Icelandic company
Carbfix is an Icelandic company founded in 2007. It has developed an approach to permanently store CO2 by dissolving it in water and injecting it into basaltic rocks. Once in the subsurface, the injected CO2 reacts with the host rock forming stable carbonate minerals, thus providing permanent storage of the injected CO2
Approximately 200 tons of CO2 were injected into subsurface basalts in a first-of-a-kind pilot injection in SW-Iceland in 2012. Research results published in 2016 showed that 95% of the injected CO2 was solidified into calcite within 2 years, using 25 tons of water per ton of CO2. Since 2014, this technology has been applied to the emissions of the Hellisheiði Geothermal Power Plant. H2S and CO2 are co-captured from the emission stream of the power station and permanently and safely stored via in-situ carbon mineralization at the Húsmúli reinjection site. The process captures approximately one-third of the CO2 emissions (12,000 tCO2/y) and 60% of the H2S emissions (6,000 tH2S/y) from the power plant. The Silverstone project aims to deploy full-scale CO2 capture, injection, and mineral storage at the Hellisheiði Geothermal Power Plant from 2025 onwards.
Carbfix is currently operating four injection sites in Iceland in relation to the Hellisheiði Geothermal Power Plant: the Nesjavellir Geothermal Power Plant, The Orca direct air capture plant near Hellisheiði and within the CO2 Seastone project in Helguvík (see chapter “Current status”).
Background.
Carbfix was founded by the then Icelandic President, Dr Ólafur Ragnar Grímsson, Einar Gunnlaugsson at Reykjavík Energy, Wallace S. Broecker at Columbia University, Eric H. Oelkers at CNRS Toulouse (France), and Sigurður Reynir Gíslason at the 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.
Method.
Captured CO2 is dissolved in water, either prior to or during injection into mafic or ultramafic formations, such as basalts. The dissolution of CO2 in water can be expressed as: 
CO2 (g) + H2O(l) ⇌ H2CO3 (aq) 
↔ H+(aq) + HCO3- (aq) 
↔ 2H+(aq) + CO32-(aq)
By dissolving the CO2 in water instant solubility trapping is achieved, which is the second most secure trapping mechanism of CO2 storage: No CO2 bubbles are present in the CO2-charged water, which is furthermore denser than the water that is present in the formation, so that the CO2-charged water has rather the tendency to sink than to migrate upwards towards the surface.
The CO2-charged water is acidic, typically having a pH of 3-5 depending on the partial pressure of CO2, water composition, and the temperature of the system. The CO2-charged water reacts with the subsurface rocks and dissolves cations such as Calcium, Magnesium, and Iron. The dissolution of cation-bearing silicate minerals; for example, the dissolution of pyroxene, a common mineral in basalt and peridotite, can be expressed as: 
2H+ + H2O + (Ca,Mg,Fe)SiO3 = Ca2+, Mg2+, Fe2+ + H4SiO4 
The cations can react with the dissolved CO2 to form stable carbonate minerals, such as Calcite (CaCO3), Magnesite (MgCO3), and Siderite (FeCO3), a reaction that can be expressed as:  
Ca2+,Mg2+,Fe2+(aq) + CO32-(aq) → CaCO3 (s), MgCO3 (s), FeCO3 (s)
Ultramafic and mafic rock formations are most efficient due to their high reactivity and their abundance in divalent metal cations. The degree to which the released cations form minerals depends on the element, the pH and the temperature.
Practicalities.
Drilling and injecting carbonated water at high pressure into basaltic rocks at Hellisheiði has been estimated to cost 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.
Cost is around US$25 per tonne of CO2.
Challenges.
Reinjection of geothermal fluid from the Hellisheiði Geothermal Power Plant started in Húsmúli reinjection field, in September 2011. Commissioning of the reinjection site caused significant induced seismicity that was felt in nearby communities. This problem was addressed by introducing a new workflow where preventive steps are taken to minimize this risk, including the adjustment of the injection rates. The implementation of the workflow resulted in the decrease of the annual number of seismic events greater than magnitude 2 in the area from 96 in 2011 to one in 2018, which is considered satisfactory and demonstrates that current operations are within regulatory boundaries.
