3D-printable circular composites as sustainable leather alternative for the valorization of tanneries' solid waste

The leather industry has environmental impacts due to tanning processes and produces substantial solid waste, with up to 80% of treated hides not disposed of sustainably. The fashion industry is seeking bio-based alternatives to genuine leather and exploring innovative technologies for the on-demand customization of accessories. This study aims to optimize a bio-based, circular, and 3D-printable composite material as an alternative to vegetable-tanned leather, employing glutaraldehyde-treated leather scraps. A versatile composite was optimized, including up to 30%(w/w) of glutaraldehyde-treated leather shavings and 55%(w/w) of hydrolyzed bacterial cellulose as fillers embedded in a gelatin-glycerol matrix. This material can be dried into sheets, acting both as a leather alternative and a printing plate for the same material in a water-based form, enabling the customization of the composite leather alternative sheet. The dried composite reached mechanical properties akin to vegetable-tanned leather grain (Tensile strength: 3.8MPa, Deformation at break: 20.1%, Young's modulus: 210.2MPa). The waterborne composite showed the required rheological properties for Direct Ink Writing. The extrudable material was successfully 3D-printed, employing the composite as a printing plate, simulating the personalization of leather alternative. These findings valorized leather waste to produce customized circular leather and leather-like alternative via additive manufacturing, promoting sustainable and avant-garde practices in the fashion sector.