Is leather sustainable?

Investigating the key issues involved in the production of this material, and the accusations levied against companies involved in its manufacture and utilisation.

by Nicola Pichel-Juan

Leather – and in particular bovine leather – has been under attack in recent years, often for its perceived lack of sustainability credentials and the belief that its production harms the environment. This article will discuss the key concerns raised about leather, investigate what the reality is (or can be), how the impacts of leather and its supply chain can be understood, what the sustainability credentials of alternative materials are, and what the future of leather could look like.

Why is leather seen as being ‘bad for the environment’? Several reasons are put forward as to why it is not a sustainable material. The majority of these are not linked to the manufacture of the leather itself, but to the raising of the cattle that provide the hides which are ultimately turned into leather.

Part of the digestive process of cows (and other ruminants, such as sheep and goats) is a process called ‘enteric fermentation’. This involves microorganisms in the animal’s rumen (its largest stomach compartment) breaking down sugars into simpler molecules for absorption into the bloodstream. A by-product of this process is methane, which is emitted from the cows in the form of eructation (‘burping’). Methane is one of the greenhouse gases linked to climate change, and it has a global warming potential (GWP) over 100 years that is 28 times higher than the GWP exhibited by carbon dioxide.

The raising of cattle has also been linked to deforestation – particularly in the Amazon basin – as growing demand for beef has led to greater areas of rainforest being cleared to create pastures for grazing. Deforestation also means that there are fewer trees to absorb carbon, as well as a loss of biodiversity. From an environmental perspective, the leather industry can be seen as energy and water intensive, as well as creating pollution due to the chemicals used in the tanning process that are thereafter discharged into the environment.

While perhaps not a sustainability consideration, the leather industry has also come under attack over animal welfare concerns in some parts of the world, and for the belief that it is responsible for cows being slaughtered.

Leather is a by-product

While it is undeniable that cows emit methane, that raising cattle in parts of the world has been linked to deforestation, and that around 300 million cows are slaughtered globally each year, it is crucial to remember that leather is a by-product (waste) from the meat industry.

If the leather industry ceased to exist overnight, cattle would still be raised and their hides would still exist. Cattle are not raised for their hides to make leather; they are raised for their meat. Due to a lack of demand for leather caused by economic factors, a trend towards veganism, and a general interest/increase in the demand for other bio-based products in sectors including footwear, it is estimated that in some parts of the world 40 to 45 per cent of hides are being thrown away and destroyed. Instead of taking waste from one industry and turning it into a valuable material, the unwanted hides are being incinerated or sent to landfill, both of which will have an adverse effect on the environment.

The sustainability credentials of leather

The fact that leather is produced from a waste product from another industry is a fantastic starting point on the journey towards having a truly sustainable and circular material. Using leather as a material to produce footwear or other goods also minimises the consumption of other virgin materials, many of which will be derived from fossil fuels. Plastic-based materials manufactured from fossil fuel inputs will have a high fossil carbon content. In comparison, leather will have a high bio-based carbon content, and the ‘type’ of carbon present in materials is becoming an increasingly important consideration within the supply chain.

Leather has been used to manufacture footwear for thousands of years. It is a long-lasting, durable and breathable material that can stand up to the rigours of modern shoemaking processes. While there have been many attempts to develop alternative materials to leather, most of them have failed to match its unique properties. The article ‘Innovative materials as alternatives to leather?’ considered the feasibility of using a number of recently-developed materials instead of the traditional choice in footwear production.

With longevity, durability and repairability now being widely recognised as key sustainability criteria, leather is finally starting to see some more positive coverage again. For example, some luxury automobile manufacturers are recognising that leather is the best option available in order to produce a high-quality, long-lasting and sustainable material to use for car interiors.

The ability to make more sustainable leather

For any organisations operating within the footwear value chain, there are several factors that can be considered in order to identify more sustainable or lower-impact leather. For instance, these include the tanning systems used, the tannery itself, hide traceability and, finally, the wider supply chain.

Most of the leather manufactured as upper material for the footwear industry has used a chromium III (chrome)-based tanning agent, due to its strength and hydrothermal stability (the ability to resist shrinkage during the heat setting process). While there have been concerns about the potential for the chromium III used in the tanning process to convert into harmful chromium VI, this risk can be almost entirely eliminated by appropriate process controls.

In recent years, there has been a surge in the number of alternative and more ‘environmentally friendly’ tanning systems coming onto the market that are chrome- and metal-free. As a result, these systems have much lower environmental impacts in terms of the chemicals used during the tanning process and at end of the leather’s life.

