Category
Mineralization
Mineralization is the reaction of CO2 with calcium- and magnesium-bearing rock to form solid carbonate. The strongest durability evidence of any pathway sits here: more than 95% of injected CO2 became carbonate in under two years, measured by tagging the CO2 with a traceable marker.
One of eight durable carbon removal pathways presented by CDR Türkiye, all intended to store carbon for centuries to millennia.
Overview
Open a heading to read the detail.
-
Carbon into rock Mineralization turns carbon into rock rather than holding it as a gas.
Calcium and magnesium in basalt and peridotite react with dissolved CO2 to form solid carbonates such as calcite and magnesite. Once carbonate has formed, release requires temperatures above 600°C or strong acid, so leakage risk effectively disappears.
-
The evidence The evidence is the field’s most solid.
At the Carbfix site more than 95% of injected CO2 mineralized to carbonate in under two years, and this was measured, not modelled, by tagging the CO2 with a traceable marker. According to Carbfix, more than 120,000 tonnes of CO2 have been permanently mineralized in rock since the method was first used at Hellisheiði. No other pathway answers the durability question this decisively.
-
Scale problems The scale problems are real in exchange.
Carbfix’s original process requires roughly 25 tonnes of water per tonne of CO2; suitable reactive rock is geographically restricted; wells take less injection over time as carbonate clogs the rock’s pores. Carbonating recycled concrete aggregate in a plant stores on average 7.2 kg of CO2 per tonne at industrial scale: storing 1 Mt means handling roughly 140 Mt of aggregate. That is a logistics problem, not a chemistry problem.
-
Türkiye: ophiolite belts Türkiye has extensive ophiolite and peridotite belts, and rocks that have naturally turned CO2 into carbonate (listvenites) are documented in Anatolia: genuine proof that the process works in nature.
But there is no national total. Published figures are limited to individual deposits such as Orhaneli and Divriği, and they assume mined rock is carbonated, not CO2 injected in place. The presence of these rocks is not a capacity estimate. The accurate framing is the country’s most important open research question, not an established advantage.
Matter et al., Science Carbfix, Hellisheiði operating results Snæbjörnsdóttir et al., Nature Reviews Earth & Environment Tiefenthaler et al., Frontiers in Climate Barış, Özarslan and Şahin, Energy Exploration & Exploitation
Technologies and applications
Choose a tab; its entries open below.
Technology types
The technical methods that capture, convert or store the carbon.
-
Technology type
In-situ basalt and ophiolite injection
CO2 dissolved in water and injected into basalt or another reactive, magnesium-rich rock formation, where it becomes carbonate underground.
- How it works
-
- CO2 source
Atmospheric or biogenic CO2 is supplied.
- Dissolution
The CO2 is dissolved in water.
- Injection
The solution is injected into reactive basaltic formation.
- Reaction
CO2 reacts with calcium and magnesium in the rock.
- Carbonate
In the Carbfix pilot, over 95% of the CO2 turned into solid carbonate mineral within two years.
- CO2 source
- Durability
- Measured
-
Mineral carbonate
More than 95% of the injected CO2 becomes carbonate in under two years.
- What it rests on
- The conversion was MEASURED, not modelled, by tagging the CO2 with a traceable marker, and release afterwards requires temperatures above 600°C or strong acid. The constraints sit elsewhere: the original process needs roughly 25 tonnes of water per tonne of CO2, and wells take less injection over time as carbonate clogs the rock’s pores.
- Matter et al., Science
- Türkiye context
- Rocks that have naturally turned CO2 into carbonate (listvenites) are documented in Anatolia: proof the process works in nature, not a capacity estimate. There is no national estimate of storage capacity in Türkiye’s ophiolites; published figures are limited to individual deposits such as Orhaneli and Divriği.
- Barış, Özarslan and Şahin, Energy Exploration & Exploitation
-
Technology type
Ex-situ reactor carbonation
Crushed reactive rock reacted with CO2 in a surface reactor and converted to carbonate.
- How it works
-
- Milling
Reactive rock is milled to give a high surface area.
- Reactor feed
The milled material is fed to the reactor together with a CO2 stream.
- Carbonation
In the reactor, CO2 dissolved in water precipitates as carbonate with calcium and magnesium released from the mineral.
- Product separation
The solid carbonate formed is separated from the stream.
- Use or storage
The solid product is directed to construction material or to storage.
- Milling
- Durability
- Calculated
-
Mineral carbonate
The product is solid carbonate; durability rests on the same chemistry as in-situ injection.
