A new humidity-driven membrane has been developed to help capture carbon dioxide (CO2) directly from the air, a significant advancement in the fight against climate change.
Direct air capture (DAC) is one of the most crucial technologies to address this global issue because CO2 is a major contributor to climate change.
However, capturing CO2 from the air is very challenging due to its low concentration (about 0.04%).
Professor Ian Metcalfe from Newcastle University, UK, explains the challenges: “Separating low-concentration CO2 from the air is difficult for two reasons.
First, the chemical reactions needed are very slow due to the low CO2 concentration. Second, concentrating this dilute CO2 requires a lot of energy.”
To tackle these challenges, researchers from Newcastle University, along with teams from New Zealand, the UK, and the University College London (UCL), developed a new membrane process.
They used natural humidity differences to drive CO2 out of the air, solving the energy problem. Water also helped speed up the transport of CO2 through the membrane, addressing the slow reaction issue.
Published in the journal Nature Energy, Dr. Greg A. Mutch from Newcastle University highlights the significance of this work: “Direct air capture will be crucial for our future energy systems.
It can capture emissions from sources of CO2 that are hard to reduce in other ways.”
In their research, they demonstrated the first synthetic membrane capable of capturing CO2 from the air and increasing its concentration without using traditional energy inputs like heat or pressure.
Dr. Mutch likens it to a water wheel in a flour mill, where they use humidity to drive CO2 capture.
Separation processes are essential in many aspects of our lives, from the food we eat to the medicines we take. They are also vital for reducing waste and cleaning up the environment, such as through DAC of CO2. In a future circular economy, DAC could provide CO2 for making many products we use today, but in a way that is carbon-neutral or even carbon-negative.
Importantly, alongside renewable energy and traditional carbon capture from power plants, DAC is necessary to achieve climate targets like the 1.5 °C goal set by the Paris Agreement.
Dr. Evangelos Papaioannou from Newcastle University explains how the new membrane works: “Our membrane operates differently from typical ones. When humidity is higher on the output side, it spontaneously pumps CO2 into that output stream.”
Using advanced imaging techniques, the team precisely characterized the membrane’s structure. This allowed them to compare its performance with other state-of-the-art membranes. They also modeled the molecular processes in the membrane, discovering unique “carriers” that transport both CO2 and water. The energy from humidity differences drives CO2 through the membrane, concentrating it from a low to a higher concentration.
Prof. Metcalfe emphasizes the collaborative effort and support from various institutions, saying, “This was a real team effort over several years, and we are grateful for the contributions from our collaborators and support from the Royal Academy of Engineering and the Engineering & Physical Sciences Research Council.”
