Leather is often framed as a byproduct of meat and dairy, but considering the scale of the industry and ubiquity of leather in clothing worldwide, it’s easy to see why it should be considered as an industry in and of itself. We know that raising cows for food can be incredibly damaging to the environment, and when we look more closely at leather production, we can see that those environmental impacts don’t end with cows’ deaths.

This study was primarily focused on the impact of three post-tanning processes: retanning, fatliquoring, and dyeing. Retanning is just what it sounds like: putting tanned leather through the tanning process again. Fatliquoring involves injecting oil into the leather before it dries such that every fiber is uniformly coated. Dyeing is the process of turning the leather different colors, such as red or blue, using substances that chemically bond to it. 

To examine the environmental effects of each step, a life-cycle assessment (LCA) was performed. LCAs typically involve looking the effects and requirements of a material from the point of extraction through processing, manufacturing, distribution, use, and disposal. LCAs were conducted for four items: the most common tanning chemical: basic chromium sulfate, two fatliquoring agents: sulpho chlorinated paraffin and epoxidized vegetable oil, and azo dyes, a common type of leather dye. The data used comes mostly from a tannery district in Tuscany, Italy. Italy is the main leather producer in the E.U. and accounts for nearly 20% of global leather production. However, the production process is usually on a smaller scale in Italy than in most other leather-exporting nations.

Several categories of environmental damage were considered: climate change, ozone depletion, terrestrial, freshwater, and marine eutrophication, human, terrestrial, freshwater, and marine toxicity, photochemical oxidant formation, particulate matter, ionizing radiation, and water, metal, and fossil depletion. Each LCA was done for the amount of each material necessary to produce 1kg of dyed crust leather, and energy and water were assessed as coming from standard Italian sources.

The production of electricity required for these processes was found to be the primary driver of most categories of damage. Greenhouse gas emissions mostly came from power production, as did most of the chemicals involved in ozone depletion and human, terrestrial, freshwater, and marine toxicity. However, some direct effects of these processes can be seen. Wastewater from retanning was found to be a major contributor to marine eutrophication, and the production of basic chromium sulfate was responsible for most metal depletion. 

The researchers found that the fatliquoring process would be less harmful with sulpho-chlorinated paraffin compared to expoxidized vegetable oil. They also saw room for improvement in solid waste recapture and reuse, as well as water consumption. Still, they argue that switching to clean power would have a greater effect than any actual production changes. It should be stressed that while electricity production was the leader in most categories, direct negative effects were observed from all of these processes.

It is worth mentioning that the E.U. has fairly stringent environmental laws. China, India, and Brazil are also major leather exporters, and have weaker environmental protections than those that bind Italy. Furthermore, these LCAs did not look at the impact of the cows themselves, who produce greenhouse gas emissions and require significant amounts of food and water. Nor was the initial tanning process considered, which has been linked to serious pollution near Indian tanneries. 

Therefore, this study is somewhat limited in its scope. It shows that these three steps, if performed in a country with good infrastructure and strict environmental protections, can be made less harmful. However, it tells us little about the true impact of leather, from the raising of the cow to the initial skinning and tanning to the finishing process. We also need to look at the differences in production between countries, especially ones with poorer infrastructure and lax environmental regulations. 

For animal advocates, the study provides good details about leather production that can be directly used in anti-leather advocacy, or included in vegan advocacy more broadly.