The Difference Between Biodegradable and Compostable Sandwich Bags
If you've searched for biodegradable sandwich bags, you've probably noticed that the results are a mix of bags labeled "biodegradable," "compostable," and sometimes both. These terms get used interchangeably in marketing, but they mean very different things. The distinction matters for your composting routine, your kitchen waste habits, and whether your bag actually does what you think it does when you're done with it.
This article breaks down what each term actually means, why "biodegradable" on a plastic product is a vague and often unverifiable claim, and what to look for when you want a sandwich bag that genuinely supports composting.
What Does Biodegradable Actually Mean?
Biodegradable means a material can be broken down by microorganisms. That sounds straightforward, but here's the problem: everything organic biodegrades eventually. A cotton t-shirt, a wooden spoon, a piece of leather. Even conventional plastic will technically biodegrade over hundreds or thousands of years.
The word "biodegradable" has no required certification standard behind it. No independent lab has to test a product before a manufacturer can print that word on the packaging. There is no defined timeframe. No requirement for what the material breaks down into. No verification that the breakdown products are safe or free of toxins.
California recognized this problem and passed laws prohibiting the use of "biodegradable" on plastic products sold in the state, because the claim cannot be substantiated in any meaningful, verifiable way. If a claim cannot be tested and confirmed, it should not be on a label. That is a reasonable standard, and California is right to hold the industry to it.
When you see a sandwich bag marketed as biodegradable, the claim may be technically true in the loosest possible sense, but it tells you almost nothing useful about how, when, or under what conditions that bag will break down. It tells you nothing about what residue it leaves behind.
What Does Certified Compostable Mean?
Compostable is a different category entirely. A product labeled certified compostable must meet specific breakdown standards and pass independent third-party testing before it can carry that label. This is not a self-declared claim.
In the United States, the relevant standard is ASTM D6400. In Europe, it is EN 13432. Products certified under these standards must demonstrate that they disintegrate significantly, that the material biodegrades at a rate comparable to known compostable materials, and that the resulting compost is not toxic to plants or soil.
For industrial composting, those conditions involve high temperatures (around 55 to 60 degrees Celsius), controlled humidity, and active microbial activity at a commercial composting facility. Under ASTM D6400, 90% disintegration must occur within 84 days. Under EN 13432, the same benchmark applies within 90 days.
Home compostable products are certified under a separate standard, TUV OK Compost HOME. These products must break down at ambient temperatures in a standard backyard compost environment, with 90% disintegration within 180 days.
BPI certification, which stands for Biodegradable Products Institute, is the leading third-party certification in the US for compostable products. BPI requires independent laboratory testing. A product cannot simply claim BPI certification. It has to earn it through verified testing.
That's the difference. Compostable comes with accountability. Biodegradable, on a plastic product, usually does not.
Biodegradable Sandwich Bags: What You're Actually Getting
Most bags marketed as biodegradable sandwich bags are either conventional plastic with an additive designed to accelerate fragmentation, or plant-based materials with no formal certification. Neither category gives you confidence about the end result.
Oxo-degradable plastics, which include an additive that causes the material to fragment faster, have been widely criticized by researchers and regulators. The plastic breaks into smaller pieces, but those pieces are still plastic. They do not biodegrade into safe, organic components. They produce microplastics. The European Union has taken action to restrict these materials for exactly this reason.
Plant-based materials without certification are a more complicated case. A bag made from plant starches might genuinely biodegrade under the right conditions. But without certification, you have no verified information about how long it takes, what conditions it requires, or whether the breakdown is complete and non-toxic. You're taking the manufacturer's word for it, with no independent verification.
If you care about where your sandwich bag ends up, and what it becomes when it gets there, "biodegradable" on the label is not enough information to act on.
Why the Label on Your Lunch Bag Matters More Than You Think
Composting facilities operate on tight contamination tolerances. When non-compostable or unverified materials enter a composting stream, they can damage the quality of the finished compost. Farmers and landscapers who buy finished compost rely on it being free of plastic fragments and chemical residue. A contaminated batch can mean rejected product or, worse, microplastics applied directly to agricultural soil.
