Analysis of the environmental impacts of waterproofing versus conventional vegetable tanning process - A life cycle analysis study

Waterproofed vegetable leather is desired for its “greenness” in front of chromium-tanned waterproofed leather. However, conferring waterproofing capabilities to vegetable tanned leather maintaining light color and a soft touch is a fact of great concern for leather goods producers. Sustainable and technical requirements are currently demanded by high-quality brands in order to pass the threshold established by Leather Working Group (LWG) initiatives to earn their environmental audit seal. The research work has focused on testing various mineral salts and hydrophobic products compatible with vegetable tanned leather. According to the obtained results, acrylic copolymers along with zirconium salts are necessary to achieve the desired leather properties. The present study provides the environmental comparison of a new vegetable tanning process to give waterproofing capabilities with the conventional vegetable tanning process. The comparison comprises both wastewater analysis and environmental impacts in a life cycle assessment (LCA) framework. The paper also outlines the comparison using different life cycle impact assessment (LCIA) methods. Further, the study provides specific data on leather vegetable tanning processes. Comparative analysis has been focused on the two diverging stages for both conventional and waterproofing vegetable tanning processes, namely retanning and fatliquoring. Conventional process environmental impacts are lower than waterproofing process impacts according to LCA methodology. However, wastewater analysis shows no major differences between both processes. Main contributors to these results are the zirconium salts, dispersing agents and acrylic copolymers used along with an increase in energy consumption due to processing times. Alternative methods used in the impact assessment lead to similar results, revealing no major differences in the comparative results between methods in this case.