Kyushu University and the National Institute of Advanced Industrial Science and Technology, Japan, investigated a new way to store carbon underground. The team studied the geological storage of low purity carbon dioxide mixed with nitrogen and oxygen produced by direct air capture using membrane-based technology.

The current carbon capture process is carried out at localized sources with concentrated CO₂ emissions. This method requires intensive purification for storage because the gas contains hazardous compounds, nitrogen oxide and sulfur oxide. The traditional method has high transportation costs because geological storage sites are typically far away from the CO₂ sources.Schematic image of low-purity CO2 storage with the membrane-based Direct Air Capture (DAC). Source: Takeshi Tsuji

Direct air capture of CO₂ can be performed anywhere. It doesn’t need an intensive purification process because its impurities are not hazardous. Low purity CO₂ can be captured and injected directly into geological formations.

While the new process is promising, the team says there is still more research to be done before it can be implemented. A better understanding is needed of how the resulting mixture behaves when injected and stored in geological formations. However, preliminary research suggests that geological storage of mixtures produced via direct air capture is environmentally safe and economically viable.

A study on the new method was published in Greenhouse Gases: Science and Technology.