A new breakthrough from MIT engineers could make one of our most powerful climate tools more efficient. Carbon capture, or the process of pulling carbon dioxide from the air, is a promising solution to help reverse the pollution that is overheating the planet. But it has faced an annoying conundrum so far — the chemicals best at trapping the gas are often the worst at releasing it and vice versa.
The researchers reported that they found a fix. By adding a simple nanofiltration step between the carbon capture and release stages, the team was able to improve efficiency by six times and make it at least 20% less expensive, according to a study published in ACS Energy Letters.
"We need to think about scale from the get-go," said mechanical engineering professor Kripa Varanasi. "Making a meaningful impact requires processing gigatons of CO2. 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."
So, how does it work? Well, most carbon capture systems use water-based chemical solutions to trap CO2 from the air. But to release that CO2 later (so it can be stored or recycled), those same chemicals become a problem. The leftover compounds interfere with the release process.
"You can see how these two steps are at odds," Varanasi said. "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."
The Massachusetts Institute of Technology's solution is a filtration process that sorts the chemicals by electrical charge in between the two steps. This allows each part of the cycle to operate more efficiently. With this nanofiltration, the system is more resilient, making it easier and cheaper to scale up.
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Right now, carbon capture costs at least $600 per ton. The new approach could drop that to $450 — with researchers optimistic that it could come down to $200 with a little more development. While transitioning away from dirty fuels is still the most crucial element of bringing Earth's temperatures back into balance, that's good news for governments and companies investing in climate solutions, and for buyers on the growing carbon credit market.
By making this process more efficient, there could soon be safer alternatives to today's more toxic chemical solutions, leading to cleaner air and less chemical waste. Plus, the system works with materials already available commercially — and could be retrofitted to existing systems. As Varanasi put it, "We're confident that we'll have something that can become economically viable.
"This is just one example of researchers' pushing climate tech forward. Other innovators — including Trashie and LanzaTech — are also proving that solutions to pollution can be smart and profitable.
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