Reducing CO2 Emissions Simply by Coating Concrete
New Technology to Change the World

Amine Compound Helps Absorb and Fix CO2

"It has long been known that concrete has an ability to fix CO2 in the air," Tsujino Masato at Shimizu Corporation said while explaining the background of the project. "However, since the absorbed carbon dioxide causes neutralization inside the originally alkaline concrete and makes reinforcing steel and other materials more prone to corrosion, it has been regarded as deterioration," he said. But the amine compound used in the project promises a solution, with its ability to promote the absorption of CO2 and at the same time prevent steel corrosion.

A joint research project between Shimizu and Hokkaido University has been underway since 2018. In 2022, when carbon neutrality became an important research topic, the Hokkaido University research team focused on amine compounds, which can absorb CO2. Professor Kitagaki Ryoma at the university said: "CO2 capture systems using amine compounds have long been utilized for factory exhaust gases and other applications, but in order to efficiently capture and fix CO2, large amounts of amine compounds are needed." Under the project, the problem has been solved by not fixing CO2 in amine compounds themselves but using a particular amine compound that can play an intermediate role in the fixing of CO2 inside concrete.

Effective Just by Coating: Corrosion Resistance Improves Building Endurance

The newly discovered amine compound can absorb CO2 and release it into water contained within concrete materials, so that the released CO2 can then combine with calcium ions to form calcium carbonate. In theory, it is possible to continuously fix CO2 inside concrete until the calcium ions are consumed. Although further research is needed, it appears possible to fix up to 100 kilograms of CO2 per cubic meter of concrete. Furthermore, based on Shimizu's long-standing research into corrosion prevention technology for reinforcing steel and other materials, it has also been found that this amine compound has the effect of increasing corrosion resistance.

What is even more revolutionary about the new technology is that its effects can be achieved simply by applying it to existing concrete. As it does not need to be mixed into concrete, it can be applied to existing buildings, highways, and bridges to promote CO2 fixation. "We are exploring various methods, such as brushing or spraying the surface like paint, or even using a drone to apply it," Tsujino said. While applications are still under consideration, this is definitely a new technology that can handily contribute to carbon neutrality.

Demonstration in Progress with Support of Tokyo Bay eSG Project

The DAC Coating technology was selected as an advanced initiative for the Tokyo Bay eSG Project in fiscal 2023, and a large-scale concrete mock-up is currently being prepared with the support of the Tokyo Metropolitan Government (TMG) for the purpose of investigating CO2 fixation and verifying corrosion resistance. Nomura Daisuke, CEO of Gorlem Inc., which is working on quantifying and visualizing the amount of CO2 fixation in this project, said: "Simply talking about fixing CO2 may be good in terms of public relations, but it cannot be incorporated into corporate strategies." It is important to properly quantify the reduction rate, and to present results in a way that is easy for ordinary people to understand, he added.

The DAC Coating technology is being developed and demonstrated at a rapid pace with the aim of practical application. The project is participating in SusHi Tech Tokyo 2024, an event starting on April 27 2024 organized by the TMG. "In terms of concrete production, we would like to use this as a promotional opportunity for not only the mature market in Japan but also emerging countries where demand is still growing," said Tsujino.Visitors to the event can experience DAC Coating works, which would be a good opportunity to promote the technology.

Concrete Jungles That Absorb CO2

The current goal is to commercialize the technology from 2026. To achieve this objective, project members are conducting proof-of-concept tests while collaborating with chemical manufacturers to select the optimal materials and evaluate their performance. The product is expected to be offered at a price not much different from that of current impregnating agents or penetration-reducing materials that are used to enhance concrete performance by inhibiting the absorption of surface water on concrete. In addition to its use on buildings, bridges, highways, and other large construction projects, the company envisions that, in the future, individuals will be able to buy the product at home improvement stores and apply it to their own homes. In a few years, it is likely to become familiar among general consumers.

High-density conurbations are often referred to as "concrete jungles," Nomura said. "We hope to realize a world where these artificial concrete buildings can absorb CO2 just like trees in a real jungle." With the development of DAC Coating, the day may not be far off when concrete supporting social infrastructure around the world will also contribute to the promotion of carbon neutrality and play a role in preventing global warming.

SusHi Tech Tokyo, short for Sustainable High City Tech Tokyo, is a Tokyo-based concept that aims to create sustainable new value by overcoming global urban challenges through cutting-edge technology, diverse ideas, and digital expertise.

SusHi Tech Tokyo 2024: 
https://www.sushi-tech-tokyo2024.metro.tokyo.lg.jp/