Despite its long history, leather is still widely misunderstood, especially in today’s search for sustainable, durable, and biodegradable materials. Its modern forms and innovations go far beyond the familiar image of traditional shoe leather, offering footwear brands valuable opportunities to strengthen their corporate image. 

To the average person, leather simply comes from the hide or skin of an animal. But there is a broader story: leather is a by-product of the meat and dairy industries. As long as humans continue to consume meat, hides and skins will remain a secondary outcome. According to the Oxford English Dictionary, a by-product is “an incidental or secondary product made in the manufacture or synthesis of something else”. Farmers do not raise livestock for hides, they raise them for food. Leather’s value lies not in its raw state, but in the durable, versatile products that can be crafted from it.

Historically, footwear has been one of leather’s most important uses, from full-coverage moccasins to today’s precision-made styles. For centuries, vegetable tanning was the dominant method. Then, in the late 19th century, chrome tanning emerged, revolutionising leather’s appearance, performance, and the way it was made. It took decades to become commercially viable, but it now accounts for around 85% of all leather globally.

Still, the definition of leather can be limiting. ISO 15115:2019 defines it as a hide or skin with its original fibrous structure more or less intact, tanned to prevent decay, and which may or may not have its hair or wool removed. It has long been considered “stabilised forever”, a positive trait for durability. But if that were truly the case, we would see far more ancient leather waste. In fact, most leather products break down over time, suggesting that biodegradability has always been part of the story – historically by circumstance, not design.

That is changing. Today, biodegradability is no longer incidental. It is a central goal, shaped by growing expectations around environmental responsibility. The leather industry is now rethinking how materials behave across their full lifecycle, including how they return to the earth after use.

New approaches

From a technical standpoint, tanning processes remained largely unchanged for decades. The main alternative to chrome – glutaraldehyde – used to make chrome free “wet white” gained prominence more than 40 years ago, but even this is now under scrutiny from regulations such as REACH due to its potential sensitising and toxicological properties. While glutaraldehyde’s future is under review, the past five years have seen a marked acceleration in tanning innovation. One of the most significant developments is a shift in perspective: tanning is no longer viewed as a permanent fixative, but rather as a temporary stabilisation phase. Leather can deliver the required performance – flexibility, breathability, durability – throughout its useful life, then biodegrade under specific post-use conditions.

These new approaches are gaining traction, driven by chemical companies, tanneries, and forward-thinking brands. Biodegradability by design is no longer just a research ambition and it is starting to shape real-world production. While it may take time for these innovations to scale, the precedent is there: chrome tanning also began as a niche development before reshaping the entire industry. We are now at the start of a similar shift, one that redefines what leather can be, and what it can do for a more sustainable future.

Redefining leather’s environmental profile

As sustainability becomes a defining challenge for the leather industry, new tanning and retanning technologies are emerging to reduce environmental impact, increase biodegradability, and improve material traceability. From the use of natural minerals and agricultural by-products to fermentation-based innovations, chemical suppliers and forward-thinking brands are working to align leather manufacturing with circular economy goals.

A notable development in recent years is Zeology, a metal-free tanning system developed by Royal Smit & Zoon. It uses zeolite, a naturally occurring mineral, as a replacement for traditional chrome and aldehyde tanning agents. The system is designed to retain key performance characteristics of leather, such as tensile strength and heat resistance, while addressing regulatory and environmental concerns.

Zeology-tanned leather is fully compatible with standard retanning and finishing processes and meets metal-free standards under frameworks such as REACH and ZDHC. According to life cycle assessment (LCA) data, the system offers measurable environmental benefits, including lower ecotoxicity and improved wastewater quality. It can also simplify waste management by reducing the generation of hazardous waste.

The manufacturers claim that zeology leather is significantly more biodegradable than chrome-tanned alternatives, supporting leather’s integration into circular product strategies. Sportswear brand Puma has incorporated it into its Re:Suede sneaker, part of its effort to create circular footwear solutions. In 2021, Puma produced 500 trial pairs made with zeology-tanned leather, hemp fibres and TPE outsoles. After six months of wear, the sneakers were composted under controlled conditions and achieved grade A compost certification. Following the trial’s success, Puma proceeded with a full commercial launch.

