Biodegradable simply means a material will break down eventually, with no required timeframe, no defined conditions, and no proof of what it leaves behind. Compostable means a material is certified to fully break down into carbon dioxide, water, and organic matter within a specific, tested timeframe, under defined conditions, verified by independent laboratories. That distinction, certification versus a vague promise, is the core of the biodegradable vs compostable question, and it matters more than most shoppers realize when they're standing in the trash bag aisle.
Both terms get used loosely on packaging, which is exactly why confusion persists. This guide breaks down what each term actually means, what has to happen for a bag to compost, which certifications back up a compostable claim, and how to use certified compostable bags correctly at home.
What's the Difference Between Biodegradable and Compostable?
"Biodegradable" is an unregulated, largely meaningless marketing term in most contexts. Technically, almost everything organic biodegrades eventually, including a plastic fork, given enough time (sometimes decades or centuries) and the right conditions. The word carries no required timeframe, no required testing, and no required proof of what residue is left behind. A product can legally be labeled "biodegradable" without any certification backing that claim at all.
"Compostable," when used correctly and paired with an actual certification, means something very different. A certified compostable product has been tested by an independent lab and shown to break down into carbon dioxide, water, and organic matter, leaving no toxic residue and no microplastics, within a specific, measured timeframe, under specific conditions. It is a scientific, testable standard, not a vague description of what might happen someday.
This is the practical answer to the biodegradable vs compostable debate: biodegradable describes an eventual outcome with no guarantees, while compostable describes a certified, time-bound, lab-verified process. GreeneWrap products are never described as "biodegradable" for this reason. They're certified compostable, meaning the claim is backed by BPI, TUV Austria, and OK Compost testing rather than left to interpretation.
How Does Composting Actually Work?
Compostable products don't break down on their own sitting in a kitchen drawer, a trash bin, or a landfill. Composting is an active biological process that requires three things working together: heat, moisture, and microbial activity. Without all three, the breakdown process doesn't meaningfully start, regardless of how the product is labeled.
There are two distinct composting environments, and they are not interchangeable:
- Industrial (commercial) composting takes place at facilities that maintain high temperatures of 55-60 degrees Celsius, along with controlled humidity and active microbial activity. These conditions are far more intense than a backyard pile can produce.
- Home composting happens at ambient outdoor temperature in a standard backyard compost bin or pile, relying on naturally occurring moisture and microbes rather than engineered heat.
A product certified for industrial composting is not automatically suited to a backyard bin, and vice versa. This is why checking which certification a product actually carries matters more than reading the word "compostable" on the front of the package.
It's also worth being clear about what compostable does not mean. It does not mean a bag will break down effectively if left in a sealed trash bin, since there's no moisture or microbial exposure there. It does not mean it will break down in the ocean. And like all organic materials, compostable bags decompose more slowly in landfill conditions where oxygen and moisture are limited. Compostable products are designed for active composting environments, not for landfills or general trash disposal.
What Certifications Prove a Bag Is Actually Compostable?
Because "compostable" is a testable claim, legitimate products carry specific third-party certifications rather than relying on self-declared marketing language. The major standards are:
- ASTM D6400 (USA): The U.S. standard for industrial compostability. It requires 90% disintegration within 84 days under commercial composting conditions.
- EN 13432 (EU): The European equivalent, requiring 90% disintegration within 90 days under similar industrial conditions.
- BPI Certified: The Biodegradable Products Institute certification confirms compliance with ASTM D6400 through independent, third-party laboratory testing. It is not a self-declared claim; products must demonstrate compliance in testing before certification is granted.
- TUV Austria / OK Compost INDUSTRIAL: Confirms a product meets industrial composting standards, verified by TUV Austria's testing process.
- TUV Austria / OK Compost HOME: A separate, distinct certification confirming a product will achieve 90% disintegration within 180 days under standard backyard composting conditions, meaning ambient temperature rather than the high heat of an industrial facility.
When a product carries both OK Compost HOME and OK Compost INDUSTRIAL certification, along with BPI certification and compliance with ASTM D6400 and EN 13432, it means the product has been independently tested and verified for both composting environments, not just one. GreeneWrap's trash bags, food storage bags, and cling wrap all carry this full set: BPI certified, TUV Austria certified, OK Compost HOME certified, OK Compost INDUSTRIAL certified, and compliant with both ASTM D6400 and EN 13432.
One more label-reading note worth flagging: some compostable products on the market may contain PFAS (per- and polyfluoroalkyl substances), so it's worth checking certification and manufacturer disclosures directly rather than assuming. GreeneWrap products specifically are PFAS free and fluorine free, confirmed by the manufacturer, but this is a product-specific fact, not an industry-wide guarantee.
What Are Compostable Bags Made Of?
Certified compostable bags are typically made from plant-based materials rather than petroleum-based plastic resins. The most common components are:
- PLA (polylactic acid): A bioplastic derived from fermented plant starch, commonly corn.
- PBAT (polybutylene adipate terephthalate): A biodegradable polyester often blended with PLA to add flexibility and strength.
- Cornstarch-based resins: Used to build the film structure while keeping the material compostable rather than conventional plastic.
