What's the Difference Between Biodegradable and Compostable Bags?
Compostable bags are certified to fully break down into carbon dioxide, water, and organic matter within a specific timeframe, verified by independent lab testing against standards like ASTM D6400 or EN 13432. Biodegradable bags carry no such guarantee: the term "biodegradable" is unregulated and can describe a bag that takes decades to break down, leaves microplastic fragments behind, or has never been tested at all. Understanding biodegradable vs compostable bags certification is the single most useful thing a shopper can do before buying a "green" trash bag, because the word on the package means almost nothing without a certification mark behind it.
What Does "Compostable" Actually Mean?
A certified compostable bag is designed to break down into carbon dioxide, water, and organic matter, leaving no toxic residue and no microplastics behind. That process only happens under active composting conditions: specifically, heat, moisture, and microbial activity working together over a defined period. A compostable bag sitting in a kitchen trash bin, a landfill, or the ocean is not composting. It is simply sitting there, because none of those environments supply the conditions the material needs to break down.
This is also where compostable and biodegradable claims diverge in practice. "Biodegradable" technically just means a material can be broken down by living organisms eventually, under unspecified conditions, over an unspecified timeframe. There is no required testing, no disintegration deadline, and no independent verification behind a bare "biodegradable" label. A plastic bag can be marketed as biodegradable and still take years to break down, or break down only into smaller plastic fragments rather than fully reverting to organic matter. "Compostable," when paired with a real certification, carries none of that ambiguity: the timeframe, the conditions, and the end result are all defined and tested.
How Does Compostable Certification Work?
Certification is not a marketing claim a manufacturer applies to its own packaging. It requires independent third-party laboratory testing before a certification body will approve the product. BPI certification, for example, requires this kind of third-party lab verification; it is not self-declared, and products must demonstrate compliance with the relevant standard before certification is granted.
During testing, samples of the material are placed under controlled conditions that replicate either an industrial composting facility or a home compost pile, and disintegration is measured over time. The material also has to pass toxicity and ecotoxicity screening, confirming that what's left behind after breakdown doesn't harm plants, soil organisms, or the finished compost. Only after passing these tests does a product earn the right to display a certification mark like the BPI logo, the TUV Austria OK Compost seal, or a reference to ASTM D6400 or EN 13432 compliance.
What Certifications and Standards Prove a Bag Is Actually Compostable?
When evaluating biodegradable vs compostable bags certification claims, look for specific standard names and numbers rather than vague language. The certifications and standards that carry real testing behind them include:
- BPI Certified: Independent third-party verification against ASTM D6400, used widely in North America.
- TUV Austria Certified: A European certification body that tests and verifies compostability claims.
- OK Compost INDUSTRIAL: Confirms a product meets industrial composting standards, requiring the high heat and controlled conditions of a commercial facility.
- OK Compost HOME: Confirms a product will break down in a standard backyard compost environment, without the high heat of an industrial facility.
- ASTM D6400 (USA): The U.S. standard requiring 90% disintegration within 84 days under industrial composting conditions.
- EN 13432 (EU): The European equivalent, requiring 90% disintegration within 90 days under similar industrial conditions.
A product that lists one or more of these certifications, by name, with the certifying body identified, has gone through testing. A product that simply says "biodegradable" or "eco-friendly" on the package, with no standard or certifying body named, has not necessarily gone through any testing at all. All GreeneWrap compostable trash bags, food storage bags, and cling wrap carry BPI, TUV Austria, OK Compost HOME, and OK Compost INDUSTRIAL certification, and meet both ASTM D6400 and EN 13432 standards.
What's the Difference Between Home and Industrial Composting?
Not all certified compostable products break down under the same conditions, which is why it's important to distinguish home compostability from industrial compostability rather than treating "compostable" as a single category.
Industrial composting requires a commercial facility capable of sustaining high temperatures of 55-60 degrees Celsius, along with controlled humidity and concentrated microbial activity. Under these conditions, ASTM D6400 requires 90% disintegration within 84 days, and EN 13432 requires the same 90% threshold within 90 days. Products certified to these standards, and carrying the BPI or OK Compost INDUSTRIAL mark, are built for drop-off at a commercial composting facility or collection through a municipal green-bin program, not for a backyard bin.
Home composting operates at ambient outdoor temperature, in a standard backyard compost pile or bin, without the sustained high heat of an industrial facility. Products certified under the TUV OK Compost HOME standard are tested to reach 90% disintegration within 180 days under these milder, slower conditions. A bag that only carries industrial certification is not guaranteed to break down fully in a backyard pile within a reasonable timeframe. Checking which certification a product carries, home, industrial, or both, matters more than the general word "compostable" on its own.
What Are Compostable Bags Made Of?
