In-situ Mineralisation
TTS v1.0 - Annex E
In-situ Mineralisation injects captured CO₂ - dissolved in water or as a supercritical stream - directly into reactive subsurface formations, where it reacts with calcium and magnesium silicate minerals to form stable solid carbonates in place. Basaltic and peridotite rock, along with reactive ultramafic mine tailings deposits, convert injected CO₂ into rock within months to a few years, offering one of the fastest routes to demonstrable, verifiable mineral permanence available to any Teravent pathway.
Submit Mineralisation Project View TTS v1.0 Annex E →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.
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.
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.
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.
- 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.
- 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.
- 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
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.
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.
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.
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.
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.
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 |
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.
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.
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.
Ready to register your
mineralisation project?
Submit a Project Concept Note under TTS v1.0 Annex E to begin your registration. Select the INM-M code matching your host formation, install continuous injection metering to ±2% accuracy, and appoint an accredited VVB to validate your PDD, reactive transport model, and storage integrity plan.