Biodegradable plastic substitutes (BPS) are substances that can be used as conventional plastics, while decomposing on disposal into water and carbon dioxide, by the action of microorganisms commonly present in the natural environment. The BPS can therefore be returned to nature since they would decompose quickly and do not adversely affect the quality of the compost produced in composting facilities.

Many compounds proposed in the industry as BPS are actually not fully satisfying plastic substitutes, either because of their poor strength, poor compliance with existing transforming devices, very high cost or because they often are bio-fragmentable (in a myriad of tiny plastic parts or powders) instead of being biodegradable (totally degraded). Bio-fragmentable mixes just save the appearance, not the problem: serious clients and consumers will not accept bio-fragmentable mixes as an appropriate choice.

Some true BPS are very expensive and restricted mainly to medical purposes, such as resorbable sutures and internal devices. Better known propositions derived from maize or starch often have poor physical qualities and appear to easily clog existing transforming machines; their use is limited to some types of bags and wrappings, and only one type of bacteria assimilate them. Moreover, the time required for the degradation of existing products is fixed and cannot be adjusted to consumers' needs. Finally it seems so far in the world that no BPS had met the requirements for reliable plastic injection, the most common production method.