Silica aerogels are among the lightest and most-insulating materials in the world. Made of ultraporous 3D networks of silica nanoparticles, they are mostly air. This airiness helps aerogels block heat flow from electric vehicle batteries and industrial pipelines. But the particles are connected weakly, and the material releases these harmful nanoparticles during use. Aerogels are also fragile, so manufacturers reinforce them with glass or ceramic fibers.
Researchers have now strengthened aerogels with keratin-rich wool and feather waste (ACS Mater. Lett. 2026, DOI: 10.1021/acsmaterialslett.6c00333). The waste-based aerogels withstand temperatures up to 500 °C and don’t shed hazardous silica dust, as conventional aerogels do.
The use of biobased waste also makes them sustainable and potentially much cheaper, says Shanyu Zhao, a materials chemist at Empa, the Swiss Federal Laboratories for Materials Science and Technology. “Our industrial partners say that ceramic or glass fiber is one of the main costs of their material. It’s a more expensive part of their product than silica aerogel.”
Keratin is a tough protein with many chemically reactive functional groups. The world produces millions of tons of waste wool, feathers, and hair every year, a cheap source for keratin, Zhao says.
To make the reinforced aerogel, Zhao, Wim J. Malfait, Diego O. Sanchez Ramirez, and colleagues start with wool fibers and first remove some of the keratin for use in other applications. This leaves behind a residue of sulfonated keratin and rigid fibers, which they treat with an alkaline solution.
They then add the pH-treated waste to a silica gel and remove the liquid by supercritical drying. During the process, sulfonated keratin coordinates with the silica particles. The particles attach to the fiber surfaces via hydrogen bonds between hydroxyl groups on the silica and the fibers, Zhao speculates.
The pH treatment is key, because it roughens the fiber surfaces and enhances their interaction with silica, resulting in a uniform and continuous silica coating on the fibers. This tight physical and chemical interaction minimizes silica-particle release, making the material virtually dust-free, and gives the composite impressive heat-resistance and insulation properties, Zhao says.
Although wool begins to degrade at around 200 °C, the composite aerogel survived temperatures up to 500 °C, he says. “After 300 °C, you start to carbonize some of the wool material, but you still have the silica aerogel, which protects the keratinous waste.”
Besides its record-low thermal conductivity, the material’s reduced dust release and upcycling of an underused keratinous waste stream are valuable, says Hyung-Ho Park, director of the Aerogel Materials Research Center at Yonsei University. One major limitation could be durability under real-world conditions, though. Keratin is organic, so long-term exposure to heat, oxygen, humidity, and compression could affect its properties, he says. “Overall . . . this is a clever and meaningful step toward more-sustainable, mechanically robust silica-aerogel insulation.”
