'Biodegradable', 'Compostable', 'Oxo-Degradable': What Do These Labels Mean?

 

BIODEGRADABLE:

A product labelled as ‘biodegradable’ can be completely degraded by micro-organisms such as bacteria, fungi and algae. However, the timeframe for this to happen is not stated – it may take hundreds of years – and in the absence of oxygen (e.g. land fill), it may never break down.

What does a ‘biodegradable’ substance break down into? The term ‘biodegradable’ says nothing about the qualities of the biodegraded substance. It does not necessarily turn into to compost. It usually turns to carbon dioxide.

Many plastic glasses marketed as ‘biodegradable’ are made from PLA. PLA derives from plants rather than oil. That may be a good thing, but not if it increases the cost of food or the crops are genetically modified.

However, the problem we are concerned with is litter (pollution), and sadly PLA is not the answer. A study that kept them in the sea for a year showed that they degraded no better than ordinary plastic. https://onlinelibrary.wiley.com/doi/full/10.1002/gch2.201700048

It would be perfect if PLA biodegraded like a discarded apple core, but ‘biodegradable plastic does not behave like that. It will disintegrate eventually, but to break down in an acceptable time frame, PLA needs to be taken to an industrial composting facility that can maintain conditions of high temperature and humidity…but you are unlikely to be able to find one.

PLA is not ‘home-compostable’.

In summary, it is hard to make the case for ‘biodegradable’ plastic when it degrades no better than ordinary plastic. It is certainly important to be aware that the label ‘biodegradable’ does not always mean ‘good’ and that its end-of-life issues are significantly more complex.

COMPOSTABLE:

Unlike a substance that is ‘biodegradable’ which may or may not break down into nutrient-rich biomass (compost), a substance that is ‘compostable’ will usually be made of organic matter to begin with and return to organic matter after it biodegrades.

However, it still needs the right conditions. To illustrate the difference, let us consider orange peel and bamboo – clearly both are organic matter, but they rates at which they decompose will vary greatly depending on the environmental conditions:

Even in your home compost heap, orange peel will break down within a year (sooner in warm conditions). However, if this orange peel was dropped as litter on the arctic tundra, it may be preserved for thousands of years. Why? Too cold. Similarly, dropped in the desert, it may desiccate and be preserved for a similar length of time. Why? Too dry.

Bamboo is made of stronger stuff than orange peel. Subsequently, it will still break down into biomass but it will take much longer. In the relatively low heat of a home compost heap, bamboo may take years to decompose. Wood from ship wrecks may be preserved for up to a thousand years in certain conditions.

Therefore, we can argue that although ‘compostable’ is superior to ‘biodegradable’ because it breaks down into a nutrient-rich biomass (whereas ‘biodegradable’ makes no such promise), even ‘compostable’ has its limitations. Not all items labelled ‘compostable’ will biodegrade in a reasonable time frame as litter.

HOME COMPOSTABLE:

An item that can be composted in conditions found at home is the closest we can get to being truly environmentally friendly. In spite of the provisos given above (that dictate the rate of decomposition depending on the conditions), products that do not need special or industrial conditions to decompose represent the last risk to the environment (not that we would advocate dropping them as litter).

For a product to be ‘home compostable’, it needs to:

Be capable of being broken down by micro-organisms into a nutrient-rich biomass (compost) AND…
Be capable of this process taking place in the conditions found in a typical home compost heap or council ‘garden waste’ facility.

INTERNATIONAL STANDARDS FOR BIODEGRADABILITY AND COMPOSTABILITY:

There are no widely used standards for consumer labelling for compostability. The nearest we have is an EU standard aimed at packaging manufacturers with a view to industrial composting: EN13432 ‘Requirements for packaging recoverable through composting and biodegradation’. A good summary of this certification standard can be found at the European Bioplastics website here.

The Organics Recycling Group is a trade organisation representing stakeholders in the bio-waste industry . They have an excellent guide for local authorities called the Concise Guide to Compostable Products and Packaging.

OXO BIODEGRADABLE:

Oxo-biodegradable plastic that regular plastic that contains additives that enables it to break down faster into smaller pieces of plastic. This substance is highly controversial and there are moves by the European Commission to ban it. You can read the full report here.  

It is common sense that keeping litter in one piece is better than having it break in to micro-plastic. A search for ‘oxo biodegradable’ will tell you everything you need to know.