Compostable vs biodegradable: what Australian shoppers need to know

"Compostable" and "biodegradable" get used as if they mean the same thing. They don't. One comes with a test and a certificate, and the other often doesn't. Here's what each means for Australian shoppers, and what to do with them at the bin.

The short version

• Biodegradable means microbes can break a material down into carbon dioxide, water and biomass. On its own, the word doesn't say how long that takes or where.
• Compostable means a product has been tested and certified to break down in compost within a set time, leaving compost that's safe for plants.
• All compostable materials are biodegradable. Not all biodegradable materials are compostable.

What does "biodegradable" mean?

Biodegradable means bacteria, fungi and other microbes can consume a material and turn it into carbon dioxide, water and biomass. That's genuinely different from plastic that just crumbles into smaller pieces.

The catch is that the word on its own has no timeframe or conditions attached. Something could biodegrade in months in a compost heap or take far longer somewhere cold and dry. That's why a bare "biodegradable" claim, with no standard behind it, doesn't tell you much about what to do with the product. The ACCC's principles for environmental claims say businesses should make claims that are clear, accurate and can be backed up.

What does "compostable" mean?

Compostable is the more specific, tested claim. A certified compostable product has passed lab tests for four things:

1. Disintegration: it physically breaks apart in compost.
2. Biodegradation: microbes convert it to carbon dioxide, water and biomass.
3. Ecotoxicity: the finished compost is safe for plants and soil life.
4. Constituents: limits on heavy metals and other substances.

Home compostable vs industrially compostable

There are two kinds of compostable, and they're tested under different conditions. In Australia, the two standards are:

• AS 5810: home compostable. Tested at the lower temperatures of a backyard compost bin.
• AS 4736: industrially compostable. Tested in the sustained heat of a commercial composting facility.

You'll also see international certifications such as TÜV Austria's OK compost HOME, which is a home composting certification, and DIN CERTCO's schemes.

Home compostable is the more demanding claim, because the product has to break down without the help of industrial heat. ZERO's bags and wrap are certified home compostable. For more on how the two compare, read home compostable vs industrial.

Where should it go?

1. Certified home compostable (AS 5810 or OK compost HOME): your home compost bin. Tearing it into smaller pieces helps.
2. Certified industrially compostable (AS 4736) only: check whether your council's FOGO (food organics and garden organics) bin accepts certified compostable packaging. Rules vary from council to council, so check its website. Our guide to compostable bags and the green bin can help.
3. Only says "biodegradable", with no certification: general waste, so it doesn't contaminate compost or recycling.
4. Never put compostables in kerbside recycling. They're a different material and can contaminate the stream.

Compostable products in landfill miss out on the oxygen and microbes they need, so compost is always the better option.

How to avoid being misled

• Look for a named standard or certification, not just a green leaf or the word "eco".
• Check whether it says home or industrial.
• Check the material is named.
• Make sure the disposal instructions are clear enough to act on.

Want to go further? Read how to spot greenwashing on compostable products and compostable certifications explained.

The easy swap

ZERO's bags and wrap are certified home compostable, so you don't need to decode anything 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), tested for food contact and freezer-friendly.
• ZERO Cling Wrap (from $6.99): mainly sugarcane-based PLA with about 20% PBAT for stretch. Certified home compostable (DIN CERTCO; TÜV Austria OK compost HOME).
• ZERO Nappy Waste Bags and Puppy Waste Bags ($14.95 for 90): certified home compostable.

FAQ

Is compostable better than biodegradable?

Certified compostable is a clearer, tested claim. It tells you where the product can go and that it's been shown to break down there.

Can compostable products go in my green bin?

It depends on your council. Check its FOGO rules for certified compostable packaging.

What does AS 5810 mean?

It's the Australian standard for home compostable plastics.