Cutting emissions requires pulling massive amounts of carbon dioxide right out of the sky, a process called direct air capture. Capturing CO2 from the air is expensive and needs high heat and pressure to work. A group led by Raffaele Mezzenga at ETH Zurich found a new way to catch CO2 using waste from tofu and dairy production.

Turning Food Waste into Carbon Sponges

CO2 capture
Still life featuring protein beads loaded with potassium hydroxide. The porous act as a sponge for CO2; Photo: Mezzenga Lab / ETH Zurich

Making dairy and tofu leaves behind a lot of liquid protein that mostly goes to waste. The researchers take this leftover protein and shape it into long threads and then add potassium hydroxide to form the material into small beads.

“The resulting material is like a sponge that can absorb large quantities of CO2 via the potassium hydroxide,” Mezzenga explained.

When normal air hits these porous beads, the chemicals react and pull the CO2 right out of the air, turning it into baking soda.

“In our tests with ambient air, we were able to extract 97 milligrams of CO2 with one gram of material,” added Zhou Dong, the study’s lead author. Surprisingly, this capacity is 10 to 50 percent higher than older methods.

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Cheaper and Built to Last

Older CO2 filters require high heat to release the trapped gas so it can be stored away, but it uses a lot of power. Instead, this new team sprays their protein beads with a mild acid and base at room temperature for about 10 minutes, easily separating the CO2.

“The synthetic materials that are used to capture CO2 today decompose quickly,” said Dong. “By contrast, our protein beads remain stable for a long time.” In the lab, the beads ran through 30 cycles without losing efficiency. When they finally wear out after a few thousand uses, they won’t sit in a landfill.

“The materials we use for this process are non-toxic and are food-grade,” Mezzenga explained. They are completely organic and can actually be turned into fertilizer or biofuel.

The team still needs to test this on a larger scale to see if the high capacity holds up outside the lab. But they are very optimistic.

“We’re confident that the technology is scalable,” he said.