Researchers at MIT have come up with a novel solution to remove carbon dioxide from the atmosphere for combating climate change.
This new approach improves the removal process of carbon dioxide by six times and cuts down costs by at least 20%.
The new findings were reported by MIT doctoral students Simon Rufer, Tal Joseph, and Zara Aamer, along with Professor of Mechanical Engineering Kripa Varanasi.
How did they solve the problem?
Attempting to remove CO₂ has two main hurdles. First, the chemical compounds that remove CO₂ from air do not easily release it after capturing it. Vice versa, the compounds that are good at releasing CO₂ aren’t equally efficient at capturing it.
The researchers at MIT used nanoscale filtering membranes and added an intermediate step that facilitates both parts of the cycle with equal efficiency.
“We need to think about scale from the get-go when it comes to carbon capture, as making a meaningful impact requires processing gigatons of CO₂,” says Varanasi. “Having this mindset helps us pinpoint critical bottlenecks and design innovative solutions with real potential for impact. That’s the driving force behind our work.”
Varanasi further pointed out the difference between the capturing and releasing systems, underlining the problems they face.
“You can see how these two steps are at odds,” says Varanasi. “These two systems are circulating the same sorbent back and forth. They’re operating on the exact same liquid. But because they need two different types of liquids to operate optimally, it’s impossible to operate both systems at their most efficient points.”
Delving deeper in the system
The system created by the researchers separates hydroxide ions and carbonates to optimize efficiency: hydroxide ions go back to absorb more CO₂, while carbonates move forward to release CO₂. This prevents wasted reactions where protons would otherwise just form water with hydroxide ions.
“If you don’t separate these hydroxides and carbonates,” Rufer said. “The way the system fails is you’ll add protons to hydroxide instead of carbonate, and so you’ll just be making water rather than extracting carbon dioxide. That’s where the efficiency is lost. Using nanofiltration to prevent this was something that we aren’t aware of anyone proposing before.”
MIT researchers added nanoscale filtering membranes to a carbon-capture system, separating the ions that carry out the capture and release steps, and enabling both steps to proceed more efficiently. Image: Courtesy of the researcher
Exploring the commercial value
A cost comparison analysis showed that the current system incurs at least $600 per ton of carbon dioxide captured. Adding the nanofiltration component to it reduces that sum to $450. Furthermore, the new system can operate at higher efficiency without losing its stability, even when ion concentrations vary in the solution.
Varanasi also stated that this technology helps us to use safer alternative chemistries for carbon capture.
“A lot of these absorbents can at times be toxic, or damaging to the environment. By using a system like ours, you can improve the reaction rate, so you can choose chemistries that might not have the best absorption rate initially but can be improved to enable safety,” she said.
A peek at the future
Carbon credits are currently available for $500 per ton, and with this new system, that cost can be brought down significantly. According to Simon Rufer, the decrease in price tag could increase the number of buyers who would consider buying credit.
Professor Varanasi further described their long-term vision with this system.
“Our goal is to provide industry scalable, cost-effective, and reliable technologies and systems that enable them to directly meet their decarbonization targets.”
The findings were published in the journal ACS Energy Letters.
