Scientists at ETH Zurich have transformed food waste into tiny beads that pull carbon dioxide from the air far more efficiently than today's industrial methods. Using whey from dairy processing and byproducts from tofu manufacturing, materials scientist Raffaele Mezzenga and his team have created protein-based carbon capture material that outperforms conventional direct air capture systems by 10 to 50 percent—a breakthrough that could reshape how the world tackles atmospheric greenhouse gases.
The climate stakes make this innovation urgent. According to the Intergovernmental Panel on Climate Change, limiting warming to below 1.5°C requires not just cutting future emissions, but removing hundreds of billions of tons of CO2 already in the air. Direct air capture (DAC) has emerged as a critical technology, with companies like Climeworks—itself an ETH Zurich spin-off founded in 2009—already deploying systems globally. Yet traditional DAC remains expensive and energy-intensive, a barrier that limits where and when it can be deployed.
Mezzenga's team saw opportunity in the waste streams of food production. Enormous volumes of protein-rich liquid are generated during dairy and tofu manufacturing; much of it is simply discarded. The researchers extracted these proteins and assembled them into long, thread-like structures called amyloid fibrils, then combined them with potassium hydroxide and formed them into porous beads roughly half a centimeter to one centimeter across. The result, Mezzenga explains, "is like a sponge that can absorb large quantities of CO2 via the potassium hydroxide."
When exposed to air, the potassium hydroxide inside the beads reacts with atmospheric CO2, producing hydrogen carbonate—effectively scrubbing carbon from the air. In laboratory tests with ambient air, postdoctoral researcher Zhou Dong extracted 97 milligrams of CO2 from just one gram of material. That single kilogram of beads could theoretically capture roughly 100 grams of CO2 in a single operating cycle, a performance level that significantly exceeds existing technologies.
What truly distinguishes this approach is how energy-efficient it is at the release stage. Conventional DAC systems rely on heat and negative pressure to free captured CO2, consuming substantial energy in the process. Mezzenga's team developed an alternative: they spray the beads alternately with mild acid and mild base for roughly ten minutes at room temperature. This gentle cycling breaks the chemical bonds holding the CO2, allowing collection without the energy penalty of heated systems. Because all three components—the acid, base, and protein beads—can be reused, the method aligns with circular economy principles.
Laboratory testing revealed the beads maintained their performance through 30 consecutive capture-and-release cycles with no significant efficiency loss. While Mezzenga estimates that replacement would eventually be needed after several thousand cycles, the beads' entirely organic composition means they can be repurposed as agricultural fertilizer or converted to biofuel—waste becomes resource once more. Life cycle analysis confirmed the technology generates less environmental pollution over its full lifespan than existing DAC methods.
The team conducted their initial work in controlled laboratory settings with small quantities of material, capturing roughly 50 grams of CO2. Scaling to industrial operations remains the next critical hurdle, and additional testing will be essential to verify that the beads maintain their exceptional efficiency at larger volumes. Yet Mezzenga, who has spent nearly two decades studying amyloid fibrils, remains optimistic about the path ahead. With climate urgency mounting and atmospheric CO2 concentrations continuing to rise, solutions that turn food waste into carbon removal tools offer a compelling vision of what climate innovation can be.