These materials are engineered specifically so that, under the right composting conditions, microorganisms can fully metabolize them into carbon dioxide, water, and biomass, rather than fragmenting into persistent plastic residue. This is the core distinction from conventional plastic, which does not break down into organic matter at all; it simply fragments into smaller and smaller pieces of plastic, including microplastics, over very long timescales.
How Long Do Compostable Bags Take to Break Down?
Breakdown time depends entirely on which composting environment the bag is in, which is why the certification type matters so much:
- Industrial composting: 90% disintegration within 84 days under ASTM D6400, or within 90 days under EN 13432, at commercial facility temperatures of 55-60 degrees Celsius.
- Home composting: 90% disintegration within 180 days under TUV OK Compost HOME conditions, at ambient backyard temperature.
Notice that home composting takes roughly twice as long as industrial composting. That's a direct result of lower, less consistent temperatures in a backyard pile compared to a controlled commercial facility. Neither timeframe applies outside an active composting environment; a bag sitting in a sealed trash bag in a bin, or buried in a landfill, is not in conditions that support this process.
How Should You Use Compostable Bags for Food Scraps and Curbside Compost?
Used correctly, certified compostable bags are a practical tool for collecting food scraps and yard waste before they reach an active compost environment, whether that's a backyard pile, a municipal green bin, or a drop-off program. A few practical guidelines apply across all certified compostable bags:
- Wet waste: These bags are suitable for wet food scraps for short-term use, but wet waste shouldn't sit in the bag for more than 1-2 days, since moisture begins accelerating the breakdown process, which can weaken the bag before it reaches the compost pile or bin.
- Storage: Unused bags are stable under normal indoor storage conditions in a cool, dry place, and are best used within 12 months of purchase.
- Sharp objects: Broken glass, bones, and other sharp items can puncture any compostable bag. This is a material limitation shared across all compostable bags, not specific to one brand, so it's worth keeping sharp waste out of compostable liners.
- Check local acceptance: Municipal curbside and drop-off composting programs vary in what they accept. Some only accept certified compostable bags carrying specific certifications like BPI or OK Compost, while others don't accept bagged waste at all. Checking local program rules before relying on a bag for curbside collection avoids contamination issues at the facility.
For everyday kitchen use, sizing matters as much as certification. Small kitchen caddy bags in the 1-2 gallon and 2-4 gallon range are built for food scrap collection under the sink or on the counter, while larger 13 gallon and 13-15 gallon drawstring bags handle general household waste headed to compost or municipal collection. On the heavier end, bags from roughly 50 gallons up to 90-95 gallons are built for yard waste, job-site cleanup, and large-volume outdoor use, where a thicker 2 mil material holds up to bulkier debris.
How Can You Spot Greenwashing in Compostable Claims?
Because "biodegradable" carries no certification requirement, it's the term most often used in vague or misleading marketing. A few practical checks help separate a genuine compostable claim from a weak one:
- Look for a specific certification logo, such as BPI, TUV Austria, or OK Compost, rather than just the word "compostable" printed on the package.
- Check which standard is referenced. A product should cite ASTM D6400, EN 13432, or OK Compost HOME, not just an unsupported claim of being "eco-friendly" or "green."
- Confirm home vs industrial. A product certified only for industrial composting will not necessarily break down in a backyard bin. If a brand doesn't specify which environment its product is certified for, that's a gap worth noting.
- Be cautious of "biodegradable" used alone. Without a paired certification and standard, it's a claim with no enforceable meaning, and no timeframe attached.
Certified compostable language should always be specific: "BPI certified compostable," "home compostable (OK Compost HOME)," or "industrially compostable (ASTM D6400 compliant)." Vague, standalone claims without a named standard or certifying body are the clearest sign of greenwashing in this category.
FAQ
Is biodegradable the same as compostable?
No. Biodegradable means a material will eventually break down, with no required timeframe, conditions, or testing. Compostable means a material is certified, through independent lab testing, to break down into carbon dioxide, water, and organic matter within a specific, measured timeframe under defined conditions.
Will a compostable bag break down in my trash can or in a landfill?
No. Compostable bags are designed for active composting environments, not for sitting in a sealed trash bin or in a landfill. Like all organic materials, biodegradation occurs significantly slower in landfill conditions due to limited oxygen and moisture.
What's the difference between home compostable and industrially compostable?
Home compostable products are certified under TUV OK Compost HOME to achieve 90% disintegration within 180 days at ambient backyard temperature. Industrially compostable products are certified under ASTM D6400 or EN 13432 to achieve 90% disintegration within 84 to 90 days, but require the higher temperatures (55-60 degrees Celsius) of a commercial composting facility.
Are all compostable bags PFAS free?
Not necessarily. Some compostable products on the market may contain PFAS, so it's worth checking certification and manufacturer confirmation directly. GreeneWrap products specifically are PFAS free and fluorine free, as confirmed by the manufacturer.
How do I know if a compostable bag claim is legitimate?
Look for a named, third-party certification such as BPI, TUV Austria, or OK Compost, along with a reference to a specific standard like ASTM D6400, EN 13432, or OK Compost HOME. BPI certification in particular requires independent laboratory testing before it's granted, so it isn't a self-declared claim. A product labeled only "biodegradable" or "eco-friendly," without any certification or standard attached, doesn't carry the same proof.