Of all the tools proposed to combat the looming threat of climate change, a technique called direct air carbon capture (DAC) has attracted a fair amount of flack in recent years. It works by employing liquid or solid materials made up of chemicals that trap carbon dioxide from the air.
This technique tends to be expensive, energy-intensive, and restricted to certain regions — there are only 18 direct air capture plants around the world, and they’re all located in the U.S., Europe, and Canada.
But a new DAC technique could change that, according to a new study published in the journal Science Advances. This novel method, which can absorb three times as much carbon dioxide as its predecessors with significantly less energy, could help developing countries participate in carbon capture efforts that have been primarily undertaken by wealthier nations.
“This is a global issue,” Arup SenGupta, an environmental engineer at Lehigh University and co-author of the study, tells Inverse. Solving it will take a global solution, he says.
Direct challenges
To limit global warming to 1.5 degrees Celsius by the century’s end, the International Panel on Climate Change (IPCC) suggests that, in addition to reaching net-zero industrial emissions by 2050, we’ll need to remove a few billion tons of carbon directly from the air.
That’s the plan for a handful of companies, including the Swiss startup Climeworks. But these businesses face some serious limitations when it comes to capturing and storing the carbon sucked up from the atmosphere.
For one, carbon dioxide still makes up a relatively low percentage of the atmosphere compared to gases like nitrogen and oxygen, so it’s tricky to suck it up from just anywhere.
Many DAC companies get around this by installing plants at places like gas flues where CO2 concentrations are much higher — around 10,000 parts per million, compared to the 400 ppm of ambient air. This strategy is effective, but it places serious limitations on where the plants can go.
Then there’s the issue of storage. The vast majority of DAC companies currently in operation store carbon by injecting it into the ground, where it’s trapped and stabilized by basalt rock. This works great in geologically stable areas. But countries including Japan, which sits above an active fault line, have expressed concern that shoving carbon into this sensitive region could trigger an earthquake.
Finally, DAC is pricey. In 2019, it cost Climeworks between $600 and $500 to pull one ton of carbon from the air, which becomes exorbitantly expensive if you’re working with multiple billions of tons of carbon. A lot of that cost comes from the massive amount of thermal energy it takes to run the plant, though the equipment itself isn’t cheap.
A new approach
SenGupta and his colleagues wanted to develop a method of direct air capture that could work anywhere, for cheap. So their new technology uses relatively low-cost and easily sourced materials, including copper, polyamine resin (an ingredient in many adhesives and floor coatings), and seawater.
They found that by binding the copper and resin and bringing it into contact with heated or salty water, they could remove carbon dioxide from the atmosphere. Using this reaction, they captured up to three times as much carbon as other DAC processes — even from air with low carbon dioxide concentrations.
The reaction produces sodium bicarbonate as a byproduct, “which is basically baking soda,” SenGupta says. Theoretically, this alkaline compound could be introduced back into the ocean to help combat ocean acidification.
Because the reaction doesn’t store carbon underground and can operate at low CO2 concentrations, you could hypothetically put a plant anywhere. And because the reaction can occur at a high or low temperature, it uses less energy than other DAC methods. Eventually, SenGupta hopes that developing nations can take advantage of this new technology.
“The way that carbon capture, especially direct air carbon capture, stands today, only two or three countries around the world are really involved,” he says. “But we do not include tens of other countries who could be effective players.”
It's important to note that DAC alone won't be enough to tackle the impacts of climate change. Even if we come up with super efficient carbon capture technologies, humans will still need to stop burning fossil fuels in order to limit warming. But effective DAC could go a long way toward stabilizing the climate and preventing the worst-case warming scenario.
Moving forward, SenGupta wants to bring the technology to countries that could benefit most, such as Barbados, Malawi, and Bangladesh.
He and two of his colleagues have a startup in place to help get the word out. Ultimately, though, he views profit-chasing as an impediment to actually implementing climate solutions — one of the reasons so many efforts have been confined to wealthier countries.
“That will never be able to solve the problem,” he says.
