Biodegradable plastic bags carry more ecological harm than good

Filed in Waste News by on June 24, 2009 27 Comments
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Biodegradable carrier bags - the solution to the issue of plastic or ecological time bomb?

Biodegradable carrier bags - the solution to the issue of plastic or ecological time bomb?

This is an issue I’ve wondered about for a long time. My understanding of biodegradable bags was that they simply broke down into tiny slivers, much like the ones lining the ocean floor. As litter they can be ingested by animals with devestating effects.

Beth, over at Fake Plastic Fish tweeted this article from the Guardian, which answered most of my concerns. However, it seems that biodegradable plastic bags breaking down into tiny slivers is the least of our worries.

Here’s the scoop.

“Biodegradable plastic bags – as handed out by Tesco, the Co-op and once even sold by the Soil Association – must be good, surely? They have a magic ingredient that means they self-destruct after a few months, breaking up into tiny pieces made of simple molecules that bugs and fungi can happily munch up. Dozens of major corporations use them, including Pizza Hut, KFC, News international, Walmart and Marriott hotels.

But last week, the European Plastics Recyclers Association warned that they “have the potential to do more harm to the environment than good.”

Technically what we are talking about here is “oxo-degradable” plastics. These are plastics made to degrade in the presence of oxygen and sunlight, thanks to the addition of tiny amounts of metals like cobalt, iron or manganese.

British manufacturers – headed by Symphony Technologies of Borehamwood – are at the sharp end of a revolution that could banish bag-strewn beauty spots and back alleys alike.

But the criticisms are twofold. First, some research suggests that the bags don’t degrade as well as claimed. And second, priming plastic bags for destruction is itself an ecological crime.

So, do they really biodegrade away to nothing? Symphony, which supplies the Co-op and Tesco, says its bags are “able to degrade completely within about three years, compared to standard bags which take 100 years or longer”. Tesco reckons they all decompose within 18 months “without leaving anything that could harm the environment”.

But whether it actually happens seems to depend a lot on where the “biodegradable” plastic ends up. If it gets buried in a landfill it probably won’t degrade at all because there is no light or oxygen. But what about elsewhere?

Studies of one brand in the US, commissioned by the Biodegradable Products Institute, found that breakdown is very dependent on temperature and humidity. It goes slow in cold weather. And high humidity virtually stops the process, making long, wet winters sound like bad news.

You might think a compost heap full of biodegrading bugs would be ideal. But a recent Swedish study found that polyethylene containing manganese additive stops breaking down when put in compost, probably due to the influence of ammonia or other gases generated by microorganisms in the compost …”

Read the rest of the story “Biodegradable plastic bags carry more ecological harm than good ” by Fred Pearce in the Guardian.

If you want to make the switch to reusable bags; we have just the thing for you! Made from recycled rice sacks, these large, heavy duty reusable shopping bags are available exclusively through us in the UK.  Buy yours here!


About the Author ()

I am a long time supporter of the Green and Sustainable lifestyle. After being caught in the Boscastle floods in 2004, our family begun a journey to respect and promote the importance of Earth's fragile ecosystem, that focussed on reducing waste. Inspired by the beauty and resourcefulness of this wonderful planet, I have published numerous magazine articles on green issues and the author of four books.

Comments (27)

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  1. John Costigane says:

    Hi mrs Green,

    Biodegradable bags sounded good to begin with but it emerged thta in decomposition in landfill, methane is released. This is useful in a controlled situation like AD, but no so good in landfill. I do not use these but polythene is recyclable (with difficulty so far) so is of some use.

    Reusable bags are the answer to plastic bags, of all types, though home compostable types would be acceptable if 100% safe in the composter.

  2. Ailbhe says:

    So what do I do to contain my landfill waste now?! We’re down to half a wheelie bin in six weeks, and if the contents aren’t contained in something things get complicated. Mine are from – I’m cross now 🙁

    Perhaps the answer is a series of those weeny cornstarch nappy sacks?

  3. Mrs Green says:

    @John Costigane: Hi John, like you I thought biodegradable bags were a great idea at first. But reading this article taught me a lot about the environmental impact of them. SOme of the issues I was not aware of and others I hadn’t thought of such as if we’ve taken the oil to make the bag anyway, then let’s try and make something that lasts from it, rather than something that degrades quickly. There is a lot to think about.

