Plastics–Fertilizer Homology: Solid-Phase Molecular Assembly Enables Natural Closed-Ring Cycle of Biomass-like Plastics

Biomasses have undergone natural closed-ring cycles for billions of years, including biodegradation, soil fertilization, and transformation to new biomass through neutralizing plants. If a bioplastic is made biomass-like, its natural closed-ring cycle would be very promising in tackling the white pollution and microplastics problems associated with petroleum plastics. Herein we report a proof-of-concept strategy employing plastics–fertilizer homology toward this goal. Biomass-like supramolecular plastics were fabricated through solid-phase molecular self-assembly of alginate and alkylammonium surfactants, followed by calcium coordination. The resultant plastics display satisfactory dry and wet mechanical strength, comparable to that of conventional petroleum plastics, while being fully biodegradable. The biodegradation products were able to increase pak choi’s wet/dry weights by 40% and 12%, respectively, promoting both soil fertility and water retention. This natural closed-ring cycle is very similar to real biomass processes, verifying the plastics–fertilizer homology as a promising solution to white pollution and microplastics crises.