Nature offers a wealth of inspiration for architecture and engineering, with many biological materials and structures serving as models for efficient, multifunctional designs, even in their unaltered forms. Among these, the natural biopolymers chitin and keratin stand out for their potential in sustainable material innovation and biomimetic construction. Their hierarchical organization, chemical structure, biodegradability, and inherent functionalities make them compelling alternatives to synthetic materials [1]. Chitin, a polysaccharide composed of β-(1→4)-linked N-acetylglucosamine units, forms crystalline, hydrogen-bonded fibril networks that provide both flexibility and rigidity. Found in marine organisms, arthropod exoskeletons, and fungal cell walls, it is primarily sourced from the food industry, including waste such as shrimp shells and squid pens. Chitin and its derivative, chitosan, offer mechanical stability, bactericidal properties, stunning structural coloration, passive radiative cooling (e.g., inspired by the Saharan silver ant [2]) and pharmaceutical applications such as drug delivery, wound healing, and tissue engineering [3]. Keratin, a versatile cysteine-rich fibrous protein found in feathers, wool, and hooves, features a coiled-coil architecture and multiscale layering, comprising both crystalline and amorphous regions, which enable mechanical resilience, lightweight design, and structural integrity. It offers exceptional thermal insulation and crack redirection mechanisms, making it a valuable model for impact-resistant and earthquake-adaptive constructions. Furthermore, its bactericidal, self-cleaning surface properties, such as those found in gecko skin, hold promise for hygienic, low-maintenance architectural components [4]. By reclaiming waste streams from the food and textile industries, such as shrimp shells, poultry feathers and wool, chitin and keratin exemplify how discarded biological matter can be transformed into high-performance, multifunctional material systems. Their functional properties could enable a wide range of applications: passive radiative cooling, non-toxic structural colouration as an alternative to potentially harmful dyes and coatings, stress- and energy-absorbing architectural systems, reversible adhesive and bactericidal surfaces, biodegradable packaging, as well as thermal insulation and water-repellent elements in building structures. These biologically informed materials support circular design approaches that integrate durability, adaptability, and environmental care, pointing towards a self-sustaining, ecologically integrated architecture [1]. [1] Freigassner, J., van Nieuwenhoven, R. & Gebeshuber, I. (2025). From nanostructure to function: hierarchical functional structures in chitin and keratin. Zeitschrift für Physikalische Chemie. https://doi.org/10.1515/zpch-2024-0913 [2] Zimmerl, M., van Nieuwenhoven, R. W., Whitmore, K., Vetter, W., & Gebeshuber, I. C. (2024). Biomimetic Cooling: Functionalizing Biodegradable Chitosan Films with Saharan Silver Ant Microstructures. Biomimetics, 9(10), 630. https://doi.org/10.3390/biomimetics9100630 [3] Rinaudo, M. (2006). Chitin and chitosan: Properties and applications. Progress in Polymer Science, 31(7), 603–632. https://doi.org/10.1016/j.progpolymsci.2006.06.001 [4] McKittrick, J., Chen, PY., Bodde, S.G. et al. The Structure, Functions, and Mechanical Properties of Keratin. JOM 64, 449–468 (2012). https://doi.org/10.1007/s11837-012-0302-8