If you want to know whether something is being eaten, it is more reliable to measure the meal than to look at the plate. That is the idea behind ISO 20136, the method designed specifically for leather.
Respiration, in a flask
Microorganisms that consume carbon-based material do what all living things do: they respire. As they break the material down they release carbon dioxide. If a material is being biodegraded, CO₂ is produced. If it is not, it is not.
In ISO 20136 the leather is exposed to bacteria and the CO₂ produced is measured using infrared equipment accurate to 1 ppm. The more CO₂, the more the material has been consumed, and so the more biodegradable it is.
Why this beats looking
Visual checks can mislead in both directions. A material can crumble into dust that is still, chemically, the same material. Equally, a material can lose very little visible mass while microbes are slowly working through it. A gas measurement avoids both traps, because it follows the chemistry rather than the appearance.
The role of a control
A single CO₂ figure means little by itself, because microbes also produce CO₂ from the other things in the mixture. Tests of this kind therefore include control vessels, so that the carbon dioxide attributable to your material can be separated from the background. Reading the result as a curve over time, rather than a single number, is what shows how quickly breakdown starts and whether it levels off.
Why leather needs its own method
Leather is not a typical test material. It has been chemically stabilised by tanning, often with chromium salts or vegetable tannins, so that it will not rot. That is exactly what makes it durable, and it is also what makes its end of life interesting. A method designed for leather accounts for this, and lets you compare different tannages, finishes and constructions fairly.
What to do with the result
Used alongside a disintegration test, a CO₂ result gives you a much fuller picture: not just that a material falls apart, but that it is genuinely being consumed. Together they form the backbone of any serious biodegradability claim.
Curious whether your leather or leather alternative is a good candidate? Send us a note and we can talk it through.
By Authenticae. Back to the blog