CarbFix is a process that captures CO2 and other acid gases in water, injects this water into the subsurface where the gases are stored as stable minerals. Work developing this process began in 2007.
CarbFix was initiated jointly by the Icelandic President, Dr Ólafur Ragnar Grímsson, Einar Gunnlaugsson at Reykjavík Energy, Wallace S. Broecker at Columbia University, Eric Oelkers at CNRS Toulouse (France) and Sigurdur Gíslason at University of Iceland to limit the Greenhouse gas emissions in Iceland.  Reykjavik Energy supplied the initial funding for CarbFix. Further funding has been supplied by The European Commission and the Department of Energy of the United States. In addition to finding a new method for permanent carbon dioxide storage, another objective of the project was to train scientists for years of work to come.
After years of preliminary experimental and field characterisation approximately 200 tons were injected into subsurface basalts in 2012. Research results published in 2016 showed that 95% of the injected CO2 was solidified into calcite within 2 years, using 25 tonnes of water per tonne of CO2. Since this time this successful carbon capture and storage approach has been upscaled at Hellisheiði and ongoing research is implementing this approach at other sites across Europe.
CO2 is captured either by its dissolution in water from power plant exhaust, or directly from the atmosphere by air capture followed by its dissolution in water. The carbonated water is injected into the subsurface where it reacts with the Ca and Mg present in the rock. Calcium and magnesium are present in rocks - but rarely as oxides where the reactions would be simply:
- CaO + CO2 → CaCO3
- MgO + CO2 → MgCO3
- Mg2SiO4 + 2CO2 → 2MgCO3 + SiO2
as a result CO2 is locked away with no dangerous byproducts.
Drilling and injecting carbonated water at high pressure into basaltic rocks at Hellisheidi  has been proven to be very cost effective. Estimates show that this approach captures and stores CO2 and other acid gases as stable mineral phases for less than $25 a ton.
This project commenced carbon injection in 2012. The funding was supplied by the University of Iceland, Columbia University, France's National Centre of Scientific Research, the United States Department of Energy, the EU, Nordic funds and Reykjavik Energy.
These funding sources include the European Union's Horizon 2020 research and innovation programme under grant agreements No. 764760 and 764810. The European Commission through the projects CarbFix (EC coordinated action 283148), Min-GRO (MC-RTN-35488), Delta-Min (PITN-GA-2008-215360), and CO2-REACT (EC Project 317235). Nordic fund 11029-NORDICCS; the Icelandic GEORG Geothermal Research fund (09-02-001) to S.R.G. and Reykjavik Energy; and the U.S. Department of Energy under award number DE-FE0004847.
This approach requires substantial water and the presence of reactive rocks, which are not available in all localities.
The nearby Hengill volcano, generated a swarm of low magnitude earthquakes as a result of pumping water without the CO2, with 250 quakes being reported on 13 September 2011. There have been earthquakes reported due to the injection of waste water in the area. Proceedings at the 2010 World Geothermal Congress reported that reinjection at Hellisheidi had induced seismic activity.
CarbFix was updated, as part of the EC funded CarbFix2 project starting in June 2014 at the Hellisheidi geothermal power plant. CarbFix2 was designed to capture all of the hydrogen sulfide and most of the carbon dioxide generated from the power plant. As of 2018, 68% of the H2S and 34% of the CO2 is being captured as a dissolved phase in water and injected to a depth of 750 metres underground into basaltic rocks. Results show that the majority of these injected gases are fixed as stable mineral phases in less than one year. Further work has focused on the direct capture of CO2 from the atmosphere coupled to its subsurface mineralization.
CarbFix is currently run by a set of 3 Scientific Directors: Edda Sif Aradóttir of Reykjavik Energy, Sigurdur Reynir Gislason of the University of Iceland, and Eric Oelkers of the CNRS Toulouse. Current efforts are aimed at generalizing the CarbFix process in part through the use of seawater for CO2 capture and storage, so the method can be adopted worldwide.
The CarbFix approach is currently being adopted at 4 new sites in Europe through the EC funded GECO project.
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- Matter, Juerg M.; Stute, Martin; Snæbjörnsdottir, Sandra O.; Oelkers, Eric H.; Gislason, Sigurdur R.; Aradottir, Edda S.; Sigfusson, Bergur; Gunnarsson, Ingvi; Sigurdardottir, Holmfridur; Gunlaugsson, Einar; Axelsson, Gudni; Alfredsson, Helgi A.; Wolff-Boenisch, Domenik; Mesfin, Kiflom; Fernandez de la Reguera Taya, Diana; Hall, Jennifer; Dideriksen, Knud; Broecker, Wallace S. (June 10, 2016). "Rapid carbon mineralization for permanent disposal of anthropogenic carbon dioxide emissions". Science. 352 (6291): 1312–1314. Bibcode:2016Sci...352.1312M. doi:10.1126/science.aad8132. PMID 27284192. Retrieved 10 June 2016.
- "Scientists turn carbon dioxide into stone to combat global warming". The Verge. Vox Media. 10 June 2016. Retrieved 11 June 2016.
- Le Page, Michael (2016-06-09). "CO2 injected deep underground turns to rock – and stays there". New Scientist. Retrieved 2017-12-04.
- "CarbFix: About the Project". Archived from the original on 21 October 2011. Retrieved 15 September 2011.
- "Iceland's Hellisheidi prepares to start injection at carbon storage project". 9 September 2011. Archived from the original on 2012-03-27. Retrieved 2011-09-16.
- "Carbfix project – from gas to rock - GREBE Project". GREBE project, European Union. 2017-02-19. Retrieved 2017-12-04.
- "Water pumping causes tremor" (in Icelandic). 13 September 2011.
- "Orkuveitan framkallar jarðskjálfta í Henglinum" (in Icelandic). 21 February 2011.
- "Human made earthquakes in Hengill volcano". 21 February 2011.
- "Geothermal Reinjection at the Hengill Triple Junction, SW Iceland" (PDF). Retrieved 27 September 2011.[permanent dead link]