Leather: Exceptional Properties, Exceptional Problems
I remember a visit to Marrakech a few years back, which included an ‘unofficial’ tour of the tanneries. I was surprised by how close they were to the souk — a huge bustling outdoor market selling a vast range of items, including food and fresh spices — and how accessible these tanneries were to passersby. I will never forget the smell that was generated as the skins were being processed. We were given sprigs of mint to hold under our nose to mask the odours, but the tannery workers were not granted this protection. I was shocked by the spectacle, but also intrigued to find out more. I’ll admit that with my privileged western upbringing, I had never had too much of a problem buying leather products, viewing it as a natural, long-lasting raw material that offered both exceptional physical performance and aesthetic characteristics. But was I wrong to still take this view after visiting Marrakech?
Generally, skins are viewed as waste products from the meat industry, rather than being bred for the value of their hides and skins as the main product. The exception is exotic animals such as alligators, ostriches and kangaroos. According to Leather Naturally, around 99% of the hides and skins used for leather are a by-product of the meat industry, in which case it might be argued that it is preferable to use this waste product rather than send it to landfill. However, Collective Fashion Justice disputes this. They claim that buying leather supports the beef and dairy industries by bringing in additional wealth, with the global leather goods market valued at 394 billion USD in 2020.
On top of that, the process of converting skins into leather can cause serious harm to the environment and to the workers involved, some of whom may be as young as ten years old. It also generates huge amounts of solid waste, and requires vast amounts of both salt and freshwater.. According to an article by N M Sivaram and Debabrata Barik, one metric ton (or 1000kg) of raw material in leather processing results in 200 kg of usable leather product — that’s just one-fifth. The solid and liquid waste includes approximately 250kg of non-tanned solid waste, 200 kg of tanned waste and 50,000 kg of wastewater effluent (with the latter two both containing levels of carcinogenic chromium).
The leather industry is also nuanced through its production process. Fresh skins and hides are unstable and prone to deterioration very quickly. They are often preserved by wet salting, brining, air drying or dry salting, all of which necessitate materials, and labour, and generate waste. According to the Leather Working Group, hides are increasingly processed without preservation due to the use of refrigerated transportation which can move the product from abattoir to tannery very quickly. The shorter cooling time reduces energy costs, and this method avoids the salt water wastage. Hides are then subject to further processing at the tannery a few hours later.
The production of leather involves several processes:
1. Cleaning
The ‘pelts’ as the skins and hides are known at this stage are cleaned to remove preserving salts, dirt, flesh, wool or hair, and are then degreased. This is an unpleasant job, particularly in less developed countries, where it may be done by hand (rather than machine). An Insider Business video highlights the tanning process at the Chouara Tannery in Fez, Morocco, which is said to be the world’s oldest leather tannery. The film shows one of the workers up to his knees in a vat containing a mix of chemicals, salt water and cow urine to clean the skins and break down excess fat, flesh and hair. The chemicals contained in the solution can cause serious injury to the tanners, including chemical burns to the skin that do not heal. Unfortunately, these workers may stand in this mixture for hours each day to clean the skin.
Once clean, the hides may be split. The top layer is used to make full grain or nubuck leathers, whilst the bottom layer is used to make ‘split’, or suede leather. At this stage, the skins and hides have limited storage time until they are stabilised by the tanning process.
2. Tanning
The tanning process stabilises the protein structure of the hides and skins to prevent decomposure. There are three key tanning methods used: chrome tanning, vegetable tanning and chrome-free (also known as white) tanning, which we’ll look at in more detail later.
3. Retanning
Retanning, or prefinishing, determines the final character of the leather and its ultimate use. It is generally performed with a mix of vegetable and synthetic tanning materials and is a relatively quick process, resulting in a leather which is light in colour. The leather can then be dyed and subject to ‘fatliquoring’, or ‘regreasing, which adds a mix of natural and/or synthetic oils and waxes to change its characteristics, adding softness as required. Leather is often dyed through completely using aniline dyes. The use of azo-dyestuff is no longer allowed as it is harmful to health. Cheap, low quality leathers dye also may have only been applied to the top surface, which are subject to wear very quickly. But one of the advantages of leather is its longevity, this is something worth looking out for when looking for a quality product..
4. Milling
Leather may be placed into a tumble drum to soften it even further. This results in a soft texture and grainy appearance.
5. Finishing
Finishing involves buffing, or sanding, with different grades of paper to create a range of textures. Oils and waxes are then applied to improve softness and colour and finishes such as waterproofing are added as required. Man-made chemicals such as perfluorinated chemicals (PFCs) are frequently used to make leather products water and stain-proof. Many PFCs persist in the environment and can impact health, accumulating in body tissue and potentially affecting the liver, as well as acting as hormone disruptors.
Taking a Closer Look at Leather Tanning
Out of these five processes, tanning, particularly chrome tanning, is the most controversial and the most likely to harm both the planet and people. Chrome tanning is the most common tanning method, accounting for around 75% of the leather made today. It uses chromium salts and tanning liquor to produce a very stable, versatile leather. Chrome tanned leather has been widely used since the early 1900’s, replacing vegetable tanning as a more cost-effective and durable method.
Collective Fashion Justice claim that 90% of leather worldwide is tanned using chemicals including chromium, formaldehyde and arsenic. They are known to cause skin ailments and diseases, including cancer amongst tannery workers, and also damage precious eco-systems. They state that every day an estimated 40 million litres of untreated waste-water flows into the Ganges River in India, which people use for both bathing and drinking.
