Multitechnique Physicochemical Characterization of Horse Hoof Trimmings as Sustainable and Untapped Keratin Source

In the keratin-rich biomass scenario, horse hoof trimmings play a marginal role due to the limited volume and the scarce background on material features, despite added values such as cruelty-free, localized and routine production and traceability. This work presents a multitechnique characterization of horse hooves, including physicochemical, structural, thermal, and compositional analysis, providing a solid background knowledge of material features, mandatory for upcycling strategy definition. FT-IR, Raman spectroscopy, X-ray powder diffraction, SEM-EDX, thermogravimetric analysis, and elemental characterization are conducted on powdered samples obtained using various approaches. The material exhibited structural features typical of hard α-keratin, with semicrystalline organization and high thermal stability. A relatively high higher heating value (21.9 MJ kg^-1) highlights its potential for energy recovery routes, while structural robustness suggests suitability for material-oriented valorization pathways. Lastly, the issue of metal contamination, attributable to shoeing practices, is systematically evaluated and correlated with shoeing habits, sampling region, and milling. Overall, this study positions horse hoof waste as a promising alternative keratin-based biomass and provides the necessary physicochemical framework to support its integration into circular bioeconomy strategies.