Are bioplastics microplastic-free?
The prefix suggests a material that leaves nothing behind. The chemistry is more complicated, and the answer depends on which question you are asking.
What bioplastics actually are
Bioplastic is an umbrella term that covers two different properties. A plastic can be bio-based, meaning it is made from renewable feedstocks such as corn starch or sugarcane rather than petroleum. A plastic can also be biodegradable, meaning it can be broken down by microorganisms under certain conditions. These properties are independent of each other, and a given material can have one, both, or neither.
Bio-based polyethylene, for example, is made from sugarcane but is chemically identical to conventional polyethylene. It is not biodegradable at all. Polylactic acid (PLA) is both bio-based and compostable, but only under industrial composting conditions. PBAT, a common ingredient in compostable bags, is biodegradable but made largely from fossil feedstocks. The word bioplastic on its own does not tell you which of these you are holding.
Biodegradable does not mean it disappears everywhere
Compostability certifications for materials like PLA are based on specific conditions: sustained elevated temperatures, controlled moisture, and active microbial populations, the environment of an industrial composting facility. Outside those conditions, in soil, in water, or in a home compost pile, degradation slows dramatically and can take years.
Fragmentation matters here. Plastics generally break into smaller pieces before they fully mineralize, and laboratory and field studies have documented microplastic-scale fragments from biodegradable plastics during that intermediate stage. A material that will eventually biodegrade under the right conditions can still exist as small plastic particles in the meantime. Whether and how quickly those particles fully break down depends on the material and the environment it ends up in.
Two different questions
Much of the confusion around bioplastics and microplastics comes from mixing two separate questions. One is a disposal question: after this product is thrown away, will it break down completely? The other is a use question: while this product is in someone's hands, mouth, or kitchen, is plastic present at all?
Biodegradability standards answer the first question. Our standard answers the second. Both are legitimate things to measure, but they are not interchangeable, and a claim built on one does not substantiate the other. A cup made of PLA may earn a compostability certification while still being a plastic cup during every moment of its use.
How the CMF standard treats bioplastics
Under CMF Standard v1.0, bio-based and biodegradable plastics are plastics. They are polymer materials, and their presence in a product's exposed surfaces is disqualifying by default, the same as conventional plastics. The standard asks whether the surfaces that touch skin, mouths, food, or beverages are free of plastics and other microplastic-forming materials during intended use, and a bioplastic surface does not meet that test.
This is a deliberately conservative position. Feedstock and end-of-life behavior are worthwhile considerations for other purposes, but they do not change what the material is while the product is in use. The full criteria are published in Certification Criteria and About the Standard.
If your brand uses or is considering bioplastics
Bioplastics can be a reasonable choice for goals like reducing fossil feedstock use, and nothing here argues otherwise. But marketing a bioplastic product as microplastic-free invites scrutiny, because the claim reads as a statement about what the product contains, not about how it decomposes. Under the FTC Green Guides, environmental claims need substantiation that matches what a reasonable consumer would understand the claim to mean. We cover that framework in Substantiating Microplastic-Free Marketing Claims.
For products designed without plastics of any kind in their exposed surfaces, our documentation-based review can verify the claim. Start with the certification criteria or apply for an initial screening, which is free.
Related reading
What does microplastic-free actually mean? and Is silicone microplastic-free?