Compostable vs Biodegradable
These two words are used interchangeably on packaging, but only one is a certified claim. Understanding the difference is the single most useful thing a sustainability buyer can learn - and it is how you avoid greenwashing.
The core distinction
What is the difference between compostable and biodegradable?
The difference comes down to whether there is a standard behind the word. "Biodegradable" has no standardized definition, no required timeframe, and no required end conditions. Almost any organic material will biodegrade eventually - the question is whether that takes months or centuries, and whether it leaves behind harmful residue or persistent fragments. On its own, an uncertified "biodegradable" label tells a buyer essentially nothing verifiable.
"Compostable" is specific and testable. A compostable material must break down into carbon dioxide, water, and biomass within a defined period, under defined composting conditions, leaving no toxic residue. In North America that is verified against ASTM D6400 (or ASTM D6868 for coated paper products); in Europe the equivalent is EN 13432, which requires roughly 90 percent disintegration within 12 weeks and 90 percent biodegradation within 6 months under industrial composting conditions. Certification marks such as BPI Certified Compostable and TUV OK Compost confirm a product actually passed those tests.
Side by side
Compostable vs biodegradable at a glance
| Attribute | Compostable | Biodegradable |
|---|---|---|
| Standard behind it | ASTM D6400 / EN 13432 | None |
| Defined timeframe | Yes (e.g. months under EN 13432) | No |
| Defined end products | CO2, water, biomass, no toxic residue | Not specified |
| Third-party marks | BPI Certified, TUV OK Compost | Typically none |
| Buyer confidence | Verifiable | Low without certification |
Greenwashing
Why is a bare "biodegradable" claim a red flag?
Because "biodegradable" is undefined, it is one of the most common greenwashing terms. A product labeled only "biodegradable," with no standard, no timeframe, and no certification mark, gives you no way to verify what it actually does at end of life - and it may fragment into persistent microplastics rather than fully breaking down. The credible signal is a compostability certification: look for BPI Certified Compostable, TUV OK Compost INDUSTRIAL, or TUV OK Compost HOME, tied to ASTM D6400 or EN 13432.
A second thing to check is which composting environment the certification covers - industrial or home - because "compostable" alone does not tell you where it will break down. That distinction is covered in the compostable bioplastics guide, which also explains how mineral fillers and additives fit into a lower-plastic formulation.
FAQ
Compostable vs biodegradable questions
Is compostable better than biodegradable?
Compostable is a more meaningful claim because it is certified: the material must convert to carbon dioxide, water, and biomass within a defined time under defined conditions with no toxic residue, per ASTM D6400 or EN 13432. Biodegradable has no standard behind it, so on its own it is not verifiable.
Does biodegradable mean it will not become microplastic?
Not necessarily. Because biodegradable is undefined, a product with only that label may fragment into persistent microplastics rather than fully breaking down. A certified-compostable material is designed and tested to convert fully, which is the more reliable route.
What certifications prove a product is compostable?
Look for BPI Certified Compostable, TUV OK Compost INDUSTRIAL, or TUV OK Compost HOME, tied to the ASTM D6400 (or D6868) or EN 13432 standard. These are third-party marks, unlike an uncertified compostable or biodegradable claim.
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