Polyurethane waste valorization: A Two-Phase process using Ozonization and Rhodococcus pyridinivorans fermentation for biofertilizer production.

A circular economy process has been developed to convert polyurethane waste into biofertilizing microorganisms through a sequential chemical/biological process. The chemical phase involves the complete depolymerization of polyurethane using ozone attack, generating an aqueous extract (OLE) composed of small, bioavailable molecules such as polyols, isocyanate derivatives, and carboxylic acids. The biological phase utilizes OLE for the generation of biomass with biofertilizing functional activity through Rhodococcus pyridinivorans fermentation. The metabolic-proteomic expression during the biodegradation of OLE involves the synthesis of numerous enzymes such as cutinases, hydrolases, proteases, esterases and oxidoreductases, which participate in the degradation of chemical compounds like benzene derivatives, phenols, or plastic polymers. OLE has been converted into microorganisms with biofertilizing properties, including nitrogen fixation, phytohormone production and siderophores. This process contributes to sustainability by diverting polyurethane waste from landfills, reducing the environmental impact of chemical fertilizers and promoting a more sustainable agricultural system.