One of my favroite blogs for scientific information about eco fashion is oecotextiles. This is a very informative piece on leather and the process of tanning the leather. Can leather really be eco? What should be the criteria we use to define eco in leather goods? A must read for all shoe and bag lovers.
Aalthough I have taken the liberty to highlight some words that is the only change and /or addition I have made to this original article.
What about chrome-free, or “eco” leather?
With the increased interest in avoidance of certain chemicals and industrial products that are particularly harmful to our environment, it’s not surprising that manufacturers are becoming ingenious in pointing out attributes that play to this script. So we now see claims for “chrome free” leather, or for “eco friendly” leather.
In last week’s post, I pointed out two kinds of leather tanning – chromium and vegetable. Although most leather is tanned using chromium (from 80 – 95% of all leather produced) there is a third type of leather tanning, called aldehyde tanning, which like vegetable tanning does not use chromium. Let’s revisit leather tanning for a minute:
- Sometimes leather manufacturers will tell you that they don’t use the toxic form of chromium in tanning – the toxic form is called chromium IV or hexavalent chromium. And that is correct: chromium tanned leathers use chromium III salts (also called trivalent chromium) in the form of chromium sulfate. This form of chromium is found naturally in the environment and is a necessary nutrient for the human body. However, the leather manufacturers fail to explain that chromium III oxidizes into chromium IV in the presence of oxygen combined with other factors, such as extremes in pH. This happens during the tanning process. Chromium-tanned leather can contain between 4 and 5% of chromium  – often hexavalent chromium, which produces allergic reactions and easily moves across membranes such as skin. End of life issues, recovery and reuse are a great concern – chromium (whether III or IV) is persistent (it cannot be destroyed) and will always be in the environment. Incineration, composting and gasification will not eliminate chromium.
- Vegetable tanning is simply the replacement of the chromium for bark or plant tannins – all other steps remain the same. And since there are about 250 chemicals used in tanning, the replacement of chromium for plant tannins, without addressing the other chemicals used, is a drop in the bucket. Last week I mentioned some of the other 249 chemicals routinely used in tanning: alcohol, coal tar , sodium sulfate, sulfuric acid, chlorinated phenols (e.g. 3,5-dichlorophenol), azo dyes, cadmium, cobalt, copper, antimony, cyanide, barium, lead, selenium, mercury, zinc, polychlorinated biphenyels (PCBs), nickel, formaldehyde and pesticide residues. Here are the steps to creating leather :
- Aldehyde tanning is the main type of leather referred to as “chrome-free”, and is often used in automobiles and baby’s shoes. Aldehyde tanning is often referred to as “wet white” due to the pale cream color it imparts to the skins. But aldehydes are a group of chemicals that contain one chemical which many people are familiar with: formaldehyde. And we all know about formaldehyde: it is highly toxic to all animals; ingestion of as little as little as 30 mL (1 oz.) of a solution containing 37% formaldehyde has been reported to cause death in an adult human and the Department of Health and Human Services has said it may reasonably be anticipated to be a carcinogen. Aldehyde tanning essentially uses formaldehyde, which reacts with proteins in the leather to prevent putrefication. BLC Leather Technology Centre, a leading independent leather testing center, states that leathers should contain no more than 200ppm of formaldehyde for articles in general use. If the item is in direct skin contact this should be 75ppm, and 20ppm for items used by babies ( Yet that far exceeds levels set elsewhere – in New Zealand, for example, acceptable levels of formaldehyde in products is set at 100 ppm – the European Union Ecolabel restricts formaldehyde to 20 ppm for infant articles, 30 ppm for children and adults, while GOTS prohibits any detectable level.
BLC Leather Technology Centre Ltd. commissioned a study by Ecobilan S.A (Reference BLC Report 002) to do a life cycle analysis to evaluate the various tanning chemicals, to see if there was an environmentally preferable choice between chrome, vegetable and aldehyde based processes. The result? They found no significant differences between the three – all have environmental impacts, just different ones. These LCA’s demonstrate that tanning is just one of the impacts – other steps may have equal impacts. Chrome was sited as having the disadvantage of being environmentally persistent. “Another consideration, in terms of end-of-life leather or management of chrome tanned leather waste, is the possibility of the valency state changing from the benign Cr III to the carcinogenic Cr VI.”
So much for “chrome free” leather. What about claims for “eco leather”?
In the strict sense of the definition, the term “eco leather” is meaningless. However, retailers want to imply improved environmental performance. So how can you evaluate their claims for “eco leathers”?
There are two main considerations in making leather:
- How is it manufactured?
- What inputs are used to produce it?
Research has shown that a significant part of the environmental impact of leather is in the manufacturing process. In this respect it is the environmental stewardship practice of tanners coupled with chemical selection that should determine how eco friendly a leather is. The following areas of leather manufacture have the most significant potential impact:
- Management of restricted substances
- Energy consumption
- Air emissions
- Waste management (hazardous and non hazardous)
- Environmental management systems
- Water consumption
- Control of manufacturing processes
- Effluent treatment
- Chrome management
- Traceability of material
In terms of the selection of inputs, we should consider the use of certain materials that could give an improved eco profile to leather. These include:
- Biodegradable wetting agents for soaking
- Reduced sulphide processing
- Non synthetic or polymeric re-tannage systems
- optimized dyestuffs
- Vegetable oil based fatliquors
- Optimised finishing systems to reduce waste such HVLP or roller coating
- Biodegradable in 12 months or less
In summary, although there is no current definition, these are the key elements which should determine an “eco leather”:
- Control of leather manufacturing processes
- Clean technology chemical selection in the process
- Effective management of restricted substances within the leather
- A measure of the end of life impact
As I mentioned in last week’s post, the production of leather can be a hellish life for the animal. I have found only one company, Organic Leather, which looks beyond the production of the leather itself to the important questions of animal husbandry and land management practices which provide the skins, and incorporate these into a tanning process which “prevents further toxicity entering our environment and our bodies.”
The Leather Working Group (LWG) is a multi-stakeholder group, whose purpose is “to develop and maintain a protocol that assesses the compliance and environmental performance of tanners and promotes sustainable and appropriate environmental business practices within the footwear leather industry.” The LWG, in conjunction with BLC Leather Technology Center Ltd., operates an eco rating system for leather. (This sort of mark is known as a first or second party certification, and lacks – I believe – the credibility of a true third party certification.) Retailers, brands or tanners who are able to meet the requirements of this standard are eligible to use the EcoSure mark. To be eligible to use this mark tanneries must have achieved at least a Bronze award in the LWG Tannery Environment Auditing Protocol, and the finished leather on which the mark is to be used must meet the requirements of the audit and testing regime. (to see the audit form, click here ).
One issue which is a hot topic in leather production is that of deforestation and the sourcing of skins from Brazil – cattle ranching in Brazil accounted for 14% of global deforestation and ranches occupy approximately 80% of all deforested land in the Amazon. Greenpeace and the National Wildlife Federation (NWF) aims to stop all deforestation in the Amazon by encouraging the meat processors to insist that their suppliers register their farms and map and log their boundaries as a minimum requirement. They also encourage companies to cancel orders with suppliers that are not prepared to stop deforestation and adhere to these minimum requirements. Many of the LWG member brands have made commitments to a moratorium on hides sourced from farms involved in deforestation and LWG itself has a project to identify and engage with the key stakeholders in Brazil, investigate traceability solutions, conduct trials and implement third party auditing solutions.