Biohydrogen and Polyhydroxyalkanoates Coupled Production

One of the main environmental concerns of the actuality is the problem of conventional plastics and their lack of biodegradability, being therefore persistent in the environment. Moreover, their degradation generates toxic by-products that threaten natural life. Bioplastics arise as new solutions to replace plastics from fossil origin, and among them, polyhydroxyalkanoates (PHAs) are increasingly gaining attention due to their interesting properties, which are comparable to conventional materials. However, the production costs are still the bottleneck of PHAs’ processes establishment at large scale, which have stimulated the scientific community and the productive sector to search for new alternatives. That is why zero-waste-integrated technologies, which will be presented in this chapter, appear as interesting solutions to couple one or more production processes in the same productive unity. One example is the use of agroindustrial wastes in fermentation to produce volatile-fatty acids (VFAs), biohydrogen, methane and carbon dioxide. VFAs are well-known precursors for PHAs synthesis, which is economically and environmentally important to promote a sustainable process. Characteristics of the synthetized PHA depend on the VFA chain length and composition, which can lead to the formation of hydroxybutyrate (HB) and hydroxyvalerate (HV). This last may promote the synthesis of P(HB-co-HV), which is interesting from an industrial point of view, as it is more elastic and flexible.