Single use plastic has found its way into almost every aspect of our lives but is compostable packaging a viable alternative? From the disposable coffee cup we pick up on the way to work, our food to go box, to the straw in our smoothies, they all use plastic.
Of the 6.3 billion tonnes of plastic we’ve disposed of globally since it went into mass production in the 1950’s, a mere 600 million tonnes has been recycled with 4.9 billion tonnes sent to landfill, or incineration or left in the natural environment.
And whilst awareness of the negative impact plastic has on our world has come to the fore in recent years, environmentally friendly alternatives are few and far between and relatively recent.
But are these alternative materials the panacea they are presented as?
Here I’d like to say that compostable and biodegradable are often freely interchanged terms and many individuals think they are different words describing the same thing, but they’re not.
Biodegradable plastics plastics can be broken down by microbes, chewed up and turned into biomass, water and carbon dioxide (or in the absence of oxygen, methane rather than CO2).
A subset of them are compostable, which means that not only are they broken down by microbes, but they can be turned into compost.
As one might expect, there is a European standard for compostable packaging: EN 13432. It requires that the packaging break down under industrial composting within 12 weeks, leaving no more than 10% of the original material in particulate sizes bigger than 2mm in size, and having no detrimental impact on the soil with which it is mixed.
Only a minority of these plastics are home compostable as there are limited uses for ‘weak’ materials and the majority of packaging used for high liquid content products have to be more robust so they need to undergo industrial treatment at specialist sites but they are far from guaranteed to make it to one with just two UK sites currently able to process them.
Part of the problem of course is being able to identify and sort a myriad of different unsegregated waste and the somewhat simplistic scheme we have in the UK of coloured bins to aid our sorting of waste is woefully inadequate.
And if we get it wrong – which we do constantly, the impact can be massive so rather than risk incorrectly sorting industrial compostable materials from mixed waste it’s less risk to send it to landfill or incineration.
How do we know what is what?
Imogen Napper at the University of Plymouth collected carrier bags with various claims about biodegradability, and put them in three different natural environments over a period of three years: buried in soil, left in the sea, and hung up in the open air.
She tested bags labelled as biodegradable, compostable, and oxo-biodegradable, as well as conventional high density polyethylene (HDPE) bags. (The UK has banned oxo-biifegradable plastics from this year because they break down into microplastics which are with us forever and get in water courses and the food chain.
In Napper’s experiment, the bag labelled ‘compostable’ and was to standard EN 13432 disappeared entirely within three months when it was left in seawater.
In soil it remained intact for two years, but disintegrated when the researchers loaded it with shopping.
The rest of the bags – including the one labelled “biodegradable” – were still present in both soil and sea water after three years, and could even hold shopping.
After nine months in the open air, all of the bags had disintegrated or were beginning to come apart, mostly breaking down into microplastics.
That’s because sunlight helps break down plastics through a process called photo-oxidation, in which the plastic becomes weathered and brittle, eventually fragmenting rather than breaking down to its organic components.
Of course, even the compostable bag tested in Napper’s experiment is not designed to break down in the sea or in soil.
But she says that the fact that these plastics have to be industrially composted is not adequately explained on the bags themselves, leaving consumers guessing about what the bags can and can’t do – and, crucially, what they should do with them once they’re finished.
‘We need to be aware that putting it in the recycling or trying to compost it or putting it in the general waste bin won’t necessarily get them the results they’re expecting’ says Napper.
Whilst thin compostable plastics like carrier bags might break down in the ocean, the thicker and more robust PLA used to line coffee cups and make cup lids, clear plastic tumblers, drinking straws, and other food packaging is expected to performance match conventional plastics and won’t break down at all.
So, are companies switching to biodegradable plastics that might not break down in the sea ‘greenwashing’? Not necessarily. These plastics might not solve our marine plastic pollution problem, but they are well suited to tackling another big environmental problem of food waste.
Cleaning up our act
The biggest potential area of impact for compostable plastics is in food service.
From coffee cups to sandwich packaging to takeaway containers, putting food in compostable plastics means that – in an ideal world, at least – the material and any food waste still stuck to them can be composted together.
So this appears to be a triple win: reducing the amount of plastic being sent to landfill, preventing recycling from being contaminated with food, and at the same time making sure food waste is returned to the soil, not left to rot in landfill where it will release methane.
But this ignores the fact that the materials to produce compostable materials is not infinite, nor is the energy to make them and after just one use, they are theoretically gone forever producing nothing more than compost and gas.
And whilst this may be a solution to materials disposal, reducing the volume of waste which goes to landfill or incineration, does this make environmental sense?
By reducing the amount of traditional plastics that contaminate food waste, we can at least ensure that some of that wasted food is eventually used as compost, rather than ending up in landfill or incineration. But how much compostable packaging is actually composted?
Industrial composting in the UK is currently thin on the ground with only a few waste processing plants capable of handling compostable materials so right now only 38% of compostable materials are composted.
Though in-vessel composting facilities exist that could process compostable cutlery, coffee cups and food packaging, councils don’t collect these items, so consumers are left with no option but to put them in the general waste where they’ll head to landfill or incineration.
Some local authorities take compostable carrier bags if they’re used to collect food waste, but at some plants those bags are removed from the food waste before it’s composted.
A clearer labelling system, similar to the way recyclability is marked on food packaging, is in development, but it will take some time for the system to be implemented and in the interim, plastics are going to end up in composting plants causing problems and much of our compostable waste will not get processed.
Closed-loop schemes with a dedicated collection for compostable plastics, like the one launched with Vegware in the UK Parliament last year, offer some hope.
But they have run into problems as a report published by Footprint in July last year revealed that in its first seven months, Parliament’s scheme had to send all of its compostable plastic to be incinerated, largely because of high levels of contamination.
But they have run into problems as a report published by Footprint in July last year revealed that in its first seven months, Parliament’s scheme had to send all of its compostable plastic to be incinerated, largely because of high levels of contamination
The UK Plastics Pact
The UK plastics pact has very clear targets for full implementation by 2025 and rightly so the focus is on reuse rather than single use with problematic or unnecessary single-use packaging eliminated through redesign, innovation or re-use models.
And whilst initially there is a focus on making all plastic packaging compostable, longer term it promotes a reduction in the use of precious natural resources as alternative solutions such as multi-use, back to origin packaging solutions become a part of our everyday lives.