Thermochemical conversion of microplastics: Kinetics refining via whale optimization algorithm for energy applications

Microplastics, while persistent environmental pollutants, also constitute an energy-rich feedstock suitable for thermochemical conversion. This study introduces the first application of the whale optimization algorithm (WOA) to model isothermal thermodegradation kinetics of polyethylene (PE), polypropylene (PP), and polystyrene (PS) using thermogravimetric analysis. A two-step reaction model optimized by WOA achieved high fit qualities of 99.75 %, 98.93 %, and 99.97 % for PE, PP, and PS, respectively, with activation energy ranges of 14.97–85.24, 68.49–95.92, and 47.99–103.58 kJ mol⁻¹. The integration of an inert dispersant such as SiO₂ improved heat transfer uniformity, enhancing the accuracy of kinetic parameter estimation. These parameters enable the design of energy-optimized torrefaction and pyrolysis systems capable of achieving over 70 % weight loss at 400 °C, maximizing volatile yields for fuel production. Compared with particle swarm optimization, WOA demonstrated superior accuracy and convergence stability, highlighting its potential for modeling complex degradation processes. The results provide a robust computational framework for scaling waste-to-energy applications, supporting both energy recovery and circular economy objectives in plastic waste management.