Carbon Capture Breakthrough: Humidity-Powered Membrane Pumps CO2 Out Of The Air

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An innovative membrane that captures carbon dioxide from the air using humidity differences has been developed. This energy-efficient method could help meet climate goals by offering a sustainable carbon dioxide source for various applications. (Artist's concept.) Credit: SciTechDaily.com

Direct air capture was identified as one of the Seven chemical separations to change the world'. This is because although carbon dioxide is the main contributor to climate change (we release ~40 billion tons into the atmosphere every year), separating carbon dioxide from air is very challenging due to its dilute concentration (~0.04%).

Prof Ian Metcalfe, Royal Academy of Engineering Chair in Emerging Technologies in the School of Engineering, Newcastle University, UK, and lead investigator states, Dilute separation processes are the most challenging separations to perform for two key reasons. First, due to the low concentration, the kinetics (speed) of chemical reactions targeting the removal of the dilute component are very slow. Second, concentrating the dilute component requires a lot of energy."

These are the two challenges that the Newcastle researchers (with colleagues at the Victoria University of Wellington, New Zealand, Imperial College London, UK, Oxford University, UK, Strathclyde University, UK, and UCL, UK) set out to address with their new membrane process. By using naturally occurring humidity differences as a driving force for pumping carbon dioxide out of air, the team overcame the energy challenge. The presence of water also accelerated the transport of carbon dioxide through the membrane, tackling the kinetic challenge.

The work is published in Nature Energy and Dr. Greg A. Mutch, Royal Academy of Engineering Fellow in the School of Engineering, Newcastle University, UK explains, Direct air capture will be a key component of the energy system of the future. It will be needed to capture the emissions from mobile, distributed sources of carbon dioxide that cannot easily be decarbonized in other ways."

In our work, we demonstrate the first synthetic membrane capable of capturing carbon dioxide from air and increasing its concentration without a traditional energy input like heat or pressure. I think a helpful analogy might be a water wheel on a flour mill. Whereas a mill uses the downhill transport of water to drive milling, we use it to pump carbon dioxide out of the air."

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