERW-M01 Basalt on cropland |
Class III · Mineral |
2–5% |
Dissolved bicarbonate transferred to ocean and locked in carbonate minerals |
Negligible - thermodynamic stability on million-year scale |
| ERW-M02 Silicate powders |
Class III · Mineral |
2–5% |
Same as ERW-M01 - dissolved bicarbonate ocean export |
Negligible once bicarbonate reaches ocean - secondary precipitation risk in soil (accounted in deduction) |
| ERW-M03 Coastal weathering |
Class III · Mineral |
3–5% |
Alkalinity generated at coastline directly enhances ocean carbonate buffer capacity |
Negligible - slightly elevated buffer for ocean attribution uncertainty |
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Why no ongoing monitoring after dissolution? Unlike geological CO₂ storage (TTS Annex G), ERW does not require post-project monitoring for storage integrity because there is no concentrated CO₂ plume at risk of leakage. Once the silicate minerals dissolve and the alkalinity is exported to the ocean, the carbon removal is permanent by thermodynamic definition. The buffer pool exists solely to cover quantification uncertainty - the risk that measured CDR overestimates actual CDR - not to cover reversal risk. No ERW project has ever had a confirmed reversal event.
Eligibility Requirements
Key registration criteria
✓
Rock feedstock must be an approved silicate mineral type - basalt, olivine, wollastonite, dunite, or TSA-approved mixed silicate. Carbonate minerals (limestone, dolomite, agricultural lime) are explicitly excluded. XRF mineralogy analysis per quarry batch confirming reactive mineral fractions submitted with PDD.
✓
Quantification approach declared at registration - cation flux, isotopic tracing, or calibrated geochemical model. If model-based, 12 months of site-specific calibration field data must be available before first credit issuance event.
✓
Lysimeter or tile drain monitoring infrastructure installed before first rock application - minimum 1 station per 25 ha, stratified by soil type. Installation confirmed by VVB at validation.
✓
Lifecycle GHG assessment per TLP v1.0 demonstrating net-negative carbon balance - quarrying + crushing + transport + application emissions must be less than gross CDR. Net-negativity demonstrated with 90% confidence. Particularly important for projects with long transport distances.
✓
Heavy metal risk assessment per HMP-01 mandatory for all olivine and dunite projects - soil Ni, Cr baseline measured before first application; crop tissue testing where edible crops are grown; sediment sampling for ERW-M03 coastal projects.
✓
10% conservative deduction applied to all projects before credit issuance unless site-specific measurement uncertainty is demonstrated below 10% at 90% confidence via cation flux or isotopic tracing data - waiver requires VVB sign-off.
✓
Secondary mineral precipitation deduction quantified by annual XRD analysis of soil samples at permanent monitoring plots - carbonate fraction measured and deducted before net CDR credit calculation.
✓
Three-test additionality demonstrated - regulatory surplus confirmed, financial analysis showing carbon revenue necessity (rock powder cost exceeds agronomic co-benefit value), TRL-based common practice test (auto-pass ≤TRL 7).
✓
For ERW-M03 coastal applications: annual independent marine ecology survey conducted before project start to establish baseline; paired treatment and control nearshore seawater monitoring stations established; marine sediment HMP-01 monitoring plan submitted with PDD.
✓
Land tenure or land access agreements secured for the full monitoring period - minimum 10 years or the period required for the declared quantification approach to generate a full crediting dataset, whichever is longer.
Co-Benefits & SDGs
Sustainable Development
Goal alignment
ERW delivers an unusually strong agricultural co-benefit profile for a Technology pathway. The pH amelioration and Ca/Mg nutrient supply from silicate rock application directly improves crop productivity on acidic tropical and subtropical soils - which represent a major constraint on food security across Sub-Saharan Africa, South and Southeast Asia, and tropical Latin America. Five SDGs are tracked.
SDG 13 · Climate Action
SDG 2 · Zero Hunger
SDG 15 · Life on Land
SDG 1 · No Poverty
SDG 9 · Industry & Innovation
Soil Health+
ERW projects demonstrating verified soil pH improvement, Ca²⁺ and Mg²⁺ increase, and reduced soil aluminium toxicity - with annual soil data submitted at each VVB verification - are eligible for the Soil Health+ co-benefit label. This is the most commonly awarded co-benefit label for ERW projects globally.
Food Security+
ERW projects on smallholder farms demonstrating verified crop yield improvements attributable to pH amelioration and nutrient supply from rock dissolution - with independently audited farm yield records compared against non-amended control plots - are eligible for the Food Security+ label.
Water+
Where ERW projects reduce surface water acidity and aluminium concentrations in acid-impacted catchments - verified by annual stream chemistry monitoring at project outlet and upstream control points - the Water+ co-benefit label is applicable, particularly for large-scale ERW deployments in tropical catchments.
Technology Innovation
ERW projects that publish monitoring data, quantification model parameters, and field trial results contributing to the global ERW evidence base are eligible for the Teravent Open Science designation. Incentivised through reduced annual VVB fees for participating projects that share data under FAIR data principles.
Priority geographies: India (Deccan Plateau basalt belt - local quarry infrastructure + acidic agricultural soils + large-scale food crop systems make India the highest-priority ERW deployment geography globally), Sub-Saharan Africa (highly weathered, acidic Oxisol and Ultisol soils with the highest yield response to silicate amendments), Southeast Asia (tropical agricultural soils, strong basalt and dunite quarrying infrastructure in Indonesia, Philippines, Vietnam), and Brazil (Cerrado and Amazon arc - major agricultural frontier with severe soil acidity constraints). Australia (Western Australia wheatbelt - large basalt exposures, highly acidic soils) is a secondary priority.
