Food Waste Becomes a Powerful Carbon Trap in Climate Breakthrough

Food waste may become a powerful climate tool thanks to tiny reusable beads that capture carbon directly from the air.

Keeping global warming below 1.5°C over the long term will require more than major cuts in greenhouse gas emissions. According to climate scenarios outlined in the latest Assessment Report from the Intergovernmental Panel on Climate Change (IPCC), the world will also need technologies capable of removing and storing hundreds of billions of tons of carbon dioxide (CO₂) already in the atmosphere.

One approach receiving increasing attention is “direct air capture” (DAC), a technology that removes CO2 directly from the air. Researchers and startups have spent years trying to improve DAC systems. One of the earliest commercial companies in the field is Climeworks, an ETH Zurich spin-off founded in 2009. Despite progress, direct air capture remains costly and requires significant amounts of energy.

Food Waste Turned Into Carbon Capture Material

Researchers at ETH Zurich have now developed a new DAC approach that could make the process more efficient and sustainable. In a study published in the journal PNAS, a team led by materials scientist Raffaele Mezzenga used waste products from dairy and tofu manufacturing to capture CO₂.

Large amounts of protein-rich liquid are generated during the production of dairy products and tofu. Only a small portion is reused in food manufacturing, while much of the rest is discarded. The researchers extracted proteins from this waste stream and assembled them into long, thread-like structures called amyloid fibrils. These fibrils were then combined with potassium hydroxide and formed into porous beads measuring about half a centimeter to one centimeter in diameter.

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

When exposed to air, the potassium hydroxide inside the beads reacts with CO₂ and converts it into hydrogen carbonate, a salt of carbonic acid. This reaction removes carbon dioxide from the atmosphere.

“In our tests with ambient air, we were able to extract 97 milligrams of CO₂ with one gram of material,” explains Zhou Dong, a postdoctoral researcher in Mezzenga’s group and lead author of the study.

According to Dong, this performance is exceptionally strong, exceeding the capacity of conventional DAC technologies by 10 to 50 percent. Based on the team’s calculations, one kilogram of the protein beads could theoretically capture and isolate 100 grams of CO₂ during a single operating cycle.

Lower Energy Carbon Removal

Most existing direct air capture systems rely on heat and negative pressure to release the captured carbon dioxide from the absorbent material. The recovered CO₂ can then be stored or converted into other products, allowing it to be removed from the atmosphere over the long term. However, generating the necessary heat requires substantial energy, making DAC economically and environmentally viable mainly in places with abundant renewable energy.

The ETH Zurich team developed a different solution. To release the captured carbon dioxide, the protein beads are sprayed alternately with a mild acid and a mild base for approximately 10 minutes at room temperature. This process breaks the chemical bonds holding the CO₂, allowing it to be collected.

The acid, base, and protein beads can all be reused afterward.

“The synthetic materials that are used to capture CO₂ today decompose quickly,” says Dong. “By contrast, our protein beads remain stable for a long time.”

Laboratory tests showed that the beads maintained their performance through 30 cycles of carbon capture and release with no significant decline in efficiency.

Designed for a Circular Economy

Although Mezzenga expects the material would eventually need replacement after several thousand cycles as its adsorption capacity gradually declines, the used beads could still serve another purpose.

The researchers say the protein beads could be applied as agricultural fertilizer or converted into biofuel after their carbon capture life ends. Because the material is entirely organic and biodegradable, it could fit naturally into a circular economy model.

“The materials we use for this process are non-toxic and are food-grade,” Mezzenga points out.

The team also conducted a life cycle analysis and found that the new method creates less environmental pollution over its full lifespan than existing DAC approaches.

Can the Technology Scale Up?

More research will be needed to determine whether the technology can operate effectively on an industrial scale and whether its high CO₂ capture performance can be maintained in larger systems.

For the current study, researchers tested only a few grams of the material in a controlled laboratory setting, capturing and isolating roughly 50 grams of CO₂.

Mezzenga remains optimistic. He has worked with amyloid fibrils for nearly two decades and has previously used them to create biodegradable plastic alternatives and water purification technologies.

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

He notes that the spray-based system used to release CO₂ is compatible with techniques already employed in industrial processes. Dong’s next research efforts will focus on evaluating large-scale implementation.

Although the team has not yet calculated the exact cost of removing a ton of CO₂ with the new system, Mezzenga expects it to be considerably less expensive than conventional direct air capture methods.

“Our technology is cheaper and more sustainable because it requires little energy and is based on a widely available waste product,” he says. “That could be a game changer for the future of removing CO₂ from the air.”

Reference: “Circular and athermal atmospheric CO₂ capture by food waste-derived amyloid sorbents” by Zhou Dong, Ming Dai, Felix Donat, Dominik Richert, Bin Dai, Paweł P. Ziemiański, Jiangtao Zhou, Milad Radiom, Mohammad Peydayesh, Yanwen Li, Xiuhuai Li, Hui Wu, Christoph R. Müller, Wenshuai Chen and Raffaele Mezzenga, 8 June 2026, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2535689123

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