Nowadays there are three very common terms: degradation, biodegradation and composting, but what are they and what is the difference between them?
Degradation is a process used in chemistry which means dissolution of organic compound to the fragments. This process is used to analyse the structures of compounds or to make a synthesis. Degradation is also used to dissolve polymers, and after that the properties of the polymer are changed.
Sometimes we can come across a term photodegradation and it is just the degradation, but with the help of the light, mostly UV.
OK, so we know what is degradation, let’s move to biodegradation.
We all know this term, for instance it is written on many packages or disposable cups, but what is it and does it mean anything good for ecology? Let’s see…
Biodegradation of plastics is a degradation process which can happen only when plastic is treated by microorganisms or other biological means. During the biodegradation, plastics (e.g. polylactic acid (PLA), polycaprolactone (PCL), polyhydroxybutyrate (PHB)) breakdown into a compounds found in the nature.
However not all the types of the plastics are biodegradable. Is it really ecology or only a process where biological organisms are being used?
Next comes the composting.
It is a process we all know from the garden, but how has it come to the plastics industry?
We know that a product of traditional composting is a humus – organic matter that has reached a point of stability (that is it won’t break any more). But many plastics companies say that their products are compostable, because they contain some percentage of natural ingredients which we can compost. For me, if the plastic product contains some amount of natural compostable ingredients, does not really mean that the whole thing is compostable. So how is it possible that they use this term?
The answer to this question can be found in the norm ASTM D 6002, where the word “compostable” has got a new definition:
“that which is capable of undergoing biological decomposition in a compost site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds and biomass at a rate consistent with known compostable materials.”
The secret is hidden behind the words “carbon dioxide, water, inorganic compounds and biomass”, which basically mean any and every substance in the universe. So the companies are allowed to label their product with “compostable” if it is capable to breakdown into some compounds, and theses compounds don’t have to necessarily have much in common with the humus as we know it from the old definition of “compostable”.
To me, the proper term here seems to be biodegradable and not compostable. Or if the “compostable” is a synonym of “biodegradable”, then yes, we can use it, but only in the plastics matter.
Interesting, isn’t it?