Overview
How this pathway works
In-situ Mineralisation permanently disposes of captured CO₂ by converting it directly into solid rock underground. CO₂ from any qualifying capture source — direct air capture, bioenergy with capture, or industrial point-source capture — is dissolved in water and injected into reactive subsurface formations rich in calcium and magnesium silicate minerals. On contact, the CO₂-charged fluid reacts with the host rock to precipitate stable calcite, magnesite, or dolomite, locking the carbon into a solid mineral phase rather than leaving it as a mobile supercritical fluid.
Under the Teravent Technology-Based Carbon Standard (TTS v1.0) Annex E, In-situ Mineralisation projects earn Teravent Technology Credits of the Removal type (TTC-R) for verified net tonnes of CO₂ converted to solid carbonate minerals in the subsurface, net of full lifecycle project emissions. This pathway is distinct from Geologic CO₂ Storage (Annex G), where CO₂ remains a supercritical fluid trapped structurally rather than chemically converted to rock.
Three methodology variants are approved under Annex E, differentiated by host formation type — basaltic and peridotite rock, ultramafic mine tailings deposits, and reactive sedimentary formations. Each specifies its own reactive transport modelling requirements, monitoring well density, and mineralisation confirmation protocol.
📌
Class III — Mineral permanence. All credits issued under TTS Annex E carry Class III permanence, reflecting a >1,000-year storage horizon once CO₂ has converted to solid carbonate mineral phases. Buffer pool contributions of 2–6% of gross verified credits apply — among the lowest in the Teravent system — reflecting the very low reversal risk of fully mineralised carbon. The specific rate is set by the project's Storage Integrity Risk Rating (SIRR) assessed at validation and each verification.
Governing Standard
TTS v1.0 — Annex E
This pathway is governed exclusively by the Teravent Technology-Based Carbon Standard (TTS v1.0). No external registry, standard, or methodology is referenced or incorporated. All requirements — additionality, quantification, durability, safeguards, and credit issuance — are defined within TTS v1.0 and Annex E specifically.
TCR›
TTS v1.0›
Annex E — In-situ Mineralisation›
INM-M01 through INM-M03
M02
Three-test additionality with TRL-based screening applied ahead of common practice test
M03
Quantification and MRV — Net TTC formula, injection/dissolution metering at ±2% accuracy, reactive transport model validation
M04
Class III Mineral permanence · Buffer pool 2–6% · SIRR assessed at each verification
M05
Environmental and social safeguards — seismic risk protocol, water use DNSH, community consultation
M06
Ten-stage registration process; 17-element PDD including storage integrity plan; Standard, Premium, Frontier tiers
M07
TTC serial: TCR–TTS–R–INM–[Country]–[ProjectID]–[Vintage]–[Unit]
Teravent Technology Credit — Serial Number Format (TTS Annex E · Removal)
TCR
–
TTS
–
R
–
INM
–
IS
–
00019
–
2025
–
000001
Methodologies Accepted
Three approved methodology variants
TTS v1.0 Annex E approves three discrete methodology types for the In-situ Mineralisation pathway. Each code represents a distinct host formation with its own reaction kinetics, monitoring well density, and reactive transport modelling requirements. A project may combine multiple host formations only where each is independently metered and monitored under a separate methodology code.
💡
Distinguishing from geologic storage: In-situ Mineralisation credits require verified conversion of CO₂ to solid carbonate minerals, confirmed through monitoring well geochemistry. Projects that only demonstrate structural or residual trapping of supercritical CO₂ without confirmed mineral conversion must instead register under Geologic CO₂ Storage (Annex G).
Captured CO₂ is dissolved into water at the wellhead, forming a carbonic-acid-charged fluid that is injected into porous basaltic or peridotite formations. The dissolved-phase approach eliminates the buoyant supercritical CO₂ plume risk associated with conventional geologic storage — once injected, the CO₂ is already in aqueous solution and reacts rapidly with calcium, magnesium, and iron-rich silicate minerals in the host rock to precipitate solid carbonates, frequently within 1–2 years of injection.
