Are Biodegradable Plastics Good For The Environment?

Want to know if biodegradable plastics are good for the environment?  Let me talk you through the facts.

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’m aiming to separate environmental fact from greenwash.

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

Are Biodegradable Plastics Good for the Environment?

Plastic bags, food wrappers, nappies, and some other plastics are often labelled as biodegradable.  Manufacturers don’t explicitly say that these products are better for the environment.  However, this choice of wording 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.

Conventional Plastic Vs. Biodegradable Plastics

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

Conventional Plastic

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

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.  However, it 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.  They 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 our waste goes.

Disposing Of Plastics

In order for biodegradation to occur three basic resources are required.  These being 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. This places them in the ‘Other’ category of plastics.  Code 7 plastics are generally not accepted for recycling by local councils.  The reason being behind this is that biodegradable plastics are harder to recycle due to the addition of chemical additives in them.

What About Composting?

If you want to get around 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.  This is because 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.  This is 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 the risk of ingestion for animals and end up in our oceans and waterways.   These kinds 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.  This is because 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, like some plastic-free tea bags.  Commercial composters reach the kind of temperatures and humidity levels you would be unable to achieve in a standard garden composter.  Therefore your bioplastics may never truly break down at home.

Other Bioplastic Points to Consider

If that isn’t enough of a headache for you, with bioplastics you also have the added headache of 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 farmland that could be used to grow food crops.  

Other potential impacts of the growth of bioplastics crops include, but aren’t limited to deforestation, monocultures, use of freshwater 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. That is apart from avoiding single-use plastics where you can. And also recognising that if a product is labelled as biodegradable then it’s often not the great 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 have access to the appropriate composting facilities.

Composting biodegradable disposable 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.  Consider how many nappies a baby goes through in a day, and the length of time it would take for a nappy to break down at home.  You would therefore 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.

If you enjoyed this post then you may enjoy my post on the plastics to avoid when you’re shopping.  It covers things like the type of plastic, but also, perhaps lesser-known, the colour of plastic.