Fostering environmental sustainability of leather industry: environmental impact assessment and improvement prospects for leather-tanning technologies

Because of various negative impacts of chromium intensive manufacturing, the leather-based fashion industry is under pressure to use environmentally friendly tanning technologies. However, there is a lack of scientific research that evaluates the environmental impacts of novel tanning processes. Thus, this study is aimed to quantify and compare the environmental impacts of traditional chromium-based process and a novel metal-free tanning technology. The novel metal-free technology is based on synthetic tannins, instead of metal or vegetable-based tannins. To achieve the objectives, a detailed life cycle assessment was done for 1 m² of finished leather. The primary data were gathered from two different leather manufacturing plants located in the same Italian municipality and the background data were extracted from the Ecoinvent database. SimaPro 9.4 was used as the modeling software tool, and the impacts were evaluated for midpoint impact categories. For the novel metal-free tanning technology, the results revealed a significant reduction in various impact categories, such as particulate matter impacts were reduced by 25%, human toxicity (non-carcinogenic) by 31%, human toxicity (carcinogenic) by 56%, and acidification by 29%. Overall, based on single point performance score, the novel metal-free tanning system showed 18.4% less environmental impacts than the chrome-based tanning. For the most relevant impact categories, the novel metal-free tanning system again showed significantly less impact. The cattle breeding phase contributed most to various relevant impact categories, including acidification, particulate matter, and terrestrial eutrophication. Two alternative scenarios were also developed and evaluated to show how the solar energy may help further reduce the environmental impacts. A sensitivity analysis was also carried out to see the influence of uncertainty linked with the choice of thermal energy source. Overall, the study highlighted how the green tanning technologies and green energy initiatives could help decarbonize and improve the environmental performance of leather manufacturing industry.