Permanence
Class III · Mineral
Buffer Pool
2–5% (by SIRR)
Metering Requirement
Dissolution + injection flow, ±2% accuracy
Mineralisation Confirmation
Monitoring wells + geochemical sampling required
Water Requirement
High — CO₂:water dissolution ratio assessed under DNSH
Time to Mineralisation
Typically 1–2 years, formation-dependent
Key Monitoring Indicators
- Continuous CO₂ dissolution and injection rate via calibrated flow metering at ±2% accuracy
- Reactive transport model validation against monitoring well geochemistry, minimum annually
- Mineralisation confirmation sampling — carbonate phase identification (calcite, magnesite) at representative monitoring well depths
- Injection pressure and induced seismicity monitoring per Module 5 seismic risk protocol
- Water sourcing, consumption, and discharge records for DNSH water stress compliance
Legacy mine tailings from nickel, chromite, diamond, and asbestos operations frequently contain finely crushed ultramafic minerals (serpentine, olivine, brucite) with exceptionally high surface area and reactivity toward CO₂. This methodology injects captured CO₂ directly into standing or capped tailings impoundments in-situ, avoiding the excavation, crushing, and material handling required for ex-situ waste carbonation. Tailings facilities are typically already permitted industrial sites, simplifying siting relative to greenfield formations.
Permanence
Class III · Mineral
Buffer Pool
2–6% (by SIRR)
Host Material Verification
Mineralogical assay confirming reactive silicate content
Metering Requirement
Continuous injection flow, ±2% accuracy
Legacy Site Additionality
Baseline weathering rate must be documented
Time to Mineralisation
Months to 2 years, tailings-mineralogy dependent
Key Monitoring Indicators
- Continuous CO₂ injection rate at tailings impoundment injection points, ±2% accuracy
- Baseline natural weathering / passive carbonation rate documented prior to project commencement
- Mineralogical assay confirming reactive olivine, serpentine, or brucite content at representative sampling grid
- Post-injection carbonate mineral confirmation via core sampling at minimum annual intervals
- Tailings dam stability and water quality monitoring per site-specific safeguard plan
Certain sedimentary formations — particularly those containing dawsonite-forming aluminosilicates or calcium-rich carbonate-associated minerals — support partial mineral trapping of injected CO₂ alongside structural and residual trapping. This methodology applies where a project can demonstrate, through site-specific geochemical modelling and monitoring, that a material fraction of injected CO₂ converts to stable mineral phases over the crediting period, distinguishing it from purely structural storage under Annex G.
Permanence
Class III · Mineral (mineralised fraction only)
Buffer Pool
3–6% (by SIRR — slower kinetics)
Crediting Basis
Only the modelled mineralised fraction is credited under Annex E
Non-Mineralised Fraction
Credited separately under Annex G if eligible
Metering Requirement
Continuous injection flow, ±2% accuracy
Time to Mineralisation
Multi-year to decadal; model-validated
Key Monitoring Indicators
- Continuous CO₂ injection rate at ±2% accuracy, apportioned between mineralised and non-mineralised fractions
- Reactive transport and geochemical model validated against monitoring well fluid chemistry, minimum every 2 years
- Core sampling at representative depths confirming carbonate mineral formation extent
- Formation pressure, plume extent, and induced seismicity monitoring per Module 5
- Independent third-party geochemical model review at each verification, given the longer confirmation timeline
Project Boundary & GHG Accounting
Which emission sources must be counted
TTS v1.0 Module 3 requires a full lifecycle GHG emissions inventory within the project boundary, deducted from gross mineralised CO₂ to arrive at the Net TTC figure. A source may be excluded only where its inclusion would reduce the net carbon benefit (conservative assumption) and this is documented in the PDD.
Required
Mineralised CO₂ (Gross)
Primary benefit quantity. Continuously metered CO₂ mass injected, confirmed as converted to solid carbonate mineral phases through monitoring well geochemistry and independently verified.
Required
Dissolution & Injection Energy
Electricity and thermal energy consumed by water sourcing, CO₂ dissolution, pumping, and injection wellhead operation, applying the applicable grid emissions factor per TLP v1.0.
Required where material
Upstream CO₂ Transport
Compression, pipeline, or truck transport emissions where captured CO₂ originates from a separate facility and is transported to the mineralisation site.
Required where material
Monitoring Well Drilling
Embodied emissions from drilling dedicated monitoring wells, amortised over the crediting period where material relative to gross mineralised tonnes.
