Capturing CO₂ from the atmosphere and storing it inside concrete. Kawasaki and Kajima working together toward carbon neutrality

I happened to be seated next to (Torichigai-san) at a reception hosted by the U.S.-Japan CCUS/Carbon Recycling Working Group.* The meeting was held in August 2023 in Pittsburgh and co-sponsored by the Ministry of Economy, Trade and Industry. CCUS stands for “carbon dioxide capture, utilization, and storage.” It refers to initiatives and technologies for the capture, utilization, and storage of CO₂. The meeting provided a platform for Japanese and U.S. companies with various CO₂ capture and utilization technologies to gather and exchange information. There, I learned about the details of CO₂-SUICOM from Torichigai-san for the first time.

I told Okumura-san that there were some challenges involving CO₂-SUICOM, such as ensuring a steady supply of CO₂. He then suggested that we use DAC to capture CO₂ from the air. I thought that was an interesting idea. We were purchasing CO₂ at the time, but it was difficult to find a supplier that could provide the right amount of CO₂ for CO₂-SUICOM. Kawasaki Heavy Industries’ DAC would let us design a system for the right amount of CO₂. I thought this might be an excellent combination.

Torichigai-san expressed an interest in Kawasaki Heavy Industries’ DAC technology. So, when I returned to Japan, I worked very hard to make it happen. Our DAC technology uses solid sorbent coated with amine, which absorbs CO₂ to directly capture CO₂ from the atmosphere. At the time, we had already conducted demonstration tests with other companies using factory exhaust with high CO₂ concentrations. However, when it came to capturing CO₂ from the surrounding air, we had only conducted tests in-house. We had never disclosed this technology before. So, we made rapid preparations for the joint research.

One of the main reasons we wanted to use Kawasaki Heavy Industries’ DAC technology was that it would be able to capture CO₂ on the spot. As I said earlier, one of the major challenges involving the development of CO₂-SUICOM was obtaining the right amount of CO₂ and supplying it to the concrete factory. We hoped to achieve “local production for local consumption” of CO₂ through this joint research. We would capture CO₂ and use it right there.

CO₂-SUICOM uses a “carbonation curing chamber.” It enables concrete to absorb and store CO₂. We have created a system to combine this chamber with Kawasaki’s DAC unit. We installed it inside a concrete factory in Kagawa Prefecture, which became our test venue.

This was the first time that we took the DAC unit outside. So, we prepared a container, put the unit in the container, and transported it to the test venue. The unit was able to capture at least 5 kg of CO₂ per day at a concentration of 99% or higher. We carefully checked to make sure that it was not damaged while being transported and installed it at the test site. We used the unit to capture CO₂ from the atmosphere at the site and sent it to Kajima Corporation’s carbonation curing tank. The concrete absorbed CO₂ and trapped it in that tank.

The test was conducted in the heat of summer. The temperature was really high, and we were directly hit by a typhoon. We were worried that the system might break. So, we went through all kinds of hardships (laughs). 

It was a difficult summer in so many ways (laughs). We worked hard to get through this challenge. We were determined to send the right amount of CO₂ into the tank, no matter what. When the test began, the tank swelled up with the CO₂ from the DAC unit. But it shrank the next morning. I was so excited to see that CO₂ had been absorbed into the concrete. I was actually so relieved.

In the demonstration tests, it was confirmed that the amount of CO₂ absorption quality of concrete are acceptal. Based on this outcome, we used a similar system to manufacture the CUCO-SUICOM block.* It will be used for part of the entrance to the CUCO-SUICOM Dome (aka Sustainability Dome) at the 2025 EXPO Osaka.

The CO₂ captured with Kawasaki’s DAC technology is used in the manufacturing of concrete, and this concrete is used at the 2025 EXPO Osaka. Nothing makes me happier. We hope that people will experience this technology at the EXPO and become more interested in CO₂ capture and utilization. This may energize Japan’s CCUS initiatives.

Efforts are underway to achieve a carbon-neutral society. In Japan, technologies for capturing CO₂ and technologies for utilizing CO₂ are both being developed, but they are being developed independently of each other. There have been very few attempts to bring these initiatives together. However, according to the Ministry of Economy, Trade and Industry, it will become more important in the future to capture and use CO₂, in addition to reducing emissions. This is where CCUS, or carbon management, plays an important role. It will become increasingly necessary to combine these two initiatives.

This project is an example of carbon management in action. I believe that we have set an example for others to follow. Looking ahead, we would like to lead Japan’s CCUS and carbon management initiatives though our endeavor.

He is absolutely right. Kajima Corporation’s CO₂-SUICOM has already been put into practical use. We should combine this technology with Kawasaki Heavy Industries’ DAC. This will make it possible to achieve “local production for local consumption” of CO₂, as Torichigai-san mentioned earlier. Our tests show that Kawasaki Heavy Industries’ DAC technology is capable of concentrating rarefied CO₂ of 400 ppm, allowing for the capture of high-purity CO₂, at around 99%. We will continue to conduct demonstration tests at various locations using this technology. We hope to contribute to the realization of carbon neutrality and carbon management.

Let me share my personal view as an individual researcher. I have been involved in CO₂ research for a long time. But this is the first time that I have created something that I can actually touch and see. I can leave something tangible behind. I am very happy about this. I would like to continue working with my teammates and promote the wider use of DAC technology.