are biodegradable plastics good for the environment

Are Biodegradable Plastics Good For The Environment?


As consumers the way products are marketed to us influence our purchasing decisions.  However, it’s often difficult to know if a product is actually green or if it’s just greenwash.  To help you navigate labels, packaging and adverts I’ve started my new Greenwash 101 series, which aims to separate environmental fact from greenwash.

I’ll start with the main one that gets touted around: biodegradability.

Plastic bags, food wrappers, nappies and some other plastics are often labelled as biodegradable.  While manufacturers don’t explicitly say that these products are better for the environment, this choice of word implies that these are better choices for the environment.

Let’s take 5 minutes here to examine whether biodegradable plastics are good for the environment or whether it’s corporate greenwash.

greenwash 101

Are Biodegradable Plastics Good For the Environment?

Conventional Plastic Vs. Biodegradable Plastics

Firstly, let’s look at the difference between conventional plastics and biodegradable plastics.

Conventional plastics are made from petroleum based products derived from oil.  They will either take hundreds of years to break down or, in the worst case, never decompose.

Biodegradable plastics are made from conventional petroleum based plastics, but also contain chemical additives.  These additives cause the plastic to break down more rapidly when exposed to air and light, but could take anywhere between 2-5 years to break down, if not longer.

The other type of biodegradable plastic is known as bioplastic.  Bioplastics tend to be made from plant biomass, such as corn starch, sugar cane or wheat, and should either completely and rapidly break down naturally, or be compostable.

However, and it’s a big however, whether a product is biodegradable or not ultimately depends on where it ends up.

Let’s think about that last sentence for a minute, and think about where out waste goes.

Disposing Of Plastics

In order for biodegradation to occur three basic resources are required – heat, light and oxygen.  If a biodegradable plastic or bioplastic ends up in a landfill site it will never decompose.  In landfill sites waste is essentially mummified, in a complete absence of light and oxygen.  Food that has ended up in landfill will not biodegrade, so there is no hope for biodegradable plastics or even bioplastics.

You would think then that the answer is therefore to ensure that you always compost or recycle your biodegradable plastics.  Unfortunately it’s not that simple.

Biodegradable Plastic Disposal

Most biodegradable plastics are classed as code 7, which places them in the ‘Other’ category of plastics.  Code 7 plastics are generally not accepted for recycling by local councils.  This reason being behind this is that biodegradable plastics are harder to recycle due to the addition of chemical additives in them.

If you want to get round the landfill and recycling issues, and pop your biodegradable bags in your compost heap then you’ll also come a cropper.  Polyethylene, which is what biodegradable bags are commonly made from, often contains a manganese additive.  This additive stops breaking down when placed in compost bins/heaps.  Scientists think this most likely occurs due to the influence of ammonia or other gases generated by microorganisms in the compost.

Even if you were to get lucky on the composting front, and your plastics did break down then you will likely encounter another problem.  Because biodegradable plastics are made from petrochemicals they aren’t always suitable for composting, as they can leave behind chemical residues in your lovely compost.  The key lesson learned here is that biodegradable is not the same as compostable.

And there’s more.  Some biodegradable plastics actually fragment rather than biodegrade, due to the addition of oxidising agents (found in so called oxo-degradable plastics).  By fragmenting, rather than degrading, they break into small pieces which can pollute soils, increase risk of ingestion for animals and end up in our oceans and waterways.   These kind of plastics are impossible to recover for recycling and aren’t suitable for composting.

Bioplastic Disposal

At this point you might be thinking that surely bioplastics are a better environmental option?  The thing is, if bioplastics are sent for recycling, these types of plastic cannot be recycled with standard plastics as the additives in bioplastics can make the recycled product less durable.

Therefore the easy answer would be to ensure that you always compost bioplastics.  However  if you don’t have the ability to compost your waste (perhaps you don’t have a garden) then you are out of luck.

Don’t be so smug if you do have the ability to compost though: some bioplastics will only compost in commercial composters.  Commercial composters reach the kind of temperatures and humidity levels you would be unable to achieve in a standard garden composter, so your bioplastics may never truly break down at home.

