Biodegradation of woody film in river and sea water and surface sediments

The development of novel biodegradable substitutes for plastics is required, as current plastic waste is not easily degraded in many environments, including seas, rivers, and soil. We developed a woody film with nearly the same composition as wood as a biodegradable substitute for plastics. A biodegradability test of the film was performed over 9 weeks in the water and surface sediments of rivers and seas. The film was degraded in river-derived water and surface sediments, as observed via weight reduction. The proportion of methanogenic bacteria increased, and gas was generated in the river surface sediment samples. However, almost no biodegradation occurred in sea-derived water and surface sediments, with only minor weight reduction observed. Sea surface sediments turned black in the region in direct contact with the film, attributed to the formation of metal sulfide, and had an increased proportion of sulfate-reducing bacteria. This film has high potential as a biodegradable plastic substitute due to its degradation in river environments. Biodegradation of the woody film occurs slowly in sea environments; however, components of wood, including cellulose, hemicellulose, and lignin, are less harmful to the environment and marine organisms upon consumption, when compared to plastics. Graphical abstract