A colourful compost scrap heap

When is compostable not compostable?

We all want to do our part for the environment, but you’d be forgiven for feeling overwhelmed when you walk into the grocery store.

You might grab glass options where possible, and maybe you even take the initiative to bring your own packaging for loose items. But when you walk into the cleaning aisle, you’re faced with a dilemma: bin liners.

Degradable, biodegradable, compostable, eco-friendly, recycled, sustainable – and then there are some with green leaves which seem to allude to being more eco-friendly, with no evidence of being anything other than standard soft plastic. So, what does it all mean? Let’s break down these definitions.


Degradable plastic is essentially made in the same way as traditional plastics, but with fossil fuel–derived chemicals added to help the plastic break down into tiny pieces. This can actually be more detrimental to the environment as tiny micro-pieces of plastic enter waterways and are consumed by animals and even humans – causing catastrophic effects that we are still in the process of uncovering.



Biodegradable is very similar to degradable plastic. The main difference is in the processes used to break down the matter. Biodegradable plastic can be broken up – although not completely – by microorganisms such as bacteria and fungi. The main risk of this process is the food chain effect, whereby micro-plastics are consumed by animals that are then consumed by other animals (including humans), disrupting the natural food chain and causing previously unforeseen risks to human health, as well as the health and safety of wildlife.

Essentially, everything is eventually ‘biodegradable’, so this term can be very misleading. In fact, the US has banned the term ‘biodegradable’ on products that cannot prove to return to natural elements within 5 years. Australia, however, does not yet have any such ban.

Compostable bioplastics

Compostable bags are generally marketed as the best option for the conscious shopper, and consumers are even advised to put them in the green-waste bin or the home compost. Compostable bags are made from plant materials, have the accredited ‘100% compostable’ tick of approval, and break down far quicker than other options on the market – but only if they’re disposed of correctly.

Thanks to the green tick of approval, many people are led to believe that compostable bags are the eco-friendly solution to Earth’s plastic epidemic. Unfortunately, it’s what remains unsaid that is important – how exactly do these items break down into compostable materials?

‘Bioplastics’ is a general term with a warm, fuzzy, eco-friendly feel. But what does it actually mean? Bioplastic is plastic that is either ‘bio-based’ (made from organic materials) or biodegradable. Sometimes (but not always) it is both, and sometimes (but not always) bioplastics are also compostable. If your bioplastic material claims to be compostable, check the logo to see if it is suitable for your home compost bin or is only industrially compostable.

Industrial composting vs home composting

Not all material that’s labelled as ‘compostable’ is suitable to throw into your home compost.

The main difference between home composting and industrial composting is in the scale and speed. While we’re probably more familiar with the home composting system, which utilises natural microorganisms to break down organic food waste, the industrial process is performed on a much larger scale and often utilises significantly more resources. ‘Industrially compostable’ bioplastics only break down under a precise set of temperature, humidity and aeration conditions, and so must be collected and taken to specific industrial composting facilities. Without a proper collection and disposal system in place, they do not break down as easily as the label may lead you to believe. Throwing industrially compostable plastics in your worm farm or landfill is not a whole lot better than throwing a plastic bottle in the ocean.

coffee cup in a pond

Image by Andrew Martin via Pixabay

Home compost systems mainly operate in one of two ways: aerobic (needing oxygen) and anaerobic (lack of oxygen). Aerobic compost systems are probably pretty similar to what you’re picturing — generally above-ground ‘heaps’ or black bins into which you can throw all your fruit and vegetable scraps. Naturally present microorganisms help to break down matter using heat, oxygen and humidity. Home compost is a great way to generate healthy, nutrient-rich soil to help grow your garden.

In anaerobic composting, microorganisms which don’t need oxygen to survive break down matter in a contained environment. Anaerobic composting is a bit more complex to operate, but has the benefit that you can compost many more organic materials in an anaerobic system (like meat and faeces from your dog or cat) that are best left out of a regular compost bin, because the heat generated in this system kills potential pathogens. Anaerobic systems such as Bokashi bins are becoming popular, especially among urban-dwellers without backyards. Through a program such as ShareWaste, you can arrange for your unwanted compost to be picked up by a neighbour or local school who can use it in their garden.

So, what’s the solution?

Although there may not be a singular perfect option, take a moment to reflect on what your bins are designed for. Most likely, you have: a general-waste bin, a recycling bin and an organic waste bin (if your council has a program for collecting organic waste).

Many of us have become so accustomed to single-use culture that we’ve begun putting anything mildly inconvenient in the red bin. That’s no longer an option. We must begin considering what is truly waste — what really must go to landfill. Additionally, you can look at ways of reducing the organic waste you create in the first place.

Check if your local council has a food waste collection service. Put your organic waste in the organic bin where possible— or even better, start composting at home with a system that works for you. But be mindful that each composting system (anaerobic, aerobic, worm farm) differs in what food waste it can accept. For example, worms can’t tolerate large quantities of citrus, onion, meat or dairy.

For bin bags, consider why you use bin liners in the first place. You want to keep the bin clean and avoid a weekly hosing. If you begin sorting your waste correctly, you’ll soon find that your ‘general waste’ is near non-existent, and you won’t have to clean your bins any more than you do now.

By making a few small changes, we can all modify how we think about waste and redesign home waste systems; we can entirely disrupt the flow of trash culture and create a world where nothing is trash and everything is treasured.


Here we have listed some common waste products which often cause confusion about the best ways to dispose of them. We’ve tried to simplify it as much as possible, but let’s face it, composting can be a ‘muddy’ topic, so it’s always good to do some further research into the kind of composting system you want to set up at home.

A table showing how to dispose of some common waste products which may or may not be compostable

Banner image by Ben Kerckx from Pixabay

About author

Chrystal Moore

In 2015, Chrystal embarked on a wildlife and conservation volunteering trip to South Africa. Somewhere among the heatstroke and the flies, she fell in love with ecology. Chrystal completed her Bachelor of Communications before moving to Melbourne to work as a Science Communicator – which she now does concurrently with her Master of Environment and Sustainability at Monash University.

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