Polyhydroxyalkanoates (PHA) are a family of biodegradable polyesters. As in many mammals, including humans, that hold energy reserves in the form of body fat some bacteria hold intracellular reserves in the form of polyhydroxyalkanoates. Here the micro organisms store a particularly high level of energy reserves (up to 80% of their body weight) for when their sources of nutrition become scarce.

By farming this type of bacteria, and feeding them on sugar or starch (mostly from maize), or at times on plant oils or other nutrients rich in carbonates, it is possible to obtain PHA's on an industrial scale. The most common types of PHA are PHB (Poly hydroxybutyrate), PHBV and PHBH. Depending on the bacteria and their food, PHAs with different mechanical properties, from rubbery soft trough stiff and hard as ABS, can be produced. Some PHAs are even biodegradable in soil or in marine environments.