The truth about compostable packaging

With the rise of individuals choosing to pass on plastic in response to environmental concerns, the range of ‘sustainable’ and compostable, packaging solutions has increased significantly.  But what is the truth about compostable packaging and is it good for the environment?

And what are the differences between biodegradable and compostable packaging and does it matter?

These two terms are often used interchangeably, but they mean very different things. In this context, oxo-biodegradable materials have been banned Europe wide because they do not meet the rapid biodegradation timescale (90% within 180 days) prescribed by composting standards such as ASTM D6400 and EN13432.

Rather these materials biodegrade into tiny fragments in around 20 years and the resulting micro-particles are indestructible and get into water courses and rivers and then into the food chain making them hugely damaging to the environment – and potentially human health too and hence the ban.

Compostable materials on the other hand must completely break down to make nutrient rich compost – but only a minority are home compostable and limited to just weaker materials as the majority of packaging used for high liquid content products have to be more robust. The more widely used, stronger materials need to undergo industrial, ‘in-vessel’ treatment at specialist sites which require significant energy to heat the waste to 70 degrees to activate the anaerobic process and their breakdown.

And with a lack of appropriate facilities across the UK, only 38% of compostable packaging is currently converted to compost with much of the rest incinerated or sent to landfill where it takes years to breakdown because of the PLA coating used in their production.

How big is the problem?

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 banned oxo-biodegradable plastics in 2019 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 still 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 food to go packaging is required to performance-match conventional plastics and won’t break down at all without the specialist treatment mentioned earlier.

And of course, the materials to produce compostable packaging 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, does continuing to seek single-use packaging solutions make environmental sense?

How do we know what is what?

The biggest potential area for reducing the impact of single-use conventional plastic packaging is in food service as in the main, there are alternative solutions that can work and indeed, we have already seen the widespread use of reusable coffee cups for example.

From sandwich packaging and cutlery to takeaway containers in particular  – putting food in compostable plastic containers means that – in an ideal world, at least – the material and any food waste stuck to them can be composted together with no impact on the processes – unlike waste-contaminated conventional plastics or paper-based solutions which can’t be recycled if they are contaminated with grease or food waste.

But here is the big, and as of now unsolvable problem – how to distinguish between conventional and compostable packaging items?

Currently, we have no way of doing so, either visually or mechanically, so whilst specialist ‘in-vessel’ composting facilities do exist that could process compostable cutlery, coffee cups and food packaging, waste management centres can’t sort them so they head to incineration or landfill instead.

So is composting the environmental panacea that it is widely believed to be? And how much compostable packaging is actually composted?

As mentioned previously, industrial composting in the UK is currently thin on the ground with only a handful of waste processing plants capable of handling these materials so right now only 38% of potentially compostable materials are 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, the use of compostable materials are making things worse as it means uncontaminated, conventional recyclable materials also become consigned to landfill or incineration because of materials mixing.

Closed-loop schemes with a dedicated collection for compostable plastics, like the one launched with Vegware in the UK Parliament two years ago offer some hope.

But they ran into problems as a report published by Footprint in July 2020 revealed that in its first seven months, the scheme had to send all of its compostable plastic to be incinerated, largely because of high levels of materials mixing with conventional plastics.

Cleaning up our act.

The Europe wide and UK adopted 2025 Single Use Materials Pact is focused on encouraging reuse and recycling rather than disposal so that we are not simply substituting the reduction of one finite resource by using another.

There is much to be done with material specification limitations (to reduce sorting and streamline processing) and improvements to recycling facilities, so that recycling rates can be increased from our current 50% reclaim level in the UK.

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 for kerbside recycling is woefully inadequate – as are high street refuse disposal systems.

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 far less risk for the waste management operators to send it to landfill or incineration instead.

The Single Use Materials Plastics Pact

The UK has very clear targets for full implementation of the Single Use Materials Pact, and rightly, the focus of this legislation is on reuse rather than single-use with problematic packaging eliminated through redesign, innovation or re-use models.

And whilst initially there is a focus on moving to making all plastic packaging compostable as a short-term fix, longer term it promotes a reduction in the use of precious natural resources through alternative solutions such as multi-use and back to origin packaging solutions. Indeed, the next step is the introduction of bottle recycling schemes next year.

And initiatives such as our very own Street Food Box are at the vanguard of not only encouraging reuse but making it possible TODAY through our super compact and convenient, fold flat, microwave and dishwasher proof and infinitely reusable container for food to go which includes a set of durable and infinite-use cutlery too.

We’re all about re-use, not recycling or composting and believe we offer a solution that can easily be adopted and make a massive dent in the 11 billion items of single-use, food to go packaging we dispose of each year in the UK alone.

If you’d like to find out more about how we are helping businesses and consumers embrace change, take a look at Street Food Box,our exciting initiative to reduce single use plastics – our launch video can be seen here.

And if you’d like to read my personal story about Street Food Box, you can find it here.

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