Fully circular shapable transparent paperboard with closed-loop recyclability and marine biodegradability across shallow to deep sea

To mitigate marine pollution from single-use plastics, it is crucial to transition to next-generation commodity materials that are derived from biomass and are recyclable and marine biodegradable even at abyssal depths in case of the accidental release to the ocean. Here, we develop an optically transparent millimeter-thick paperboard called transparent paperboard (tPB) through dissolution and coagulation of cellulose. The tPB is made entirely of pristine cellulose and compositionally identical to paper. A cup-shaped tPB can hold just-boiled water without an internal film coating because of its high wet tensile properties and anisotropic thermal properties. In addition, the spent tPB is material recyclable in a closed system, where all chemicals and water are also recyclable. Furthermore, the marine biodegradability of tPB across shallow to abyssal depths is confirmed by on-site degradation tests and metagenomic analyses. Hence, tPB is expected to serve as a key fully circular commodity material in sustainable societies of the future.