Biodegradable does not always mean compostable.

The Federal Trade Commission Green Guides has very specific labeling requirements for items that are marketed as “biodegradable” or “compostable,” as a means to avoid deception.

Just because something is labeled as “compostable,” does not mean that your local compost facility will process it.
In California, Senate Bill 567 prohibits labeling of any plastic or bioplastic product as biodegradable, oxo-degradable, oxo-biodegradable, or photodegradable.