The effect of this pollution is very movingly portrayed in the video ‘The Toxic Price of Leather’ by Sean Gallagher and the Pulitzer Centre. which highlights how the tanneries have polluted the local land and rivers around Kanpur in India. It has caused health issues, including tuberculosis, eyesight problems, skin discolouration, rashes and asthma. Local politician Javad is close to tears as he describes how his wife died from asthma as a result of the pollution. Collective Fashion Justice also claims that China, which is a major tanning country, has certain communal areas now referred to as ‘cancer villages’, due to the effects of tanning and other industrial activities.
However information from Leather Naturally claims that there is a mistaken belief that carcinogenic hexavalent chrome, or chromium VI (CrVI), is used for tanning when, in fact, this has been phased out of production, and the process uses trivalent chromium (CrIII) which is a safe substance. However, if the tanning process is not tightly controlled, chromium VI can form in leather after tanning, potentially causing allergic reactions. Strict industry guidelines set out by the Leather Working Group are designed to prevent this. Adherence to such regulations does of course mean that firms have to bear additional costs. As a result there has been a shift in the processing of hides from developed to developing countries where environmental compliance is less strict and labour costs are lower.
According to Leather Naturally, the top three leather producing countries by volume are Italy, China and Brazil. We referred earlier to China’s ‘cancer villages’ whilst in Brazil, land clearing for cattle for meat and the fashion industry accounts for 80% of the Amazon’s deforestation, according to Collective Fashion Justice.
Chrome- free tanning
There has been a lot of talk in the ready-to-wear industry recently about chrome-free tanning, suggesting that this is a better choice for those who care about a greener solution. Chrome-free tanning produces a soft leather, also known as ‘wet white’, which can easily be dyed in pastel colours. However, production of these chrome-free leathers requires the use of a synthetic product called glutaraldehyde, which can cause respiratory problems, alongside other tanning agents such as aluminium, zirconium, triazines, aluminium silicates or syntan-vegetable. The process is more expensive than chrome tanning, is water intensive and the leather requires further processing with chemicals such as vegetable extracts, syntans and acrylics to improve finish and performance. This also means that the liquid waste requires additional treatment before it can be discharged.
Vegetable tanning
This is the oldest tanning method, dating back over 2000 years. It uses natural, sustainable and renewable raw materials such as extracts from wood, nuts of trees and shrubs, including mimosa, chestnut, quebracho and tara extracts. Whilst vegetable tanning may use raw materials, it relies heavily on tree bark, which can lead to deforestation. However, responsible suppliers provide raw material from sustainable sources. Vegetable tanning is also a longer process than chrome tanning, and produces leathers that are dense and light brown in colour.
This leather is more ideal for footwear — the dominant segment in the leather goods market. Whilst the Common Objective states that vegetable tanning produces far less harmful waste and a leather product that is biodegradable, it’s limited in colour and texture. And whilst it may use natural, renewable resources, it still produces effluent which needs treatment before it can be discharged. The tannins also have low biodegradability and the effluent is highly coloured, taking a long time to disperse.
Leather is not alone in using a large amount of chemicals in its processing, nor the vast amount of water it requires, or the waste water it produces. As with all textiles, it pays to be aware of the production processes in order to purchase more responsibly. But this is far from straightforward. When buying leather goods from a High Street — or indeed luxury — retailer, it is likely that very little information is available regarding its supply chain production process.
However, there are certain standards which the consumer can look for. The Oeko-Tex leather standard is ‘a globally standardised testing and certification system for leather and leather goods at all production levels’, and it includes leather fibre materials and some skins, such as sheepskin, lambskin and cowskin. The provision of the Leather Standard label means that the article has successfully passed a test for chemicals that are harmful to health.
It’s also worth checking the Leather Working Group (LWG) website which provides a list of those companies or brands which meet its criteria for certification. The LWG audit assesses the environmental impact of traders of raw and part-processed material and finished leather and helps to facilitate traceability through the supply chain. Other certifications include ZDHC — Zero Discharge of Hazardous Chemicals; ICEC — Institute of Quality Certification for the leather sector, and also the CSCB — Brazilian Leather Certification of Sustainability which ensures the use of sustainable processes within Brazilian leather production. Also look out for brands that have achieved B corp certification, which measures a company’s social and environmental impact, assessing their commitment to governance, workers, environment, community and customers.
So, did my trip to the Marrakech tanneries and subsequent research change my views on leather? Absolutely, yes. The production of leather raises appalling ethical, humanitarian and environmental issues which cannot be ignored. Animal skins may be excused as a waste product, but it’s shocking to discover that the meat industry produces enough skins to create three pyramids, each the size of the Great Pyramid of Giza every year. But leather has been in circulation for many, many years and it undeniably produces a versatile material which offers a lot of very valuable qualities, including comfort, performance, insulation and durability. Only you, as an individual, can decide whether wearing leather feels right to you. There is no singular, straightforward, planet-friendly solution. I, for one, will be taking steps to ensure that the leather items I already own are looked after very carefully to ensure that they remain in circulation for many years. And if, and when, I decide that I require another leather garment or bag, I will be looking at second-hand options rather than hitting the high street stores.
By Donna Gilbert
Donna is based in the south east of England. Her interest in slow fashion was ignited by a degree in fashion and dress history at Brighton University. A keen dressmaker, Donna makes and mends her own clothes in an effort to reduce her consumption of fast fashion.
