ABSTRACT
Polyhydroxyalkanoates (PHA) are well-known to be naturally and readily biodegradable under ambient conditions by PHA degraders present in most natural environments, through enzyme-catalyzed hydrolytic chain scissioning. This produces monomers that can be further metabolized to methane under anaerobic conditions, and to carbon dioxide and water under aerobic conditions. As such, the use of these materials in many and varied products is growing strongly. One of the key considerations for practical applications of such products is their in-use lifetimes, both in terms of mechanical performance (time to failure) as well as time to ultimate biodegradation and conversion to methane and/or CO2. However, while there is extensive literature dealing with the gross indicators of biodegradation of PHA (principally mass loss), there are much more limited quantitative studies analyzing the complex changes associated with that biodegradation in the field or laboratory that can provide guidance for estimating the practical lifetimes of these products. This is particularly the case for composite materials, where the controlling mechanisms can be very different from those of a homogeneous matrix. Recent studies have shone some light on some of the fundamental drivers of biodegradation of PHA and its composites, and this chapter will present an overview of these developments.
