The Problem with Compostable Plastics

Composting is one of the most powerful ways our community can fight climate change—but only when the right materials go into the green cart.

When food scraps, yard waste, and food-soiled paper (like napkins and pizza boxes) decompose in a landfill, they release methane, a greenhouse gas that is up to 80 times more potent than carbon dioxide. Composting keeps these materials out of landfills, reduces methane emissions, and returns valuable water and nutrients back into the soil—helping local farmers grow food right here in Marin.

Why Compostable Plastics Can’t Go in the Green Cart

Marin Sanitary Service’s compost processor, WM EarthCare, produces high-quality compost that is certified for organic farming by the Organic Materials Review Institute (OMRI).
OMRI does not allow compostable or biodegradable plastics—even those labeled “plant-based.” Accepting them would cause the compost to lose its organic certification, making it unusable for local agriculture.
Another challenge? Compostable plastics look almost identical to regular plastic, making it extremely difficult to sort them out at the processing facility.

Even though the label may sound eco-friendly, all compostable and biodegradable plastics belong in the garbage cart.