DyTan is another recent example of alternative tanning chemistry designed to meet environmental and performance targets. Developed by German leather chemicals group Trumpler in collaboration with Archroma and UK based Dr Leather Ltd, DyTan uses sulfonyl ethyl-based chemistry, originally from the textile sector, to crosslink collagen fibres in a pH-controlled process, avoiding metal salts, aldehydes, and bisphenols. The system also allows for simultaneous tanning and dyeing using coloured agents, improving process efficiency, and reducing reliance on additional dyestuffs.
Leathers tanned with it are said to show strong hydrothermal stability and high abrasion resistance, and the clarity of the material makes it suitable for both pastel shades and deep, uniform colours. The process uses globally available, REACH-registered chemicals and operates at low temperatures, without a pickling step. Leather tanned with it contains a high bio-based content and has demonstrated biodegradability and compostability in laboratory and industrial tests. The leather and its shavings disintegrate fully under composting conditions, and enzymatic hydrolysis enables potential reuse in further applications.

Food industry wastes

In parallel, renewed interest in vegetable tanning has led to experimentation with new sources of tannins, particularly agricultural waste. Traditionally, vegetable tanning has relied on extracts from tree bark and leaves from the timber trade, but some companies are now turning to the olive sector for alternative raw materials.

Olivenleder, originally based in Reutlingen, Germany, and now part of the Italian leather chemicals group Silvateam, has pioneered a method that uses discarded olive leaves, typically a waste stream from olive harvesting. The leaves are rich in polyphenols, especially oleuropein, that serve as effective tanning agents. The process avoids both heavy metals and aldehydes, resulting in a fully biodegradable leather that carries certifications from Cradle to Cradle and OEKO-TEX. It also retains a distinctive pale hue – often referred to as “wet green” – a nod to the gentle, non-aggressive chemistry involved. So mild, in fact, that the company regularly hosts tasting sessions where visitors are invited to sample the liquid tannin extract. [Editor’s note: it’s a bit like Marmite - you either like it or you don’t - but it shares that same astringent kick on the tongue!]

Footwear brands such as Tricker’s, Moral Code, and Grenson have adopted this leather, while Patagonia selected it for its American bison work boots, seeing eco-friendly tanning as an essential component of durable, responsibly made products.

Meanwhile, Italian chemicals company GSC has developed a tanning system based on olive mill wastewater (OMW), a challenging by-product of olive oil production. Globally, millions of cubic metres of OMW are produced annually, often containing high concentrations of organic compounds and polyphenols that make disposal and treatment problematic. GSC’s approach extracts tannins from this material and combines them with synthetic agents to create effective tanning and retanning solutions.

The raw material includes compounds such as hydroxytyrosol, catechol, and gallic acid, which contribute to leather stabilisation. The patented formulation works with both vegetable- and mineral-tanned leathers, enabling a higher bio-based content, particularly in retanning. Independent testing under EN ISO 20136:2020 found leather produced using GSC’s system achieved an 87.14% biodegradability rate, close to that of pure bovine collagen and considerably higher than glutaraldehyde-tanned leather.

A different pathway to greener leather comes from German leather chemicals manufacturer Schill & Seilacher, which has launched Succuir, a new retanning agent based on bio-succinic acid. Made by fermenting waste sugars from agriculture and the food industry, it aims to replace fossil-derived and bisphenol-based synthetics with a lower-impact alternative that still delivers performance in softness, durability, and finish quality.

Designed to integrate into existing processes, Succuir is said to be suitable for footwear, leathergoods and upholstery. Its manufacturers assert it eliminates heavy metals and organic solvents and reduces water and energy consumption during production. In biodegradability testing (ISO 20136), leather retanned with it reached 99.3% degradation in just 27 days. The system also supports circularity: production waste such as shavings and offcuts can be recovered and potentially reprocessed.

With regulatory scrutiny on chemical inputs tightening, especially in the European Union, systems such as these are gaining attention as traceable, bio-based options for tanneries looking to future-proof their processes and meet environmental targets without compromising material quality.

Taken together, these developments signal a shift in how the industry views tanning: not only to preserve hides, but as a platform for material innovation, and for footwear manufacturers to enhance their products. Whether using minerals, plant waste or microbial fermentation, new tanning chemistry is redefining what leather can be, and how it fits into a circular, sustainable future. 

Re:Suede sneaker – part of Puma’s circular design drive. Made with zeology-tanned leather, hemp fibres and TPE outsoles, these shoes proved compostable in trials and are 
now commercially available.
Credit: PUMA

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