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.

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The environmental impacts of typical fatliquors were diagnosed by the life cycle assessment of industrial production and use (post-tanning) processes. Life cycle impact assessment and sensitivity analysis showed that fatliquor and fatliquoring operation were the major contributors to the environmental impacts of post-tanning because a large amount of fatliquors was consumed during fatliquoring operation. The environmental impacts of fatliquors decreased in the following order: chlorinated paraffin (CP) > sulfonated rape oil (SNR) > sulfated rape oil (SR) > phosphated rape oil (PR) > oxidized–sulfited rape oil (OSR). Sulfuric acid, fuming sulfuric acid, and chlorine used for fatliquor modification gave the main contribution to most impact categories for SR, SNR, and CP production, whereas rape oil contributed the most for PR and OSR production. OSR use process reduced the primary energy demand, abiotic depletion potential, and global warming potential by 38.5%, 56.0%, and 48.5%, respectively, compared with CP use process. These results suggested that biomass-derived fatliquors, especially oxidized–sulfited and phosphate modified fatiliquors, helped reduce the environmental burdens in leather manufacturing. Graphical Abstract