Plastic pollution is threatening human health and ecosystems, resulting in one of the biggest challenges that humanity has ever faced. Therefore, this study focuses on the preparation of macroporous carbon from biowaste (MC)-supported manganese oxide (MnO₂) as an efficient, reusable, and robust catalyst for the recycling of poly(ethylene terephthalate) (PET) waste. As-prepared MnO₂/MC composites have a hierarchical pore network and a large surface area (376.16 m²/g) with a narrow size distribution. MnO₂/MC shows a maximum yield (98%) of bis(2-hydroxyethyl)terephthalate (BHET) after glycolysis reaction for 120 min. Furthermore, MnO₂/MC can be reused at least nine times with a negligible decrease in BHET yield. Based on this remarkable catalytic performance, we expect that MnO₂-based heterogeneous catalysts have the potential to be introduced into the PET recycling industry.