Leather is a long contested material – hated by vegetarians and vegans as an animal byproduct but revered by many as a durable and luxurious material for clothing, furniture, books and more. No matter where you stand on the leather debate, it is certainly true that the tanning industry leaves a lot to be desired on the environmental front. The main reason for this is the tanning process used industry wide. Although there is now an expanding demand for naturally tanned leather, and those products are making their way onto the market, it’s worth it to explore the most common tanning processes and their environmental impact.
Tanning is the process by which animal skin is actually turned into leather. In modern tanning, this takes place in multiple stages:
1. Basic Preparation – Preparation begins with treating the hide with salt, or curing, which removes collagen, bacteria and water from the hide to prevent rotting. There are several methods of curing hides including brine curing and wet-salting – all techniques occur at a low temperature to further reduce chance of bacteria. The hides are then rinsed and rehydrated for the next process.
2. Un-hairing – At this point the leather is treated to remove the hair. Various chemicals can be used in this process, the idea being to break down the hair while leaving the skin of the hide itself intact. Ultimately a machine is used to remove the hair from the hide.
3. The hides are then treated with a combination of salt and sulphuric acid to soften it again for processing.
4. The tanning itself occurs – and can be accomplished in two ways:
a. Vegetable Tanning – This method involves the use of tannin – from which Tanning gets its name. Using the barks of various trees from which tannin can be extracted, the hide is stretched and then soaked in a tannin concentrated bath for several weeks. Different concentrations of tannin produce different tanning results.
b. Mineral Tanning – This method uses chemicals and minerals, primarily chromium sulfate to tan the material in a similar method to that of the vegetable tanning. This method is much faster but produces more effluent chemical waste.
5. Finally, the hide may be oiled, waxed, dyed, rolled or shaved depending on the desired outcome.
The problems with this process are many. Not only are many chemicals used in the standard process – because obviously modern tanneries are more attracted to the speed and efficiency of mineral tanning – usually discarded without regard to the environment, but the amount of water and power used to complete leather tanning are also environmentally damaging.
In September of 2008, Hands On completed a study of the tanning industry in Pakistan, one of the largest epicenters of leather tanning in the world. The environmental challenges included some of the following:
o Inefficient Water Use – in some cases over three times the estimated amount of water actually needed for the process of rinsing and soaking the hides throughout the process.
o Polluted Waste Water – not only are many factories using too much of this valuable resource, but the waste water is merely dumped back into the local environment with little or no treatment to remove chemical waste.
o Solid Waste – Untanned and tanned solids are also thrown away and fed back into local markets for waste materials. This can be as much 12,000 lbs per day from a tannery processing 22,000 lbs of hide for tanning per day. Many of these waste materials are exposed to chromium which means potential chemical leeching into the local environment and some waste materials are used by industries like glue manufacturers and poultry feed processors – but again chromium has been used and can pollute chicken feed and the chickens sold by those companies.
o Air Emissions – in most tanneries, any chemicals that are used can cause air pollution – like ammonia and hydrogen sulphide, and these tanneries often use diesel engines and generators to power plants and boilers which create CO2 emissions.
The good news is that new eco-friendly tanneries are being built – in fact, one is opening up in 2009. Understanding the environmental impact of materials that are so often used and sold in the US, like leather, is an important step towards becoming more environmentally aware, and in choosing companies that support eco-friendly business practices and materials.
For example, there are several shoe companies who are using sustainable leather, or who are planning to purchase leather from environmentally conscious providers. In fact, New Balance sneakers, Timberland shoes, Simple Shoes and Keen shoes all plan to purchase leather from the new eco-friendly tannery in Vietnam opening next year. Support companies that support sustainable leather manufacturing and understand the impact of you fashionable style!