Why I don’t like Biodegradable / Compostable Plastics 2022

Grass in Soft Focus

Ireland is slowing waking up to the problem of plastic waste. This is a good thing, particularly if it encourages to reduce our creation of it. But has it? I’m worried that we’ve just swapped our addiction to recyclable or compostable plastic instead. I’ve written before on why recycling isn’t the answer, so in this article I’m going to pick through all the reasons why biodegradable or compostable plastic is a red herring too.

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In Ireland we tend to be very good at saying what we don’t want but then we end up in circular discussions on what to replace it with.  It’s very easy to call for the ban of this or the taxation of that but if we don’t carefully consider a viable alternative and design a processes that support its use we’ll just end up in the situation again with a different material in a decades time. For example a lead away from animal based oils in products led to surge in use of palm oil, which is now causing concern as the farming of it has led to huge swaths of rain forests being felled.

The Problem with Biodegradable / Compostable Plastic

Biodegradable versus Compostable

First things first, biodegradable isn’t the same thing as compostable. When plastic is certified compostable it has been independently tested and shown to confirm to legal standards for compostability, which outline how long the process should take, under what conditions and what residue is allowed.

On the contrary the term biodegradable is not legally define, therefore anyone can call something biodegradable, even if it lasts a 1000 years, and face no legal sanctions. In reality most people use the term biodegradable when talking about composability, but don’t assume so. I’ve caught out quite a few companies using the term incorrectly, sometimes intentionally.

While I’m on the issue of misleading labels I want to let you know that the term bio-based plastic is not always as good as it sounds. A material only needs to contain 20 percent renewable material to call itself bioplastic; the other 80 percent could be fossil fuel-based plastic resins and synthetic additives.

So let’s look at all the reason why compostable plastic isn’t necessarily the ‘wundermaterial’ it’s being touted as.

Compostable plastic uses virgin resources

This is particularly true in the food industry, due to concern over cross contamination from non-food packaging, which makes sense. Making materials from virgin feedstocks generally requires more energy than making from recycled materials or simply reusing packaging over and over again.

Compostable plastic can be made from GMO crops

Quite a few of the compostable plastics on the market are made from corn starch, which may or may not have been genetically modified. I don’t know enough about GMO crops to say definitively if GMO corn needs to be avoided, but I do know that there are concerns around it and we need to have a conversation about it before ploughing headlong down this road.

Compostable plastic may not be vegan

Some biodegradable plastic is made from chicken feathers or shrimp shells, which would be an issue for vegans or anyone wanting to avoid animal products. Will these be clearly marked and will we be facing a call for vegan plastic in the future?

Compostable plastic can use up valuable land

If derived from plants, this material diverts land away from food production, which is the opposite of what we need to be doing now. We’re in the middle of the 6th Mass Extinction of Life on this planet, partly because of the sprawl of humans across the natural world. We need to be giving more land back to nature, not using it to grow plastic.

Compostable plastic puts carbon back into the atmosphere

Plastic whatever it’s type, is made of carbon. When we make it in a form that is biodegradable and let it break down we release all the carbon in it back into the atmosphere. It would be much better or us to recycle that plastic so that we can keep the carbon locked in permanently.

Compostable plastic  needs careful segregation

Waste has to be divided up into different streams in order to go the right processor for recycling / composting. The only way to make sure your compostable plastic gets into the right waste stream is to put it in an bin designated for industrial composting, and that generally isn’t easy, meaning most compostable plastic ends up going to incineration or landfill.

Also biodegradable/compostable plastic is virtually indistinguishable from standard plastic to the naked eye. This can lead to waste processors picking it out of organic waste for fear of contamination, leading to some of it going to landfill or incineration.

Similarly compostable plastic can end up in the recyclable plastics stream, leading to problems in the recycling of standard plastics.

Compostable plastic can release methane

If biodegradable / compostable plastic gets sent to landfill it could degrade and in doing so release methane into the atmosphere. Methane is up to 30times more damaging than CO2 in terms of climate change so landfill management companies try hard to prevent materials in landfill from decomposing. Therefore it stands to reason that compostable plastic that finds it’s way into black bins is contributing to climate change.

