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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 CO2 sequestration 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. DOES CARBFIX REQUIRE A LOT OF WATER?

The Carbfix process require substantial amounts of water to carry the the CO2 in dissolution and to promote reactions underground. However, the water is sourced from the same reservoir in which the injection takes place and is therefore circulated and reused to a certain extent. But even dry regions that lack fresh water may still be good candidates. Carbfix has developed the scientific basis for using seawater to dissolve CO2 instead prior to injection, significantly expanding the applicability of the technology. A field site demonstration of mineral storage using seawater is scheduled in 2021.

12. WHAT IS SULFIX?

During the preparation stages of Carbfix, it was realized that the same process could be used to capture and mineralize hydrogen sulfide (H2S), another polluting gas that is detrimental to human health. Since hydrogen sulfide is, like CO2, a water soluble gas it can be co-captured in the Carbfix water scrubbing process which offers considerable added value for industries (the same is also true of other common industrial gases, such as NOx and SOx). The Hellisheidi geothermal power plant emits around 9500 tons of H2S every year and is subject to environmental regulations. The original Sulfix R&D project was carried out by Reykjavik Energy at Hellisheidi in 2009-2012 with the objective of determining the fate of dissolved H2S injected into the basaltic reservoir. The current system captures roughly 85% of the H2S and injects it underground where it rapidly mineralizes into pyrite mostly (fool's gold). The Sulfix process is significantly more economical and more environmentally friendly than existing industrial sulfur removal processes. In Iceland, it is a common misunderstanding that Sulfix preceded Carbfix and was somehow the precursor to the implementation of Carbfix. In fact, Carbfix was established in 2006 by a team of scientists that were focused on CO2 abatement to combat climate change.