The Concrete Jungle Is Greener Than You Think

Cement production generates a lot of carbon dioxide, but the good news is it it also acts as a carbon sink.

AsianScientist (Dec. 30, 2016) – Concrete may have a bad reputation for it’s impact on the environment, but researchers in China have now found an unexpected silver lining: cement absorbs up to 43 percent of the carbon dioxide produced during its manufacture. These findings have been published in Nature Geoscience.

The concrete industry is one of the largest producers of carbon dioxide emissions, accounting for five percent of global emissions in 2013. In particular, cement production is considered doubly carbon-intensive because emissions come from both energy combustion and the calcination chemical reaction used to turn carbonate rocks into cement.

In the present study, an international team led by Xi Fengmeng, an associate professor at the Institute of Applied Ecology of the Chinese Academy of Sciences investigated the impact of carbonation, the reverse process of calcination which naturally occurs over time.

As carbon dioxide diffuses into the pores of cement, it reacts with calcium oxide through a process called carbonation. Using new and existing data on cement service life, demolition and secondary use of concrete waste, Xi and his team developed an analytical model describing carbonation chemistry to estimate regional and global carbon dioxide uptake between 1930 and 2013.

In total, more than 76 billion tons of cement were produced around the world from 1930 to 2013 with four billion tons produced in 2013 alone. The researchers found that carbonation of cement materials over their life cycle represents a large and growing net sink of carbon dioxide, increasing from 0.10 gigatons of carbon per year (GtC/y) in 1998 to 0.25 GtC/y in 2013.

According to the study, a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43 percent of the carbon dioxide emissions from the production of cement over the same period, not including emissions associated with fossil use during cement production.

“The global carbon uptake by cement carbonation is large and substantial, which give a new perspective for missing sink mystery and the carbon sink from human activities have not revealed comprehensively, the new technologies of carbon capture and storage using the cement wastes should be developed for climate change mitigation,” Xi said.

The article can be found at: Xi et al. (2016) Substantial Global Carbon Uptake by Cement Carbonation.


Source: Chinese Academy of Sciences; Photo: Pixabay.
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