Biodegradable and compostable are not interchangeable terms. Compostable products meet specific, independently tested standards for breakdown conditions and timeframes, while biodegradable is a broader and often vague claim with no universal certification requirement.
What Is the Difference Between Biodegradable vs Compostable?
The word biodegradable describes any material that can be broken down by bacteria, fungi, or other living organisms over time. In scientific terms, biodegradation is simply the biological decomposition process that organic matter undergoes. The problem with the label "biodegradable" on a product is that it says almost nothing specific. There is no regulated timeframe, no required set of conditions, and no independent verification standard that a manufacturer must meet before printing that word on a bag or package. A product could technically biodegrade over decades and still legally carry the label.
Compostable, by contrast, is a defined term backed by testable standards. A certified compostable product must demonstrate that it breaks down into carbon dioxide, water, and organic matter within a specific timeframe, under specific conditions, without leaving behind toxic residue or microplastics. These requirements are set out in standards such as ASTM D6400 in the United States and EN 13432 in the European Union. Products that carry certification marks like BPI or TUV Austria OK Compost have been tested by independent third-party laboratories to verify they meet those standards before the certification is granted.
In short: all certified compostable products biodegrade, but not all biodegradable products are compostable. The distinction matters because it determines whether a product is genuinely useful in a composting system or simply marketed to appear more sustainable than it is.
What Does Compostable Actually Mean?
A product labeled certified compostable has been verified to meet one or more recognized standards for composting performance. Those standards define three things: the conditions under which breakdown must occur, the timeframe within which it must happen, and the quality of the residual material left behind.
Under ASTM D6400 (the US standard) and EN 13432 (the EU standard), a compostable material must achieve 90 percent disintegration within a defined period, and the resulting compost must not show toxicity to plants or soil. The breakdown process requires an active composting environment with sufficient heat, moisture, and microbial activity to initiate and sustain decomposition.
Two tiers of composting apply to certified products:
- Industrial composting takes place at commercial composting facilities where temperatures are maintained between 55 and 60 degrees Celsius with controlled humidity and dense microbial populations. Under ASTM D6400, products must reach 90 percent disintegration within 84 days under these conditions. Under EN 13432, the equivalent window is 90 days. BPI certification and TUV OK Compost INDUSTRIAL certification both verify compliance with these conditions.
- Home composting takes place in a standard backyard compost environment at ambient temperatures. Because conditions are less controlled and microbial activity is lower, the timeframe is longer. Under TUV OK Compost HOME certification, products must reach 90 percent disintegration within 180 days.
It is important to understand that composting only begins when a product is exposed to the right combination of heat, moisture, and microbial activity. A compostable bag sitting unused in a storage cupboard, or sitting in a trash bin without those conditions, will not begin to break down in any meaningful way. The certification describes performance in an active compost environment, not performance in ambient room conditions or a landfill.
What Does Biodegradable Mean, and Why Is the Label Often Vague?
Biodegradation is a natural process. Leaves, food scraps, cotton, paper, and many plastics all biodegrade to some degree, given enough time and the right conditions. The term describes the mechanism, not the outcome in any practical sense. When a manufacturer places "biodegradable" on a product label without accompanying certification, there is no guarantee about how long breakdown will take, what conditions are needed, or what residual materials will remain.
Some biodegradable plastics, for example, are designed to fragment into smaller pieces under UV light or mechanical stress. This fragmentation does not equal full biodegradation into harmless organic matter. In some cases, fragmented plastic pieces can persist in soil or water for extended periods. Without a certification standard to verify the full breakdown pathway, the label tells the consumer very little.
This is the core problem with the biodegradable vs compostable distinction in the marketplace: biodegradable is often used as a marketing term rather than a technical one. Compostable certification exists precisely to provide the specificity that biodegradable claims lack.
How Do You Read and Verify Compostability Certifications?
When evaluating any compostable product, the most reliable approach is to look for third-party certification marks rather than manufacturer claims alone. The key certifications and standards to recognize are:
- ASTM D6400: The US standard for industrial compostability. Specifies breakdown performance in commercial composting conditions.
- EN 13432: The EU equivalent of ASTM D6400. Required for compostable packaging sold in European markets.
- BPI (Biodegradable Products Institute): A North American certification body. BPI certification requires independent third-party laboratory testing and must be demonstrated before certification is granted. It is not a self-declared claim.
- TUV Austria OK Compost INDUSTRIAL: A European certification verifying compliance with EN 13432 for industrial composting conditions.
- TUV Austria OK Compost HOME: A separate certification verifying breakdown in home composting conditions at ambient temperature within 180 days. This is a higher bar than industrial certification alone, because home compost piles operate without the elevated heat of commercial facilities.
A product that carries both BPI certification and TUV Austria certification, and that meets both ASTM D6400 and EN 13432, has been independently verified to meet the most rigorous compostability standards available in North America and Europe. GreeneWrap products carry BPI certification, TUV Austria certification, and meet both ASTM D6400 and EN 13432 standards.
When a product claims to be compostable without displaying any of these marks, it is worth asking what standard was used to make that determination, and whether an independent laboratory verified it. In the absence of certification, the claim carries no more weight than any other unverified marketing statement.
What Are Compostable Bags Made Of?
Most certified compostable bags are made from a combination of plant-derived and synthetic biopolymers. The most common materials are:
- PLA (polylactic acid): Derived from plant starches, typically corn. PLA is rigid at room temperature and is often blended with other materials to improve flexibility in bag applications.
