Interactive co-pyrolysis of end-of-life tires and plastic wastes: A combined TGA-IR-MS and COMSOL investigation

The accumulation of waste tires (WT) poses a significant environmental challenge due to the rubbery structure, which makes them difficult to store, digest, or recycle in typical waste recycling facilities. Thermal degradation of WT has often been investigated as a potential waste-to-energy approach, but products obtained from the pyrolysis of tires render them not suitable for direct use. Therefore, this research highlights products and degradation behavior of WT pyrolysis and their co-pyrolysis with plastic wastes such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). The integrated TGA-IR-MS system effectively mimics real-life thermal degradation and gas evolution processes by sequentially analyzing the decomposition behavior, gaseous emissions, and final pyrolysis byproducts, which resemble those found in large-scale industrial thermal recycling systems. The results revealed that plastic waste alters the thermal profile of WT, reduces residue formation, and promotes the conversion of D-limonene into BTX compounds (benzene, toluene, xylene) via radical mechanisms. Moreover, the experimental setup was modeled using COMSOL to understand the temperature profile. Outcomes reported herein address multiple Sustainable Development Goals (SDGs), specifically related to affordable and clean energy and sustainable cities (7, 11, and 13). • Co-pyrolysis of waste tires with PE, PP, and PET was studied using TGA-FTIR-GCMS. • Plastics cut residual by 40 % and shifted product yields toward lighter hydrocarbons. • Benzene yield reached the maximum using the WT + PET blend at 470 °C–35 %. • D-limonene yield dropped from ∼67 % to <5 % with increasing temperature and plastic content. • COMSOL modeling confirmed uniform temperature profiles and product flow consistency.