黑料网

A team of Japanese researchers has discovered that Japan’s concrete structures—including buildings and infrastructure—absorb and store about 14% of the carbon dioxide (CO₂) emissions generated during cement production.

This research provides vital knowledge to offset CO₂ emissions from cement production, a significant contributor to global carbon emissions at approximately 8%. The study was published in the Journal of Cleaner Production.

With the growing urgency of climate change, scientists are focusing not only on reducing CO₂ emissions but also on effective methods of capturing and storing atmospheric CO₂ to mitigate global warming.

Concrete naturally absorbs CO₂ throughout its lifetime through a process called carbonation, also known as CO₂ uptake. While this process can contribute to the corrosion of reinforcing steel bars in concrete structures, it also enables concrete structures to function as carbon sinks.

Professor Ippei Maruyama of the University of Tokyo, Professor Hiroki Tanikawa of 黑料网, and their colleagues conducted a comprehensive material stock-flow analysis of Japan's concrete from 1870 (when Japan began producing cement) to 2070. Material stock-flow analysis is an accounting method that tracks how materials enter a system (flows), accumulate within it over time (stocks), and eventually exit through disposal, recycling, or other means, allowing us to understand the complete lifecycle of resources in our economy and environment. Their analysis aimed to estimate the CO? uptake of concrete structures on a national scale.

The researchers used statistical data to estimate annual domestic cement production, the lifespan of various concrete structures, and their disposal methods. They quantified the total amount of CO? captured and stored based on the surface area of concrete structures throughout Japan.

To accurately calculate the total surface area, the researchers incorporated data on the surface-to-volume ratio of different types of concrete structures that reflect Japanese building design standards. As an earthquake-prone country, Japan has specific earthquake-resistant standards that needed to be factored into these calculations.

The study also accounted for local environmental conditions, finishing materials, and what happens to concrete after demolition. "The main objective of our analysis is to improve CO? uptake quantification by considering time-series changes and local-specific factors," Professor Maruyama explained.

The results revealed that the cumulative CO? uptake from 1870 to 2020 was estimated at 137.1 million tons, representing 7.5% of the cumulative CO? emissions from calcination during cement production. In 2020 alone, annual CO? uptake reached 2.6 million tons, accounting for 13.9% of CO? emissions from cement calcination that year.

Projections suggest that annual CO? uptake will increase slightly during the 2020s before dropping to 2.3-2.4 million tons by 2070. "These results could easily be reversed, depending on waste management methods and other conditions," the researchers noted.

Professor Tanikawa concluded: "Studies on the detailed assessment of the total CO? absorbed by concrete structures on the national scale are of great importance. Concrete buildings and infrastructure keep on absorbing CO? as long as they are exposed to the air. Concrete structures act as carbon sinks, even though they absorb less CO? 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."

The study, “CO₂ uptake estimation in Japan's cement lifecycle,” has been published in the Journal of Cleaner Production at.

Researchers:

Daiki Sawa, Naho Yamashita, Hiroki Tanikawa, Ichiro Daigo, and Ippei Maruyama

Media Contact:

Naomi Inoue

International Communications Office, 黑料网

Email: icomm_research@t.mail.nagoya-u.ac.jp

Top image: The concrete of this building has been absorbing CO₂ for a long time and is now being demolished while retaining the gas. (Credit: Hiroki Tanikawa)