Compostable vs Biodegradable vs Degradable: What is the Difference?

The three words are not interchangeable. Degradable plastic breaks into smaller fragments. Biodegradable means microorganisms can break it down, with no guaranteed timeframe or conditions. Compostable means it is certified to break down fully into water, carbon dioxide and biomass within a set time under defined composting conditions. In Australia that certification is AS 4736 or AS 5810.

Shop reusable and eco options ↓

Degradable: the weakest of the three claims

Degradable is the broadest and least demanding word of the three. On its own the label tells you almost nothing about how long it takes or what is left behind. In practice, degradable plastic usually means conventional polyethylene made with an additive that speeds up oxidation, so heat, light and oxygen cause the film to become brittle and fall apart.

The important distinction is fragmenting versus breaking down. Fragmenting means the film loses its physical integrity and turns into progressively smaller pieces of the same plastic. Breaking down means the polymer chain itself is consumed and converted into water, carbon dioxide and biomass. A degradable bag that fragments in a landfill or in the ocean has not disappeared. It has become smaller plastic. That is why degradable is not a composting claim, and why composters generally will not accept it.

Biodegradable: a real process, but no promise attached

Biodegradable means microorganisms, bacteria and fungi, can metabolise the material. That is a genuine mechanism rather than simple fragmentation, but the word by itself carries no timeframe and no defined conditions. A material can be truthfully described as biodegradable while taking decades, or while only biodegrading in conditions that a household or a council facility will never reproduce.

This is why "biodegradable" on a pack is not a substitute for certification. Unless the claim names a standard and a test method, there is nothing a buyer can verify or a waste facility can act on.

Compostable: the only one with a definition you can check

Compostable is the strongest of the three because it is the only one backed by a testable Australian standard. A compostable product has been tested to disintegrate and biodegrade within a set period under specified composting conditions, to leave no harmful residue, and to produce compost that will not harm plant growth. The standard also caps heavy metals and requires a plant toxicity test.

The catch is that compostable is always compostable under stated conditions. There are two sets of conditions in Australia, and a product certified for one is not automatically suitable for the other.

The three terms compared

Claim	What actually happens	Timeframe	Conditions needed	Certified against a standard	Which bin
Degradable	The plastic fragments into smaller pieces of the same plastic. The polymer is not consumed.	None stated	Usually heat, light and oxygen	No Australian composting standard applies	General waste. Not compost, not kerbside recycling.
Biodegradable	Microorganisms can metabolise the material, but the word alone sets no limit on how long that takes.	None stated	Undefined	No, unless a specific standard is named	General waste unless a certification says otherwise.
Compostable, commercial	Disintegrates and biodegrades fully to water, carbon dioxide and biomass, leaving usable compost.	Set by the standard	Controlled commercial composting: monitored heat, moisture, air and feedstock	Yes, AS 4736-2006	Only where a commercial composter or council FOGO service accepts certified compostables. Many do not, so check locally.
Compostable, home	Same end result, verified at the lower and less consistent temperatures of a backyard heap.	Set by the standard	Typical household composting conditions	Yes, AS 5810-2010	Home compost bin, or a local service that accepts it.

Being straight about what QIS sells

QIS stocks green degradable bin liners that use EPI additive technology. They are degradable. They are not certified compostable, they do not carry AS 4736 or AS 5810 certification, and they should not be put in a food organics or garden organics bin. If a supplier tells you a degradable liner is compostable, ask for the certification number, because there will not be one.

We would rather say that plainly than sell a vague green claim. Where a customer wants to cut plastic out of the carry bag, the honest answer is usually reuse rather than a different disposable film: calico bags made from unbleached natural cotton and washable for years, or non woven polypropylene totes that survive hundreds of shops. Neither is a composting claim, and neither pretends to be one.

Australian context: the certification that actually means something

Two Australian Standards carry weight here, and both are still the current editions. AS 4736-2006 covers biodegradable plastics suitable for composting in a commercial or industrial facility. AS 5810-2010 covers plastics suitable for home composting. The Australasian Bioplastics Association runs the verification programmes behind both and licenses the logos. The seedling logo relates to the commercial standard, so a seedling on a pack does not mean the item will break down in a backyard compost heap. Home compostable products carry the ABA's separate home compostable verification logo instead. Commercial composting is a monitored process with managed heat, moisture, air and feedstock, and a backyard heap simply does not reach or hold those conditions, so certification for one does not transfer to the other. Rules and standards below were checked in August 2026.

The bag bans are where this becomes a purchasing decision rather than a technicality, and the states do not agree with each other.

• Queensland allows a shopping bag that is wholly made from compostable plastic certified to AS 4736 or AS 5810, and such a bag does not have to meet the recycled content requirement that applies to conventional plastic bags.
• Tasmania exempts compostable biodegradable plastic bags consistent with AS 4736 from its lightweight bag ban.
• South Australia banned plastic film shopping bags from 1 September 2024 unless they are AS certified compostable and clearly labelled with the certification details.
• Victoria does not offer this exemption. EPA Victoria states that the ban on lightweight bags covers plastic bags that are degradable, biodegradable or compostable, so a certified compostable bag under the thickness limit is still caught.
• Western Australia bans all shopping bags with handles made from plastic or compostable plastic film, regardless of thickness or reusability.

Two lessons follow. First, a compostable certification is not a national exemption from anything. Second, degradable and biodegradable claims buy you nothing at all under any of these laws.

How to read a claim on a pack

Ignore the colour of the packaging and the leaf motif. Look for the standard number, AS 4736 or AS 5810, printed on the product or its carton, and for the matching ABA verification logo. Ask the supplier for the licence or certificate number, and confirm whether the certification covers the whole item or only the film, since inks, labels and closures can sit outside the scope. If none of that can be produced, treat the pack as ordinary plastic.

Related guides

For the additive behind our green bin liners, read What is EPI?. For the two reusable materials named above, read What are calico bags made from? and What is NWPP?. If you want the underlying plastic explained, What is LDPE? covers the film most bin liners are made from.

Our eco friendly and compostable packaging page lists the current range, and every term on this site is indexed in the packaging glossary.

Need help matching a product to your state's rules or your council's FOGO service? Contact our Brisbane team or call 1800 555 343.