Biodegradation – a definition:
Biodegradation is the total breakdown of a product (by microorganisms) to something found in nature.
Do plastics biodegrade?
Current culture is led to believe that plastics do not biodegrade. This is, in fact, incorrect. All plastics are organic and have been proven to biodegrade by microorganisms. The issue is the speed at which plastic biodegrades that has led to the assumption that it does not as most plastics will take 1,000 years or more to do so.
To promote quicker degradation, work has been done to develop additives and materials which have been aimed at helping speed up this process.
One of the first was the introduction of Photodegradable plastics, later renamed Oxo-Biodegradable materials. Developed for the producers of the plastic ring collars found on multi-pack drinks cans, as the name suggests, this plastic requires sunlight for it to break down. When exposed to sunlight Photodegradable/Oxo-Biodegradable plastic fragments into ever smaller plastic particles. The aim is to make the particles small enough to allow naturally occurring organisms to be able consume them and break them down.
Whether these materials can be truly classed as biodegradable is up for debate as there is no scientific evidence to show that these plastic fragments are then consumed at an increased rate due to this technology.
A further drawback with this technology is that if products are sent to landfill, they will not break down as they require exposure to UV light. This means they need to be, in effect, littered in order to work.
PLA Based Polymers
Although it is true that these materials degrade, it is debateable whether they can be classed as Biodegradable as they require particular conditions which rarely, if ever, occur naturally. To degrade PLA requires both moisture and a temperature of at least 60 deg C and to come into contact with a specific enzyme – Proteinase K.
Consequently, products made from PLA will only degrade if they go through a controlled industrial compost facility otherwise little, if any degradation, will occur.
The latest technology is based on additives which work by allowing acids, secreted naturally by microbes, to soften the macromolecules/bonds within plastic. Microbes are then able to consume the softened macromolecules much more quickly than would normally be the case. This accelerates the biodegradation process so much that degradation can take as little as 2-3 years for some plastics and does not need an artificial environment to work.
With these systems UV light does not have any affect and biodegradation only occurs when the plastic material comes into contact with these naturally occurring microbes in, for example, a landfill or compost environment.
The biproduct from this process is the same as with any other organic matter which biodegrades, ie CH4, CO2, biomass, and water.
For more information on Biodegradable additives contact Eddie Thurloway at Colourmaster NIP.