Compostable vs. Biodegradable Mailers

If you’ve spent any time sourcing sustainable packaging, you’ve probably seen “compostable” and “biodegradable” used like they mean the same thing. They don’t.

And in Australia, that difference matters. It affects your environmental claims, your legal risk, and what actually happens to your packaging after your customer opens their order.

This guide cuts through the confusion. No vague eco language. No greenwash. Just what you need to know to make a smart call for your business.

The TLDR: Certified compostable mailers have defined breakdown standards and a clear end-of-life outcome. “Biodegradable” mailers usually don’t. That makes compostable the safer, clearer, and more defensible option for most Australian ecommerce brands.

What’s the actual difference?

The short version is this: compostable has rules, biodegradable doesn’t.

Compostable means a material is designed to break down into non-toxic organic matter under specific conditions within a defined timeframe. Check out our guide on composting with HeapsGood Ecomailers to find out more about the process.

Biodegradable sounds similar, but it’s far less precise. In Australia, there’s no single regulated standard for an unqualified biodegradable claim, and no guaranteed outcome for what the material turns into or how long it takes.

That’s where a lot of the confusion comes from. One term describes a measurable process. The other often gets used as a loose bit of marketing language.

If you want a deeper primer on the terminology, have a read of our guide to biodegradable vs compostable packaging.

Why this matters in Australia

This isn’t just semantics. It affects how safely you can talk about your packaging.

The ACCC’s environmental claims guidance makes it clear that environmental claims need to be accurate, specific, and backed by evidence. Broad claims like “biodegradable” can be risky when they don’t explain the conditions needed for breakdown, how long it takes, or what the product breaks down into.

That means brands using vague claims can leave themselves exposed under Australian Consumer Law, especially if customers are led to believe the packaging will harmlessly disappear in normal conditions.

Certified compostable packaging is usually the safer path because it gives you something specific to point to. Not just a vibe. An actual standard.

What compostable actually means

When a compostable mailer is properly certified, it has been tested against a defined standard.

In Australia, the main standards are:

AS 5810 for home compostable products
AS 4736 for industrial compostable products

You may also see EN 13432 referenced, which is an internationally recognised compostability standard commonly used across packaging markets.

In plain English, compostable means the material is designed to break down into non-toxic biomass rather than lingering as conventional plastic waste.

If you want to get into the material side of it, our article on what PBAT is breaks that down.

What “biodegradable” usually means

This is where things get murky.

A biodegradable mailer may break down eventually, but that claim on its own doesn’t tell you much. It doesn’t automatically tell you how quickly it breaks down, whether it needs specific heat or moisture conditions, or whether it leaves behind microplastic fragments during the process.

That lack of clarity is exactly why the term is often criticised. It sounds good, but it can mean very little in practice.

What actually happens after disposal

End-of-life matters just as much as the material itself.

A certified compostable mailer that goes into the right composting environment has a clear pathway. It is designed to break down properly and return to the earth as organic matter. Check out our guide on how to compost your Ecomailers to find out more.

A biodegradable mailer may not. In many cases, it ends up in landfill, where low oxygen and poor composting conditions mean breakdown is slow or negligible. Some products marketed as biodegradable may also fragment rather than fully decompose.

So while both terms can sound eco-friendly, they do not lead to the same real-world outcome.

The Australian infrastructure reality

This part gets overlooked a lot.

Even the best compostable packaging only works as intended if it ends up in the right environment. For most Australian customers, that means home compost is the most reliable disposal pathway.

Kerbside organics systems are inconsistent around the country, and many councils do not accept compostable packaging in green bins. So the most practical message for customers is usually simple: put it in your home compost bin or worm farm.

That’s clear, useful, and realistic. It also gives your customer a proper next step rather than a fuzzy green claim.

Environmental impact, without the fluff

When compostable mailers are genuinely compostable and disposed of properly, the outcome is far more meaningful than a vague biodegradable claim.

Certified compostable materials are designed to break down into non-toxic organic matter. Unqualified biodegradable products may leave behind fragments, create confusion, or simply end up in landfill where their claimed benefit doesn’t really play out.

So the better question isn’t just “is it greener?” It’s “what actually happens next?”

What you’re really paying for

Certified compostable packaging often costs more than conventional plastic alternatives. That part is true.

But what you’re paying for is more than the material itself. You’re paying for testing, certification, clearer customer communication, and a claim that is much easier to stand behind.

Cheap biodegradable packaging can look good on paper, but if the claim is vague or can’t be substantiated, the savings can come at the expense of trust.

Still weighing up formats? Our sample pack is the easiest way to compare options before committing.

What certifications to look for

If you’re comparing options, don’t stop at the word on the product page. Look for actual certification.

AS 5810 for home compostable
AS 4736 for industrial compostable
EN 13432 as a recognised international compostability standard

If a product just says “biodegradable” without a cited standard or clear supporting evidence, that’s a red flag.

When compostable mailers make sense

Compostable mailers are usually the right fit when sustainability is a visible part of your brand and packaging is part of the customer experience.

They make a lot of sense for ecommerce businesses shipping lighter products like apparel, beauty, wellness, gifts, and other soft goods where a flexible mailer is the natural format.

For that kind of order, our Ecomailers are a natural place to start.

When recyclable packaging might be the better option

Here’s the honest version: compostable is not always the best answer for every order.

If your customers are unlikely to compost, or your products need more structure and protection, recyclable paper-based packaging may be the smarter real-world choice.

A recyclable box that actually gets recycled can be a better environmental outcome than a compostable mailer that goes straight to landfill.

Good packaging decisions are about context, not just claims.

For flatter items, check out our Rigid Mailers. For bulkier orders, our Mailing Boxes may be the better fit. If you need a bit more cushioning, our Padded Mailers are worth a look too.

Frequently asked questions

Can compostable mailers go in the kerbside green bin?

Sometimes, but not reliably. Rules vary by council, and many Australian councils do not accept compostable packaging in kerbside organics bins. Home compost is usually the safest guidance.

What happens if a compostable mailer goes to landfill?

It will generally break down much more slowly because landfill conditions are not ideal for composting. That’s why disposal guidance matters.

Is biodegradable packaging illegal in Australia?

No, but vague biodegradable claims can create legal risk if they are misleading or can’t be backed up with evidence.

How should brands talk about compostable packaging?

Keep it specific. Talk about certification, explain the right disposal method, and avoid broad unqualified environmental claims.

The bottom line

If you’re choosing between compostable and biodegradable mailers for your ecommerce business, certified compostable is usually the clearer and safer option.

It gives you a more defensible claim, a better customer message, and a more defined end-of-life outcome.

Biodegradable might sound good, but compostable is the term that actually tells you something useful.