Kinetic perspective on biodegradable plastics degradability

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Since the age of plastics is under way, biodegradable plastics are gaining great popularity. Not only public promote these substituents of oil-based plastics, but a huge scientific interest was also attracted and further triggered an avalanche of praising and opposing studies. For instance, biodegradable polymers such as poly(lactic acid) (PLA) or polyhydroxyalkanoates (PHA) are intensively investigated from different perspectives in order to consider its suitability for commercial plastics replacement. There were several studies of accusing these biodegradable plastics of microplastics release and harming natural environments. Although common consumers put still higher demands on the environmental friendliness of purchased products, the end-of-life fate of the biodegradable plastics is still poorly understood. In this study, we have investigated the biodegradation of commercial polyhydroxybutyrate (PHB) and PLA under thermophilic composting conditions from the kinetic perspective. Two different kinetic models have been applied to analyse the differences in the degradation mechanism – reaction order kinetics and release kinetics model. Evident differences in the degradation rate constants have been observed and together with SEM micrographs indicate different ways of degradation for PHB and PLA under thermophilic composting conditions. The results of this study highlight the necessity to deal with genuine biodegradability of plastics and to distinguish plastics generating durable microplastics from those truly biodegradable.

Plastic degradation kinetics

17. 4. 2024

International Conference on Chemical Technology Mikulov