Carbonation: why it is time to absorb the facts

24 Jan 2022

Here’s a fact that is well known: buildings account for 42% of greenhouse gas emissions.  Now here’s a concept that is less understood: concrete buildings naturally absorb carbon dioxide over their lifetimes.  This happens through a process called carbonation, which is where CO2 in the air reacts with the minerals in concrete. 

The design community’s understanding of the process is evolving. Now, on behalf of Government, the Mineral Products Association is developing an approach to fully understand the role carbonation plays across the UK built environment.  

Is carbonation a new phenomenon?

No. Concrete has naturally been absorbing carbon dioxide from the atmosphere since the first time it was ever used (some thousands of years ago).  It’s also well understood as a technical design consideration for engineers for managing and optimising the design of reinforced concrete.

In the IPCC’s Sixth Assessment Report, published in 2021, the UN acknowledged for the first time that carbonation absorbs a significant proportion of CO2 emissions over the lifecycle of concrete infrastructure.

Is the UK measuring carbonation?

UK Government has recognised that this process needs to be accounted for when the UK calculates its greenhouse gas emissions.  The Department for Business, Engineering and Industrial Strategy (BEIS) has appointed the Mineral Products Association (MPA) to conduct research to develop a robust method to assess the role of concrete in the absorption of carbon across our built environment.

As only the second country in the world to explore this, after Sweden, this research will help to improve the accuracy of UK greenhouse gas accounting.  When implemented, the national emissions reporting method will be able to calculate the carbon sink benefit provided by the carbonation of concrete over its lifecycle.

What does this mean for the built environment?

To establish where we stand in the climate emergency, we need to be able to accurately determine how much carbon we are emitting and how much carbon we are absorbing. This research will help us to answer questions about how much carbonation is actually happening and the extent to which existing and new concrete provides a carbon sink in the UK.

The industry’s roadmap to beyond net zero by 2050 is predicated on key levers such as fuel switching, greater use of low-carbon cements and concretes as well as Carbon Capture, Use or Storage (CCUS).  Acknowledging the carbon absorption of concrete through carbonation is an inherent feature of concrete that can help take the industry beyond net zero.

You can see the extent of carbonation in action here:

Elaine Toogood, Head of Architecture at The Concrete Centre.