These two words get used as if they meant the same thing. They do not, and the gap between them is where packaging claims turn into packaging complaints. If you sell into the US, the EU, the UK or Australia, the difference matters legally as well as technically.
The short version
Compostable means the material has been tested to a published standard and breaks down within a defined time, under defined conditions, leaving no toxic residue. The standard and the timeframe are part of the claim: a pack is not "compostable", it is compostable to EN 13432 in industrial composting, or home compostable to a named home-compost standard.
Biodegradable only says that the material will break down eventually, through biological action. It says nothing about how long that takes, what conditions it needs, or whether those conditions exist anywhere your customer actually throws the pack away. A material can be biodegradable and still sit unchanged in a landfill for years.
What sits behind the word compostable
Compostable claims are testable, which is why they are the ones regulators accept. For industrial composting, EN 13432 is the European standard and ASTM D6400 is the US equivalent; AS 4736 covers Australia and New Zealand. Home composting has its own, stricter standards — AS 5810 in Australia, NF T51-800 in France, and the TUV OK compost HOME certification — because a home heap never reaches the temperatures of an industrial windrow.
A certified material comes with a certificate number, an issuing body and a scope that names the film structure and the production site. That scope is the part buyers miss: the same format made from a different laminate at a different factory is not automatically covered.
Why regulators are tightening up
In the United States, the FTC Green Guides require competent and reliable evidence for any degradable claim, and several states have moved to restrict the word "compostable" to products that are certified to a recognised standard. California in particular treats unqualified compostable labelling as misleading. In the EU, the packaging regulation tightens green claims and puts the burden of substantiation on the seller. Australia and New Zealand expect a compostable claim to reference AS 4736 or AS 5810.
The direction of travel is the same everywhere: a vague environmental word is now a claim you have to be able to defend with a document.
What we recommend for small brands
Pick a certified grade, not a description. Ask for the certificate before you approve artwork, and keep a copy in your compliance file.
Match the claim to the market. Industrial compostability is a strong claim in the EU and a weak one in a US city with no industrial composting collection. If the infrastructure is not there, say so on the pack.
Print the standard, not just the word. "Compostable to EN 13432" or "Home compostable to AS 5810" is defensible. "100% biodegradable" is not.
Tell the customer what to do with it. Orders of magnitude more packs get composted because the label explained the disposal route than because the film was technically capable.
Keep the wording proportionate. If only the film is certified and the zipper is not, the claim needs to reflect that.
What we can supply
We run compostable structures in NK, NKME, PLA and PBS, plus kraft paper options, and recyclable mono-material PE and PP where composting is not the right answer. Digital printing starts at 100 pcs, so you can test a compostable line before committing to a full run.
Tell us the product, the fill weight and the market you sell into. We will tell you which structure is actually certified for the claim you want to make — and send the paperwork. This article is a general explainer, not legal advice; your market rules and your buyer's own specification always come first.