Innovate Blog
The mis-leading term – biodegradable plastic

Tuesday February 26, 2019

Ask the Expert: Jo Gilroy (Head of Sustainability).

We asked our Sustainability expert ‘Are biodegradable plastics the answer to ocean plastic pollution?’

And here’s what she told us…

Sustainability Expert – Jo Gilroy Twitter – @JoannaGilroy

The term biodegradable is certainly the buzz word of the moment when it comes to finding environmentally responsible alternatives to everyday disposable plastics.  Rapid growth in the biodegradable plastics market is largely being driven by conscientious consumers demanding environmentally friendly products. Consequently, the global bio-based plastics market grew at around the 20 per cent mark in 2018, and this year the European bio-plastics market is projected to grow by 12 per cent.

It is very easy to understand this sudden demand and the appeal of biodegradable plastic.  It sounds environmentally friendly.  The very term, biodegradable, strongly suggests that the material will just disappear after use.  However, before we all buy into this solution, we need to challenge assumptions and ask the question:  What makes biodegradable plastics a credible, long-term, sustainable option?

The simple answer is that the term, biodegradable, is unfortunately one of the most misleading (green-wash) terms used to promote products as better for the environment.  If a material is biodegradable, what this means is that the material has the ability to break down over time.  What is often lacking when materials, especially plastics, are described as being biodegradable is clarity over how long the material will take to break down, what environmental conditions are required for the break down to happen, and critically what the material will break down into.

What muddies the waters even further is that when it comes to plastics, the term biodegradable is often used interchangeably with the term bio-based.  Though connected, the two are not the same.  Bio-based refers to the raw material source of the plastic.  If a plastic is bio-based this means that the material has been produced from a biological source, such as plants or other types of renewable agricultural, marine or forestry materials, rather than the traditional petro-chemical source for plastics.  However, bio-based does not necessarily mean biodegradable.

Though a very general term, biodegradability can vary significantly between different biodegradable and bio-based materials.  For example, some biodegradable plastics can break down within 12 weeks, whereas others can take as long as traditional plastics.  Additionally, some biodegradable plastics can break down into a fibrous material used to produce compost, whereas others actually break down into micro-plastics.  Equally, we have bio-based plastics that will biodegrade and others that do not.

Contrary to general understanding, there are actually 3 broad categories of bio-based and biodegradable plastics:

The first are bio-based, non-biodegradable plastics.  These are essentially common plastics types, such as PET and PE, which traditionally have been made from petro-chemical sources but can now be produced from alternative renewable sources.  Though not biodegradable, these plastics can actually be recycled by existing recycling infrastructure.  The Coca Cola plant based bottle is an excellent example of this.

The second broad category are plastics that are made from traditional petro-chemical non-renewable sources (so non-bio-based) but are biodegradable.  It is these biodegradable plastics that are arguably the most dangerous.  These plastics will often only biodegrade because the process is triggered by a chemical reaction created when the the plastic comes into contact with a certain element, such as water or oxygen   These biodegradable plastics are also known as oxo-biodegradables and are not environmentally friendly for a number of reasons, the most significant being that they create micro plastics as the material biodegrades.   These biodegradable plastics are so harmful to our environment that the Ellen MacArthur Foundation has called for an international ban, supported by more than 150 organisations.

The third and final category includes bio-based plastics that are also biodegradable.  These are the plant or starch based plastics such as PLA, PHA or PBS which are produced from renewable sources and will biodegrade under the right conditions to produce a fibrous material which when added with the nutrient content from food waste, produces compost.

Despite the term suggesting the possibility of a quick fix to plastic pollution, biodegradable plastics are anything but.  Both bio-based plastics which can be recycled, and bio-based biodegradable plastics that can create compost have merit but taking ownership and responsibility for the correct end of life is still critical. Whether bio based and/or biodegradable, these materials are still plastic and if incorrectly disposed of, or littered into our marine and land environments, will create just as much long lasting harm as our traditional plastic materials.

Biodegradability alone does not have the ability to undo today’s damaging plastic legacy.  Smarter, more ecologically minded material design must still be coupled with smarter recycling systems so that all bio based, biodegradable materials can continue to be a resource after use.