The Difference Between Biodegradable and Compostable Actually Matters
If you've been trying to reduce your plastic waste, you've probably stood in a store aisle weighing the biodegradable plastic bags vs compostable options and wondered whether the distinction matters. It does, and significantly. These two terms are not interchangeable, even though brands and marketers have used them that way for years. One comes with third-party certification and verifiable breakdown standards. The other is essentially a marketing claim with no regulatory definition, no required testing, and no accountability. Understanding the difference protects your composting efforts and helps you avoid products that undermine them.
What "Biodegradable" Actually Means (And Doesn't Mean)
Biodegradable describes any material that breaks down through biological processes, meaning bacteria, fungi, or other microorganisms decompose it over time. On paper, this sounds good. In practice, it tells you almost nothing useful.
There is no required certification for biodegradable claims on plastic products. There is no standard testing protocol that manufacturers must follow. There is no defined timeframe, no maximum for toxic residue left behind, and no specification for what the material must break down into. A product could technically biodegrade over 500 years under very specific conditions and still qualify for the label. That is not a useful environmental claim.
California has outright prohibited the use of "biodegradable" on plastic products because the claim cannot be verified. That decision came from a practical recognition that vague, unsubstantiated environmental claims mislead consumers and damage recycling and composting infrastructure. If your state hasn't banned the term yet, the underlying problem still exists everywhere. Biodegradable plastic bags often look identical to certified compostable bags, but they behave very differently when they enter a composting system.
What Compostable Actually Requires
Compostable is a different standard entirely. To call a product compostable and back it up with legitimate certification, manufacturers must prove that the product breaks down into carbon dioxide, water, and organic matter, within a specific timeframe, without leaving toxic residue or microplastics behind.
In the United States, the relevant standard is ASTM D6400. In Europe, it's EN 13432. Both require 90% disintegration within a defined period under active composting conditions, which means high temperatures, controlled humidity, and microbial activity. Both also require that the resulting compost is safe for soil and plant growth. These are not self-declared claims. They require independent, third-party laboratory testing before certification is granted.
BPI certification, which stands for the Biodegradable Products Institute, is the primary compostability certification in North America and requires exactly that kind of rigorous testing. TUV Austria certification covers both industrial composting (TUV OK Compost INDUSTRIAL) and home composting (TUV OK Compost HOME). A product carrying these marks has been tested, reviewed, and approved by an independent body. A product labeled simply "biodegradable" has not.
Why Biodegradable Plastic Bags Don't Work in a Compost System
The issue isn't just labeling. Biodegradable plastic bags actively cause problems when they end up in composting systems.
Commercial composting facilities operate on tight cycles. They need materials that break down predictably within a specific window, typically 84 to 90 days depending on the applicable standard. Biodegradable bags don't follow that schedule. Many are made from conventional plastic blended with additives designed to cause fragmentation, not full biological breakdown. They break into smaller pieces rather than decomposing into safe organic matter. Those fragments contaminate the finished compost, which then ends up in agricultural soil.
This contamination problem is real and documented. Composting facilities that accept non-certified materials often produce compost that fails quality standards, which creates downstream consequences for farms and gardens that rely on finished compost. Some facilities have had to reject entire batches because of plastic contamination from bags that looked compostable but weren't certified. That's a significant operational and financial problem, and it explains why many municipal composting programs now specifically require BPI certified bags rather than accepting any bag labeled biodegradable or compostable.
Certified compostable bags solve this because they're tested to meet the same breakdown standards the facility is operating under. The certification gives facilities confidence that the bag will behave predictably. Biodegradable bags offer no such assurance.
The PFAS Problem Makes This More Urgent
There's another layer to this. Some compostable products, particularly fiber-based items like plates and bowls, have been manufactured with PFAS (per- and polyfluoroalkyl substances) to improve grease resistance. PFAS are persistent chemicals that don't break down in composting and accumulate in soil over time.
This is a real contamination risk that the industry has worked to address. BPI no longer certifies compostable fiber products with intentionally added fluorine. California's AB 1201 explicitly prohibits compostable labeling on products that contain PFAS. These are meaningful policy responses to a verified problem.
