Biodegradable Plastics. Biodegradable plastic is plastic that decomposes naturally in the environment. This is achieved when microorganisms in the environment metabolize and break down the structure of biodegradable plastic. The end result is one which is less harmful to the environment than traditional plastics.ith biodegradable plastic, you get a substance made from natural sources that does not contain these chemical fillers, and does not pose the same risk to the environment. The process of making biodegradable plastics begins with the melting down of all the materials.