Degradable, biodegradable, compostable. They sound interchangeable, but they describe very different things. Mix them up and you end up with the wrong product in the wrong bin. Here's how to tell them apart.
- Degradable: breaks into smaller pieces. No promise about what those pieces become.
- Biodegradable: broken down by microbes into carbon dioxide, water and biomass, given the right conditions.
- Compostable: certified to biodegrade in compost within a set time, leaving no harmful residue.
Degradable
"Degradable" is the loosest of the three. It just means a material changes physically or chemically over time, through sunlight, heat or an additive. It says nothing about what it turns into. A degradable plastic bag can simply crumble into smaller and smaller pieces of plastic.
Oxo-degradable plastics deserve a special mention. These are conventional plastics with an additive that speeds up fragmentation. A review of the scientific literature for New Zealand's Parliamentary Commissioner for the Environment found no reliable evidence that they go on to fully biodegrade in real-world conditions. Several Australian states have now banned them as part of their single-use plastic laws. More in single-use plastic bans in Australia.
Biodegradable
"Biodegradable" means microorganisms such as bacteria and fungi can actually consume the material and turn it into carbon dioxide, water and biomass. That's a real step up from just falling apart.
The catch is that "biodegradable" on its own doesn't say how long it takes or under what conditions. So a bare "biodegradable" claim, with no standard or certification, doesn't give you much to go on. The ACCC's principles for environmental claims say claims like this should be clear, accurate and able to be backed up.
Compostable
"Compostable" is the strictest of the three. A certified compostable product has passed lab testing showing it biodegrades in compost within a defined time, and that the resulting compost is safe for plants. In Australia there are two standards to know:
- AS 5810: home compostable, tested at backyard compost temperatures.
- AS 4736: industrially compostable, tested in the heat of a commercial facility.
International certifications such as TÜV Austria OK compost HOME are also common on home compostable products. For a deeper dive, see AS 4736 vs AS 5810.
| Term | What happens | What to look for |
|---|---|---|
| Degradable | Breaks into fragments | Best avoided |
| Biodegradable | Broken down by microbes, if conditions suit | A named standard or certification |
| Compostable | Certified to break down in compost within a set time | AS 5810 (home) or AS 4736 (industrial) |
Where do bioplastics fit?
"Bioplastic" is a broad term. It covers plastics made from plants, plastics designed to biodegrade, or both. That's why it pays to read further. Look for the material name and, above all, a compostable certification. A certified compostable bioplastic, such as PLA or PBAT in a tested finished product, breaks down to carbon dioxide, water and biomass in compost. Read more in bioplastic vs plastic.
Where should each one go?
- Certified home compostable (AS 5810 or OK compost HOME): your home compost.
- Certified industrially compostable (AS 4736) only: check whether your council's FOGO bin accepts certified compostable packaging. See compostable bags and the green bin.
- Recyclable conventional plastic: follow your council's recycling rules.
- Degradable, oxo-degradable or unverified "biodegradable": general waste, so it doesn't contaminate compost or recycling.
One more thing: compostable items in landfill don't get the oxygen and microbes they need, so compost is always the better destination.
Quick label checklist
- Is the material named?
- Is there a certification scheme, not just a green leaf?
- Does it say home or industrial?
- Are the disposal instructions clear enough to act on?
The easy swap
ZERO's bags and wrap are certified home compostable, so there's no guesswork at the bin:
- ZERO Resealable Food Storage Bags (from $4.99): PBAT, corn starch and calcium carbonate. Certified home compostable (TÜV Austria OK compost HOME) and freezer-friendly.
- ZERO Cling Wrap (from $6.99): mainly sugarcane-based PLA. Certified home compostable (DIN CERTCO; TÜV Austria OK compost HOME).
- ZERO Compostable Produce Bags – Commercial Roll ($39.95 for 470 bags): single-use roll bags for greengrocers, supermarkets and markets, certified home compostable.
FAQ
Is biodegradable the same as compostable?
No. All compostable materials are biodegradable, but not all biodegradable materials are compostable. Compostable means certified to break down in compost within a set time.
Are degradable plastics bad?
They can just fragment into smaller plastic pieces, which is why several Australian states have banned oxo-degradable plastics.
What's the difference between AS 5810 and AS 4736?
AS 5810 is for home compostable plastics. AS 4736 is for industrially compostable plastics.
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