A bio-based material with unique properties
Leather, the primary material of the tanning industry, is recovered from another production sector: the food industry.
More precisely, leather is classified as an Animal By-Product (ABP) under EU Regulation 1069/2009
Rather than being disposed of as waste, hides are recovered by tanneries and processed into a high-value material.
Globally, nearly 99% of the leather produced originates as a by-product of the meat industry, derived from cattle, sheep, goats, and pigs.
Importantly, no animals are bred or slaughtered for the sole purpose of producing leather.
Leather is a circular, renewable, durable, and biodegradable material: in short, it is sustainable and bio-based by nature. However, public perception is often skewed by misinformation, stemming from historical misconceptions and misleading narratives promoted by ideological opponents of animal-derived products.
The term leather refers to hides that, after undergoing physical, chemical, and mechanical treatments, namely the tanning process (click here to learn about all the different main types of tanning),become a rot-proof material suitable for use in the manufacturing industry for an extensive range of products. These include footwear, leather accessories, clothing, furniture and interior design items, car interiors, and technical articles. It is a unique material, both in its nature and characteristics, that has always been highly valued by consumers for its technical and sensory performance. This appreciation is a value that must be transparently safeguarded, including from the perspective of commercial terminology (click here to learn more about correct leather terminology and the regulations in force).
Given the current climate and environmental context, consumer choices are shifting towards materials with a lower impact.
In this regard, bio-based materials, derived from renewable sources such as plant or animal biomass, have gained significant interest. These materials, for obvious reasons, differ from fossil-based, petroleum-derived materials, such as synthetics.
Leather, due to its origin, is a bio-based material in its own right, as scientifically demonstrated by the analysis presented in the publication “Material Circularity: A Novel Method for Biobased Carbon Quantification of Leather, Artificial Leather, and Trendy Alternatives.” This study, published in MDPI – Coating Journals, was conducted by the research company Ars Tinctoria, academics from the University of Florence, and researchers from CNR-INO and LENS. It analyzed radiocarbon content using SCAR spectroscopy to determine the percentage of bio-based carbon in various material samples, including leather, synthetic alternatives, and so-called plant-based materials, to assess their composition. The findings confirm that leather’s natural composition surpasses that of the so-called green alternatives. In tanned leather, the bio-based carbon content ranges from 65% to 96%, depending on the specific processing method, whereas in “leather alternative” materials that claim bio-based origins, the majority component actually derives from fossil sources.
Click here to access the full study
Both bio-based and fossil-based materials are carbon-based.
Structurally, there is no difference between carbon derived from biomass and carbon from fossil sources. The key distinction emerges when these materials reach the end of their life cycle and are disposed of.
The most common disposal method, which also applies to recycled materials, is incineration. This process releases the carbon atoms contained in the material into the atmosphere in the form of CO₂.
Carbon dioxide (CO₂) is one of the greenhouse gases (GHGs) that significantly contribute to global warming. Maintaining a balanced level of CO₂ in the atmosphere is therefore crucial.
From this perspective, the CO₂ emitted from the incineration of bio-based materials is considered neutral. This is because it consists of carbon dioxide that was already present in the environment and, through the carbon cycle, was absorbed by plants and later assimilated by animals through feeding. When bio-based materials, such as leather, are disposed of at the end of their life, the CO₂ is simply returned to the atmosphere.
CO₂ Emissions from the Disposal of High-Percentage Bio-Based Materials
CO2 absorbed = CO2 generated
On the other hand, the CO₂ released from the disposal of fossil fuel-based materials is additional carbon entering the atmosphere. These are carbon atoms that have remained trapped in oil reserves for millions of years and are now reintroduced, increasing atmospheric CO₂ levels. In the case of synthetic materials, no CO₂ is absorbed, while 100% of their carbon content is emitted as CO₂.
CO2 Emissions from the Disposal of Fossil-Based Materials
CO2 absorbed = 0% ; CO2 generated =100%
The Inimitable Characteristics of Leather and Its Imitations
Leather is composed of at least 85% collagen fibers, a fibrous protein that reacts directly with the substances used in the tanning process.
