Durability and Biodegradability:

Is there a contradiction?

 

 

 

Leather is renowned for its durability and performance characteristics. At the same time, the material is increasingly discussed in the context of biodegradability, circularity, and the bioeconomy.

At first glance, this may seem contradictory. How can a material designed to last a long time also be biodegradable?

In this issue, produced together with Elisabetta Scaglia, Head of Environmental Services at UNIC – Concerie Italiane, and Dietrich Tegtmeyer, freelance leather consultant, we clear up common misunderstandings and explain—in a clear and evidence-based way—how durability and biodegradability can coexist in leather.

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Understanding the basics

When it comes to leather, durability and biodegradability are not opposites. They operate on different timescales and under different conditions.

Leather is made from animal hides and skins, which are rich in collagen—a natural, bio-based protein structure. Through tanning, this collagen structure is purified of impurities and stabilized so that bacteria can no longer use it as a nutrient source, effectively stopping the decay process.

“Tanning is a process that transforms an organic material that would otherwise rot into a stable material that resists degradation caused by microorganisms, thereby increasing its durability.”

Elisabetta Scaglia
Head of Environmental Services and Specifications,
UNIC – Concerie Italiane

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This stabilization does not remove the leather’s natural origin—however, it changes the chemical nature of the fibrous collagen structure so that it remains stable, flexible, and durable. When leather is used in consumer products, this allows the products to be used for many years, reducing waste and preventing products from being discarded prematurely.

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Tanning chemistry and biodegradability:

Clearing up misunderstandings

One of the most common misconceptions is that tanning uses so many chemicals that leather must subsequently be “sealed” with a heavy plastic-based finish—which in practice would turn leather into plastic. This is incorrect.

What tanning does

• cross-links the collagen fibres using vegetable, mineral or synthetic tanning agents depending on the end product (shoes, bags, gloves, furniture, etc.)
• improves resistance to heat, moisture and mechanical stress thanks to selected functional chemicals
• by definition, a surface coating or finish applied to protect leather must not be thicker than 0.15 mm. If it is thicker, the material must be called coated leather, and even in such cases the coating must not exceed one third of the material’s total thickness.

What tanning does not do

• it does not turn leather into a synthetic material
• it does not remove the material’s natural protein-based structure

It is true that the leather surface needs protection after tanning to enable long-term use, and in many cases, this is done with a synthetic layer. However, this layer is very thin (<150 µm). Therefore, normally less than 5% of leather in use consists of plastic.

As a result, a sustainable leather today contains over 90% bio-based materials, despite the use of chemicals and protective surface layers. This means that leather often has significantly better biodegradability than many other so-called bio-based alternatives.

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Biodegradability in practice

Biodegradable materials are substances that can be broken down by microorganisms (bacteria, fungi, algae) and natural factors (sun, water, oxygen) into non-toxic natural components such as water, carbon dioxide, and biomass.

As Elisabetta Scaglia explains:

“Biodegradation is the metabolic transformation of an organic material into simpler natural constituents through the activity of microorganisms under suitable environmental conditions.”

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A material with a higher proportion of bio-based chemistry may have a greater tendency to biodegrade, but the terms cannot be used synonymously.

More generally, all leather is in principle biodegradable. But for leather to break down—like other natural materials (for example, wood)—the right conditions are required, which normally do not occur during use.

The rate of degradation depends heavily on environmental conditions and the presence of suitable microorganisms.

What varies is how quickly the degradation occurs, depending on which tanning and finishing chemistry is used.

Biodegradation does not occur while leather is in use, as the necessary conditions—prolonged moisture, microbial activity, temperature, and oxygen—are usually absent.

When the leather reaches the end of its life cycle, however, these conditions can enable biodegradation. If leather ends up in the environment as waste, the degradation process can start for all its bio-based components.

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Why this is important for sustainability and circularity

Durability and biodegradability allow leather to be positioned as:

• a long-lasting material that helps prevent products from becoming waste prematurely and promotes slow fashion
• a bio-based product that can return to nature’s cycle at the end of its life cycle, depending on the chemistry used
• a source of inspiration for the development of a science-based circular economy

As EU policy increasingly focuses on ecodesign, durability, circularity, and life-cycle thinking, it is crucial that decisions are based on facts, scientific evidence, and systems analysis.

Durability and biodegradability in leather are not contradictions—they are complementary properties of this natural, bio-based material, which only needs public support to develop its full potential.

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This post is also available in: Swedish