Bio-Based Tanning Agents from Olive-Derived Lignin: A Sustainable Alternative for the Leather Industry

In response to growing demands for more efficient and environmentally friendly leather tanning processes, developing sustainable alternatives to conventional tanning agents has become a pressing priority.[1-2] Traditional tanning approaches—such as chrome tanning and the use of vegetable tannins—still fall short in terms of sustainability and environmental impact. [3] This study examines the potential of lignin extracted from olive prunings as a bio-based tanning agent. The lignin was obtained via alkaline fractionation, and its structure was further modified through sulfonation to enhance its solubility and reactivity. Both raw lignin and its sulfonated derivative were tested in various stages of the tanning process, including re-tanning and as auxiliary tanning agents. Due to its aromatic structure and functional groups, lignin shows promise as a filler during the re-tanning phase. Fillers are typically employed to improve leather grain smoothness and compactness, helping to mask imperfections such as insect bites, cuts, and scratches. They also contribute to enhanced durability and compactness of the finished product. Furthermore, lignin can act synergistically with synthetic and vegetable tannins through electrostatic interactions with collagen, providing a sustainable and eco-compatible solution for the leather industry.