Upcycled Keratinous Waste Enables Robust, Dust-Free Silica Aerogel Superinsulators

Keratin extraction generates large amounts of underutilized waste streams that are typically discarded despite retaining functional molecular components. Here, keratinous waste composed of cysteine-S-sulfonated keratin (CSSK) and non-dissolved fibers (NDF) is directly upcycled to reinforce silica aerogels via a co-gelation strategy. Partial dissolution of CSSK and structural bridging by NDF enable the formation of an interconnected hybrid network with enhanced interfacial coupling. pH modulation governs both interfacial interactions and pore architecture: alkaline conditions promote homogeneous silica deposition and stronger bonding, whereas acidic conditions induce a denser, microporous structure. The resulting composites exhibit improved mechanical robustness and reduced dust release. All samples show superinsulating behavior (λ < 26 mW m−1 K−1), with thermal transport determined by the interplay between the pore structure and density. Under a combined thermal gradient (∼300/∼65 °C) and compressive load, the composite materials maintain structural integrity and stable insulation performance, demonstrating suitability for harsh environments.