What is ISO 20136 about?
ISO 20136 discusses leather. ISO 20136 specifies a test method to determine the degree and rate of aerobic biodegradation of hides and skins of different animal origins, whether they are tanned or not, through the indirect determination of CO2 produced by the degradation of collagen.
ISO 20136 applies to the following materials:
- Natural polymers of animal stroma (animal tissue/skins)
- Animal hides and skins tanned (leather) using organic or inorganic tanning agents
- Leathers that, under testing conditions, do not inhibit the activity of microorganisms present in the inoculum.
Note: The conditions established in ISO 20136 correspond to optimum laboratory conditions to achieve the maximum level of biodegradation. However, they might not necessarily correspond to the optimum conditions or maximum level of biodegradation in the natural medium.
Who is ISO 20136 for?
ISO 20136 on the determination of degradability by microorganisms for leather is useful for:
- Leather manufacturers
- Quality control personnel
- Research and development personnel
Why should you use ISO 20136?
One of the key issues faced by the footwear industry is waste treatment. Such wastes, and especially leather, even though they are considered non-hazardous by the regulations in force, are generated in vast quantities and mostly end up in landfills, where natural degradation time is much longer than the product’s useful life. The reduction of a chemical compound to one less complex, as by splitting off one or more groups is called degradation. Biological degradation of natural and some synthetic polymers occurs when polymer depolymerization takes place as the result of enzyme secretions by some microorganisms.
ISO 20136 allows the measurement of leather biodegradability in a liquid system by using aerobic microorganisms as an inoculum. Protein and lipidic compounds are particularly dominant. Enzymes, like proteases and lipases, have a significant role in the biodegradation of collagen, keratin, and fats in leather waste. 
These microorganisms identified by microscopic analysis can be used for the improvement of the waste leather biodegradation process. Therefore ISO 20136 ensures to determine the degradability by a microorganism for improvement of the leather biodegradation process. It also meets promises of producing environment-friendly products without harming the environment.
What is changed since the last update?
BS EN ISO 20136:2020 supersedes ISO 20136:2017. BS EN ISO 20136:2020 includes some technical changes concerning ISO 20136:2017. These include:
- Method B in the first edition described a closed O2 circuit system. This system had the inconvenience that, over time, the O2 concentration decreased and, therefore, so did the activity of the microorganism. Now an open O2 circuit system has been developed where there is no O2 limitation and, therefore, the activity of the microorganism is always optimal
- An explanation about the results calculation method has been added to method B. The CO2 accumulated in the test (area under the CO2 mole’s curve vs time) is calculated
- The possibility of using municipal wastewater instead of tannery wastewater as an inoculum has been included
- A new Annex C has been added which compares the biodegradability with different inoculum sources
