• Extending buildings' lifespan can improve their role as carbon sinks, but concrete structures absorb less carbon than natural carbon sinks like forests and oceans.
• In 2020, Japanese buildings stored 2.6 million tonnes of CO2.

Japanese concrete structures and buildings can store and absorb about 14% of the carbon dioxide (CO2) emissions produced during cement production, note researchers from Tokyo and Nagoya Universities.

The study, published in the Journal of Cleaner Production, said cement production emits about 8% of global CO2 emissions. The discovery marks an important juncture in understanding how to offset these emissions.

According to the researchers, this is because of a natural phenomenon called carbonation (or CO2 uptake). When concrete structures or buildings are exposed to air, they naturally absorb CO2 over time, but it happens slowly and steadily. However, it comes with its disadvantages. The carbonation process can weaken concrete by corroding the steel reinforcement inside.

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The researchers considered various factors to estimate the amount of CO2 absorbed by buildings, including tracking cement production, the lifespan of structures, and what happens after demolition. They used this information to calculate the surface area of concrete exposed to air and how much CO2 it could capture.

In Japan, from 1870 to 2020, buildings absorbed over 135 million tonnes of CO2, equivalent to about 7.5% of the emissions from cement production during that time. Meanwhile, concrete structures captured 2.6 million tonnes in 2020 alone, approximately 14% of cement emissions that year.

Finally, the study concludes that CO2 absorption will slightly increase between 2020 and 2029 but is expected to drop by 2027.

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Professor Hiroki Tanikawa of Nagoya University, one of the lead researchers, said: "Studies on the detailed assessment of the total CO2 absorbed by concrete structures on the national scale are of great importance. Concrete buildings and infrastructure keep on absorbing CO2 as long as they are exposed to the air.

"Concrete structures act as carbon sinks, even though they absorb less CO2 than forests. With this in mind, we should take good care of buildings and infrastructure around us so that they have a long service life."

To learn more about the study and for a detailed view, click here.

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Source: Tech Xplore