Certified compostable bags are typically made from plant-based materials rather than petroleum-based plastic. Common materials include PLA (polylactic acid, derived from fermented plant starch, often corn), PBAT (a biodegradable polyester blended in to add flexibility and strength), and cornstarch-based resins. These materials are engineered specifically so that, under composting conditions, microorganisms can metabolize them into carbon dioxide, water, and organic matter, rather than fragmenting into persistent plastic residue.
This is a meaningful structural difference from a conventional plastic bag that has simply been labeled "biodegradable." Many biodegradable plastics are still fundamentally petroleum-based polyethylene with additives meant to speed up fragmentation. Without certification testing behind that claim, there's no verified evidence of what the material actually breaks down into, or how long that process takes.
How Do You Spot Greenwashing in "Biodegradable" Claims?
Because "biodegradable" is not a regulated or standardized term, it is one of the more common vectors for greenwashing in the waste bag category. A few practical checks help separate a verified claim from a vague one:
- Look for a named certifying body (BPI, TUV Austria) rather than just the word "certified" on its own.
- Look for a referenced standard number, such as ASTM D6400 or EN 13432, rather than an unsupported claim of "compostable" or "biodegradable."
- Check whether the claim specifies home or industrial compostability, since a product tested only for industrial conditions may not perform the same way in a backyard pile.
- Be cautious of claims that combine "biodegradable" with no timeframe or testing standard at all. A material can technically biodegrade over fifty years and still be marketed as biodegradable.
It's worth noting that some compostable products on the market may contain PFAS, so checking certification and manufacturer disclosures matters on that front too. GreeneWrap products are confirmed PFAS free and fluorine free by the manufacturer; this status applies specifically to GreeneWrap products and should not be assumed for other brands without their own confirmation.
How Should You Use Compostable Bags in Practice?
Once a bag is verified as certified compostable, using it correctly still matters for getting the intended result. A few practical guidelines apply across certified compostable bags generally:
- Match the bag to the composting environment available. A bag with OK Compost INDUSTRIAL certification is suited to municipal green-bin collection or drop-off at a commercial facility. A bag with OK Compost HOME certification is suited to backyard composting.
- Use wet waste bags promptly. Compostable bags are suitable for wet food scraps for short-term use, but wet waste shouldn't sit in the bag for more than one to two days, since moisture accelerates the breakdown process and can compromise the bag before it reaches the compost pile or bin.
- Avoid sharp contents. Broken glass, bones, and other sharp objects can puncture any compostable bag, a limitation shared across the category regardless of brand.
- Store bags properly before use. Compostable bags remain stable under normal indoor storage, kept cool and dry, and are best used within 12 months of purchase.
- Remember that landfill conditions are different. Compostable bags are designed for active composting environments, not landfills; like all organic materials, biodegradation occurs significantly slower in landfill conditions due to limited oxygen and moisture.
For households just getting started, matching bag size to actual use case helps avoid waste: a small kitchen countertop bin for food scraps calls for something like a 1-2 gallon or 2-4 gallon bag, while a backyard compost or yard waste routine calls for something closer to the 13 gallon or 30-35 gallon range. Larger sizes, from roughly 50 gallon up through 90-95 gallon, are built heavy-duty enough for yard waste cleanup or job-site use, where volume and durability matter more than countertop convenience.
FAQ
Is a biodegradable bag the same as a compostable bag?
No. A compostable bag is certified to fully break down into carbon dioxide, water, and organic matter within a tested timeframe under specific conditions, verified by independent lab testing. A biodegradable bag may eventually break down, but the term carries no required testing, timeframe, or certification, so the claim alone doesn't guarantee a specific outcome.
What certifications should I look for on a compostable bag?
Look for BPI Certified, TUV Austria Certified, OK Compost HOME or OK Compost INDUSTRIAL, and a reference to ASTM D6400 (USA) or EN 13432 (EU). These indicate the product underwent independent third-party testing rather than relying on a self-declared claim.
Will a compostable bag break down in my regular trash can or a landfill?
No. Compostable bags are designed for active composting environments, not landfills or ordinary trash bins. Like all organic materials, biodegradation occurs significantly slower in landfill conditions due to limited oxygen and moisture, and a trash bin provides none of the heat, moisture, or microbial activity composting requires.
What's the difference between home and industrial compostable certification?
Industrial compostability (BPI, OK Compost INDUSTRIAL, ASTM D6400, EN 13432) requires high heat of 55-60 degrees Celsius in a commercial facility, with 90% disintegration within 84 to 90 days. Home compostability (TUV OK Compost HOME) is tested at ambient backyard temperatures, with 90% disintegration within 180 days. A product certified for one is not automatically certified for the other.
Can compostable bags contain PFAS?
Some compostable products on the market may contain PFAS, so checking a brand's specific disclosure matters. GreeneWrap products are confirmed PFAS free and fluorine free by the manufacturer, though this confirmation applies to GreeneWrap products specifically and shouldn't be assumed for other brands.