Like degradable bags, biodegradable are often still plastic bags that have microorganisms added to break down the plastic. Compostable bags are made of natural plant starch, and do not produce any toxic material. Compostable bags break down readily in a composting system through microbial activity to form compost.

Biodegradable products break down much faster than other types of products. Biodegradable products break down into carbon dioxide, water vapor, and organic material, which aren't harmful to the environment. Typically, they're made from sustainable materials and plant by-products, such as cornstarch or sugarcane.