This is not a minor edge case. It is a documented problem that composting facilities deal with regularly. California's AB 1201 was signed into law partly to address it. The law requires that any product labeled compostable in California must be third-party certified. It also prohibits compostable labels on products containing PFAS, a class of persistent chemicals that have been found in some compostable fiber packaging.
The practical takeaway: when you put a bag into your compost bin or curbside composting program, the bag's certification determines whether it helps or harms the system. A bag with no certification, no matter what the label says, is an unknown variable that composting facilities generally cannot afford to accept.
PFAS in Food Bags: A Specific Risk Worth Knowing
PFAS, or per- and polyfluoroalkyl substances, are a group of synthetic chemicals used in some food packaging for grease and moisture resistance. They are persistent in the environment and in the human body, and they do not break down during composting. If a compostable product contains PFAS, those chemicals end up in the finished compost and potentially in soil and water.
This is particularly relevant for compostable food bags and fiber-based food containers. Some products that look certified, or present themselves as sustainable, have been found to contain intentionally added fluorine as a processing aid or coating. BPI no longer certifies compostable fiber products with intentionally added fluorine, which is a meaningful policy shift.
GreeneWrap products are PFAS free and fluorine free, confirmed by the manufacturer. This applies to GreeneWrap's product line specifically. When evaluating other brands, some compostable products may contain PFAS, so checking certification details is always worth doing.
What to Look for in a Certified Compostable Food Bag
When you're shopping for compostable food bags to use for sandwiches or other lunch items, here's a practical checklist:
- BPI certification: Confirms independent third-party testing to ASTM D6400 standards. This is the most recognized certification for compostable products in the US.
- ASTM D6400 or EN 13432 compliance: The actual performance standards behind the certification. If a product claims compostability but does not reference either of these standards, that's a gap worth noting.
- TUV OK Compost HOME (if home composting): If you're composting at home in a backyard bin, look for this specific certification. Industrial compost certification alone does not guarantee performance in a home compost environment.
- PFAS free confirmation: Ask the manufacturer or look for explicit documentation. This is not always labeled clearly on packaging.
- No vague biodegradable claims: A product that leads with "biodegradable" and offers no certification details is telling you less than you need to know.
Using Compostable Sandwich Bags Correctly
Certified compostable bags require active composting conditions to break down properly. This means heat, moisture, and microbial activity. A bag sitting in a trash bin, or in a landfill where oxygen and moisture are limited, will biodegrade significantly more slowly than in an active composting environment. Compostable bags are designed for composting systems, not general waste disposal.
For sandwich and lunch use, compostable bags work well for short-term food storage. If you're also using them to collect food scraps for a compost bin, avoid leaving wet waste in the bag for more than one to two days, because moisture accelerates the breakdown process. Store unused bags in a cool, dry place and use them within 12 months of purchase.
If your city has a curbside composting program, most US municipal programs accept BPI certified bags, but policies vary. Always check your local program's specific requirements before putting certified compostable bags in the bin.
Sharp objects like bones can puncture any compostable bag. This applies across all brands and is just a practical reality of the material.
The Bottom Line on Biodegradable vs Compostable Sandwich Bags
The word "biodegradable" on a sandwich bag is not a certification. It is not verified by any independent body. It does not tell you what the bag breaks down into, how long it takes, or whether it is safe for composting systems. For anyone trying to reduce plastic waste and support a composting habit, a vague biodegradable claim is not a reliable foundation to build on.
Certified compostable is the standard that holds up. BPI certification, ASTM D6400 compliance, EN 13432 compliance. These are testable, verified, and meaningful. If you want your lunch bag choice to connect to an actual sustainable outcome, those are the labels to look for.
GreeneWrap's compostable bags carry BPI certification, TUV Austria certification, and meet both ASTM D6400 and EN 13432 standards. They are also PFAS free and fluorine free. That is what verified compostability looks like in practice.
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