Environmental performance of three innovative leather production processes using less chromium and water

Leather production contributes positively to economic developments but can create severe environmental impacts, due to the associated consumptions of water and chemicals. The substance of main concern is the basic chromium sulphate, widely used as tanning agent, which provides high-technical performance to the finished leather. This study quantifies the environmental sustainability of a conventional leather production process and those of three innovative processes, characterised by limited consumptions of chromium and water. Standardised life cycle assessments were implemented, with reference to the production chains starting from pickled skins until the production of two finished leathers (for goods and footwear), having the same technical and aesthetic characteristics of those from the conventional process. The innovative tanning processes adopt conventional rotating drums or substitute them with spray nozzles or aerosol rooms, and require a specific pre-treatment that includes de-pickling, drying and stabilisation of input skins. Tests at industrial scale (or at pilot scale for the solution with aerosol rooms) indicate that the new processes strongly reduce impacts in terms of Human toxicity-cancer, Ecotoxicity freshwater and Resource use-minerals and metals (up to 57 %, 29 % and 48 %, respectively) even though they imply an increase in terms of Climate Change (up to 51 %). Losses of chromium in wastewater and solid waste are reduced from >33 g/m²_{finished leather}, for the conventional process, to about 8 g/m²_{finished leather}, 5 g/m²_{finished leather}, and 1 g/m²_{finished leather}, for the innovative processes.

The environmental sustainability of the proposed new processes increases from the solution with drums (and less water and chromium) to that utilising spray nozzles and aerosol rooms. A great improving can be obtained even just with the “simple” new drum solution, able to reduce the Human toxicity-cancer potential up to 53 % and Resource use-minerals and metals potential up to 42 %.