Synergistic atmospheric influence on the co-pyrolysis of antibiotic sludge and waste bicycle tires: Optimal drivers, products, and pathways

Effective management of antibiotic sludge (AS) is essential for disease prevention. This study investigated the co-pyrolysis of AS with polyurethane (PU) and rubber tires (RT), focusing on its key drivers, synergies, resulting products, and atmospheric (N₂ versus CO₂) dependency. Composite pyrolysis index indicated superior co-pyrolysis properties of AS with PU or RT in the CO₂ atmosphere compared with those in the N₂ atmosphere. The strongest synergistic effect occurred at an optimal ratio of 75 % AS to 25 % PU (AP31) or 25 % RT (AR31), regardless of the atmosphere. Real-time gas analysis revealed greater product diversity in N₂ than in CO₂, with AS-derived products predominating. The co-pyrolysis altered AS nitrogen groups, promoting pyrrolic-N and pyridinic-N formation, and accelerated organic sulfur decomposition. Experimental results combined with univariate and multivariate joint optimizations identified the co-pyrolysis pathways of AP31 (650 - 800 °C) and AR31 (600 - 800 °C), respectively, in the CO₂ atmosphere as synergistically optimal for maximizing resource recovery while minimizing waste and pollutant generation. This study provides actionable insights into the synergistic co-pyrolysis of AS with PU or RT, facilitating optimized gas emissions, energy recovery, and resource reuse.