Plastic plates, bowls, cups, utensils, bags, or other food service ware labeled "biodegradable" or "compostable" cannot be composted in the backyard or placed in curbside carts. Please do not place them into the recycling either, as these compostable plastics are different from regular plastic and have different melting points. They must be placed in the garbage.
The food scraps and other organic materials you place in green curbside carts or dumpsters are sent to industrial composting facilities in Marin, Napa, Mendocino, and Contra Costa Counties. Due to inconsistency in product labeling, these composting facilities cannot easily distinguish compostable products from conventional/petroleum-based plastic products. To avoid creating microplastics that will end up in the finished compost and may contaminate waterways, facility operators use machinery to screen out anything that resembles plastic, whether or not they are compostable, and send them to the landfill.
On the other hand, it is also not advisable to compost "biodegradable" or "compostable" products in a backyard hot pile. Many of these products are made from plant polymers such as polylactic acid (PLA) which only break down at high temperatures around 110 - 140 degrees Fahrenheit. Backyard compost piles are often too small to reach these temperatures. However, wood or fiber based products without any plastic coating or lining might be more likely to break down in the backyard.
Since "biodegradable" or "compostable" products are often expensive, and since there is not a local outlet for them to be composted, Zero Waste Sonoma recommends choosing and buying reusable items whenever possible, and avoiding "biodegradable" or "compostable" products completely.
Curbside Services: Compost Cart
Compost for the Climate
Reusable Food Service Ware Grant
Zero Waste Lifestyle During the Pandemic