Synergistic effects of simulated red-category biomedical waste and biomass co-pyrolysis on the distribution of PAHs in pyrolysis oil

According to India’s biomedical waste management (BMW) framework, red-category biomedical waste refers to contaminated but recyclable single-use biomedical waste items. In this study, five common red-category BMW items (rubber gloves, pipette tips, test kits, syringes, and intravenous sets) were equally mixed to form simulated red-category biomedical waste (SRBW) and co-pyrolysed with biomass (black pine pellets) at 75:25, 50:50, and 25:75 (BMW: Biomass) ratios to examine the synergistic effects on the composition of PAHs in the pyrolysis oil (condensate). Experiments were conducted at 600 °C with a heating rate of 10 °C min −1 , a hold time of 120 min, and N 2 flow rate of 200 mL min −1 . Synergy index (ΔX) for condensate yield was predominantly negative (-9.0 pp), while calculated gas yield showed positive deviations, reaching + 11.7 pp. Relative gas composition also changed with biomass addition, with CO 2 increasing from 24 to 64 vol% in raw BMW items to 83–92 vol% at the 25:75 ratio, while H 2 decreased correspondingly across the feedstocks. In condensate, three-ring PAHs generally predominated across the feedstocks, while individual PAHs exhibited both positive and negative deviations from feed-mass-fraction-weighted reference composition depending on the feedstock and blend ratio. Five- and six-ring PAHs were not detected under the present analytical conditions. The relative toxic equivalency quotient (TEQ Relative ) showed negative deviations from feed-mass-fraction-weighted reference composition across feedstocks and blend ratios, except for rubber gloves at 25:75 (+0.0447), which showed a positive deviation associated with relatively high benzo[ a ]anthracene. These findings highlight feedstock-dependent deviations in PAH composition and TEQ Relative during co-pyrolysis.