Thermal Plasma Treatment of Simulated Medical Waste Using CO2 as a Gasification Agent for Carbon Utilization at Pilot Scale

Treatment of hazardous medical waste streams represents a significant environmental challenge, commonly associated with greenhouse gas emissions and limited energy recovery. This study experimentally and theoretically investigates the valorization of simulated medical waste (SMW) via a thermochemical upcycling approch, employing a pilot-scale (up to 160 kW) high-enthalpy (>100 MJ kg⁻¹) direct-current (DC) discharge thermal plasma reactor processing 6.2-9.0 kg h-1 of feedstock with carbon dioxide (CO2) injection rates of 0-164 slm as a reactive gasifying agent. The unique reactor environment, characterized by temperatures of 1250–1450 °C and intense UV radiation, ensured the decomposition of hazardous intermediates while enabling Carbon capture and utilization (CCU). The results demonstrate that externally supplied CO2 actively participates in high-temperature gasification, promoting carbon monoxide formation through dry reforming and Boudouard reactions. The produced syngas was rich in CO and H2, with lower heating values (LHV) ranging from 13.9 to 18.8 MJ kg⁻¹. A key finding was the successful upgrading of low-grade waste into a valuable fuel, evidenced by a chemical energy ratio of the output syngas to the input waste fuel reaching up to 1.9. The cold gas efficiency experimentally reached nearly 56%, while equilibrium-based analysis indicates a theoretical upper limit exceeding 62% under optimized power matching. Deviations between experimental results and equilibrium predictions observed at extreme (marginal) operating regimes were attributed to pilot-scale effects such as non-uniform mixing, residence time limitations, and heterogeneous reaction kinetics. Overall, this study shows that CO₂-assisted thermal plasma gasification of simulated medical waste has strong application potential for the treatment of real hazardous medical wastes, enabling efficient syngas production while utilizing CO₂ as a reactive gasification agent.