Locking captured CO₂ into concrete through mineralisation provides permanent carbon storage while reducing cement-related emissions, helping to decarbonise construction and create low-carbon building materials.
Turning Buildings into Carbon Sinks
Concrete is the second most-used substance in the world after water, and construction and buildings have the infamous claim of contributing a hefty 37% of the 38 billion tonnes of CO₂e (CO2 equivalent) emitted globally each year (UN Environment Programme report (2023))
As efforts to tackle climate change intensify, innovative ideas are emerging such as storing CO₂ in concrete, effectively turning buildings into carbon sinks. A study led by Elisabeth Van Roijen at the University of California, Davis, explores how transforming traditional building materials into carbon-capturing alternatives could remove up to 16.6 billion tonnes of CO₂ annually. The results of the study were published in the journal Science (2025).
Using Direct Air Capture to Capture CO2 to Store in Concrete
“Where do you get the CO₂ to add to the concrete?”
Direct Air Capture (DAC) plays a major part in this vision by extracting CO₂ directly from the atmosphere at any location. (See: How Does Direct Air Capture Work?) The captured CO₂ can then be integrated into the building materials supply chain, ensuring a closed loop that removes CO₂ and stores it permanently.
This solution tackles the issue of providing sustainably sourced CO₂ for concrete while also addressing another question: what should be done with the CO2 captured via DAC? (See: What is CO₂ Sequestration? and What is CO₂ Utilisation?)
Two Methods for Locking Carbon into Concrete
1. Add carbon-absorbing aggregates to concrete
Van Roijen et al. show that replacing traditional cement and concrete aggregates with CO2-storing materials could remove 13.1 billion tonnes of atmospheric CO2 annually.
2. Injecting captured CO₂ into wet concrete
Once the CO2 has been injected into the concrete, it reacts with the cement – with calcium (Ca) or magnesium (Mg) compounds – to form stable calcium carbonate, mimicking natural carbonisation in rocks but at a much faster pace.
Why Portland cement is bad for the environment
To make Portland cement, which is used extensively in concrete, limestone or chalk are heated with clay at an extremely high temperature (1450 °C) to make clinker, which is then ground to produce cement. Firing at this high temperature uses mostly fossil fuel energy which makes this process emissions intensive. This is then exacerbated by the CO2 emitted when heating limestone. In fact, one tonne of carbon dioxide is emitted for every tonne of cement produced.
Benefits of Trapping CO₂ in Concrete
Efficiency and Permanence
Efficiency and PermanenceBetween 85% and 94% of the injected CO₂ is absorbed in the concrete and secured for good.
Strength of Concrete
The chemical reactions not only lock in carbon but also improve the concrete’s durability.
Environmental Impact
With an annual global concrete production of 30 billion tonnes (and 4.25 billion tonnes of cement), the potential for a positive impact is enormous.
Although concrete’s weight-related carbon storage is relatively low, it is so widely used that it is an excellent carbon sink when implemented on a global scale. For every cubic metre of concrete, about 13 kgs of CO₂ can be locked away. Also, and more importantly, emissions are lower because about 5% less cement is used resulting in approximately 10% CO₂ less net emissions from cement utilisation.
Sustainable Concrete – Looking Ahead
Supply chain issues around sourcing and transporting CO₂ at scale remain complex. However, with advancements in technologies like Direct Air Capture, a consistent supply of CO2 can be provided. Interest is certainly rising in this approach to carbon sequestration and carbon-capturing materials present a compelling option for reducing global CO₂ emissions, particularly when scaled across industries as vast as construction.
For more:
- Direct Air Capture Decarbonises Hard to Abate Industries
- Sustainable Data Centres with Direct Air Capture
- Sustainable Aviation Fuel (SAF)
- Industrial Decarbonisation with Direct Air Capture
- Sustainable Plastic Manufacturing
- Sustainability in the Chemicals Industry
- Decarbonising the Steel Industry