Thanks to alchemical formulations, tanning transforms naturally biodegradable skins into leather, a decay-proof material capable of standing up to time and wear. So how can we “reverse” the process and allow leather to return to a biodegradable state?
All materials, both natural and petrochemical, will eventually disappear, however the timetable can vary from a few months to hundreds of years, and toxic traces can remain after decomposition.
Tannins, whether of mineral (chrome or aluminum), vegetable (mimosa or quebracho) or synthetic origin formulated from natural or petrochemical resources, produce an important chemical action on skins that transforms them into leather.
These components, whatever their typology, can also have an impact on the environment. For this reason, biodegradability is regulated by methods that determine the degree and time required for the material to be qualified as such.
The international standard ISO 20136 is the method of reference for testing the biodegradability of leathers to evaluate the optimal conditions for obtaining a maximum level of biodegradation.
Biodegradability therefore implies specific environments (fresh water, sea water or soil) and special conditions (temperature, humidity, pH, oxygen supply, microorganisms activating the process…), as well as non-toxicity and the absence of heavy metals.
When used alone without explanation of the atmospheres required to guarantee it, the term “biodegradable” can lead to confusion and must be used with caution.
Contrary to popular belief, vegetable tanning is not the only way to achieve optimal biodegradability.
Using the latest formulations for metal-free synthetic tanning on skins has allowed Dani and Mastrotto to guarantee the biodegradability of their leathers. Cortadoria also excels, having obtained a rigorous certification dedicated to Cradle to Cradle circularity for rabbit skins developed with synthetic tannins.
Ictyos, which specializes in the valorization of fish skins from the food industry, favors tanning done entirely with vegetable tannins for its biodegradable marine leather ranges.
To test and confirm a product’s biodegradability is above all a gauge of reassurance with respect to using formulations with a strong sustainable focus. However, this quality should not encourage the notion that a discarded product will disappear quickly, because when the right conditions are not met, biodegradability can go from a few months to several years.
Compostability is the ultimate gauge of biodegradability and guarantees that a fertilizing material is obtained after the fermentation and maturation stages, characterized by heat production, loss of mass and volume, and transformation of the material. Certifications such as OK Compost ensure a disintegration rate of over 90%, the absence of heavy metals in the material produced, and also that residues from the transformation stages can provide an enrichment agent that improves soil’s structure and fertileness. This is how solid waste can be used as fertilizer, an approach adopted by Nova Kaeru, a specialist in the synthetic tanning of exotic leaves, and Raynaud Jeune, a leader in vegetable tanning.