Plastic was the name given to early synthetic products (such as cellophane), that were derived from cellulose. These early plastics were biodegradable. Later the same name was given the oil derived product. This was made in a very different way and did not biodegrade. It is now applied to corn starch plastic which is made differently again, from plant starch and is certified compostable. Want to know more about plastic? Read up here
plastics can be made in a variety of ways from a variety of materials; shale gas, oil, plants even chicken feathers;
different plastics have very different qualities.
Currently, non- biodegradable, oil derived plastics are the most commonly used and so we tend to ascribe their qualities to all types of plastic.
Which is of course incorrect not least because most oil derived plastics do not biodegrade and last for centuries possibly for ever, while there are other plastics that are truly compostable with a lifespan of months.
Read more about plastic types here…
Biodegradable, Compostable Plastics
What is biodegradable? Biodegradable products break down through a naturally occurring microorganism into simple, stable compounds which can be absorbed into the ecosystem. More about biodegrading here
What is compostable? To be classed compostable, items must biodegrade within a certain time (around the rate at which paper biodegrades), and the resulting biomass must be free of toxins, able to sustain plant life and be used as an organic fertilizer or soil additive. For a man-made product to be sold as compostable, it has to meet certain standards. One such is the European Norm EN13432. You can find out more here.
- Cellulose derived plastics such as Cellophane. These plant derived plastics are amongst the first examples of the product and do biodegrade.
- Starch based plastics which are compostable such as PLA plastics. They are certified compostable and do biodegrade.
- Polyhydroxyalkanoates or PHAs are linear polyesters produced in nature by bacterial fermentation of sugar or lipids. They are produced by the bacteria to store carbon and energy. They do biodegrade
- chicken feathers bioplastic – biodegrades.
Composting PLA Plastic At Home
While most agree that PLA plastic is indeed compostable, many say that it can only composted in large scale municipal schemes. As we don’t have many large scale municipal schemes this they say is a pointless advantage.I say the days of large scale municipal schemes is fast approaching as governments aim to divert biodegradable rubbish from landfill sites.
AND I have been composting my PLA plastic for years. We have used and composted a number PLA plastic products (including Biobags , Deli pots and disposable Cutlery)
It does take longer than other products and sometimes I have found shreds of it in my compost but I dig it into the soil where it quickly disappears.
Most compostable plastics are bioplastics. Bioplastics are made from natural materials such as corn starch. However not all are compostable. For exampleEthane based plastics as used Coca-Cola’s PlantBottle which replaces 30 percent of the ethanol in their normal polyethylene terephthalate (PET) plastic bottle with 30 percent plant-derived ethanol. This means the bottle is still considered PET and can be recycled but is NOT biodegradable. Find out more here.
There is research being done into developing a compostable, oil-derived plastic. Watch this space BUT don’t fall for the old *biodegradable plastic bag trick see below.
*Compostable versus biodegradable plastics
You might see some plastics labelled described as biodegradable. You could be forgiven for thinking that this is the same as compostable plastic. It is not. Some “biodegradable plastics” are oil derived plastics with a degrading initiator added to make them fall apart (degrade) more quickly. Unlike compostable plastics they don’t always break down into harmless substances and may leave behind a toxic residue. Read more here