- What it rests on
- Milling, heat and pressure are needed to accelerate the reaction, and their energy cost is the item that determines net removal. The advantage over in-situ injection is that it can be applied where no suitable formation exists.
- State of CDR, 3rd edition
Application areas
The sectors, facilities and end uses where the method is applied.
-
Application area
Carbonation in concrete recycling
Demolition concrete exposed to CO2 so that its cement phase converts to carbonate.
- How it works
-
- Crushing
Demolition concrete is crushed to aggregate size.
- CO2 exposure
The rubble is exposed to a CO2-bearing gas stream in a closed volume.
- Carbonation
Calcium in the cement phase binds as carbonate.
- Recycling
The treated material is used as recycled aggregate.
- Crushing
- Durability
- Calculated
-
Mineral carbonate
The carbon is bound as solid carbonate and stays for the life of the material.
- What it rests on
- The chemistry works and the scale does not: carbonating recycled concrete aggregate in a plant stores on average 7.2 kg of CO2 per tonne, so 1 Mt of storage means handling roughly 140 Mt of aggregate. That is a logistics problem. Whether it counts as removal also depends on the source of the CO2 used.
- State of CDR, 3rd edition
-
Application area
Mine tailings carbonation
Fine-grained, magnesium-rich tailings from mining exposed to air or a CO2 stream so that they carbonate.
- How it works
-
- Tailings selection
Tailings sites rich in magnesium and calcium are identified.
- Spreading and aeration
Tailings are spread in thin layers to increase contact with air.
- Carbonation
CO2 from the air or from a supplied stream reacts with the mineral.
- Measurement
The carbonate formed is quantified through sample analysis.
- Tailings selection
- Durability
- Calculated
-
Mineral carbonate
The carbonate formed is permanent; measured conversion varies from site to site.
- What it rests on
- The material is already milled, so the most expensive step is skipped; that is the method’s main attraction. Against that, conversion depends on tailings composition and climate, and a result from one site does not transfer to another. Additionality is a separate question here too: some tailings carbonate on their own.
-
Application area
Steel slag carbonation in a reactor
Steel slag reacted with CO2 under controlled reactor conditions and converted to solid carbonate.
- How it works
-
- Sourcing and milling
Slag is taken and milled to reactor size.
- Reactor
The slurry is brought into contact with a CO2-bearing gas in a closed reactor.
- Carbonation
Calcium in the slag binds as carbonate.
- Separation and testing
The product is separated and tested for heavy metal release.
- Sourcing and milling
- Durability
- Calculated
-
Mineral carbonate
The product is solid carbonate; durability rests on the same basis as other carbonation routes.
- What it rests on
- Slag has high calcium content and reacts quickly, so the material needs only a short time in the reactor. Two constraints are independent: chromium and vanadium release has to be controlled, and because slag is already a used by-product, a removal claim has to show which use it displaces.
Frequently asked questions
What is mineralization?
Mineralization is the reaction of CO2 with calcium- and magnesium-bearing reactive rock to form solid carbonate minerals. Once carbonate has formed, release requires temperatures above 600°C or strong acid.
Does mineralization count as carbon removal on its own?
It depends on the route. When reactive materials such as mine tailings or steel slag bind CO2 directly from open air, the result is a removal; this surface mineralization is close to enhanced rock weathering. When a captured CO2 stream is injected into rock or turned into carbonate in a reactor, mineralization is a storage step: it counts as removal only if the CO2 came from the atmosphere or from biomass. Mineralizing fossil CO2 is an emission reduction.
How strong is the durability evidence?
It is the strongest in the field: more than 95% of injected CO2 mineralized to carbonate in under two years, measured, not modelled, by tagging the CO2 with a traceable marker. According to Carbfix, more than 120,000 tonnes of CO2 have been permanently mineralized in rock at Hellisheiði.
How much CO2 can concrete carbonation store?
Carbonating recycled concrete aggregate in a plant stores on average 7.2 kg of CO2 per tonne at industrial scale, so storing 1 million tonnes means handling roughly 140 million tonnes of aggregate. That is a logistics problem rather than a chemistry problem.
Where can mineralization be built first?
Four conditions have to meet on one site: reactive rock, permeability that will take the injection, a CO2 source nearby, and water. They rarely coincide, which is why existing sites cluster into a narrow geographic set. Where water is scarce, injection with seawater is a research question rather than an established practice.