'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 be preserved indefinitely.

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 in to compost. It may turn in to carbon dioxide.

COMPOSTABLE:

Unlike a material that is 'biodegradable', one that is ‘compostable’ will usually be made of organic matter to begin with and return to organic matter as it biodegrades. A material that is just 'biodegradable' gives no such promise. Therefore, it can be argued that 'compostable' is superior to 'biodegradable'. But the issues are more complex than that.

'Compostable' still needs the right conditions to biodegrade - heat and humidity - and this will affect the rate of decomposition. To illustrate the difference, let us consider orange peel and bamboo – clearly both are organic matter and will compost in to biomass. However, the rates at which they decompose will vary greatly depending on the environmental conditions. Desert or permafrost will preserve them both indefinitely, and even in conditions of high heat and humidity, tough woody materials like bamboo may last for decades. 

Many plastic glasses labelled ‘compostable’ are made from PLA. and meet regulation EN13432. PLA is plant derived, making them sustainable and it is claimed that its carbon footprint is 75% smaller than traditional plastic. These are good qualities. However, if the problem is litter, then 'compostable' is not an automatic answer. A study that kept them in the sea for a year showed that they degraded no better than ordinary plastic. The fact is that plastic marked 'compostable' needs the heat and humidity of an industrial composting facility to biodegrade, and that these facilities are not yet widely available. 

The key thing to know is that items marked 'compostable' and ‘biodegradable’ may be better in some ways but that does not mean that we have solved their end-of-life issues. They should never be dropped as litter and should always be disposed of properly. Often, because biodegradable materials make bad candidates for recycling, the best place for them is the bin.

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 least risk to the environment (not that we would ever 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 and timescales 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.

OXO BIODEGRADABLE:

Oxo-biodegradable plastic that regular plastic that contains additives that enables it to break down faster into smaller pieces of plastic. Its sale is banned in the EU and there are moves to do the same in the UK.

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.