Check out our website home page for how manytons 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 ofCO2.
Chemical reactions between the basaltic host rock and CO2loaded 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 CO2prior 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 ironthat can combine with the injectedCO2to form stable carbonate minerals) play an even larger role in the efficiency of permanent mineral storage in basalts.
Themineralizationof the injected gases isobservedusingtracers andby 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 CO2mineralization.The mineralization has also been quantified using different isotopes.
Basaltic rocks are highly reactive and contain the metals needed for permanently immobilizing CO2through 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 CO2stemming 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.
Thepore space, chemical composition, and wide distribution of basalts makes it the perfect candidate to develop theCarbfixprocess. However, other reactive rockssuch asandesites,peridotites, brecciasand sedimentaryformationscontainingcalcium, magnesium and iron rich silicatemineralscan also do the job. Studies on that subject areundertaken in Carbfix2 and the relatedGECOproject.
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-fracturingdue to mineralization andopening of new pathways for the injected fluidthat channels the fluid towardsnew available pore space and fractures.
The 5% is the uncertainty of the measurements – we can be surethat over 95% of what we injected was mineralized within two years of injection. The final fraction might have taken longer to mineralize – but eventuallyall ofthe injectedCO2is turned into stone, andwe have provedthis happens rapidly, or within a few years of injection.
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.
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.