    @Ailbhe: Hi Ailbhe; it’s a difficult one isn’t it. I find that I’m ok when I don’t know the facts, but once presented with them it can make decision making incredibly difficult! Ignorance can often be bliss 😀
    Half a wheelie bin in 6 weeks is fantastic. I’m not sure I understand why things get ‘complicated’ if the contents are not contained. Perhaps you prefer not to say, but if you can elaborate, perhaps we can come up with some suggestions; as my first suggestion would be not to bother bagging it all up.
    It’s worth looking into the cornstarch nappy sacks I guess; but I’m not sure how I feel about plastic made from food stuff when half the world is starving.

    it’s not easy being green, eh?!

  4. Layla says:

    I thought biodegradable bags were suspicious for quite some time!

    Apparently there are also different kinds: just the ‘degradable’ ones that still leave tiny plastic particles & the ‘biodegradable’ that were said to be better – though I still had doubts about those.. & even if they were totally ‘okay’ they’d still encourage the throwaway ‘waste of resources’ mentality…

    still need to read more about this all I think..

    Ailbhe half a wheelie bin in 6 weeks is fantastic indeed!! 🙂 Congratulations!!
    /Maybe you can aim for 2 months now? ;)/

  5. Mrs Green says:

    @Layla: Hi Layla, yes there is lots of material to read around, understand and digest; it’s never straight forward as the public are rarely privy to all the information.

    I’m just so glad we have people like you who care enough to find out what they can in order to make positive choices 🙂

  6. Rob Whittle,Nail2 says:

    I’ve looked at the Biodegradable bag idea and concluded 2 years ago it was a bad idea coming from trendy companies like Ikea, and alike..then Tescos.

    I my mind fibre jute/ hessian or cloth bags are the best for general purposes. One such bag has lasted 3 years prior to being put on the compost was the bottom corners and handles that went first. The others I purchased are still in action.

    I guess the only biodegradable plastic bags that are acceptable are the special corn starch ones issued for food waste collections that are centrally processed via a masher and anaerobic digester.

  7. Mrs Green says:

    @Rob Whittle,Nail2: Hi Rob, it is a minefield, but as I said in my radio interview this week, we have to try things out and find the right tool for the job with reusable bags, just as we do any other purchase in our lives.

    3 years is pretty good for a bag; most of mine have lasted longer than that. I am yet to ditch one – fingers crossed!

  8. michael says:

    I flush my dog’s poop down the toilet with a flushable doggy waste bag. Most eco-friendly way to get ride of dog poop.

    The company is called Flush Doggy.

    There are flushable dog poop bags. The best answer probably because dog poop can get treated just as your poop is.

    FlushDoggy, is a fully biodegradable, flushable(water soluble) dog waste bag that is very eco-friendly.

    Dog doodies are best to be flushed down the toilet and degrade naturally , just as our own doodies. Stop destroying our earth and start educating the public, one poop at a time. Be a responsible owner and go green for our pets.

  9. Mrs Green says:

    @michael: Thanks for the standing ovation speech there Michael LOL! Interesting stuff. I’m **very** uncomfortable with the idea of flushing a bag down the toilet; I can forsee terrible blockages and the bag filling with air and bobbing around like a buoyancy aid.

    Why not empty the dog crap into the toilet instead of flushing a bag down there?

    You say flushing down the toilet in a waste bag is the “Most eco-friendly way to get ride of dog poop.” according to whom? Do you have some research stats on this? I would have thought putting it all in one corner of the garden or in a dog loo was the best way, but I do not know enough about it and am open to being educated on this topic.

    I look forward to your answers 🙂

  10. Rob Whittle,Nail2 says:

    @ Mrs Green; lol, the jute bag that lasted 3 years was stress loaded daily for work with 5-7kgs (akin to loading a Mini car with half a tonne of bricks daily); so one amazing jute bag. The broken one I used to take food waste to the allotment before eventually composting it. The others 3.5yrs are still going strong”lol.

  11. Mrs Green says:

    @Rob Whittle,Nail2: Oh my goodness; you’re a task master; three years is GREAT then!
    You could be a product tester 😀

    I wonder if the onya bags would suit you – made from parachute material. Not biodegradable though; so, I guess they give with one hand and take with the other.

    it’s not an easy choice.

