‘Bioplastics’: help or hindrance to achieving a circular plastics economy?

Julie Hill, Chair, WRAP

The recent summit of The UK Plastics Pact aired many successes, but also some challenges, and one was the role of biodegradable and compostable plastics. 

The Pact target is for all packaging to be re-useable, recyclable or compostable by 2025. 

The ability for plastic to join food or garden waste in a compost heap and return to the soil, or, if loose in the environment, to magically melt away as it ‘rots down’, seems very appealing. Unfortunately, it is not that simple. 

The task for The UK Plastics Pact is therefore to define the conditions under which compostable packaging is a help, not a hindrance to circularity. WRAP’s work to date provides an excellent starting point and we’re already seeing successes in this space.

Innovation is a great place to start. I am always staggered by the extent of material innovation. Even more so since attending the European Forum for Industrial Biotechnology conference recently to talk about The UK Plastics Pact, and witnessing the number of biotech innovators seeking new business opportunities in plastic solutions.  

There is an increasing and bewildering array of types of plastic that meet the description of ‘bio-derived’ (made from plant material instead of oil), ‘biodegradable’ (broken down by biological organisms) or ‘compostable’ (will break down in industrial or home composting). Even more confusing, there are some oil-based plastics that will biodegrade, given enough time, and some plant-based plastics that don’t!    

As the concerns about plastics have grown, these materials have been mentioned as providing a solution to everything from the plastics in the ocean to new types of crisp packet. Where they presently fall down is that the innovation in material properties is not matched by innovation downstream. Our choices of route for any material can almost be counted on the fingers of one hand – re-use, reprocessing for recycling, anaerobic digestion, composting, energy generation and landfill (not forgetting avoiding having the material/thing in the first place).  

This complexity of material and restriction of options for end routes is excellently illustrated in one of the first outputs from The UK Plastics Pact, ‘Understanding Plastic Packaging and the Language we use to describe it

Where do these new plastics fit in? Just because a material is ‘biodegradable’ does not necessarily mean it is compostable. Certified compostable plastics should obviously go to composting, but not all will work in the cool conditions of a home compost heap. The majority of compostable plastics need the conditions present in an industrial process. 

Around half of local authorities now provide food waste collection services, with anaerobic digestion (AD) being a popular choice of subsequent treatment, where the energy from the gas is a bonus. But AD alone can’t break-down plastics, and with the risk of conventional plastics getting into the process, many of these facilities have a ‘de-packaging’ step which remove all plastic regardless. To be confident of this route, we would also need to be certain that no unacceptable ‘microplastics’ are left in the compost.  

That leaves energy from waste, or landfill as main destinations, and in landfill the ability to biodegrade is a minus not a plus, as it will produce methane like any other biodegradable material. 

What about recycling?  By their nature, biodegradable plastics are designed to break down, not to be recycled. Worse, if biodegradable plastics are mixed with conventional plastic recycling streams they are a contaminant and risk undermining the markets for recycled materials – who wants a damp proof membrane that might end up breaking down?  

It was also clearly stated at the EFIB conference that biodegradable plastics are not a solution to ocean plastics.  The sea is too cool, with not enough oxygen present, for most of the plastics available now to degrade effectively. There is in any case a danger of this route providing a ‘licence to pollute’. 

So when your coffee cup tells you it is ‘compostable’ – i.e. has a coating of compostable plastic – how likely is it that it will eventually return to the soil? Only if it is part of what is effectively a ‘closed loop’ system, for instance at an event or building that has commissioned special collection and treatment.  The London Olympics operated such a system for catering waste with WRAP’s help and with considerable success. WRAP has produced a detailed guide for other event organisers to use compostable materials effectively. I was heartened to read about the collaboration between Vegware and the UK Parliament to replace their single-use plastic food and drink packaging with plant-based products, which are then separately collected and sent to composting facilities.

It is likely that other defined applications such as these could take advantage of compostable plastics, but only if both the material and its appropriate destination are clearly understood by everyone.  There are already some compostable sweet wrappers – such a tiny piece of material may be hard to recycle but perhaps suitable for composting.  The key is to have a logic that makes sense to consumers about what belongs where – tiny and flimsy = compostable, rigid = recycling might be one way of approaching it. 

In the New Year, The UK Plastics Pact is initiating work which will look specifically at what lessons we can draw from the applications and situations where compostables are working well and where there are challenges, as well as how consumer labelling and information could play its part. Like all aspects of the Pact, progress will be guided by the evidence.