Novel Strategies for Recycling Poly(butylene adipate-co-terephthalate)-Starch-Based Plastics: Selective Solubilization and Depolymerization-Repolymerization Processes

Starch-based plastics (SBPs) containing poly(butylene adipate-co-terephthalate) (PBAT) are among the most produced bioplastics on the market and are currently managed at their end of life (EoL) through composting. In view of developing novel EoL approaches, SBPs were characterized here in terms of their main components (PBAT, starch, and plasticizer), and three strategies for their recycling were investigated: (I) the selective solubilization of PBAT with ethyl acetate; (II) a two-step depolymerization-repolymerization process that consists of the catalytic selective alcoholysis of PBAT into its oligomers, followed by their repolymerization to PBAT with no need of adding a new catalyst; and (III) the complete selective depolymerization of PBAT, followed by the recovery and purification of butanediol (1,4-BD), dimethyl terephthalate (DMT), and dimethyl adipate (DMA). Up to 99, 95, and 93% recovery of the SBP components was obtained, respectively, following these three methods. Extensive characterization of the recovered PBAT was performed through molecular weight and thermal and thermomechanical analyses, demonstrating the efficiency of the processes. The environmental sustainability of the proposed approaches was also preliminarily evaluated through the calculation of their environmental factor (E-factor).