Process intensification of the ultra-rapid pyrolysis of bamboo by spatially separated microwave electric and magnetic fields

• Tuned microwave electric field achieved rapid biomass pyrolysis. • Scaling-up was achieved using a 915 MHz microwave cavity resonator. • Magnetic field heating was effective for semi-carbonized biochar. • Flow magnetic field microwave system enables continuous carbonization. This study demonstrates the efficient microwave “ultra-rapid” pyrolysis of bamboo using a spatially separated electric- (E-) and magnetic (H-) field and microwave reactor equipped with a semiconductor generator. The microwave E-field promoted the gasification and carbonization of the bamboo within 30 s. Extensive formation of gases (mainly H 2 and CO) and tar (fragments of guaiacyl and syringyl lignin) was achieved by E-field heating. However, microwave reflection became prominent after extensive carbonization of the bamboo under a microwave E-field. The carbonized bamboo was more effectively heated in the H-field, which was effective in preventing microwave reflection and yielding biochar with more defects and an amorphous structure than the electric furnace. We also achieved process intensification by employing a higher quality--factor (Q-factor) cavity resonator (915 MHz). The continuous-flow H-field microwave heating reactor effectively improved the carbon content of the pyrolyzed biomass. A synergistic use of microwave E- and H- fields enables the intensification of microwave “ultra-rapid” pyrolysis of lignocellulosic biomass.