A University of Edinburgh-led study has demonstrated a lower-intervention way to verify underground CO₂ mineralisation — using the “natural fingerprints” already present in captured CO₂ and formation fluids, rather than adding artificial tracers.
The work tracked injected CO₂ at Carbfix’s CarbFix2 operation in Iceland, where carbonated water is injected into basalt so that the gas reacts with the host rock and forms solid carbonate minerals. Using small, naturally occurring variations in carbon isotopes, water isotopes, and noble gas signatures, researchers were able to distinguish injected CO₂ from background fluids and follow how the injected carbon changed over time.
The study, published in the International Journal of Greenhouse Gas Control and funded by the Natural Environment Research Council (NERC), frames the technique as a monitoring, reporting, and verification (MRV) tool that could reduce cost and complexity as mineral storage projects scale. MRV is a practical pinch-point for carbon capture and storage: operators must demonstrate containment, permanence, and predictable behaviour to satisfy regulators, investors, and credit buyers.
CarbFix2 offers a high-contrast test case because mineralisation is intended to be rapid and durable. The researchers assessed the CO₂ stream through the scrubbing process and then monitored changes once injected, using shifts in key isotope ratios as indicators of dissolution and subsequent reactions in the reservoir. Results from monitoring points aligned with mineralisation levels reported previously at the site, adding weight to earlier evidence that the basalt route can convert injected CO₂ into solid minerals on operational timescales.
Lead author Dr Chris Holdsworth, now an MRV technical specialist at Carbfix after completing the work during his PhD at the University of Edinburgh, said: “We can use the natural fingerprints already present in the CO₂ and water to track when CO₂ dissolves and turns to stone, without adding anything extra underground. This has real potential to simplify and reduce the cost of monitoring as storage projects scale up.”
Professor Stuart Gilfillan, Personal Chair of Geochemistry at the University of Edinburgh, said: “Simple, reliable checks are essential for public trust in carbon storage and for regulators and investors to sign off major projects. Using these natural fingerprints can streamline monitoring while providing the evidence that mineral storage is permanent.”
Verification is also tied to market value. Mineral storage is generally positioned as “durable” carbon removal because the carbon is locked into rock, rather than stored in biological systems that can be reversed by land-use change, fire, or degradation. For developers and offtakers, proving that permanence with defensible evidence is becoming a differentiator as carbon markets tighten requirements on durability and auditability.
The research also sits alongside wider UK-focused work on the potential for reactive volcanic formations to store industrial CO₂ through mineralisation. For industrial operators weighing CCS pathways, the message is less about any single reservoir and more about removing friction from the “prove it” layer that determines whether projects clear permitting, insurance, and finance.
