Scott Morton | Contributors - Nourish plant-based living

23rd October 2021

Words by Scott Morton

Category: Earth | Features

Degradable vs biodegradable vs compostable plastic. What does it all mean? And is there such a thing as a good plastic choice?

We’ve all been hearing a lot over recent years about the impact of plastics on the natural world, and many of us are actively embracing alternatives in a bid to protect our planet and wildlife. But what if plastics labelled ‘green and degradable’, ‘biodegradable’ or ‘planet friendly’ were actually worse than normal plastic? Unfortunately, due to being unregulated terms in Australia, this is often the case. Let’s sort the truth from the trash.

Degradable means microplastics

Some plastic bags that are labelled ‘green and degradable’ or ‘naturally degradable’ contain an additive to make them break down faster into smaller fragments. The correct term for these degradable bags is oxo-degradable. They are made from fossil fuel-derived polymers such as polyethylene, polypropylene, and polystyrene, with a metal salt added to speed up the oxidation process. In many cases, when this type of plastic degrades it fragments into tiny pieces, leaving residual microplastic pollution behind.

An independent study of oxo-biodegradable plastic bags in the marine environment found that after 40 weeks, more than 90 percent of the bag was still present. A global initiative by the Ellen MacArthur Foundation’s New Plastics Economy has united 150 organisations in a call to ban oxo-degradable plastic packaging from the market, due to the risks that microplastics pose to the ocean and other ecosystems, potentially for decades into the future.

Biodegradable labelling lowdown

Without laws to limit its use, even the term biodegradable doesn’t mean anything, because everything is biodegradable eventually. Something that is biodegradable doesn’t necessarily break down in a way that will save the planet.

Legislation in the US forbids the term biodegradable to appear on any product unless that product is shown to break down into elements in nature within five years. Unfortunately, in Australia we don’t have any legislation that limits the use of the term biodegradable.

There are plastic bags labelled biodegradable that are misleading us to think they’re made from natural materials, but this isn’t always the case. To be truly biodegradable, a bag must tick all three of these boxes:

It must leave no toxic residues or traces of plastic behind.
It must be capable of being decomposed by bacteria and other living organisms to avoid pollution.
It must break down into organic matter anywhere microorganisms are present, including on land and in water.

The compostable solution

Compostable plastic is a type of bioplastic made from substances obtained from plants, such as non-genetically modified corn starch and biodegradable, compostable polymers. Compostable bags break down like plants anywhere there is oxygen and microorganisms – without leaving any microplastics behind. These bags break down at normal compost temperatures and don’t need to be heated to high temperatures. Composting is nature’s way of sequestering carbon back into the earth as organic matter with no toxic residues.

The Australasian Bioplastics Association has launched the ‘seedling logo’ certification in Australia and New Zealand to help us clearly identify certified compostable packaging materials. To be certified compostable and carry the seedling logo, suitable biopolymer materials must undergo a stringent test regime outlined by Australian Standard AS4736 and carried out by a recognised independent accredited laboratory.

What about plastic in landfill?

An independent study in the US compared how polyethylene bags, oxo-degradable bags and compostable bags break down. To simulate a composting environment, a set of bags were buried six inches deep in clay flower pots and left untouched in an open-air box. Another set of bags was submerged in a crate in the ocean. Within six months on land and two years in water, the compostable bags had completely disappeared, while the oxo-degradable bags had broken down into small fragments of microplastics, and the polyethylene bags remained the same.

So, if a compostable plastic bag goes into landfill, it is much better for the environment than polyethylene and oxo-degradable plastic because it has a lower carbon footprint and will not release microplastics.

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Our increasing use of plastic and our inability to manage plastic waste has resulted in one-third of plastic waste becoming land or marine pollution. With awareness we can all make small changes and be part of the solution. In an ideal world, no plastic would go to landfill, but choosing compostable means it will properly break down without leaving harmful microplastics.

At least half of what goes into most household bins is compostable, but instead ends up in landfill. Composting reduces greenhouse gas emissions and returns vital nutrients to the soil, and we can all make a difference.

Food waste that breaks down without oxygen emits the greenhouse gas methane, which is one of the main causes of climate change. The amount of greenhouse gases produced by food waste in Australian landfill each year is equivalent to the emissions of Australia’s entire aviation industry or our steel and iron ore industries combined.

Not only that, but when organic material breaks down in landfill and water filters through it, a highly toxic liquid called leachate is released, which can pollute land, groundwater and waterways. So, sending food waste to landfill is not a sustainable solution.

At the same time, an estimated 33% of the world’s soil is severely degraded, and food waste converted to compost could help solve this problem.

So, is it time to invite composting into your life? Here’s how.

Composting at home

If you have space at home, consider building your own compost bin with recycled timber. These can be more effective than plastic units because they’re so easy to access, turn and aerate. Aerating your compost is important to ensure it’s an oxygen-rich, aerobic environment. You’ll also need to add water to keep your compost damp but not soggy.

Compost bins break down organic matter faster in warmer temperatures, so adding a layer of lawn trimmings to the top of your compost will help insulate it and get it going. It’s best to position your compost bin in a shady area away from direct sunlight.

Setting up a simple compost caddy on your kitchen bench makes it easy to collect food scraps for your compost bin. If you don’t take your scraps out to the compost bin every day, you could use a ventilated caddy lined with a compostable bag instead. You’ll be able to leave it on your kitchen bench for a few days and it won’t smell, for the same reason your compost bin doesn’t smell – because oxygen can get in. This also reduces methane emissions by promoting aerobic decomposition.

Get the right mix

The key to a well-functioning compost bin is to add the right mix of green matter and brown matter.

Green matter that can be added to a home compost bin includes fruit and vegetable scraps, breads, grains, rice, flour, cereal, pasta, coffee grounds and tea leaves.
Brown matter includes lawn clippings, leaves, plant trimmings, and natural fibres like cotton, linen, hair, paper, napkins, tissues, toilet rolls, cut up cardboard and 100% compostable plastic bags.

Animal products, oils and pet faeces do not belong in your compost – these will cause bad smells and attract pests. Also, avoid adding weeds with mature seeds as these will spread weeds in your garden when you spread the compost.

Use a FOGO bin

A growing number of local councils are offering residents kerbside green bins for recycling food organics and garden organics (FOGO). Councils offering FOGO bins usually supply compost caddies and compostable bags to collect food scraps. Organic waste collected in green bins is recycled at industrial composting facilities.

Currently, around 30% of Australian councils offer these bins. This number is slowly growing as landfill levies rise and councils realise composting organic waste makes more sense than sending it to landfill. You’ll need to check if your local council provides FOGO bins. If not, you can always ask if they can help with a subsidised compost bin. Or, even better, campaign for them to start offering FOGO bins.

Share your scraps

If you don’t have space for a compost bin, you can get together with members of your local community to compost together or otherwise find someone willing to compost your food scraps via www.sharewaste.com. You can also contact your local community garden to see if there is an existing composting hub near you.

Setting up a community compost bin in a central area is a great idea for people who live in unit blocks and inner-city areas. If your compost bin is used by many people, it’s important to create clear labels explaining how the system works and the steps you want everyone to follow. You could paint or write instructions on the bins or even add a QR code for more detailed instructions.

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Organic waste contains valuable resources that can’t be recovered from landfill, yet that’s where 87% of Australia’s food waste ends up. We need to recycle organic waste to fertilise our soil instead of dumping it in landfills where it contributes to climate change by producing harmful greenhouse gases. There’s no such thing as waste in nature. Organics belong in our soil, not in landfill, and composting is the key.