A recent study from Japan highlights an important environmental feature of concrete buildings: their ability to absorb and store carbon dioxide (CO₂) emissions. Researchers from the University of Tokyo and Nagoya University found that Japan’s concrete structures—including buildings and infrastructure—capture approximately 14% of the CO₂ emitted during cement production.

Published in the Journal of Cleaner Production, the study provides crucial insights into offsetting CO₂ emissions from cement manufacturing, a sector responsible for around 8% of global carbon emissions. This finding is particularly relevant for architects, interior designers, and product designers focused on sustainable material use and circular design.

The Carbonation Process in Concrete
Concrete naturally absorbs CO₂ over time through a process called carbonation. While carbonation can contribute to the corrosion of reinforcing steel in buildings, it also enables concrete to function as a long-term carbon sink. This characteristic is particularly important in the context of climate change, where designers and builders are seeking materials that contribute to carbon sequestration.

Material Flow Analysis: Understanding Concrete’s Lifecycle
The research team, led by Professor Ippei Maruyama and Professor Hiroki Tanikawa, conducted a detailed material stock-flow analysis of Japan’s concrete use from 1870 to 2020. This method tracks how materials enter, accumulate, and exit a system, allowing for a comprehensive understanding of their lifecycle within the built environment.

By integrating data on different concrete structures, Japanese earthquake-resistant design standards, environmental conditions, and construction materials, the study quantified how much CO₂ has been absorbed and stored in concrete across the country.

Key Findings and Future Projections
The results revealed that, between 1870 and 2020, cumulative CO₂ uptake in Japanese concrete structures reached 13.7 million tonnes—7.5% of the cumulative CO₂ emissions from cement calcination. In 2020 alone, annual CO₂ uptake was estimated at 2.6 million tonnes, accounting for 13.9% of that year’s cement production emissions.

Looking ahead, CO₂ uptake is expected to continue rising slightly during the 2020s, peaking at 2.3–2.4 million tonnes per year, before gradually declining as older buildings are demolished or replaced. However, the researchers note that effective waste management and extended building lifespans could enhance CO₂ retention, making concrete an even more viable tool for reducing atmospheric carbon.

Implications for Sustainable Design
For designers focused on sustainability, this research underscores the importance of considering concrete as a functional carbon sink in addition to its structural role. While concrete absorbs less CO₂ than forests, it remains a valuable contributor to carbon capture, provided buildings and infrastructure are maintained and managed responsibly.

The findings reinforce the need for longevity in architecture and product design, encouraging the use of durable, recyclable, and low-carbon concrete formulations. Integrating innovative cement alternatives—such as bio-based or recycled aggregates—could further enhance concrete’s environmental benefits.

As sustainability becomes an increasingly pressing concern, understanding material properties and their environmental impact is essential for architects and designers seeking to develop climate-conscious, future-proof structures.

Source: EurekAlert!
Photo: Hiroki Tanikawa