Microwave heating of biomass waste residues for sustainable bioenergy and biomass materials preparation: A parametric simulation study

Sustainable bioenergy and biomass materials preparation from biomass waste residues using microwave heating has attracted widespread attention. However, the microwave heating process still has limitations of uneven temperature distribution and low energy conversion efficiency. This study constructed a coupled electromagnetic and heat transfer model for the microwave heating of waste tobacco stem (TS) biomass using COMSOL Multiphysics® software. The microwave heating behavior of TS biomass was predicted using the finite element method for different parameters, and this model has been experimentally verified to be dependable with a maximum relative error of less than 10%. Simulation results show that hot spots caused by interface polarization and standing waves generate inhomogeneous temperature distributions. The microwave cavity design with two waveguides and controlled frequency changes can improve microwave energy absorption and heating uniformity. A suitable microwave power can improve efficiency and reduce energy consumption during heating. Meanwhile, the TS biomass with 30% moisture content and in the cavity's low region (0–10 cm) can make maximum use of microwave energy, and the average and maximum energy efficiency achieve 59.15% and 87.79%, respectively. The results provide technical support and new perspectives for preparing sustainable bioenergy and biomass materials from waste TS biomass via microwave irradiation.