Life Cycle Assessment for Chrome Tanning, Chrome-Free Metal Tanning, and Metal-Free Tanning Systems

Life cycle assessment (LCA) was applied to compare environmental impacts of a chrome tanning system (CTS) using basic chrome sulfate (Cr), a chrome-free metal tanning system (CFMTS) using complexes of highly oxidized starch and Al–Zr (HOS–AZ), and a metal-free tanning system (MFTS) using oxidized sodium alginate (OSA). The preparation processes of Cr, HOS–AZ, and OSA were first evaluated by LCA to make the life cycle inventory available for their tanning systems. Life cycle impact assessment results showed that Cr, HOS–AZ, and OSA were the most significant substance factors in their tanning operations. The tanning operation was the main contributor to the environmental impacts of a tanning system followed by retanning and fatliquoring operations. The environmental impacts on resource consumption and climate change presented CTS > CFMTS > MFTS, while those on ecosystem quality and human health were comparable. The MFTS is a more sustainable tanning system for leather production. This work provides basic data support for the ecological design of leather products and gives new insights into the LCA of complex leather processing systems.