- PBAT (polybutylene adipate terephthalate): A flexible, petroleum-derived biopolymer that is certified compostable under the relevant standards. PBAT gives compostable bags much of their stretch and durability.
- Cornstarch and other plant-based starches: Often used as fillers or blending agents to increase the proportion of bio-based content in the final material.
The blend of these materials determines the bag's physical properties, including thickness, strength, and flexibility. Thicker bags, measured in mils (one mil equals one thousandth of an inch), provide more puncture resistance and are suited to heavier or bulkier waste. It is worth noting that sharp objects such as broken glass or bones may puncture any compostable bag. This is a physical limitation of the material category, not a defect specific to any one product.
One question that comes up in discussions of compostable packaging is whether these products contain PFAS (per- and polyfluoroalkyl substances), a class of synthetic chemicals associated with environmental persistence and potential health concerns. Some compostable products on the market have tested positive for PFAS. GreeneWrap products are PFAS free and fluorine free, confirmed by the manufacturer. When evaluating other brands, always check certification documentation, as PFAS-free status is not universal across the industry.
How Should Compostable Bags Be Used Correctly?
Understanding what compostable bags are designed to do helps avoid common misuse and ensures the certification delivers its intended environmental benefit.
Compostable bags are designed for active composting environments. This means they are well suited for:
- Lining kitchen countertop compost bins to collect food scraps before transferring to a backyard compost pile or municipal green-bin collection.
- Use in municipal organics programs where bags and food waste are collected together and processed at a commercial composting facility. Many programs accept certified compostable bags, though it is always worth confirming with the local program what certifications are accepted.
- Yard waste collection, where larger certified compostable bags can hold garden trimmings and leaf litter for composting.
A few practical guidelines apply regardless of the product used:
- Store compostable bags in a cool, dry place and use them within 12 months of purchase. Under normal indoor storage conditions, the material remains stable.
- When using compostable bags for wet food scraps, do not leave wet waste sitting in the bag for more than one to two days. Moisture accelerates the breakdown process, so prolonged exposure to wet organic matter can weaken the bag before it reaches the compost system.
- Compostable bags are designed for active composting environments, not landfills. Like all organic materials, they decompose more slowly in landfill conditions where oxygen and moisture are limited. Sending a compostable bag to landfill does not deliver the composting outcome the certification is designed to achieve.
How Can You Spot Greenwashing on Packaging?
The biodegradable vs compostable distinction is one of the most common areas where greenwashing occurs in sustainable packaging. Several signals can help identify claims that lack substance:
- No certification mark: A product that claims to be compostable or biodegradable without displaying a recognized certification mark such as BPI, TUV Austria OK Compost, or an ASTM D6400 or EN 13432 reference has not been independently verified.
- Vague biodegradable claims: Phrases like "breaks down naturally" or "eco-friendly and biodegradable" without specifying conditions, timeframes, or certifications are not technically meaningful.
- No distinction between home and industrial composting: A product certified only for industrial composting is not suitable for home compost piles. If a product claims to be compostable without specifying which type, this is an incomplete claim. Look for TUV OK Compost HOME certification if home composting is the intended use.
- PFAS disclosure gaps: Some compostable products may contain PFAS. If a manufacturer does not address PFAS content in their documentation or certification disclosures, it is reasonable to ask before purchasing.
Independent certification is the most reliable filter. Organizations like BPI require testing by independent third-party laboratories before a product can display their mark. That verification process is what distinguishes a certified compostable product from a self-declared one.
Frequently Asked Questions
Is biodegradable the same as compostable?
No. Biodegradable describes a general process of biological decomposition that applies to many materials over varying timeframes and conditions. Compostable is a more specific term backed by defined standards such as ASTM D6400 and EN 13432, verified by third-party certifications like BPI and TUV Austria. All certified compostable products biodegrade, but not all biodegradable products meet compostability standards.
Can I put compostable bags in my home compost pile?
Only if the product carries TUV OK Compost HOME certification. This certification verifies that the bag will reach 90 percent disintegration within 180 days in a standard backyard compost environment at ambient temperatures. Industrial composting certification alone, such as BPI or ASTM D6400, does not verify performance in a home compost pile, which operates at lower temperatures.
How long does it take for a certified compostable bag to break down?
Under industrial composting conditions (55 to 60 degrees Celsius with controlled humidity and microbial activity), ASTM D6400 requires 90 percent disintegration within 84 days. EN 13432 sets the equivalent window at 90 days. Under home composting conditions, TUV OK Compost HOME certification requires 90 percent disintegration within 180 days. These timeframes apply only when the bags are actively composting in the appropriate environment.
Do compostable bags break down in a landfill?
Compostable bags are designed for active composting environments, not landfills. Like all organic materials, they decompose more slowly in landfill conditions where oxygen and moisture are limited. No composting certification covers landfill performance. To achieve the outcome the certification is designed for, compostable bags should be directed to a composting system.
How do I verify that a compostable product is genuinely certified and not just self-declared?
Look for independently issued certification marks on the product or packaging, specifically BPI, TUV Austria OK Compost INDUSTRIAL, or TUV Austria OK Compost HOME. These certifications require independent third-party laboratory testing before they can be used. A manufacturer stating that a product is compostable without displaying one of these marks is making a self-declared claim that has not been externally verified. You can also search the BPI certified products database directly to confirm whether a specific product appears.