Commercial examples include tanning systems such as ‘Succuir’, ‘Zeology’, ‘Avicuero’, ‘Ecotan’ and ‘EasyWhite’. Some of these tanning systems also support the production of compostable leather, the intention being that once the leather is composted, it can be used to support the growth of nutritious crops, thus providing a truly circular solution. There are footwear brands using this type of leather to develop and commercialise compostable shoes (see the article ‘Are compostable shoes the future?’).

The tannery itself is another important consideration, and there is a world of difference between the images of traditional open tanning pits and older industrial tanneries when compared to the modern tanneries in operation today. A tannery that takes its environmental impacts seriously will have significantly reduced its energy and water consumption. The facility will also have effluent treatment technology in place to ensure that harmful chemicals are not discharged from the site, as well as potentially using lower impact tanning methods as described above.

In terms of concerns relating to animal welfare and deforestation, traceability is key. It is vital that brands, retailers, footwear manufacturers and the tanneries themselves understand the wider supply chain and can ultimately track back the source of the hide to where the cow was raised. There are a number of initiatives within the leather industry focusing on traceability. Modern technology such as ‘DNA tagging’ can also be used to facilitate the tracking and tracing of hides back to the abattoir and farm.

In fact, a recent deforestation regulation introduced in the European Union requires that any organisations importing raw hides and derived bovine leather must complete a due diligence statement relating to the material’s origin and trace it back to the specific geo-location where the animal was born. The EU’s Deforestation Regulation 2023/1115 (known as ‘EUDR’) on deforestation-free products came into force on 29th June 2023, and will come into effect – at which time action must be taken by the company – from 30th December 2024. The UK is in the process of introducing similar legislation. It is important to note that the legislation only applies to hides or leather imported into the European Union under certain tariff codes, and does not currently apply to items such as footwear made from leather.

The wider supply chain and product lifecycle must also be considered. For instance, if finished leather must be routinely shipped by air from the tannery to the footwear production site in order to meet production deadlines, the huge impact of the air freight will likely outweigh any lower environmental impacts achieved up to that point.

Verifying and testing sustainability

To verify how ‘sustainable’ a leather is, factors such as supply chain visibility, hide traceability and tannery efficiency can be considered. A lifecycle assessment (LCA) studying environmental impacts such as global warming potential (greenhouse gas emissions) could also be used to compare materials and production processes, and to understand the location of any emissions ‘hot spots’.

In addition, there are various tests that can be used to assess and measure certain credentials relating to the sustainability of leather. As previously mentioned, leather is typically an exceptionally durable and long-lasting material. This can be verified through physical laboratory testing to ensure that it is fit for purpose and suitable for its intended application. Testing for restricted substances can be used to confirm that no harmful substances are present in the leather. For compostable leather, there is a series of tests that can be conducted to determine if a material disintegrates, biodegrades and supports the growth of healthy plants. Finally, testing can be undertaken to verify the bio-based carbon content of leather.

What are the alternatives?

There is a definite trend within the footwear industry to move towards bio-based materials, sometimes as a replacement for leather (which itself is bio-based), but increasingly also to support a transition away from fossil-based materials. These materials include i) a resurgence in the use of traditional materials, such as jute, hemp, cork and, of course, leather, ii) materials that repurpose waste from the food industry – such as those containing raw material input from pineapples, apples, grapes, mangos or bananas, iii) laboratory-grown materials such as mycelium, and iv) other materials that are derived from such sources as sugar cane, algae, cactus and even dandelions.

A number of the innovative new materials initially marketed as alternatives to leather contained a high proportion of plastic in the form of fillers or backers used to give strength to the material. However, there are now some truly bio-based materials on offer to the footwear industry that do provide viable and interesting alternatives to both leather and synthetic materials.

What is the future for leather?

After coming under significant pressure in recent years, the leather industry is now starting to re-establish itself as an industry that can (and does) produce sustainable materials. Many tanneries are commissioning detailed LCA studies from SATRA to demonstrate that their products do not have a high carbon footprint. It is also important to educate consumers so that they understand the properties of leather and its origins. There is, for example, the common misconception referred to earlier that cows are raised and killed for their skins. With legislation coming into force to tackle ‘greenwashing’ (defined as ‘the use of advertising and public messaging to try to appear to be more environmentally sustainable and green than is really the case’) and vague or misleading environmental claims, the leather industry should be in a strong enough position to effectively communicate its sustainability credentials.

The question therefore is not whether leather can be sustainable (it can), but if a particular leather made within a particular supply chain is sustainable. The same questions should be asked of materials of any type.

Publishing Data

This article was originally published on page 8 of the July/August 2024 issue of SATRA Bulletin.

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