Biodegradable polymers have undergone extensive investigation since the 1970s. They can be either natural or synthetic and can be derived from either renewable or nonrenewable resources. A series of truly biodegradable petroleum-based synthetic polymers has been developed. However, owing to concerns over environmental pollution and the depletion of fossil oils, intensive research is being conducted for developing biodegradable polymers and plastic materials from renewable natural resources such as starch, cellulose, and soy protein