Evaluation of the biodegradation of polymeric materials in the freshwater environment—An attempt to prolong and accelerate the biodegradation experiment

Abstract

Available international standards describing the biodegradability testing in freshwater were designed primarily for chemicals that undergo relatively fast biodegradation (in the order of days). The current study was undertaken to verify their applicability for testing of slowly degradable polymeric materials, and also describes an attempt to accelerate the biodegradation testing by the increase of the incubation temperature from 25 °C to 37 °C. The polymers tested include TÜV AUSTRIA Belgium certified polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polybutylene adipate-terephthalate, and polylactic acid blend (PBAT/PLA), and an experimental polyester network (ICL-PN). The biodegradation rates of the given polymers at the two temperatures were examined by carbon dioxide evolution and additional information was collected from microscopy observations of the materials and the investigation of the microbial community composition and dynamics. Testing was done at two independent laboratories and the results were compared. It was found that at 25 °C the testing environment was relatively stable, and the incubation can be prolonged up to 12 months. At 37 °C however some undesirable phenomena like higher variability between replicates and laboratories, fungi development, and biomass autolysis were observed. Moreover, the increase in temperature did not accelerate the biodegradation process. Based on the comparison of results from the two laboratories, recommendations for the experimental procedure are given.