The fate of biodegradable bioplastics (PHB and PHBV) in agricultural soils

The recent surge in scientific exploration of bioplastics highlights notable interest and importance among researchers, manufacturers, and government agencies. This burgeoning field is expected to undergo rapid expansion in the forthcoming years. The ongoing exploration in bioplastic research suggests significant potential for its integration across various sectors. As a result, the widespread utilization and application of bioplastics may inevitably introduce their residues into the soil environment and groundwater resources, either directly or indirectly. This highlights the crucial necessity for a thorough comprehension of the biodegradation mechanisms and the environmental implications of bioplastics, as well as their effects on interconnected ecosystems. This requires a multidisciplinary approach to be adopted. The aim of this thesis is to study the fate of two biodegradable bioplastics specifically Polyhydroxybutyrate (PHB) and Polyhydroxybutyrate-co-polyhydroxyvalerate (PHBV) within agricultural soil. Two different concentrations are analysed (0.2% w/w and 2% w/w of bioplastics). The research entails monitoring the changes in the physicochemical properties of these bioplastics and observing the development of biofilms on their surfaces over a 120-day period of exposure to agricultural. Furthermore, this study encompasses an analysis of the secondary microplastics (MPs) and nanoplastics (NPs) generated as a result of their interaction with the soil. The results indicated minimal alterations that biopolymers over the experimental duration. Discernible changes in the pellets' appearance, size, or weight fluctuations were observed. Spectroscopic and microscopic analyses did not reveal notable variations in surface topography, elemental composition, or chemical bonding. The quantity of biofilm suggested an interaction with biological factors but lacks a consistent pattern. These results carry significant implications for design and development of biopolymer consumer products in various fields. Understanding the mechanisms of PHB and PHBV biodegradation could pave the way for the development of more effective products characterized by a finite operational lifespan, while preserving essential mechanical and thermal properties.