Here below are frequently asked questions (FAQ) listed up for your convenience. If you still have any unanswered questions or concerns, please contact us!

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.

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. 

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 to CO2 sources and thus contributes to reducing greenhouse gas emissions. 

Is Carbfix the ultimate solution to climate change?

Check out our website home page for how many tons of CO2 have been injected for permanent storage by Carbfix into reactive basalts. Currently, the annual capacity of the injection system is about 12,000 tons of CO2. 

How much CO2 has been mineralized so far? 

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.

Mineralization is so quick because 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.

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.

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 (400 billion tons of 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.

Yes, with time basalt can become saturated. However, the potential for mineralization is greater than burning of all fossil fuel carbon on Earth. There can occur some micro-fracturing due to mineralization and opening of new pathways for the injected fluid that channels the fluid towards new available pore space and fractures. 

Does the basalt become saturated at some point? 

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 a few years of injection. 

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

The Carbfix process requires substantial amounts of water to carry 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 geological 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 2022.

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 9,500 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, FeS). 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.

The main energy requirement associated with the Carbfix technology is the energy to pressurize CO2-charged water to 25 bar at 25 °C. The energy demand at 25 °C as a function of CO2 partial pressure for the pressurization of 1 tonne of CO2-charged pure water is approximately 75 kWh.

Independent seismic risk assessments are conducted during the preparation phases of injection activities. At present, on-site seismic networks are deployed and combined with selected stations from the national permanent seismic network to increase the detection level and location accuracy of detectable seismic activity. Injection sites are monitored before and during the preparation phases of well drilling activities. In addition, storage sites are typically developed in a stepwise manner, where each development stage accounts for any possible induced seismicity due to previous stages. This approach minimizes the risk of seismicity felt at or near the injection site.

Are there any risks from potential seismic activity? 

The Carbfix method is operational at Hellisheiði Geothermal Powerplant, and soon to be applied to the Nesjavellir geothermal system. Monitoring programmes for both systems have been developed alongside environmental impact assessments (EIAs). Furthermore, environmental impacts of the combined heat and power (CHP) plant at Hellisheiði and the carbon intensity of its electricity production has been quantified from a life-cycle perspective, see here for more details. 

Hellisheiði Geothermal Project has been subject to the Geothermal Sustainability Assessment Protocol (GSAP). GSAP assess the environmental, social, technical, and financial performance of geothermal power projects in accordance with a defined list of sustainability categories. Click here to view Hellisheiði´s sustainability profile (Figure 4, Page 119).

Have environmental impact assessments been conducted? 

Life cycle assessments (LCAs) are conducted to assess the environmental impacts associated with the total life cycle of goods, services, or processes, i.e., from resource extraction to end-of-life. An LCA conducted by Karlsdottir et al. (2020) on the Hellisheiði Geothermal Power showed that the Carbfix method, used for reinjection of CO2 at Hellisheiði, reduces the Global Warming Potential (GWP100) by 27.8% for electricity production over the 30-year operational time. In addition, the Sulfix method, developed for the reinjection of H2S at Hellisheiði decreased the Acidification Potential (AP) by 62.5%. For more information click here.

Have life cycle assessments been conducted?

The primary focus of Carbfix is to remove CO2 from the air and be a part of the solution to the climate change crisis. As the Carbfix method relies on CO2 injection into basaltic rocks for it to mineralize into carbonate minerals deep within the basaltic bedrock (>500 m) it is not beneficial for the cost nor carbon emissions to use the basaltic rocks as building material or cement. This way, we permanently dispose of the injected CO2. Mineralised CO2 can be found naturally as carbonate minerals in various settings. 

Carbon capture and storage (CCS) for cement production has not yet been proven at an industrial scale though there are various projects ongoing worldwide. Most of these projects utilise fine crushed material, which subsequently binds CO2.

Can the Carbfix stones be reused or retrieved in some way?

Carbfix’s injected CO2-dissolved water is denser than pure water and thus sinks relative to the groundwater table having little to no interaction with it, eliminating the risk of leakage. In the initial phase of injection, the CO2-dissolved water dissolves a part of the rocks, releasing metals which then form stable carbonate minerals. These carbonate minerals have the potential to draw up the released and associated metals. 

In addition, injection has led to an increase in the mass of subsurface biota. However, carbon isotope measurements have shown that the biota increased negligibly compared to subsurface carbon fixation. There are neglible effects from the CO2 injection at the surface.

Can groundwater or biodiversity be contaminated? 

CO2 at relatively high concentrations in the air can be harmful to ecosystems and is one of the causes of anthropogenic climate change. CO2 that is dissolved in water and injected into basaltic rocks (the Carbfix method) is not polluting as the previously buoyant CO2 gas is trapped within this dissolved solution and reacts to form nontoxic carbonate minerals at great depths (<500 m). Therefore, the carbonate minerals formed from the Carbfix method are safe and non-polluting.

When evaluating suitable rock types for the Carbfix method, the following parameters must be considered: host-rock chemistry, reactivity, porosity, and permeability, as well as reservoir pressure and temperature conditions during CO2 injection. The most favourable rock types for carbon mineralization are mafic and ultramafic rocks (magnesium- and iron-rich) due to their high reactivity and abundant pore space, as in the case of young basalts. Basaltic rocks, peridotites, and other rocks with more intermediate compositions, such as andesite, dacite and rhyolite have been demonstrated to show potential for carbon mineralisation. There have been experimental studies on andesitic, dacitic and rhyolitic rocks with successful mineralisation. Thus, indicating that the application of Carbfix extends beyond just Icelandic basalt.

Can other rock types than basalt be used?

The ON Power Geothermal Exhibition, located at the Hellisheiði Geothermal Power Plant, is open for visitors. That is where the Carbfix method is being conducted at an industrial scale - guided tours are available.

There are scientific papers that have been published over the years and for the younger generation an article in Frontiers for Young Minds. For general information on how Carbfix works, see here.   

Additionally, Carbfix has been in the media, news, and series, for a list click here.

Is there any additional outreach for education?

Carbfix ohf., is fully owned by Orkuveita Reykjavikur ohf., (Reykjavík Energy) and is not a publicly listed company. Therefore, no equity shares can be aquired in Carbfix ohf. 

We specialize in capturing CO2 emissions from concentrated sources such as power plants and industrial production facilities and injecting them into favourable rock formations for permanent storage. At present, Carbfix does not have a carbon offsetting program for individuals and companies to offset their emissions. However, please check again in the near future!

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