Excluded
Host Rock or Tailings Extraction
Emissions from the original extraction of ore that produced mine tailings (INM-M02) are excluded — the tailings already exist as legacy waste independent of the mineralisation project.
Excluded — Prohibited Use
Enhanced Oil Recovery (EOR)
Use of injected CO₂ for enhanced oil recovery is categorically excluded from TTS v1.0 eligibility under Module 1 project exclusions.
MRV Confidence
Measurement, reporting
& verification
Teravent's Science Advisory Board assesses each pathway against four MRV dimensions. In-situ Mineralisation scores highest on permanence confidence of any pathway once mineral conversion is confirmed, though confirmation timelines vary by host formation.
Injection QuantificationVery High
Mineralisation ConfirmationHigh
Permanence ConfidenceVery High
Additionality ClarityVery High
🔬 Measurement Requirements — TTS Module 3
Quantification requires continuous flow metering at ±2% accuracy for both CO₂ dissolution and wellhead injection. Mineralisation confirmation — the defining MRV challenge for this pathway — requires a site-specific reactive transport model calibrated against dedicated monitoring well geochemical sampling, with core sampling used to directly identify carbonate mineral phases at representative depths. Formations with faster reaction kinetics (INM-M01, INM-M02) typically confirm mineralisation within 1–2 years; slower sedimentary systems (INM-M03) require model-based projection validated by an independent third-party geochemical reviewer at each verification. All monitoring instrumentation is calibrated by an accredited VVB.
Additionality
Demonstrating additionality
TTS v1.0 Module 2 requires all projects to pass a three-test additionality framework, with a Technology Readiness Level (TRL) screen applied ahead of the common practice test. In-situ mineralisation at commercial scale remains an early-stage technology, so most facilities qualify for the streamlined TRL-based screen.
1
TRL-Based Common Practice Screen
Projects deploying in-situ mineralisation at Technology Readiness Level 7 or below automatically satisfy the common practice test — commercial-scale mineral trapping remains uncommon outside a small number of reference facilities globally. Higher-TRL deployments require a full common practice survey of comparable regional or global projects.
2
Regulatory Surplus Test
The mineralisation activity must not be mandated by any legally binding remediation obligation, mine closure requirement, or facility permit condition. For mine tailings projects (INM-M02), where jurisdictions require passive tailings stabilisation, projects must demonstrate the active CO₂ injection programme goes materially beyond any mandated closure or remediation baseline.
3
Financial Additionality Test
Carbon revenue must be necessary for project viability. Developers must submit a discounted cash flow analysis, net of any government grants or tax incentives (disclosed under Module 8), demonstrating that the levelised cost of dissolution, injection, and monitoring exceeds available offtake or product revenue absent carbon credit income.
ℹ️
Government incentive disclosure: Where a project receives direct government grants, capital cost subsidies, or per-tonne tax credits for the same mineralised CO₂, this must be disclosed to the TSA at registration under Module 8. Double-claiming the same carbon benefit under both a government incentive programme and Teravent credits is prohibited.
Leakage Assessment
Leakage types & deductions
TTS v1.0 Module 3 defines three leakage types applicable across all engineered pathways. In-situ Mineralisation projects are primarily subject to energy-source leakage and, for mine tailings projects, a baseline weathering counterfactual.
Energy-Source Leakage
Grid Electricity Displacement
Where dissolution, pumping, and injection equipment draws electricity from a constrained grid, its consumption may increase marginal fossil generation elsewhere. Facilities without a dedicated renewable or nuclear power purchase agreement must apply the regional marginal emissions factor.
Deduction: applicable regional grid factor, TLP v1.0
Baseline Weathering Leakage
Passive Carbonation Counterfactual
Applies specifically to INM-M02. Ultramafic tailings undergo slow passive carbonation from atmospheric exposure even without active injection. The baseline natural weathering rate, documented prior to project commencement, must be deducted from the gross injected and mineralised quantity.
Site-specific baseline rate; deducted from gross credit
Induced Fossil Extraction Leakage
Enhanced Oil Recovery Risk
Because EOR use is categorically prohibited under TTS v1.0, projects must demonstrate through chain-of-custody documentation that injected CO₂ is not directed to any oil or gas recovery operation at the primary site or via third-party offtake.