GreeneWrap products are PFAS free and fluorine free, confirmed by the manufacturer. That matters because you can't always tell from packaging alone what a product contains. When in doubt about any brand, check whether it carries BPI certification. That certification process involves testing that goes beyond just breakdown rate, and it's the most reliable way to know you're not introducing persistent chemicals into your compost.
For the industry generally, some compostable products may contain PFAS. Always check certification before assuming a product is safe for your compost bin.
How California AB 1201 Is Changing the Standard
California's AB 1201 is one of the most substantive pieces of compostable product legislation passed in the United States. It requires that any product labeled compostable must be third-party certified. It prohibits compostable labeling on products containing PFAS. It also prohibits deceptive look-alike products, meaning products designed to visually mimic certified compostable items without meeting the underlying standards.
The law directs CalRecycle to develop labeling requirements to help consumers identify genuinely certified products. This addresses a real and persistent problem: non-compostable products are often visually indistinguishable from certified ones. A shopper trying to do the right thing can easily pick up the wrong product because the packaging looks similar and the claims sound equivalent. AB 1201 is designed to close that gap.
Even if you don't live in California, this legislation reflects a broader direction that composting standards are moving. Certification is becoming the expected baseline, not a premium feature. Vague biodegradable claims are losing credibility in regulation and in practice.
What to Look for When Buying Bags for Composting
Here's the practical side. When you're buying bags to use for food scraps or as compostable trash bags, look for these specific markers.
- BPI certification: confirms independent third-party testing in the US context
- ASTM D6400 compliance: the US standard for industrial compostability
- EN 13432 compliance: the EU equivalent, often seen on products sold internationally
- TUV OK Compost INDUSTRIAL: certification for use in commercial composting facilities
- TUV OK Compost HOME: certification for use in backyard compost bins, with a longer breakdown window of up to 180 days
If you're sending bags through a curbside composting program, check your local program's requirements. Most US municipal programs that accept compostable bags specifically require BPI certification. Some programs are more restrictive and only accept food scraps without any bags. Checking before you buy saves wasted effort and avoids contaminating your local composting stream.
For home composters running a backyard bin, look specifically for the TUV OK Compost HOME certification alongside BPI. Industrial certification alone doesn't guarantee the bag will break down at ambient backyard temperatures. Home composting operates differently, at lower temperatures with less controlled conditions, and the certification standards reflect that.
How to Use Certified Compostable Bags Correctly
Even a certified compostable bag needs to be used and stored correctly to perform as intended. A few practical points worth knowing.
Store bags in a cool, dry place and use them within 12 months of purchase. The materials are designed to be stable under normal indoor storage conditions, but they're not indefinitely shelf-stable the way conventional plastic is.
For wet food scraps, certified compostable bags handle short-term use well. Don't leave wet waste sitting in the bag for more than one to two days. Moisture accelerates the breakdown process, which is exactly what you want in a compost bin but not while the bag is still sitting in your kitchen.
Sharp objects like broken glass or bones can puncture compostable bags. This applies across the category, not just to any single brand. Use a separate bin liner or container for sharp waste.
When the bag is full, it goes into your compost bin, curbside compost cart, or drop-off at a composting facility. It does not belong in a recycling bin. It should not go into general trash if you can avoid it. Compostable bags are designed for active composting environments, and biodegradation occurs significantly slower in landfill conditions due to limited oxygen and moisture.
The Bottom Line on Certification
The gap between biodegradable plastic bags vs compostable certified products is not a technicality. It's the difference between a claim with no standards and a claim that has been independently verified against specific, measurable criteria. Choosing certified compostable bags protects your home composting system, keeps your local composting program running cleanly, and ensures the finished compost going back into soil is actually safe.
Look for BPI certification, ASTM D6400 or EN 13432 compliance, and PFAS-free confirmation from the manufacturer. Those three markers together give you the confidence that the product you're buying will do what it says. Biodegradable alone does not.
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