New air filter could turn every building into a carbon sink

Despite decades of warnings and increasing efforts to fight climate change, global carbon emissions are still rising. While cutting emissions from the source is a common way we address this problem, another crucial strategy is actively removing carbon from the atmosphere. Current centralized DAC (direct-air-capture) plants are expensive and take up a lot of land, so scientists have developed a carbon dioxide-catching air filter that can fit into existing ventilation systems of homes and offices around the world.

The researchers describe their filter in a paper published in Science Advances. It is made of tiny carbon threads known as nanofibers that are coated with a polyethylenimine polymer. This combination makes an incredibly effective carbon sponge that captures carbon dioxide molecules from the air, even at low concentrations. The filter can also be cleaned by solar heating or low-energy electricity methods.

The team put their new carbon filter through its paces to see how well it worked. First, they checked how much it could soak up carbon by placing it in a flow system and passing air with a known concentration of carbon dioxide through it. The filter proved highly selective and fast, capturing the molecules and letting the rest of the air pass through.

The second phase of testing aimed to determine if the filter could be cheaply and efficiently reused without the massive energy costs associated with large, centralized DAC plants. Both a low-grade source of solar heating and the passing of low-voltage electric current directly through the conductive nanofibers forced the carbon dioxide molecules to break free of the polymer coating, meaning the filter can be easily reused. In a real-world setting, the released carbon can be collected as a pure, concentrated stream for permanent storage or reuse.

The study also confirmed the filter’s real-world potential. A life cycle assessment found the process to be remarkably clean, achieving a net carbon removal efficiency of 92.1%. Meanwhile, an economic analysis revealed that capturing one ton of carbon dioxide with this filter costs between an estimated $209 and $668, which is often cheaper than large-scale carbon capture technologies.

The study authors point out that if widely adopted, their filter could remove up to 596 million tons of carbon dioxide per year globally, which is about 2% of annual carbon emissions. “By taking advantage of billions of ventilation systems in the world, distributed DAC air filter technology can shift the paradigm and strengthen the present joint force to confront climate change.”

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