  12. Walter says:

    It does seem that all the work to find a bag that is truly recyclable was invented before the plastic bag, anyone remember the paper bag. Totally recyclable and with tree farms all over the world, paper bags are basically the answer. We will come full circle once this is done. Now we just need the environmentalist to agree that they were wrong for once and get paper bags back. The nice thing about paper bags is that they had many uses to extend the life of the bag ie: book protectors, garbage bags, recyclable, compostalble, and they were reusable if they didn’t get wet, etc. The only problem that I see is that they can not believe that they were wrong all these years ago and admit it.

  13. Mrs Green says:

    @Walter: Hello Walter; thank you for your comment. Until a very short time ago, I agreed 100% with you – paper bags seemed like the no-brainer idea that had gone out of fashion.

    Then we got talking to a lady who has worked with WRAP and studied the whole polythene /. paper issue. Her take is that paper can only be recycled a handful of times before the fibres become so weak they are useless.

    polythene can be recycled many times.

    You can read more about it here:

    It certainly opened my eyes and got me thinking in new ways about the whole plastic / paper debate. It appears it is not quite as clear cut as I thought 🙂

  14. Poppy says:

    @Mrs Green:

    I have a ‘plastic’ bag that has me puzzled. It says Degradable on it, but the small print goes onto say the same as the Trackback posts. So what do I do with it? Compost or rubbish?

    The post by Michael reads like an advert to me and like you Mrs G, I would worry about flushing plastics down the loo.

  15. Mrs Green says:

    @Poppy: Where is the bag from, pop socks? I would personally call the retailer if you can, to find out more.

    I think the word ‘degradable’ on a bag is a bit like ‘natural’ on a shampoo – it’s meaningless. I mean, **everything** degrades eventually??

    You need more information, my sleuth friend.

  16. Poppy says:

    ‘Pop socks’! You’re showing your age Mrs G!

    It was from Lidl … I’ll see what I can do 😉

  17. Poppy says:

    Ooops! Aldi!! They are so much alike, it’s easy to get confuzzed!

  18. FR. Peter says:

    Some ‘degradable’ plastic bags have an addition of corn starch in their structure, this seems to be about 10%. The corn starch breaks down OK but the plastic still remains, tiny slivers or not, it still pollutes.

    Pop one in your compost and see what happens, but don’t hold your breath, certainly they degrade quicker if they are left in hedges to the vagaries of the sun, wind and rain but that is not how they are marketed to us. The claims sound good but are disingenuous.

  19. Ben says:

    @michael: Waste flushed down the drain in the UK goes to sewage treatment plants, which is a very energy intensive process and also results in a lot of solid waste for landfill.

    I wonder if it’s best to just bag and bin them (in the appropriate dog mess bins) so they go straight to landfill rather than mixing them up with clean water just to transport it to the sewage plant where they spend energy removing it from the water to then just put it in the landfill anyway.

  20. Mrs Green says:

    @FR. Peter: I Agree Peter, this whole thing about degradable bags is confusing and much of it is greenwashing. It’s tiny slivers, as you say; which is creating a carpet on our ocean floors.

  21. Rob Whittle,Nail2 says:

    The whole biodegradable retail bag direction is a big greenwash scam IMO; and should be kicked into touch. If it doesn’t fully biodegrad; it shouldn’t be used.

  22. John Costigane says:

    @Rob Whittle,Nail2: The thinking behind biodegradable was well-meaning but fell well short of home compostable which has value. Companies, like Aldi, are stuck with the material.

  23. Layla says:

    Hmm, I agree that dog poo in a bag is a big question, wherever you put it..

    Sludge from sewage treatment plants is not even ‘just landfilled’ – here, they built an incinerator to co-burn it, & it doesn’t burn (well)!! bad technology, I hear..

    it makes more sense to leave the poo to biodegrade innature, depends on where it happens, I guess..

  24. Sil says:

    I appreciate your intention of having a low impact on the earth using biodegradable bags but i do think that’s it is a psicological manipulation. Using those bags we think that our impact on the earth is gonna be lower because they are biodegradable but no many people think how much energy and petrol has been used to produce them.

  25. Mrs Green says:

    @Sil: Hello Sil, welcome to the site; we agree with your comment. If you read my thoughts, it is that biodegradable plastic bags are NOT good for the environment. So, you are in good company!
    Thank you for sharing your thoughts on this important issue.

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