What Are CMA-Certified Compostable Bags and Why Do They Matter in Denver?
- Ethan Babil
- Aug 17
- 3 min read
CMA stands for the Compost Manufacturing Alliance, which certifies compostable products based on how they perform in real commercial composting facilities rather than laboratory conditions. In Denver, 3-gallon CMA-certified compostable bags are the only permitted liner for organics collection.
Not any compostable bag. Not any size. This post explains what CMA certification actually tests, why it survived when other certifications did not, and how to buy the right bags.
What is the Compost Manufacturing Alliance?
An organization that field-tests compostable products at working commercial composting facilities and certifies what actually breaks down there.
That distinction is the entire point. Most compostability certifications are based on controlled laboratory conditions. CMA certification is based on results at real facilities running real timelines with real equipment.
Why does field testing matter?
Because lab conditions and field conditions diverged badly.
A material can meet a laboratory compostability standard and still emerge intact from a commercial windrow, because the facility does not run at lab temperatures, lab moisture, or lab duration. Composters across Colorado ended up screening out or landfilling material that was technically certified compostable.
That gap is why A1 Organics stopped accepting compostable packaging and serviceware entirely, and why CMA-certified bags remained acceptable when other products did not.
Why only 3-gallon bags?
Size is part of the acceptance rule in Denver. The permitted liner is a 3-gallon CMA-certified compostable bag.
Larger compostable bags, even certified ones, are not covered by that allowance. If you are lining a 32-gallon or larger container, the answer is to run it loose or to line smaller interior collection pails that get emptied into it.
How do you tell if a bag is CMA-certified?
Look for the Compost Manufacturing Alliance certification specifically. Not a generic "compostable" claim, not a leaf logo, not a BPI mark alone.
Vendors selling into the Denver market should be able to tell you directly and provide documentation. If a supplier cannot confirm CMA certification in writing, treat the answer as no.
Colorado also has labeling requirements around compostable product claims, which reduces some of the worst marketing behavior but does not remove your obligation to verify.
What happens if you use the wrong bag?
The bag becomes a contaminant, and so does everything inside it.
A standard trash bag in an organics container is the single most common contamination source in Denver. Plastic film shreds during processing and cannot be fully removed, which is why it drives load rejection more than almost anything else.
What is the practical setup?
Two workable approaches:
Loose collection. No liner. Cleanest from a contamination standpoint, harder on container cleaning. Requires a regular container washing routine, which URCO expects anyway for pest and odor control.
3-gallon CMA-certified liners at interior stations. Small pails at prep lines, desks, or in-unit, emptied into the central container. Contains mess, keeps the stream clean, and matches the permitted size.
Most kitchens and apartment programs end up running the second approach with a container-cleaning routine layered on top.
Frequently asked questions
Can I use a compostable bag that is not CMA-certified? No. The permitted liner is 3-gallon CMA-certified.
Are compostable bags the same as compostable serviceware? No, and the distinction matters. Certified compostable serviceware is not accepted in Denver organics. CMA-certified 3-gallon bags are.
Where do I buy them? Commercial janitorial and foodservice suppliers serving the Denver market. Confirm CMA certification in writing before ordering.
Are they more expensive? Somewhat, compared to conventional trash bags. Considerably less expensive than a rejected load or a contamination fee.
Can I skip liners entirely? Yes. Loose collection is fully acceptable and requires a container-cleaning routine.
Get the whole setup right
Melly's Recycling is a Denver URCO compliance company, not a hauler. Liner selection is one small piece of a program that also needs correct capacity in gallons, compliant bilingual signage, trained staff, a Waste Diversion Plan, and a records file. We build all of it, and coordinate licensed Denver haulers through a sealed-bid process.
You finish what you started.
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