If that isn’t enough of a headache for you, with bioplastics you also have the added headache on how the plant material that was used to create the bioplastic was grown.  Concerns include the use of GM crops, and the use of valuable farm land that could be used to grow food crops.  Other potential impacts of growth of bioplastics crops include, but aren’t limited to: deforestation, monocultures, use of fresh water supplies, soil erosion, fertiliser use (which often comes from petrochemical sources), pesticide use, food supplies, food prices and food security.  Makes for quite heavy reading, doesn’t it?

What’s The Answer?

I’m afraid to say that there is no easy answer to the plastics conundrum, apart from avoiding single use plastics where you can and recognising that if a product is labelled as biodegradable then it’s often not the environmental choice that it seems.

Biodegradable plastics are rarely recyclable, and biodegradable does not mean the same thing as compostable.  Compostable goods are often a better choice than biodegradable ones, but only if you can compost appropriately.

Composting nappies, for example, is almost never a good choice because of the mix you would need of green material (e.g. grass clippings, leaves, etc) to nappy.  Considering how many nappies a baby goes through in a day, you would need more than a few compost heaps and a ready supply of green material to be able to compost effectively.  A better choice in this example would be washable nappies.

Check back again soon for the next Greenwashing 101 installment!


  1. Wow, that’s certainly eye-opening – you just re-awakened away the quieted conscience :)

    One question though regarding “Concerns include the use of GM crops”. What is the problem there? Are you concerned the introduced DNA is attacking the compost? (it will degrade just like any other plant DNA) Land and pesticide use is reduced with GE crops which is good, right?

    • The main concern over the use of GM crops is that other crops and wild plants may become contaminated with the foreign genes added to the GM crop – e.g. from pollen, which can travel long distances on the wind/insects.

      I’ve also read that there are concerns that new ‘super-weeds’ may evolve which will be difficult or even impossible to eradicate, and may impact on local biodiversity, and there are concerns for wildlife, which may be harmed by new toxins in the environment or by changes in agricultural practices.

  2. I live in San Francisco where all buildings and businesses have a ‘green can’ for compost – including bioplastic, which are now about the only bag you can put produce in at the local healthy food markets. My question is a bit different. I’ve noticed that bioplastic bags have a terrible smell – very similar to slightly old fish. Since air and damp is what begins the composting process, I feel that the bags are composting already as I shop, and certainly in the fridge right along with my fresh organic veggies! Is this healthy??

    • Wow, we are so far behind over here in the UK! I wouldn’t imagine the bags would cause you any problems, but if you’re at all worried then remove your fruit and vegetables from their packaging as soon as you get home. You can also buy reusable fruit and veg bags if the markets let you use them – like these ones

  3. This is really insightful! I have no garden and would turn to the biodegradable garbage bag (which I try to make sure is the only single use plastic I buy) as the ‘less damaging option’ without really considering the points you make! Ah, what to choose as an alternative though?!

    • If it’s to use for waste going to landfill then to be honest it doesn’t matter what you use as nothing really decomposes in landfill. Biodegradable plastics are still made from oil based petrochemicals so you’re not even getting the benefit of using a product not derived from oil.

    • I know it’s been a while since you posted this comment, but I think that if the type of plastic you use doesn’t directly affect the environment (as they fail to decompose in landfills anyway) then you should try to support whichever technology you think is best in the long term. The more demand there is for certain types of plastic, the more it is likely to be supported through special rubbish collections etc. and the more likely it is to be used frequently.

  4. Quiet an interesting info, I always have been known, that there is a major difference between plastics and biodegradable plastics, but you’ve made a deep research!

  5. I think the hurry to develop greener options cause this: new options that are not really options, just different versions of the same problem! They keep launching new types instead of finding the best and developing the required processes and infrastruture to handle it.

  6. Thank you. This article was incredibly helpful. Though, as another comment noted, the knowledge can make life more complicated. Sigh. SaraBella, out of Portland, Oregon makes gorgeous totes out of plastic bags that were on their way to the landfill. (I have some on my new site please forgive the plug (-:

  7. Biotecbags in India claim to have created a truly bio-degradable plastic that uses a particular type of enzyme additive to effect the biodegradation. If you have a chance to look into the site, let know what you think of it.


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