As the world seeks effective solutions for climate change, direct air capture (DAC) technology is gaining traction. This innovative method focuses on extracting CO2 directly from the atmosphere. Among the pioneers in this field is Climeworks, a spin-off from ETH Zurich, founded in 2009. Despite significant advancements, the high costs and energy demands of current DAC systems remain a challenge.
Turning Food Waste into Carbon Solutions
Researchers at ETH Zurich have unveiled a groundbreaking carbon capture material derived from an unexpected source: waste from dairy and tofu production. In a recent study published in PNAS, a team led by materials scientist Raffaele Mezzenga describes how they utilized whey and byproducts from tofu to create a CO2-absorbing material.
During the manufacturing process of dairy and tofu, a substantial amount of protein-rich liquid is generated, with much of it going to waste. The researchers extracted proteins from this excess and fashioned them into long, thread-like structures known as amyloid fibrils. These fibrils were then combined with potassium hydroxide, forming porous beads that range from half a centimeter to one centimeter in diameter.
"The resulting material acts like a sponge, absorbing significant quantities of CO2 thanks to the potassium hydroxide," explains Mezzenga.
Exceptional Carbon Capture Efficiency
When exposed to air, the potassium hydroxide within these beads reacts with CO2, producing hydrogen carbonate, a salt of carbonic acid, effectively sequestering carbon from the atmosphere. "In our experiments with ambient air, we successfully extracted 97 milligrams of CO2 per gram of material," states Zhou Dong, a postdoctoral researcher and lead author of the study. This performance surpasses traditional DAC technologies by 10 to 50 percent, with one kilogram of these protein beads potentially capturing around 100 grams of CO2 in a single cycle.
Energy-Efficient Carbon Extraction
Conventional DAC systems often rely on heat and negative pressure to release captured CO2, which can be energy-intensive. In contrast, the ETH Zurich team developed a novel method that involves alternately spraying the protein beads with a mild acid and base at room temperature for about 10 minutes. This technique effectively breaks the chemical bonds holding the CO2, allowing for its collection.
The materials used in this process are reusable, with the protein beads demonstrating remarkable stability over time. Laboratory tests revealed that the beads maintained their efficiency across 30 cycles of carbon capture and release. Once their effectiveness declines, they can be repurposed as agricultural fertilizer or converted into biofuel, aligning with a circular economy model.
Future Potential of the Technology
While the initial results are promising, further testing is essential to assess the technology's scalability for industrial applications. Mezzenga is optimistic, having spent nearly 20 years researching amyloid fibrils for various sustainable applications. He believes that the spray-based CO2 release system is compatible with existing industrial processes, paving the way for future advancements.
Although the exact cost of capturing CO2 with this new material is yet to be determined, Mezzenga anticipates it will be significantly lower than traditional DAC systems. "Our technology is more affordable and sustainable, utilizing readily available waste products," he concludes, suggesting it could revolutionize CO2 removal strategies in the future.