Carbfix started injection of CO2 captured from the Hellisheiði Geothermal Power Plant and dissolved in condensate from the plant’s turbines into one of the existing reinjection wells in the Húsmúli reinjection field in April 2014. No increased seismicity was noted after the injection of CO2 started implying that seismicity is not induced by the injection of the condensate-dissolved CO2.
Current status.
Carbfix is currently operating four injection sites in Iceland with emphasis on injection of CO2 captured from point-sources of CO2, CO2 that is captured and transported to an injection site, and CO2 that is captured directly from the atmosphere using direct air capture (DAC) technology.
Point source capture and mineral storage of CO2 
Carbfix has since June 2014 captured and injected CO2 and hydrogen sulfide (H2S) from Hellisheiði Geothermal Power Plant. The geothermal gases are dissolved in condensate from the power plant’s turbines in a specially designed scrubbing tower and injected to a depth of 750 m underground into basaltic rocks. Currently about 68% of the H2S and 34% of the CO2 from the plant’s emissions are captured and injected, which amounts to about 12,000 tons of CO2 per year, and about 5,000 tons of H2S per year. Results show that over 60% of the injected CO2 was mineralized within 4 months of injection, and over 85% of the injected H2S within 4 months of injection.
Carbfix is currently working on scaling up the operations at the Hellisheiði Geothermal Power Plant through the EU Innovation Fund project Silverstone, aiming for near-zero geothermal power production from 2025 by capturing over 95% of CO2 and 99% of H2S from the plant’s emissions. This accounts for up to 40,000 tons of CO2 and up to 12,000 tons of H2S per year. 
Carbfix has since early 2023 started the capture and injection of CO2 and H2S from the Nesjavellir Geothermal Power Plant in SW-Iceland as a part of the Europe Horizon 2020 funded GECO project. The same approach is used as at the Hellisheiði Geothermal Power Plant, but with optimized capturing efficiency of the scrubbing tower. The gases are dissolved in condensate from the plant‘s turbines and injected into the basaltic subsurface below 900 m.
Injection and mineral storage of CO2 captured from the atmosphere using direct air capture technologies
The world’s first injection of CO2 captured from the atmosphere was carried out in Hellisheiði in SW-Iceland in 2017, as part of the Europe H2020 funded project CarbFix2. The CO2 was captured using a Direct Air Capture (DAC) unit developed by the Swiss green-tech company Climeworks. The CO2 was then dissolved in water and injected into the basaltic subsurface.
In 2021, the world’s first commercial DAC combined with storage plant, Orca, was commissioned in Hellisheiði in collaboration between Climeworks and Carbfix. The plant has the capacity to capture up to 3,600 tons of CO2 directly from the atmosphere that are injected into basalts for permanent mineral storage.
In 2024 Climeworks and Carbfix are commissioning the Mammoth DAC plant, with the capacity to capture up to 36,000 tons per year which will be injected into the basalt for permanent mineral storage at the Geothermal Park in Hellisheiði.
CO2 capture, transport and storage
Cross-border transport of CO2 was first demonstrated as part of the DemoUpCarma project in August 2022. The project was funded by the Swiss Federal Offices and led by ETH. The CO2 was captured from a biogas upgrading plant in Bern, Switzerland, and transported to Iceland where it was first injected at the Hellisheiði site. The current injection site of DemoUpCarma project is in Helguvík, Iceland, where the CO2 is co-injected with seawater as part of the R&amp;D project CO2Seastone.
In July 2021, Carbfix was awarded the largest research grant ever granted to an Icelandic company, when it was nominated for the EU Innovation Fund grant of 15 million EU for the Coda Terminal project. 
The Coda Terminal will be developed in Straumsvík, SW-Iceland as the first cross-border carbon transport and storage hub in Iceland. CO₂ will be captured at industrial sites in N-Europe, focusing on the hard-to-abate sector, and shipped to the Terminal where it will be unloaded into onshore tanks for temporary storage. The CO₂ will then be pumped into a network of nearby injection wells where it will be dissolved in water during injection into the basaltic bedrock. The operations will be scaled up in steps reaching up to 3 million tons of CO₂ per year from 2031. 
References.
 ;templatestyles src="Reflist/styles.css" / ;