Enabling CO2 mineralisation through pore to field-scale tracking of carbonate precipitation: INCLUSION

Lead Research Organisation: University of Edinburgh


The Intergovernmental Panel on Climate Change (IPCC) and International Energy Agency (IEA) both cite that carbon capture and storage (CCS) is the only technology capable of decarbonising major industry, particularly the high emitting cement, steel and petrochemical sectors. These industries are major sources of employment and economic growth that will remain important in our evolving societies.

Despite the urgent need for CCS, global rollout has been slow, held back by concerns that CO2 injected underground for storage may leak to the surface. The safety and public buy-in for CCS depends on secure long-term storage of CO2. The majority of existing CCS projects inject CO2 into sedimentary basins, which depend on a cap rock seal to prevent CO2 leakage and require costly monitoring to assure secure storage. In contrast, injection of CO2 into suitable, reactive basaltic rocks, can result in rapid reaction of the CO2 into new stable minerals, effectively turning the CO2 to stone, locking it away for good.

Suitable reactive rocks for CO2 mineralisation comprise almost two-thirds of the Earth, forming most ocean floor and some ten percent of continental landmasses. This includes several vast flood basalts located near to the countries that release the most CO2 to the atmosphere (e.g. Columbia River Basalts, USA, Deccan Traps, India). It is cited that 30-40 GtCO2, equal to all man-made CO2 emitted in 2012, is already locked-up in minerals within Icelandic geothermal systems.

Scale up of these estimates implies that CO2 mineralisation in basaltic rocks offers secure storage for 10 to 100 times more carbon than will be emitted through combustion of all fossil fuels remaining on Earth. However, despite this vast potential, the true storage resource is not yet known, as the technique has so far remained limited to lab and small volume field experiments. The only industrial-scale example are the CarbFix projects, at the Hellisheidi geothermal field in Iceland. This project, operating since 2012, captures CO2 and H2S by bubbling them through water, injecting the resulting gas-charged water into subsurface basalts, liberating mineral ions and inducing precipitation of carbonate and sulphide minerals.

The CO2 mineralisation process relies on the continued exposure of reactive mineral surfaces and hence on the maintenance of fluid flow through the reactive rocks. Current estimates of the amount of CO2 that can be mineralised do not take into account how long CO2 injection at a site can be economical, posing uncertainty as to where it can take place and on how much CO2 can be mineralised at different locations. This is because rapid carbonate mineral precipitation could quickly clog up existing space, limiting the capacity for locking away CO2. However, field and laboratory observations show that the newly precipitated minerals can break the rocks and increase fluid flow through them, enabling precipitation to continue. How these processes compete and balance is uncertain at present, which is a critical issue that limits investment in industrial scale mineralisation projects.

This project will address this key knowledge gap by determining how pore scale processes control industrial scale CO2 mineralisation through integration of micro-scale carbonate mineral analysis, state-of-the-art core scale 4D x-ray imaging and novel field-scale inherent CO2 fingerprinting tools. This will be directly facilitated by collaboration with CarbFix, the world's leading CO2 mineralisation tests.

The project will provide unrivalled pore to field scale understanding of CO2 mineralisation and produce an evidence-based framework for optimising industrial-scale CO2 mineralisation and refining global estimates of where and how much CO2 can be mineralised. This will de-risk global storage estimates and aid commercial rollout of the process, enabling the technique to contribute to the CO2 emissions reduction urgently required to limit climate change.


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