Scientists at Lehigh University in Pennsylvania have identified a new material that could revolutionise the direct air capture (DAC) industry by turning captured carbon dioxide (CO2) into baking soda, which could then be stored in the ocean.
Carbon capture technology has traditionally focused on removing CO2 from pollution sites before it enters the atmosphere, such as from the chimneys of coal and steel plants. However, direct air capture is far more difficult as CO2 in the atmosphere is more dilute and therefore requires more energy and materials to extract. Current DAC plants are expensive to run, with a tonne of CO2 costing hundreds of dollars to remove from the air.
To address this, researchers modified existing amine solvents with a copper solution to create a new absorbent material, or sorbent, which they say can pull up to two or three times more CO2 from the air than existing materials can.
This breakthrough could radically boost the potential of DAC as a commercially viable technology for mitigating climate change, as the materials needed to produce the sorbent are readily available and low cost, according to Arup SenGupta at Lehigh University.
Captured CO2 can be converted into sodium bicarbonate, or baking soda, by adding seawater. This can then be safely stored in the ocean, representing an “infinite sink” for captured CO2. The team suggests that releasing baking soda into the ocean would not pose any ecological harm and could offer benefits by reversing ocean acidification caused by CO2, thus encouraging more biological activity and CO2 sequestration. DAC plants using this sorbent could even be installed offshore, enabling countries without geological carbon storage potential to remove carbon from the atmosphere.
While the proposal is described as “elegant and clever chemistry” by Stuart Haszeldine at the University of Edinburgh, he notes that further research is needed to understand how the material performs on an industrial scale after absorbing and releasing CO2 hundreds of times.
There may also be legal barriers to discharging baking soda into the ocean, which could be classified as industrial waste.
“Carbon removal technologies must be rapidly scaled up to limit global warming to 1.5°C,” according to the International Energy Agency.
Although the new sorbent may offer a technical breakthrough to improve DAC efficiency, Myles Allen at the University of Oxford suggests that government intervention may be needed to encourage investment by energy companies in the rapidly expanding market.