ETH Zurich turns dairy and tofu waste into low-energy CO2 captors
ETH Zurich researchers turned cheese and tofu production waste into protein beads that capture 97 mg of CO2 per gram from air, using little energy.
Photo by Jan van der Wolf on Pexels
Researchers at ETH Zurich have built a direct air capture material out of food-industry waste that pulls carbon dioxide from ambient air and releases it again at room temperature, using only a small amount of energy. The method, reported in the journal “Proceedings of the National Academy of Sciences” (PNAS) on 8 June 2026 and described by ETH Zurich on 11 June, turns by-products of cheese and tofu production into porous protein beads. Each gram of the material extracted 97 milligrams of CO2 from the air in laboratory tests.
The work was led by materials scientist Raffaele Mezzenga, a professor in ETH Zurich’s Department of Health Sciences and Technology, with postdoc Zhou Dong as lead author. It targets a known weakness of carbon removal: pulling CO2 out of thin air usually takes a lot of heat and money.
How the direct air capture method works
Dairy and tofu production generate large volumes of protein-rich liquid, only part of which is reused; the rest is discarded. From that waste the team isolates proteins and assembles them into long, thread-like chains called amyloid fibrils. The fibrils are loaded with potassium hydroxide and formed into beads roughly half a centimetre to one centimetre across. Exposed to open air, the potassium hydroxide reacts with CO2 to form hydrogen carbonate — a bicarbonate salt — pulling the gas out of the atmosphere. “The resulting material is like a sponge that can absorb large quantities of CO2 via the potassium hydroxide,” Mezzenga said.
In tests with ambient air, the beads captured 97 mg of CO2 per gram of material, which Dong said is 10 to 50% above the capacity of conventional direct air capture methods. On that basis, one kilogram of beads could in theory bind and isolate about 100 grams of CO2 per cycle.
A low-energy, circular approach
Conventional direct air capture releases the trapped CO2 by applying heat and reduced pressure — an energy-heavy step that makes the technology viable mainly where cheap renewable power is on hand. The ETH team instead sprays the beads alternately with a mild acid and a mild base for about ten minutes at room temperature, breaking the chemical bonds so the CO2 can be drawn off. The acid, base and beads can all be reused. In the laboratory, the researchers ran 30 capture-and-release cycles without a notable loss of efficiency. “By contrast, our protein beads remain stable for a long time,” Dong said.
Mezzenga expects the beads would need replacing after a few thousand cycles, as their capacity falls. Because they are made entirely of organic, readily degradable material, spent beads could then be used as fertiliser in agriculture or converted into biofuel — closing a loop rather than creating new waste. Food waste is usually framed as a kitchen problem, the subject of advice such as Winss Solutions’ ten tips to prevent food waste; here an industrial by-product becomes the feedstock for carbon removal. The researchers add that the materials are non-toxic and food-grade, and that a life-cycle analysis found the method causes less environmental harm across its full life than other direct air capture routes.
| Measure | Value |
|---|---|
| CO2 captured per gram of beads | 97 mg (ambient air) |
| Capacity vs conventional DAC | 10–50% higher |
| Theoretical capture per kg of beads | ~100 g CO2 per cycle |
| Bead diameter | 0.5–1 cm |
| CO2 release conditions | Mild acid + base spray, ~10 min, room temperature |
| Reuse cycles tested | 30, without notable efficiency loss |
| Estimated material lifetime | Up to a few thousand cycles |
| Lab-scale CO2 bound and isolated | ~50 g, from a few grams of beads |
Source: ETH Zurich; Dong et al., “Circular and athermal atmospheric CO2 capture by waste-derived amyloid sorbents”, PNAS, 8 June 2026.
Scalability and cost still to be proven
For the published study the method was tested in a controlled laboratory with a few grams of beads, binding and isolating about 50 grams of CO2. Whether the high capture rate holds at larger volumes is not yet established. The team has also not calculated a cost per tonne of captured CO2, though Mezzenga expects it to come out markedly lower than conventional direct air capture because the process uses little energy and a widely available waste feedstock. He noted that the spray system used to free the CO2 is built around techniques already common in industry. Dong will examine scalability next.
The wider context is that removing CO2 from the air is only one half of climate strategy. Scenarios for holding warming to 1.5°C still depend chiefly on cutting emissions, the aim behind packages such as the EU’s “Fit for 55” climate plan, and on understanding where emissions are concentrated, as set out in the status of carbon emissions in China, the USA and Europe.
Background: direct air capture and ETH Zurich
Plans to hold global warming to 1.5°C, including the scenarios in the latest Intergovernmental Panel on Climate Change assessment, rely on removing hundreds of billions of tonnes of CO2 from the atmosphere over this century alongside steep emission cuts. Direct air capture is one route, pulling CO2 straight from open air for storage or reuse. Climeworks, founded as an ETH spin-off in 2009, was among the first companies to operate it commercially, yet the process has remained energy-intensive and expensive. Mezzenga has worked with amyloid fibrils for nearly two decades, previously using them to make biodegradable alternatives to plastics and techniques for water purification. The new study, published as “Circular and athermal atmospheric CO2 capture by waste-derived amyloid sorbents” (DOI 10.1073/pnas.2535689123), applies that material to carbon removal — with the team now testing whether laboratory results carry over to industrial scale.
Sources: PNAS; ETH Zurich; ScienceDaily
Featured image: photo by Jan van der Wolf on Pexels (free Pexels license).
Become a Sponsor
Our website is the heart of the mission of WINSS – it’s where we share updates, publish research, highlight community impact, and connect with supporters around the world. To keep this essential platform running, updated, and accessible, we rely on the generosity of you, who believe in our work.
We offer the option to sponsor monthly, or just once choosing the amount of your choice. If you run a company, please contact us via info@winssolutions.org.
I specialize in sustainability education, curriculum co-creation, and early-stage project strategy. At WINSS, I craft articles on sustainability, transformative AI, and related topics. When I’m not writing, you’ll find me chasing the perfect sushi roll, exploring cities around the globe, or unwinding with my dog Puffy — the world’s most loyal sidekick.