Compostable plastic doesn’t always compost

Compostable plastic only degrade in certain conditions, conditions that generally aren’t available in home composters. So even if we were to do a straight swap of recyclable plastics with compostable we’re still going to need all those bin lorries coming around collecting our refuse to take it off for industrial composting.

Also even if something says it’s home compostable doesn’t mean it will successfully break down in every home composter, which is why material scientist Mark Miodownik and his team in the University of London launched the Big Home Composting Experiment in Nov 2019 to see if home compostable plastic do actually do need to break down in home composters. Spoiler alert: It doesn’t

Compostable plastic can be harmful to health

Compostable plastic isn’t natural, i.e. it doesn’t occur in nature. It’s created using chemical processes. A thorough investigation of the issue by the non-profit US based New Food Economy revealed that moulded plant fibres, like those used to create compostable take-away containers contain chemicals that have been show to harm human health. and a study carried out in 2019 concluded that ‘all PLA products induced strong baseline toxicity similar to PVC and PUR. This demonstrates that this bio-based and biodegradable material, despite being marketed as better alternative, is not necessarily safer than conventional plastics

If they’re having this impact on our health what are they doing to the microbes in the soil? will soil mulched with compostable plastic be no longer suitable for farming? Are you going to be happy to buy food that’s been mulched with compost containing these chemicals?

Here’s a nice little infographic on the concerns around biodegradable and bio-plastics.

The Solution

As I see it we’ve ended up going down a road that can’t be fixed by tinkering around the edges. We now have a great opportunity to radically review how we generate and process waste in this country and I hope for our sake and that of our children we’re brave enough to do it. Here are some of the ways I think we can avoid repeating the same mistakes;

Buy local

Plastic packaging, in particular, has increased in line with globalisation. If you’re buying apples from the local shop who gets them from the local farmer you really don’t need to package them heavily because the supply chain is so short and the apples aren’t travelling far. It also makes it possible to give packaging back to the farmer, via the shop, to reuse, reducing the reliance on single-use packaging. Whereas if you’re buying mangetout from Kenya and it’s going to be in transit for 4-5 days then you’re going to have to package it heavily to 1) protect it and 2) keep it as fresh as possible. To me it seems clear if you want to reduce packaging you must support local producers

Include the full cost of packaging in the retail price of the product

Who is paying the true cost of plastic? We are; through taxation and bin charges. If manufacturers and retailers had to integrate the cost of collecting and disposing, in a sustainable manner, of the plastic we’d see a huge change in product costs. Wouldn’t we suffer? Yes and no. With a level playing field local producers, who can supply with less or no plastic could compete with multi-nationals who defer the true cost of waste onto citizens of the countries that they operate in. And in theory bin charges and taxation should come down or go to financing other services.

Some will argue that companies are paying the true cost of waste through their membership of Repak, a non-profit self-certifying industry body. Surely if this was the case waste management facilities in this country would be state of the art, our bin charges would be minimal and our litter warden departments would be the best paid in Europe!

Interestingly part of Repak’s remit to help its members reduce the packaging that they put onto the market and yet they base their fees on the amount of packaging their members produce. Somehow I don’t think their business model matches up with their objectives!

Apply a multi-pronged approach

I’m not saying that compostable plastics don’t have their place, but there is a hierarchy, with elimination / reuse as the overriding principle before single-use, even compostable.

Plastic Packaging Hierarchy

I can see why people are hoping that compostable plastics are the future. Switching to compostable plastic means we don’t need to change our behaviour. We can continue to import cheap food from around the world, use plastic bags to carry our shopping home and drink bottled water with abandon. People want change, they just don’t want to change. I hope I’m wrong.


Published by Elaine Butler

I am a circular design consultant helping manfacturers prepare for the circular economy

5 thoughts on “Why I don’t like Biodegradable / Compostable Plastics 2022

  1. Nice post! I like your pyramid. You could divide the top section into recyclable plastic that’s made from recycled post-consumer plastic (and then virgin recyclable plastic at the top). I agree with you – no plastic is the best option πŸ™‚ I think that compostable plastic is an improvement and (like some other ideas that were not perfect) is hopefully stepping stone towards something truly sustainable. I’ve written a review comparing three companies that make compostable plastic, from a Green Stars point of view (social and environmental impact). You can read the review here if interested πŸ™‚


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