Biodegradation of PHB-Based Bioplastic Films in Soil

Plastic materials produced from fossil fuel derivatives cause serious environmental problems due to their non-degradable nature. In general, such synthetic polymers are inexpensive, but their abundance has a significant negative environmental impact. Even most of the bioplastic materials produced currently are non-biodegradable, including Bio-PP, Bio-PET, and Bio-PA. Accordingly, recent research has focused on developing biodegradable polymers such as polymers produced by microorganisms, which have lower carbon footprints and greater ability to be recycled. Recently, Polyhydroxyalkanoates (PHAs) have attracted considerable attention as a biodegradable thermoplastic resin. In particular, polyhydroxybutyrate (PHB), which is the most well-known among PHAs, has been shown to rapidly degrade within 6 months under various natural active environments. The biodegradation of PHB takes place either under anaerobic or aerobic conditions. Implementation of the anaerobic condition will lead PHB to produce H₂O, CO₂, and methane. Under aerobic conditions PHB will produce CO₂ and H₂O. In anaerobic conditions a sludge containing several microorganisms is produced and can degrade PHB in different environments such as soil, salt water, and fresh water. However, soil was found to be the most natural environment for PHB degradation.<br/>In this study, we propose a new type of biodegradable bioplastic composite film made of PHB bearing green additives. The green additives implemented to overcome the mechanical instability of PHB and to substantially increase the elongation property of the film. In addition, we have investigated the degradation of two different types of PHB-based biodegradable composite films over a 6 week period in compostable soil. The degradation was evaluated by measuring polymeric material molecular weight loss, crystallinity, mechanical properties, and physical changes within the surface of polymeric films.