Foaming enables material-efficient bioplastic products with minimal persistence

Mismanaged plastic products should be designed to inherently reduce their environmental impacts by optimizing material efficiency and minimizing environmental persistence. Foaming biodegradable bioplastics (i.e., introducing microstructural pores into the material) was hypothesized to achieve this objective. To test this hypothesis, the marine biodegradation of novel cellulose diacetate (CDA) foams of varying relative density (ρ_foam/ρ_solid =0.09-1.00) was evaluated in a flow-through seawater mesocosm. After 36 weeks, the CDA foams (ρ_foam/ρ_solid =0.09) lost 65-70% of their mass, while equivalent polystyrene foams persisted with no change in mass. The degradation rates of the CDA foams were ~15 times that of solid CDA and the fastest of any plastic reported in the ocean. Material indices, value functions, and qualitative descriptors for circularity indicated that CDA foams could be the favorable choice of material for food-packaging applications with potential benefits to society worth hundreds of millions of dollars annually. Foaming of biodegradable bioplastics thus represents a promising strategy toward minimizing the environmental impacts of frequently mismanaged consumer plastics.