1. What is Carbfix?

Carbfix is pioneering the process of rapid underground mineralization of CO2 i.e. turning otherwise emitted CO2, - or CO2 captured directly from the atmosphere, into stone to mitigate climate change. Climeworks is involved in the follow-up project Carbfix2. 

Here you can find more information about the history of Carbfix.

2. Why Carbfix?

Reducing CO2 levels in the atmosphere is considered one of the main challenges of this century. The Carbfix technology mitigates climate change by injecting CO2 at selected geological sites. The geology required for CO2 injection through the Carbfix technology differs from geology required for conventional Carbon Capture and Storage (CCS) technologies. Therefore, Carbfix enables the possibility of doing CCS in areas where it had not previously been considered feasible. Additionally, the Carbfix method adds to the storage security by dissolving the CO2 prior to or during injection, and by the rapid and permanent mineralization of the injected CO2

3. Is Carbfix the ultimate solution to climate change?

Carbfix is not the ultimate solution to climate change but rather one of the methods that can be used to tackle global warming. Carbfix is a new tool that can be used concurrently with other known and future methods.  

The International Energy Agency (IEA) has estimated that large scale application of carbon capture and storage is vital if the world is to limit global temperature increase to below 2°C. The Carbfix method increases the portfolio of CCS by providing a safe, efficient way to permanently immobilize CO2 where basalts and water sources are located near CO2 sources and thus contributes to reducing greenhouse gas emissions. 

4. How much CO2 has been mineralized so far?

In January 2020, over 50,000 tonnes have been injected into reactive basalts at Hellisheiði, SW-Iceland, for permanent storage. Currently, the annual capacity of the injection system is about 12,000 tonnes of CO2. The total amount of CO2 the Carbfix project has mineralized to date can be found on the Carbfix website home page.

5. How long does mineralization take?

Chemical reactions between the basaltic host rock and CO2 loaded injection water have been shown to be rapid, resulting in over 95% permanent mineral CO2sequestration in under two years.

6. How is mineralization measured?

The mineralization of the injected gases is observed using tracers and by following geochemical signals, both of which are monitored by the sampling of fluids from wells in the vicinity of the injection point. Measured tracer concentration in monitoring wells and mass balance calculations enable evaluation of CO2 mineralization. The mineralization has also been quantified using different isotopes.

7. Why is mineralization so quick?

Dissolution of CO2 prior to or during injection ensures that chemical reactions between host rock and injected fluid begin to take place immediately after injection. The high reactivity and chemical composition of the basaltic host rock (up to 25% by weight of calcium, magnesium and iron that can combine with the injected CO2 to form stable carbonate minerals) play an even larger role in the efficiency of permanent mineral storage in basalts.

8. What is so special about basalts?

Basaltic rocks are highly reactive and contain the metals needed for permanently immobilizing CO2 through the formation of carbonate minerals. They are often fractured and porous, containing storage space for the mineralized CO2. Furthermore, basalt is the most common rock type on the surface of Earth, covering ~5% of the continents and most of the oceanic floor. 

It has been estimated that the active rift zone in Iceland could store over 400 Gt CO2. The theoretical storage capacity of the ocean ridges is significantly larger than the estimated 18,500 Gt CO2 stemming from the burning of all fossil fuel carbon on Earth. The question remains, how much of this theoretical storage capacity is feasible to use for mineral storage of CO2. 

The pore space, chemical composition, and wide distribution of basalts makes it the perfect candidate to develop the Carbfix process. However, other reactive rocks such as andesites, peridotites, breccias and sedimentary formations containing calcium, magnesium and iron rich silicate minerals can also do the job. Studies on that subject are undertaken in Carbfix2 and the related GECO project.

9. Does the basalt become saturated at some point?

Yes, with time basalt can become saturated. However, microfracturing due to mineralization and opening of new pathways for the injected fluid would channel this fluid towards new available pore space and fractures. 

10. You state 95% is mineralized within 2 years. What happens to the final 5%?

The 5% is the uncertainty of the measurements – we can be sure that over 95% of what we injected was mineralized within two years of injection. The final fraction might have taken longer to mineralize – but eventually all of the injected CO2 is turned into stone, and we have proved this happens rapidly, or within years of injection. 

11. How many injection wells are currently available?

For the current operations in Hellisheiði two injection wells have been retrofitted to be able to receive gas-charged water: One is mainly used but the second one is a backup for instances when the main injection well needs to be taken out of operations due to e.g. maintenance. The main injection well could receive all of the CO2 from the Hellisheidi Power Plant. With increased demand, more wells could be made available and/or new wells drilled. 

12. Is it safe?

The Carbfix method is considered safer than conventional CCS methods because it involves immediate solubility storage as well as rapid mineral storage which permanently immobilizes the injected CO2 by turning it into stone. Solubility storage refers to the process where CO2 has been fully dissolved in water and does not have the tendency to rise back to the surface. Mineral storage refers to the process where CO2 has been converted to stone. 

