Why I don’t like Biodegradable / Compostable Plastics

Grass in Soft Focus

In recent months there’s been a lot of talk about plastic waste in Ireland. I’m hoping that this is a sign of things to come and that we’ll soon be waving bye, bye to unnecessary, excessive use of plastic. Most commentators seem to agree that our use of plastic has got out of hand but I’ve noticed very little discussion about what we replace it with. This worries me.

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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.

At the moment the talk is about banning all non-recyclable plastics in Europe by 2030, again this is worrying. Firstly because it’s too far off but also because recycling isn’t the holy grail and will only work as part of a multi-prong solution with reduction at its heart. Yes it’s better to recycle than send to landfill or incineration but recycling is not a planet positive activity. Realistically we’re always going to need to recycle some of the waste we generate but I’d hate for us to miss a great opportunity to overhaul our waste system completely in favour of just replacing non-recyclable plastic with recyclable plastic. Sure it’s a stepping stone but it shouldn’t be seen as the end game. If you’d like to read why recycling isn’t the answer you can check out an earlier article I wrote.

Another topic that I’m hearing murmurings about is that of biodegradeble / compostable plastics. I’m being a bit facetious with the title of this article . I do think that biodegradeble / compostable plastic could play part in a matrix of solutions required to resolve our waste problems but it is not the silver bullet that some people would like it to be. This is for a number of reasons;

It Uses Virgin Resources. Biodegradeble / compostable plastic, particularly for use in the food industry, is made using ‘virgin’ materials, i.e. materials that aren’t recycled. This is to prevent cross contamination from non-food packaging. This means that the even if the packaging is biodegradeble / compostable some of the energy used in making, transporting, collecting and disposing of it can never fully be recouped making it a negative process in terms of environmental impact, albeit, less than petroleum-based plastics . It also means that it can never form part of a circular recycling system, which is what we should be working towards.

Also quite a few of the compostable plastics 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.

Some biodegradable plastic is made from chicken feathers or shrimp shells, which would be an issue for vegans. Will these be clearly marked and will be facing a call for Vegan plastic in the future?

It’s weaker than standard plastic meaning you use more. Because of the way biodegradable plastic is made it tends to be less strong than other forms of plastic. This means we can end up using more of it to make a biodegradable bag than we would have used to make a regular plastic bag.

It May Use up Valuable Land. 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. Can we really afford to take even more land to grow the plants required to make biodegradable / compostable plastic ?

It 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 allow it to break down we’re releasing that carbon into the atmosphere. It would be much better or us to recycle that plastic so that we can keep the carbon locked in permanently.

It Needs Careful Segregation. Waste has to be divided up into different streams so that it can be sent to the right processor for recycling / composting. Currently organic materials found in plastic recycling streams are seen as a contaminate and risk having the entire load landfilled or incinerated. Will this be the same for biodegradeble / compostable plastics?

And what if some biodegradeble / compostable accidentally gets into landfill? Biodegradable matter generates methane as it decomposes in the anaerobic conditions of landfill. Will this be the same for biodegradeble / compostable plastics? Considering that methane is said to be many time worse for climate change than the carbon we’re all focused on, this could be a massive issue.

Considering the issues with biodegradeble / compostable ending up in the recyclable plastics stream, how will current recycling process ensure that it doesn’t happen? Are we back to replying on the individual to keep the waste streams separate? After all, that worked so well!!!!

It’s Won’t Always Compost. Biodegradeble / compostable plastics 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 biodegradeble / compostable we’re still going to need all those bin lorries coming around collecting our refuse to take it off for industrial composting.

It is worth noting the biodegradeble doesn’t mean the same as compostable. When something is called biodegradable, it means it can be broken down by the metabolism by micro-organisms. There is no stipulation for avoiding toxic residue, nor a requirement that the plastic breaks down into constituent parts, just that it is no longer visible . When something is compostable, it also biodegrades but within a certain amount of time, under certain conditions, (source: Treading My Own Path Blog). 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.

Currently there is no standard for biodegradable plastics in this jurisdiction, only a standard for compostable plastics. Considering the global nature of our food markets, it would be very important to have a global standard for biodegradeble / compostable plastics going forward. Otherwise we could be importing packaging labelled as compostable but only under conditions available in another country.

Similarly labelling needs to be unambiguous and easy for an individual to understand. For example the term bio-based plastic sounds positive until you learn that to be called a bioplastic, a material only needs 20 percent of renewable material; the other 80 percent could be fossil fuel-based plastic resins and synthetic additives.

It may cause Unforeseen Consequences. Biodegradeble / compostable plastic isn’t natural, i.e. it doesn’t occur in nature. It’s created using chemical processes. When I first published this article I said that the chemicals in compostable products must be harmless to humans or they wouldn’t be allowed to use them. How naive I am sometimes. 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? Are we going to find out that the soil with degraded plastic in it is damaged and no longer suitable for farming? Are you going to be happy to buy food that’s been mulched with compost containing these chemicals? Afterall the standards for biodegradeble plastic don’t require them not to leave a toxic residue. (source: Treehugger)

We’re only now discovering the negative impact that processed food has on our own gut biome and how it can affect gut health, even weight maintenance. Are we going to discover the same thing with compostable plastics in years to come?

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;

Staying 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 growers. 

The true cost of Plastic. 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!

A Multi-pronged Approach. Now I’m not saying that biodegradeble / compostable plastics don’t have their place. In the same way as I’m not saying that recycling can play a part but there is a hierarchy, with elimination / reuse as the overriding principle.

Plastic Packaging Hierarchy

I can see why people are hoping that biodegradeble / compostable plastics are the future. If we opt for this as an option 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.

If you’d like to hear more about biodegradable plastic I heartily recommend this very accessible interview with UK based material scientist Mark Miodownik.



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

  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 🙂 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 🙂


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