Future of aerial CO2 capture tech on display at Osaka Expo

Asahi Shimbun

23-04-2025

The direct air capture (DAC) system is tested to recover carbon dioxide in the atmosphere at the site of the Osaka Kansai Expo on Yumeshima island in Osaka's Konohana Ward on March 13. (Takahiro Takenouchi)
Japan's largest test plant for direct air capture (DAC) technology, which combats global warming by extracting carbon dioxide from the atmosphere, is currently operational at the Osaka Kansai Expo.
Expo visitors can make reservations to tour the facility.
'FOREST OF THE FUTURE'
As preparations for the world's fair were under way on Yumeshima island in Osaka's Konohana Ward, three white cylindrical devices sat on the ground near the pavilions in the middle of March.
Measuring 7 meters long and 1.2 meters in diameter, each device can absorb 100 kilograms of CO2 a day directly from the air.
Together, this triple-cylinder system can absorb the total emissions of about 40 households. This is roughly equivalent to the amount of CO2 absorbed by a forest five times the size of Koshien baseball stadium in nearby Hyogo Prefecture.
The facility is still in the research stage. However, if operated using carbon-free electricity being supplied to the expo grounds, the facility will reduce the amount of CO2 emissions in the atmosphere.
'Our exhibition showcases a functional experimental plant,' said Yoshiyuki Shimoda, director-general of the Research Institute of Innovative Technology for the Earth (RITE), during a ceremony in March to commemorate the system's completion.
'This is a forest of the future,' Shimoda said.
RITE has been researching amine's potential to capture CO2 in environments such as space stations. Achieving high absorption performance while easily releasing CO2 at low temperatures is particularly challenging.
HOW IT WORKS
A fan inside the cylinder draws air into the DAC system through its snake-like mouth. The air then comes into contact with a mesh-like honeycomb structure coated with amine, a substance that reacts with CO2 and absorbs it.
Once the CO2 is absorbed and trapped, the area around the mesh is sealed. The amine releases the captured CO2 when steam at around 60 degrees is pumped in.
The CO2 is then pumped out and collected, so the amine mesh is ready to absorb again.
The concentration of the CO2 extracted from the expo's DAC cylinders exceeds 95 percent.
The retrieved CO2 is converted into fuel, unlike most DAC research projects worldwide, which are designed to simply bury the captured CO2 underground.
CO2 collected at the expo will be sent from RITE's DAC factory to the adjacent facility of Osaka Gas Co. There, it will be turned into methane via synthetic reactions with hydrogen.
The methane will then be used at the expo's formal reception hall to fuel gas stoves and other components.
BREAKTHROUGHS ON DISPLAY
A separate team from Kyushu University will exhibit its own DAC machine with a thin membrane at the Osaka Expo. The team's goal is to use its small device in recovering CO2 at a range of locations, including homes.
'We would like visitors to the expo site to view our futuristic system that enables anyone, anywhere, to gather and recycle CO2 into fuel for reuse,' said Shigenori Fujikawa, a chemistry professor at Kyushu University.
The expo is also featuring a research unit from Nagoya University that has developed a method to reduce the energy consumption of DAC, by using the cooling effect of liquefied natural gas during vaporization.
The research of Nagoya University is funded by the central government's Moonshot Research and Development Program.
A major challenge facing DAC is improving efficiency.
According to the National Institute for Environmental Studies, the atmospheric CO2 concentration in 2024 was 421 parts per million.
This means that capturing one ton of CO2 requires filtering a Tokyo Dome's amount of air through DAC equipment, demanding advanced technology and vast amounts of energy.
Another absorption technology, carbon dioxide capture and storage (CCS), is therefore leading the global green trend for now.
CCS also uses amine, but collects CO2 from the exhaust of thermal power plants and other sources and stores it underground. The higher CO2 concentrations at these locations ensure higher efficiency.
DAC, despite its disadvantages, has a role to play.
For example, CCS at the site of combustion is unrealistic in a variety of cases, such as in aircraft, which are unlikely to become electrically powered anytime soon.
But DAC devices can still remove CO2 from the air without immediate proximity to the source, even if their efficiency is lower.
CONSIDERABLE COSTS
According to Katsunori Yogo, a chief researcher at RITE, estimates suggest that 200 million tons of 'negative emissions' (using DAC or other methods) will be required annually for Japan to attain the government's target of carbon neutrality by 2050.
A host of nations are committed to increasing DAC research.
The United States extended dedicated research support under the Inflation Reduction Law of the previous Biden administration.
Installed by Swiss company Climeworks in Iceland, the Mammoth plant for DAC began operations in May 2024, aiming for a yearly recovery capacity of up to 36,000 tons.
However, the technology's high operational costs present a major obstacle. With the current technology, recovery costs are believed to be reduced to 90,000 yen ($625) per ton at the lowest.
'The current method costs 30 trillion yen to capture 200 million tons of CO2 from the atmosphere in Japan,' Yogo said. 'This highlights the significance of shrinking the overall emission scale while developing the technology to slash costs.'
There is criticism that DAC, along with other negative emission techniques, could be used as an excuse to divert public attention away from efforts to reduce CO2 emissions. Additionally, DAC machines run on electricity.
'Power consumption is projected to continue increasing, given the demand for DAC and data centers,' Yogo said. 'What is important is to refine electricity-saving technologies in response.'
Yogo commented on the future of DAC.
'Conversion to renewable energy sources of electricity should be done as much as possible, while difficult-to-electrify systems should operate with hydrogen and ammonia and the use of CCS should be expanded,' Yogo said. 'The costly DAC method should be employed for collecting CO2 that cannot be retrieved by other means. This technology will undoubtedly become essential in the future.'
Yogo touted the exhibition space at the Osaka Expo, which opened April 13 and runs through Oct. 13.
'I would be delighted for visitors to witness both the current technological level and the future potential at the fair,' he said.