While they sound similar, be sure not to mix up biodegradable and compostable! The main difference is the time it takes for the material to break down, which is an important factor in deciding what to accept into a compost pile. While biodegradable items are any material that breaks down and decomposes in the environment, compostable refers to organic matter that breaks down to become a pile of nutrient-rich soil. If an item is certified compostable, then it has been tested to completely breakdown, leaving no residues, after 90 days in the heated and microbial conditions of a commercial compost facility. At best, biodegradable means that the product will break down into its constituent components, but this does leave residues. Biodegradable products can also take years (or decades!) to break down, which is a long time to wait!