Leather tanning: Life cycle assessment of retanning, fatliquoring and dyeing

Tanneries boost the local economic development, but lead to severe environmental pollution; hence, improving the environmental assessment of this sector is essential. In this paper, the Life Cycle Assessment method was applied to estimate impacts on the environment and human health of retanning, fatliquoring and dyeing. The analysis was performed from a “gate to gate” perspective. Moreover, sulpho chlorinated paraffin and epoxidized vegetable oil have been evaluated as alternative fatliquoring agents. The production of electricity required for the rotation of drums gives the main contribute to most of the impact categories, followed by the azo-dye production. Emissions of sulfur dioxide, nitrogen oxides, manganese, vanadium and nickel associated to power plants are the main sources of terrestrial acidification and particulate matter formation, as well as of human and marine toxicity (4.48·10−1 and 1.09·10−2 kg of 1,4-DBeq kg−1 crust leather, respectively). Nitrate loads from wastewater treatment and oxidative treatments affect heavily marine eutrophication (6.9·10−1 g N eq kg−1 crust leather). The use of epoxidized vegetable oil would affect human toxicity, ecosystem, metal and water resources depletion more than the use of sulpho chlorinated paraffin, mainly due to pesticides distribution and other cultivation practices. Phosphate and nitrate releases due to fertilization determine the high impact on the categories freshwater and marine eutrophication. Progress in increasing the conversion efficiency is demanded, but overall focus must be made on the substitution of fossil fuels with cleaner alternatives. The transition towards a circular economy is encouraged; increasing rates of reduction, reuse, recycle and recover of solid waste and tannery effluents are recommended. Agricultural practices with a reduced consumption of phytosanitary products and mineral fertilizers, alternative to conventional farming, would strongly contribute to increase the sustainability of epoxidized vegetable oil as alternative fatliquoring agent.