Compostable courier bags are everywhere in eCommerce marketing right now, and the claims on them range from accurate to wishful. If you send parcels for a living, it pays to know exactly what "compostable" means under Australian standards, where these mailers actually end up after delivery, and when a recycled courier bag is the smarter buy. This guide covers all of it, without the greenwash.
What makes a courier bag compostable?
A compostable courier bag is designed to break down into carbon dioxide, water and biomass under composting conditions, leaving no toxic residue behind. Most are made from a blend of PBAT (a compostable polymer), PLA (usually derived from corn starch) and plant starches. The result looks and feels similar to a soft plastic satchel, though typically with a softer, slightly stretchy texture.
The key phrase is "under composting conditions". These materials need heat, moisture, oxygen and microbes to break down as intended. Toss one in a landfill bin and it behaves very differently, which we cover below.
One thing compostable bags are not: degradable. Degradable plastics simply fragment into smaller pieces of plastic. If you want the full story on that distinction, read our guide on degradable and biodegradable bags.
The Australian standards: AS 4736 and AS 5810
Australia has two composting standards worth knowing, and the difference between them matters a lot for courier bags.
AS 4736 (commercial compostability)
AS 4736-2006 covers plastics suitable for industrial composting facilities, where temperatures reach around 55-60°C. A bag certified to AS 4736 should biodegrade within the timeframes set by the standard, but only in a commercial facility. Here is the problem: most Australian council food and garden organics (FOGO) services do not accept compostable packaging, so a bag that is only commercially compostable often has nowhere practical to go.
AS 5810 (home compostability)
AS 5810-2010 is the stricter standard. It covers biodegradation at ambient backyard temperatures, so a bag certified to AS 5810 can genuinely go in a home compost bin. If a supplier claims their mailers are compostable, ask which standard applies. Home compostable (AS 5810) is the claim that holds up in practice for most Australian households.
Check for certification, not just claims
The Australasian Bioplastics Association (ABA) runs a verification program for both standards, with a seedling logo for commercial compostability and a separate home compostable logo. A printed leaf graphic and the word "eco" certify nothing. Look for the certification number, and be wary of bags that say "biodegradable" without naming a standard.
Where compostable mailers actually end up
This is the uncomfortable part of the compostable story, and any honest supplier should tell you about it.
Research on parcel waste suggests the majority of mailers, compostable or not, end up in the general waste bin. In landfill, compostable materials break down slowly and anaerobically, which can generate methane. So a compostable bag only delivers its environmental benefit if your customer actually composts it, and that depends on clear disposal instructions and a motivated recipient.
There are also practical trade-offs to weigh before switching your whole operation:
- Shelf life: compostable mailers are designed to break down, so they typically have a usable life of around 6-12 months. Buy more than you can use and the back of the pallet may become brittle or tacky before it ships anything.
- Storage: they need cool, dry storage away from direct sunlight. Hot warehouses and shipping containers shorten their life.
- Strength: quality has improved, but starch-blend films are generally less puncture resistant than recycled LDPE at the same thickness, which matters for heavy or sharp-edged items.
- Cost: expect to pay a meaningful premium per bag against a comparable recycled poly mailer.
None of this makes compostable mailers a bad choice. For light garments sent to eco-conscious customers who will home compost the bag, they are a strong fit. It does mean the "compostable equals better" assumption deserves scrutiny.
Compostable vs recycled courier bags: the honest comparison
Here is where we put our cards on the table. QIS Packaging does not currently stock certified compostable courier satchels. Our courier air bag range is made from 100% recycled material instead, and there is a solid environmental argument for that choice.
A recycled mailer puts existing plastic back to work rather than creating demand for new polymer, and recycled LDPE film has a substantially lower production footprint than virgin plastic. It is also strong, fully waterproof and has no shelf-life clock ticking in your storeroom. For most parcels, the greenest bag is the one that protects the contents first time; a damaged item that needs replacing and reshipping wipes out any packaging saving many times over.
A fair way to decide:
- Choose compostable mailers when your customers are highly engaged with sustainability, your products are light and low-risk (clothing, soft goods), and you can print or include clear home-composting instructions.
- Choose recycled mailers when you need reliable puncture and moisture protection, you buy in bulk and store stock for months, or you want an eco story that does not depend on what the customer does with the bag.
You can also make the rest of the parcel greener regardless of the mailer. Sealing cartons with compostable kraft paper tape keeps the whole box kerbside recyclable, and swapping retail carry bags to reusable calico or NWPP bags cuts single-use plastic at the counter.
Sizing your courier bags
Whichever material you choose, the size logic is the same: the bag should close with room for the adhesive strip to seal fully, without so much spare film that the parcel flaps around in transit. Our full courier satchel sizing guide walks through measuring, but as a quick reference: A5 suits accessories and cosmetics, A4 suits single garments and books, and the larger 440x500mm bags handle multi-item orders and bulky soft goods.
Popular recycled courier bag sizes:
The full range runs to nine sizes in white and black, and every bag in the collection is made from 100% recycled material with a strong self-seal strip.
Buying and storage tips
If you go compostable, buy in quantities you will use within about six months, store the cartons off the concrete floor in a cool spot, and rotate stock so the oldest bags ship first. Print disposal instructions on the bag or a card inside; a compostable bag without instructions usually ends up in landfill.
If you go recycled, you can buy deeper because there is no shelf-life issue. Bulk buying is where the savings sit, and for pallet quantities or mixed-size orders you can request a bulk quote rather than ordering carton by carton.
Compostable courier bag FAQs
Are compostable courier bags home compostable?
Only if they are certified to AS 5810. Bags certified only to AS 4736 need a commercial composting facility, and most Australian council FOGO services do not accept compostable packaging. Check the certification logo and number before assuming a bag can go in your backyard compost.
Can compostable mailers go in the recycling bin?
No. Compostable films contaminate soft plastic and kerbside recycling streams. Their correct end of life is composting (home or commercial, depending on certification). If neither is available, they go in general waste.
How long do compostable courier bags last in storage?
Typically around 6-12 months from manufacture, depending on the material blend and storage conditions. Heat, humidity and sunlight all shorten that window. Recycled poly mailers have no comparable expiry.
Are recycled courier bags better for the environment than compostable ones?
It depends on end of life. If the recipient genuinely composts the bag, compostable wins. If the bag ends up in general waste, as most do, a 100% recycled mailer arguably delivers the more reliable benefit because its environmental saving happens at production, not disposal.
Does QIS Packaging sell compostable courier bags?
Not at present. Our courier air bags are made from 100% recycled material in nine sizes, and we stock compostable kraft paper tape for carton sealing. If you need certified compostable satchels for a specific project, call us on 1800 555 343 and we can talk through options.
What size courier bag do I need?
Measure your packed item, then allow enough extra for the seal strip to close fully. See our courier satchel sizes guide for a size-by-size breakdown from A5 through to 750x900mm.
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