In an "urgently needed" discovery that could revolutionise direct air capture, researchers from Lehigh University have found a way to potentially make the removal of carbon dioxide from the atmosphere cheaper and more efficient.
The novel process, published in the Science Advances journal, works with the standard direct air capture (DAC) machines being used by companies like Climeworks, which suck in air before running it through filters and sorbents that extract the CO2.
But in this case, the researchers introduced a new type of hybrid sorbent that contains copper and discovered that it has a carbon capture capacity "nearly two to three times greater" than any other sorbent used to date.
Direct air capture uptake has been "slow and inadequate"
Using this hybrid sorbent has the potential to make DAC more time and cost-efficient, potentially bringing down the price from upwards of $600 per tonne to just $100 a tonne, the researchers estimate.
Unlike traditional sorbents, the researcher's copper-enriched version also doesn't have to be heated to 100 degrees Celsius to extract the CO2 for storage, providing further energy savings.
This is crucial, considering that the industry has to go from capturing 0.01 megatonnes to almost 60 megatonnes per year by the end of the decade if the world hopes to reach net zero by 2050 and limit global warming to the crucial 1.5-degree threshold set out by the IPCC.
So far, progress on this front has been held back by the fact that DAC is hugely inefficient and requires vast amounts of energy, as the carbon dioxide is relatively diluted in the atmosphere – taking up about 400 parts per million (ppm) despite its outsized impact on global warming.
"The prospect of CO2 removal by DAC was articulated nearly two decades ago," the report in Science Advances reads. "However, the progress has been slow and inadequate."
"High-capacity CO2 capture under ambient conditions is urgently needed for timely DAC system implementation to meet the IPCC target by 2050."
Ocean could be "infinite sink" for captured carbon
Integrating the hybrid sorbent into direct air capture processes could also open up new ways of storing the carbon once it is removed from the atmosphere, the report says.
Currently, companies like Climeworks have to pressurise and liquefy this CO2 so that it can be injected into the ground, where it will eventually turn into calcite rock.
But the copper-enriched hybrid sorbent only needs to be exposed to seawater to turn the carbon into sodium bicarbonate, effectively sequestering it by turning it from a gas into a solid.
Depending on industrial waste regulations, the researchers said this sorbent could be deposited in the ocean, potentially turning it into "an infinite sink for captured CO2".
This could allow direct air capture and storage to work even in regions that don't have the necessary storage capacity underground.
"The entire plant can be conveniently located offshore," the study said. "Geographic locations in close proximity to oceans where geological storage is unavailable or CO2 transport is difficult may find this approach attractive."
Impact on oceans not fully considered
The researchers are now planning to set up a dedicated company to develop the technology further and test whether it could work at scale outside of the lab.
So far, no tests have been done to see whether introducing large amounts of sodium bicarbonate into the ocean would affect its chemistry and ecosystems.
But lead author professor Arup SenGupta claims that since sodium bicarbonate is alkaline, it could potentially help to reduce the ocean acidification that is a knock-on effect from having an excess of CO2 in the atmosphere.
Similar geoengineering approaches to mitigating climate change include enhanced weathering – as pioneered by companies including Mineral Carbonation International – which involves speeding up the earth's natural weathering process to sequester carbon.
The top image is by Matthias Heyde via Unsplash.