Is "Biodegradable" the Same as "Compostable"? What the Labels Actually Mean

Walk down any "eco-friendly" aisle and you'll see the words everywhere: biodegradable, compostable, eco, green, natural. They sound interchangeable. They are not — and the gap between them is costing consumers money and, ironically, adding more plastic to landfills.

Here's what each term actually means, why it matters, and how to tell if a product is the real deal.

"Biodegradable" Is Basically Meaningless

Here's the uncomfortable truth: almost everything is biodegradable. Given enough time — and we're talking decades or centuries in some cases — even plastic breaks down. There's no legal standard in the U.S. that requires a timeframe, a testing method, or a specific environment for a company to slap "biodegradable" on a label.

That means a product can say "biodegradable" and still:

• Take 20+ years to break down
• Never disclose what conditions it actually needs to break down — so you have no way of knowing if your home setup, or any facility you have access to, will do the job
• Break down into smaller and smaller plastic fragments — microplastics — rather than fully disappearing

To be clear, needing industrial composting isn't itself a red flag — plenty of legitimately certified compostable products do. The problem with "biodegradable" alone is that it makes no testable promise at all, so you're left guessing. "Biodegradable" tells you almost nothing about how, where, or when something actually goes away.

"Compostable" Is a Real, Testable Standard

Compostable is a different story. To legitimately claim a product is compostable, it has to meet a specific standard — in the U.S., that's ASTM D6400 for plastics. This standard requires the material to:

• Break down into water, CO2, and biomass (not plastic fragments)
• Do so within a defined timeframe, typically 90 to 180 days in composting conditions
• Leave no toxic residue behind

That's a testable, verifiable claim — not a marketing word.

The Certification That Actually Backs It Up: BPI

Even "compostable" gets used loosely sometimes, which is where third-party certification comes in. The Biodegradable Products Institute (BPI) independently tests products against the ASTM D6400 standard before they're allowed to carry the BPI certification mark.

If you see the BPI logo on a product, it means an outside lab — not the company itself — verified the compostability claim. That's the difference between "trust us" and "this was actually tested." One important detail: BPI certification confirms a product is industrially compostable — it's not a home compostable claim, which is a separate distinction covered below.

Home Compostable vs. Industrial Compostable

Not all compostable products break down the same way. There are two separate certifications to look for:

• Industrially compostable — certified to fully break down using the higher, sustained heat of a commercial composting facility.
• Home compostable — certified to break down in a standard backyard compost pile, at regular outdoor temperatures, no facility required.

A product can hold one certification or both. That matters, because it determines whether you actually need municipal composting access to make the product compost — or whether your own backyard bin will do the job.

How to Actually Check a Product

Next time you're comparing products, skip the marketing copy and look for:

1. The word "compostable," not just "biodegradable." Biodegradable alone isn't a meaningful promise.
2. A certification logo — BPI in the U.S., or TÜV Austria's OK Compost mark internationally. These mean the claim was independently verified.
3. Home vs. industrial labeling, so you know whether it'll break down in your own backyard or needs a facility.

"What If I Don't Have Access to Either — Should I Still Buy Compostable?"

Here's the honest edge case: if you don't have a backyard compost setup and your city doesn't offer industrial composting pickup, a compostable bag will likely end up in a landfill along with your regular trash. Landfills are largely oxygen-free, so decomposition there happens much more slowly than in a compost facility, through a different process that isn't what the compostable certification was designed around.

Even then - it's still worth it. The material itself is fundamentally different from conventional plastic, regardless of where it ends up: it's made from plant-based materials instead of fossil fuels, so choosing it means less plastic being produced in the first place. Even slowly, it degrades into natural elements rather than fragmenting into permanent microplastics the way conventional plastic does.

So even in the worst-case scenario, you're still avoiding fossil-fuel-based plastic and its microplastic legacy. That's not nothing.

Where This Matters Most: Trash Bags

Trash bags are one of the biggest offenders here, because "biodegradable trash bags" is an incredibly common — and incredibly vague — claim. A bag that's technically biodegradable but not certified compostable can still take years to break down and shed microplastics in the process, which somewhat defeats the purpose of buying it in the first place.

That's why every Gardener's Daughter bag is BPI and TÜV certified compostable — for both industrial AND home composting — tested to actually meet the ASTM D6400 standard rather than just claiming to. Shop compostable trash bags →