Zero-tolerance exclusion · verified each period
Permanence & Storage Integrity Risk
Buffer pool & reversal risk
All Annex E credits carry Class III Mineral permanence (>1,000-year storage horizon), among the highest-confidence durability ratings in the Teravent system once mineralisation is confirmed. Buffer pool contributions protect credit buyers against the pre-mineralisation window, during which injected CO₂ remains in dissolved or supercritical phase before full carbonate conversion. Buffer rates are set by the project's Storage Integrity Risk Rating (SIRR).
| Methodology |
SIRR Rating |
Buffer Pool Rate |
Primary Reversal Risks |
| INM-M01 Basalt / Peridotite |
Very Low |
2–5% |
Pre-mineralisation dissolved-phase migration prior to carbonate formation; induced seismicity |
| INM-M02 Mine Tailings |
Very Low |
2–6% |
Tailings dam integrity; pre-mineralisation CO₂ release to atmosphere during injection |
| INM-M03 Reactive Sedimentary |
Low–Medium |
3–6% |
Slower kinetics extend the pre-mineralisation window; non-mineralised fraction requires separate structural trapping confirmation |
⚠️
Reversal notification: Project proponents must notify the TSA within 72 hours of discovering a reversal event — detected CO₂ migration outside the injection zone, wellbore integrity failure, or confirmed seepage prior to mineralisation exceeding the monitoring threshold. Buffer pool credits are cancelled proportionally to the verified carbon loss. Operators additionally carry 30-year post-closure monitoring obligations following the end of injection activity, or until mineralisation is fully confirmed, whichever is later.
Eligibility Requirements
Key registration criteria
Projects must meet all of the following minimum requirements to qualify for registration under TTS Annex E. Additional methodology-specific requirements are detailed in the Annex E methodology tables for each INM-M code.
✓
Continuous CO₂ dissolution and injection flow metering installed at the wellhead, calibrated to ±2% accuracy by an accredited instrumentation provider
✓
Site-specific reactive transport model submitted at registration and validated against monitoring well geochemistry at each verification
✓
Ten-stage registration process completed, from technology eligibility assessment through validation to ongoing verification, per TTS Module 6
✓
Seventeen-element Project Design Document submitted, including a storage integrity plan and a post-closure obligations statement
✓
Three-test additionality demonstrated with TRL-based screening applied first; TRL documentation updated at each verification
✓
Storage Integrity Risk Rating (SIRR) assessed by an accredited VVB at validation; buffer pool contribution of 2–6% applied to gross verified credits
✓
Mineralogical assay confirming reactive silicate mineral content of the host formation or tailings material submitted with the PDD
✓
Explicit written confirmation that no injected CO₂ is directed to enhanced oil recovery or any other prohibited use under Module 1
✓
Seismic risk assessment and Do No Significant Harm review covering water use, water quality, and induced seismicity
✓
30-year post-closure monitoring commitment documented through a legal instrument acceptable to the TSA
Co-Benefits & SDGs
Sustainable Development
Goal alignment
All Teravent registered In-situ Mineralisation projects must complete an SDG impact assessment at registration and at each verification period. Three SDGs are systematically tracked for this pathway. Projects may apply for co-benefit quality labels where independently verified indicators are met.
SDG 13 · Climate Action
SDG 9 · Industry, Innovation & Infrastructure
SDG 12 · Responsible Consumption & Production
Permanent Removal
Facilities with an independently verified geochemical model confirming >1,000-year unqualified mineral storage integrity are eligible for the Teravent Permanent Removal label — the highest durability designation in the system.
Circular Feedstock+
Mine tailings mineralisation projects (INM-M02) that put legacy waste material to productive climate use, rather than requiring new resource extraction, are eligible for the Circular Feedstock co-benefit label.
Zero Fossil Input+
Facilities powered entirely by verified renewable or nuclear electricity, with REC or PPA documentation, are eligible for the Zero Fossil Input co-benefit label.
Community Benefit+
Projects sited at legacy mining regions that demonstrate local employment creation, land remediation, or community consultation outcomes exceeding baseline requirements are eligible for the Community Benefit+ label.
Deployment scope: Regions with exposed basaltic or peridotite geology (Iceland, the Pacific Northwest, the Deccan Traps) and legacy ultramafic mining districts (nickel, chromite, asbestos tailings) worldwide offer the most favourable host formations for this pathway.