The natural structure of these interwoven fibers gives leather its distinctive and inimitable aesthetic and performance qualities, ensuring strength, durability, elasticity, flexibility, and adaptability to various shapes. At the same time, leather remains both breathable and insulating.
Tanning enhances these characteristics, making leather incredibly versatile in both function and aesthetics. This adaptability makes it an ideal material for a wide range of manufacturing applications.
Leather embodies a perfect balance between tradition and innovation. It carries a legacy of craftsmanship while also fitting into a future where natural materials play a central role. Thanks to its durability, leather maintains its high-performance qualities and intrinsic value over time.
Because of these attributes, many attempts have been made to imitate leather. However, none have successfully replicated its performance, technical features, or stylistic appeal.
Historically, the only alternative to leather has been synthetic materials, which, as mentioned earlier, are entirely derived from fossil sources, with significant sustainability implications. In recent years, a variety of so-called plant-based materials have gained public attention. These materials often claim to be greener and more sustainable than leather, but such claims are frequently based on selective comparisons rather than comprehensive environmental assessments.
While material innovation is undoubtedly important in advancing sustainability, there is a notable lack of transparency regarding the composition and performance of many of these new materials. Marketing strategies often emphasize isolated advantages without providing scientifically supported data or full disclosure of their technical properties.
In contrast, leather is well-documented in terms of its sustainability, characteristics, performance, and tanning processes.
One of the most significant studies on this topic is ’Comparison of the Technical Performance of Leather, Artificial Leather, and Trendy Alternatives’ conducted by FILK, an independent German institute specializing in materials analysis. This research compared the physical properties and durability of leather with those of various alternative materials.
The study’s findings clearly demonstrate that none of the so-called alternative materials possess all of leather’s high-performance attributes, proving that they do not offer a true substitute for it.
The Tanning Process in a Nutshell
Tanning makes raw hides rot-proof and resistant to moisture.
Depending on the tanning agents used, there are different production processes, which take place in drums or tanks according to the specific characteristics required for the final product.
The three main tanning methods are:
Chrome Tanning
Approximately 85% of leather produced today is chrome tanned. This process uses trivalent chromium sulfate (Cr III), a tanning agent that is non-toxic and poses no risk to human health or the environment.
Despite this, misinformation about the leather industry sometimes suggests that hexavalent chromium (Chromium VI, Cr VI), is used. Chromium VI is a highly toxic oxidation state of chromium, known to be carcinogenic and risky for consumers and operators.
It is essential to clarify: CHROMIUM VI IS NOT USED IN LEATHER MANUFACTURING.
Strict industry standards and well-defined procedures are in place to prevent the formation of Chromium VI in post-tanning stages.
Chrome tanning is a modern, widely used, and safe process that is continuously improved to enhance efficiency and sustainability. Advanced techniques ensure better absorption of tanning agents, reducing their overall use—starting with Chromium III—and minimizing water consumption.
Best practices in chrome tanning require half the chemicals used in other tanning methods while maintaining water emissions below legal limits. Additionally, this method allows for the complete recycling of Chromium III sulfate.
The benefits of chrome tanning are clear. It produces durable, high-quality leather used in shoes, bags, clothing, and various other products that retain their properties for years.
Vegetable Tanning
Vegetable tanning is the oldest tanning method, using tannins extracted from tree bark and plant matter. These tannins are sourced from suppliers that guarantee sustainable forestry practices.
Compared to chrome tanning, vegetable tanning requires a longer processing time. However, it results in leather with a distinctive aesthetic and a hand that improves with age.
Because the tanning agents are plant-based, vegetable tanning is often perceived as the more environmentally friendly option. However, a full environmental impact assessment must consider the entire process. For example, vegetable tanning consumes less tannins, natural and renewable raw materials, than chrome tanning. The resulting effluent, however, requires more treatment before it can be discharged.
Chrome-Free and Metal-Free Tanning
All other tanning methods fall under the category of chrome-free tanning. Chrome-free leathers are typically developed for specific performance requirements, particularly in the automotive sector. The most common method is aldehyde tanning, which uses glutaraldehyde as a tanning agent.
Leathers produced through this process require additional chemical treatments after tanning to enhance their properties. As a result, the wastewater from chrome-free tanning demands more extensive treatment before it can be released into the environment.