Comparative Evaluation of Metal-Free Vegetable Tanning for Tilapia Leather Using a DOE–QFD–FMEA Framework Toward Cleaner Production

[Cr(VI)] released from conventional chrome-tanned leathers poses severe environmental and occupational risks and complicates the circular use of tannery wastes. Valorizing tilapia skins into leather requires chromium-free tanning to meet footwear requirements. This study integrates Design of Experiments (DOE), Quality Function Deployment (QFD), and Failure Mode and Effects Analysis (FMEA) to compare three vegetable tanning systems – mimosa, quebracho, and tara – against a chrome-tanned reference for tilapia leather. DOE quantifies vegetable tanning agent type effects and formulation level on shrinkage temperature, tensile strength, elongation at break, and thickness; QFD translates the voice of footwear designers into weighted technical priorities; and FMEA evaluates chrome-tanned risks. Mimosa had the highest vegetable-system shrinkage temperature (∼ 80 oC mean), yet failed to consistently meet the ≥ 80 oC QFD target. Tara and quebracho exhibited superior tensile strength and elongation at break, with lower thickness variability. While vegetable systems still lag behind chrome tanning (26.8 ± 2.7Nmm2) in mechanical performance, they reduced overall RPNs by ∼60% versus chrome-tanned benchmarks. Thus, tara and quebracho offer the most balanced performance for metal-free tilapia leather, whereas mimosa is best suited as a stabilizing agent in blends. The integrated DOE–QFD–FMEA framework provides transparent, decision-ready support for cleaner production transitions in leather and other bio-based materials.