The fate of biodegradable polyesters in the marine environment

The fate of polymeric materials depends on the chemical structure of the polymer and on environmental conditions. To mitigate environmental issues associated with plastic mismanagement at the end of life, great attention has been addressed to compostable and biodegradable polymers. Some of these polymers, even if biodegradable, are found in the form of microplastics in the environment. In this work, the degradation behavior of five biodegradable polymers, poly(butylene succinate), PBS, poly(butylene succinate-co-butylene adipate), PBSA, poly(ε-caprolactone), PCL, polyhydroxy butyrate, PHB, and poly (lactic acid), PLA, was evaluated using ad hoc set mesocosms simulating their presence in marine environment at different water depths for 363 days. Higher mass loss during aging was recorded for PCL and PHB. Cracks, grooves and holes were detected on all the samples at the end of the test. Exposure into seawater induces hydrolytic degradation of the polyesters confirmed by Fourier transform infrared and NMR spectroscopies. The identification of the polymer phase in the sand suggests the occurrence of fragmentation phenomena of some samples, particularly PCL, during ageing. Remarkably, not all biodegradable polyesters are biodegraded in the sea, thus their mismanagement at the end of life is likely to induce progressive accumulation in the environment.