In typical parlance, the word biodegradable is distinct in meaning from compostable. While biodegradable simply means an object is capable of being decomposed by bacteria or other living organisms, "compostable" in the plastic industry is defined as able to decompose in aerobic environments that are maintained under specific controlled temperature and humidity conditions. Compostable means capable of undergoing biological decomposition in a compost site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds and biomass at a rate consistent with known compostable materials.
Most bags that are manufactured from plastic are made from corn-based materials, like polylactic acid blends. Biodegradable plastic bags are nowadays as strong and reliable as traditional (mostly polyethylene)-bags. Many bags are also made from paper, organic materials, or polycaprolactone.
"The public looks at biodegradable as something magical," even though the term is broadly used, according to Ramani Narayan, a chemical engineer at Michigan State University in East Lansing, and science consultant to the Biodegradable Plastics Institute. "This is the most used and abused and misused word in our dictionary right now. In the Great Pacific garbage patch, biodegradable plastics break up into small pieces that can more easily enter the food chain by being consumed."