| Summary: | There are discrepancies concerning the time frame for biodegradation of different commercially available foils labeled as biodegradable; thus, it is essential to provide information about their biodegradability in the context of their end of life in waste management. Therefore, one-year mesophilic (37 °C) anaerobic degradation tests of two bio-based foils (based on starch (F<sub>S</sub>), polylactic acid (F<sub>PLA</sub>)) and oxo-degradable material (F<sub>OXO</sub>) were conducted in an OxiTop system. Biodegradation was investigated by measuring biogas production (BP) and analyzing structural changes with differential scanning calorimetry, polarizing and digital microscopic analyses, and Fourier transform infrared spectroscopy. After 1 year, F<sub>OXO</sub> had not degraded; thus, there were no visible changes on its surface and no BP. The bio-based materials produced small amounts of biogas (25.2, F<sub>PLA</sub>, and 30.4 L/kg VS, F<sub>S</sub>), constituting 2.1–2.5% of theoretical methane potential. The foil pieces were still visible and only starting to show damage; some pores had appeared in their structure. The structure of F<sub>PLA</sub> became more heterogeneous due to water diffusing into the structure. In contrast, the structure of F<sub>S</sub> became more homogenous although individual cracks and fissures appeared. The color of F<sub>S</sub> had changed, indicating that it was beginning to biodegrade. The fact that F<sub>S</sub> and F<sub>PLA</sub> showed only minor structural damage after a one-year mesophilic degradation indicates that, in these conditions, these materials would persist for an unknown but long amount of time.
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