13. Is there risk of leakage?

The risk of leakage is generally considered to be very low. Much of this risk is eliminated once the injected CO2 is dissolved into the aqueous phase, as CO2 saturated water is denser than CO2-free water and has the tendency to sink rather than to rise back to the surface.

14. Can "blocked" basalt pores have a negative influence on the steam/hot water production of the production wells?

No, within the geothermal reservoirs most of the pores are already filled with minerals due to the water-rock interaction taking place. The permeability is mostly fracture-dominated, and since the geothermal fields are located within seismically active areas, new flowpaths are constantly opening up, providing pathways for the geothermal fluid and steam.     

15. Does injection impact the geology?

The Carbfix process involves a series of reactions that affect the bedrocks of the storage site by accelerating a natural process. The injected fluids dissolve a portion of the rocks immediately adjacent to the injection well. The fluids then transport cations dissolved from the bedrock and injected CO2 further into the reservoir where they are eventually mineralized. However, only a small fraction of the subsurface bedrock is affected by the injection.  

16. Does injection increase the risk of earthquakes?

Injection of fluids and/or gas can pose risk of earthquakes. In the United States there are over 180,000 injection wells that have been or are currently in use. Induced seismicity has been associated with about 10% of these wells – but the dominant trigger is high injection rates (Weingarten et al., 2015).

Before commencing an injection, a risk assessment has to take place. To mitigate the seicmic risk, the injection rate is increased in steps while monitoring closely any seismicity in the area. The risk of induced seismicity may also be minimized by supplying injection water from the target injection reservoir therefore preventing pressure build-up in the system. 

17. Is it safe to drill new injection walls (in particular regarding earthquakes)?

Yes, drilling operations rarely cause induced seismicity – and in the rare cases the earthquakes recorded have been well below M 3. For best practises, seismicity during drilling operations is always monitored, and if needed special precautions are taken including the gradual increase and decrease of water-pumping during drilling operations.

18. Will it still be safe if millions of tons of CO2 are injected?

Yes, this would of course require proper infrastructure for such operation, but by managing the injection properly it can safely be applied for operations of millions of tonnes of CO2.

19. Why does Carbfix also capture from point source?

Capturing CO2 from point sources is more economically feasible than capturing directly from the atmosphere since the CO2 concentration in the exhaust gas is higher than in the atmosphere. However, both methods are needed to be able to achieve the goals of the Paris agreement.

20. What is the storage potential?

One of the advantages of carbon capture and mineralisation is the great storage potential of these rocks: The theoretical storage potential of basalts exceeds the CO2 derived from burning of all fossil fuels on Earth. As for other carbon storage methods, the storage potential is very site specific: The most feasible formations are young and fresh rocks where fractures are still open and pore space is not yet filled with minerals.

The Carbfix method can be applied wherever a CO2 source is located near feasible rock formations and a water source (fresh water, water from the storage formation or sea water).  

The most feasible formations are young basalts, where faults and fractures are still open, and pore space is not yet filled with secondary minerals, but other rock types could also be considered. 

21. How much water is needed for dissolving CO2?

At 25 bar CO2 pressure and 25°C, the water demand to fully dissolve CO2 is 27 tons of pure water for each ton of CO2, but 31 tons of seawater are required at the same temperature. The amount of water required for dissolving CO2 decreases with increasing CO2 partial pressure in the gas stream, lowering the temperature and lowering the salinity of the water. 

22. Can seawater be used instead of freshwater?

Yes, seawater can be used for dissolving CO2 instead of freshwater, enabling the applicability of the Carbfix method offshore and in coastal areas.  

The basaltic ocean ridges are porous and vast amounts of seawater are circulated annually through them by natural processes or about 100 Gtonnes annually; this is about three times greater than the present mass of anthropogenic release of CO2 to the atmosphere. 

One of the aims of the EU-funded Carbfix2 project is to optimize the use of seawater for capture and injection of CO2. This is an important step in the development of Carbfix which can increase the geographical applicability of the method. 

23. Can the water used for dissolving CO2 be reused or is it contaminated?

Yes, the water can be circulated and reused after CO2 has been removed from it via carbonate formation. At our pilot injection site in Iceland, we can even drink the water after the CO2 is gone.  

A positive side effect of the carbonation process is that heavy metals tend to precipitate into the carbonates along with Ca, Mg, Fe, and CO2, resulting in even lower concentrations than those found naturally in the storage formation. 


All applications go through our official job position website. We recommend that you sign up as a general applicant (“Almenn Umsókn”) and your application will be active for the next 4 months. This site is used for applications for job positions, internships, thesis opportunities and other CarbFix related work. 

As all our positions are advertised, we also recommend that you regularly visit our hiring website, and twitter account for information on job openings.