More Australian shoppers are looking for brands that ship sustainably, and compostable mailers have become one of the most popular ways for eCommerce businesses to cut back on conventional plastic.
But the word "compostable" gets used loosely. Some bags marketed as eco-friendly aren't compostable at all, and even genuine compostable mailers won't break down if they end up in the wrong bin. If you're making a green claim to your customers, it pays to know exactly what you're buying.
This guide explains what compostable really means in Australia, how it differs from biodegradable, and how to choose and use compostable mailers properly.
Compostable vs Biodegradable: What's the Difference?
These two words are often used as if they mean the same thing. They don't.
Biodegradable
"Biodegradable" simply means a material can be broken down by microorganisms eventually. There's no set time frame and no guarantee about what's left behind. Almost anything will biodegrade given enough time, so on its own the word tells you very little.
Be especially wary of oxo-degradable or oxo-biodegradable plastics. These are conventional plastics with additives that make them break into smaller pieces. Australian organics recycling and bioplastics industry bodies have made it clear these materials are not certified compostable and aren't suitable for composting.
Compostable
"Compostable" is a much stronger claim. A compostable material breaks down into natural elements (water, carbon dioxide and biomass) within a set time under composting conditions, and leaves no toxic residue behind. In Australia, that claim can be tested and certified against Australian Standards.
In short: all compostable materials are biodegradable, but most biodegradable materials are not compostable.
The Two Australian Standards: AS 4736 and AS 5810
Australia has two standards for compostable plastics, and they cover different composting environments.
| AS 4736 (Commercial compostable) | AS 5810 (Home compostable) | |
|---|---|---|
| Where it breaks down | Industrial or commercial composting facilities | Home compost bins and heaps |
| Conditions | Controlled high temperatures and humidity | Lower, everyday temperatures |
| Certification logo | ABA "seedling" logo | ABA home compostable logo |
| What it means for your customer | Must go to a facility that accepts compostable packaging | Can go in their own compost at home |
Certification in Australia and New Zealand is run by the Australasian Bioplastics Association (ABA). Products are tested by independent accredited laboratories, and only verified products are allowed to carry the ABA logos. If a mailer carries one of these logos, you can check the certification number on the ABA website.
Home compostable is the harder test to pass, because the material has to break down without the heat of an industrial facility. That's why home compostable products are generally the most convenient for consumers.
What Are Compostable Mailers Made From?
Most compostable mailers are made from a blend of plant-based and compostable materials. Common ingredients include:
- PLA (polylactic acid): made from fermented plant starches such as corn
- PBAT: a compostable polymer that adds flexibility and strength
- Corn starch and other plant starches
The blend gives the mailer a soft, slightly textured feel and enough strength for everyday courier handling, while allowing it to break down under the right conditions.
Do Compostable Mailers Perform as Well as Poly Mailers?
For most clothing and soft goods, yes. Compostable mailers are self-sealing, water-resistant and tear-resistant enough for normal courier handling. There are a few differences to know about:
- Shelf life: because they're designed to break down, compostable mailers have a limited storage life, often around 9 to 12 months. Buy quantities you'll use within that time rather than stockpiling.
- Storage: keep them somewhere cool, dry and out of direct sunlight. Heat and humidity speed up breakdown.
- Stretch: they have a little more give than conventional poly, so avoid overfilling.
- Cost: they generally cost more per unit than standard poly mailers.
How Should Customers Dispose of Compostable Mailers?
This is the part that's most often missed. A compostable mailer only delivers its environmental benefit if it ends up in the right place.
- Home compostable (AS 5810): cut into strips and add to a home compost bin or heap.
- Commercially compostable (AS 4736): put in a council food organics and garden organics (FOGO) bin only if the local council accepts certified compostable packaging. Rules vary between councils, so customers should check.
- Not in the recycling bin. Compostable plastics are not recyclable with conventional soft plastics and can contaminate recycling streams.
- Landfill: if there's no composting option, it goes in general waste. In landfill it won't break down the way it would in compost.
Tip: add a short line to your packing slip, website or the mailer itself telling customers how to dispose of it. It turns a packaging choice into a positive brand moment and makes sure the bag ends up where it should.
Making Honest Eco Claims
The ACCC has been cracking down on misleading environmental claims (often called greenwashing). If you tell customers your packaging is compostable, make sure you can back it up:
- Ask your supplier which standard the mailer meets and whether it's certified.
- Say whether it's home or commercially compostable, rather than just "eco-friendly".
- Avoid vague terms like "green", "earth-friendly" or "biodegradable" without explanation.
Other Plastic-Free Options
Compostable mailers aren't the only way to reduce plastic. Depending on what you ship, these may suit you better:
- Kraft paper courier bags: plastic-free and kerbside recyclable
- Kraft paper bubble mailers
- Brown cardboard mailing boxes: widely recyclable
- BioFill packing peanuts as void fill (see our guide to biodegradable vs traditional packing peanuts)
You can explore the full range in our post on eBPak's eco-friendly packaging.
Compostable Satchels From eBPak
Our compostable mailers come in the most popular courier bag sizes, from small to extra large:
- #01, 190 x 260mm
- #02, 255 x 330mm
- #03, 310 x 405mm
- #04, 350 x 480mm
- #05W, 430 x 545mm
- #06, 500 x 650mm
Not sure which size you need? Our poly mailer size guide uses the same sizing, so you can match your current satchels exactly. If you have questions about our compostable range, get in touch with our team.