Natural Leathers from Natural Materials:  Progressing toward a New Arena in Leather Processing

• Published in: Environmental science & technology Vol. 38; no. 3; pp. 871 - 879
• Main Authors: Saravanabhavan, Subramani, Thanikaivelan, Palanisamy, Rao, Jonnalagadda Raghava, Nair, Balachandran Unni, Ramasami, Thirumalachari
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.02.2004
• Subjects: Animals; Applied sciences; Cattle; Chemical contaminants; Conservation of Natural Resources; Environmental cleanup; Exact sciences and technology; Global environmental pollution; Hair; Hydrogen-Ion Concentration; leather; Leather & leather products; Microscopy, Electron, Scanning; near zero pollution load; Other techniques and industries; Pollution; pollution load; processing technology; Skin; Studies; tanning; Tannins - chemistry; Textile Industry; Water - chemistry; Water Pollutants, Chemical - analysis; Water Pollution - prevention & control; Biotechnology; Pollution prevention; Enzymatic catalysis; Tannery; Wasteless technology; Biocatalyst; Depilating; Industrial waste; Tanning(technique); Industrial waste water; Environment impact; Leather industry; Water quality; Liming; Water pollution; Manufacturing; Environmental protection
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/es034554o

Globally, the leather industry is currently undergoing radical transformation due to pollution and discharge legislations. Thus, the leather industry is pressurized to look for cleaner options for processing the raw hides and skins. Conventional methods of pre-tanning, tanning and post-tanning processes are known to contribute more than 98% of the total pollution load from the leather processing. The conventional method of the tanning process involves the “do−undo” principle. Furthermore, the conventional methods employed in leather processing subject the skin/hide to a wide variation in pH (2.8−13.0). This results in the emission of huge amounts of pollution loads such as BOD, COD, TDS, TS, sulfates, chlorides and chromium. In the approach illustrated here, the hair and flesh removal as well as fiber opening have been achieved using biocatalysts at pH 8.0, pickle-free natural tanning employing vegetable tannins, and post-tanning using environmentally friendly chemicals. Hence, this process involves dehairing, fiber opening, and pickle-free natural tanning followed by ecofriendly post-tanning. It has been found that the extent of hair removal and opening up of fiber bundles is comparable to that of conventionally processed leathers. This has been substantiated through scanning electron microscopic analysis and softness measurements. Performance of the leathers is shown to be on par with conventionally chrome-tanned leathers through physical and hand evaluation. The process also exhibits zero metal (chromium) discharge and significant reduction in BOD, COD, TDS, and TS loads by 83, 69, 96, and 96%, respectively. Furthermore, the developed process seems to be economically viable.