About biodegradable plastic


Are you noticing a trend towards bio degradable packaging? Thinking about joining in?

If so, read this first to make sure you are not just adding to a problem rather than finding a solution.

You probably know that traditional plastic is made of oil. Plastic is a very versatile, durable and cheap material. It can help to conserve resources, lighten transport loads and apparently make fresh food last longer. Maybe because it is such an amazingly versatile and durable product, that is why its use has become so prolific. But we are victims of our own success here. We are now messing up our planet with all the plastic we’ve used over the last 100 years. The problem is, we didn’t think about what was going to happen to all this plastic when we no longer needed it – which is often very soon after we used it in the first place. Traditional oil-based plastic doesn’t biodegrade. It can remain in its manufactured form form many years. It hasn’t been around long enough for us to know exactly how long. Estimates for a plastic bag are between 10 and 1000 years. A plastic bottle is thought to take 450 years or more to break down.

Biodegradation is a process whereby a material iOS broken down by bacteria turning it into soil. Most bacteria will not process oil based plastic. But we do know that plastic sometimes does degrade. You may have seen a very old plastic bags, picked it up and the bag just drops down leaving you holding only the handle. So annoying, right? So how is it degrading, why and into what?

Oil based plastic will degrade by reacting with sunlight. UV rays break up the bonds that make the long molecule chains that form the plastic.  What that means is that plastic will “break up” into lots of smaller pieces of plastic. The smaller the pieces, the harder they are to remove from the environment. When they are really small they are known as microplastics. And we’ve heard a lot lately about how our oceans are full of microplastic.

So, what is biodegradable plastic?

I would describe it as an alternative way of making plastic from plant based materials such as corn starch. To be called bio plastic or marked as compostable, the plant-based plastics must go through rigorous and time consuming testing to ensure that it fully biodegrades into soil, that it contains an amount of heavy metals that is within an acceptable standard to not cause environmental harm and that the soil will successfully germinate seeds.

However, biodegradable (or compostable) plastic will only biodegrade in certain conditions (similar or more favourable than the conditions of the test environment that gained them the certification.

What are those conditions? Biodegradable (or compostable) plastics will break down completely into water, carbon dioxide, biomass (soil) and inorganic compounds (such as metals) by composting microorganisms, but to do this they need oxygen. Compostable plastic breaks down within  a few weeks to a few months. But many biodegradable plastics can take up to a few years to break down. In order for this breakdown process to happen there needs to be a combination, of heat, moisture, air and microorganisms. Oxygen (from the air) is the key ingredient to the efficient and ecologically sound breakdown cycle.

Without oxygen, such as in a landfill site or anaerobic digestion facility, the plastic will either not breakdown at all or will breakdown in a different way, forming methane rather than carbon dioxide. Methane is roughly 30 times more potent as a greenhouse gas than carbon dioxide. In with these cases, you are adding to the problem of plastic pollution – the very problem you are trying to solve by switching to biodegradable or compostable packaging in the first place.

A further problem is that it is very difficult for consumers to tell the difference between bioplastic and traditional oil based plastic (unless it shouts the fact out around its circumference, like the one in the picture). Furthermore, many people don’t understand enough about plastics to know that their compostable cup can’t be recycled like other plastic cups. This can result in contamination of recyclable plastic.  If enough compostable plastic ends up in a batch of recycled plastic it can mean that whole batch is rejected as could end up being landfilled. Again, adding to the problem we are trying to solve.

So what to do?

You have 2 paths you can take.

Path 1.

Forget the expensive compostable plastic and contact a plastic recycling company to get a collection facility for all your recyclable plastic and make sure it gets turned back into plastic. Make sure the plastic cups you buy in have recycled content in them. That way you are starting to close the loop.

Path 2.

Go down the compostable plastic route but make sure that you set up a collection facility for your compostable plastic and ensure that it gets taken to a composting facility. This might mean that you will need to set up your own composting facility.

The worse thang you can do is to have a combination of recyclable traditional plastic and compostable plastic and not provide the appropriate clearly labelled collection facilities.

You are completely wasting your money switching to compostable plastic if your waste collection doesn’t provide a facility whereby the compostable plastic goes to be composted.

Whichever path you take, it is far better to encourage people to use reusable bowls, plates, cutlery etc. than any use of disposables. If you don’t have facilities to wash such reusables then people can bring their own.  They can just wash them when they get back home. So give an incentive to those who bring their own reusables – give them money off, or a loyalty card stamp for a free drink when they have reused their cup/bowl a certain number of times.

And if you don’t need it at all – such as in the case of a straw (with the exception of accessibility needs) then don’t provide it.


Posted in

Anna Pitt


  1. Barbara McGillivray on June 26, 2019 at 11:30 am

    I didn’t know about this and have been buying compostable facial wipes which I put on the compost heap. I hope that is ok.

    • Anna Pitt on July 5, 2019 at 6:40 am

      Hi Barbara. Compostable facial wipes are ok if you are composting them, which you are! They become a problem when people don’t compost them. I’d be interested to know how long your compostable wipes take to break down. And is the packaging compostable too? Being a just splash my face with water person myself I haven’t come across compostable wipes, but makeup is a rare thing for me so I’m no expert on how to remove it. Have you tried reusable cloths? I have a few of these for the occasional makeup day, but I’d be interested to know if it is a workable thing for people who wear makeup regularly.

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