Photo: Phil Roeder, Flickr Creative Commons

We are reminded of this episode of a podcast dealing with concrete’s surprising awesomeness, with some new science to add support:

Concrete jungles can soak up carbon

by Prachi Patel

Cement has a bad rep in environmental circles. That’s mainly because its production creates 5 percent of the world’s industrial carbon emissions. But a new study gives this climate rogue a bit of a reprieve.

Cement-based materials such as concrete can, over their lifetime, absorb some of the carbon released during cement production, researchers have found. Almost a quarter of cement’s carbon dioxide emissions over the past 80 years have been sequestered in the ubiquitous building material, they report in a paper published in the journal Nature Geoscience.

Making cement involves heating limestone at high temperatures to convert it to lime. The process releases carbon dioxide, accounting for half of cement’s total carbon emissions. Burning fossil fuels in the kilns releases the other half.

But as cement-based materials sit around for years exposed to air, carbon dioxide enters the material’s pores, reacts with water and other chemicals there, and gets converted into other chemicals that stay buried. This process is called carbonation. And it has been the missing piece in calculations of cement’s carbon footprint…

…Policies to reduce emissions from cement production should focus on fossil fuel use rather than the limestone-to-lime process, the researchers say. If the emissions from cement factories can be captured and stored, they add, cement could become carbon negative, sucking up more carbon dioxide than it produces.

Source: Fengming Xi et al. Substantial global carbon uptake by cement carbonation. Nature Geoscience 2016.

Read the whole summary here.