Utilization of microwave steam pyrolysis to produce biochar for thermal energy storage

Microwave steam pyrolysis (MSP) is an innovative thermochemical approach to converting biomass into high-quality biochar using steam to improve the dielectric heating of microwave radiation. Biochar shows high fixed carbon and carbon contents at a maximum temperature of 550 °C in 10 min. The MSP achieved a heating rate of 112 °C/min from 200 °C to 400 °C to produce biochar effectively. Furthermore, the thermal properties of biochar in microwave heating were investigated in this study to explore its potential as a microwave heat-absorbent material. Microwave is able to perform volumetric and controllable heating to the biochar. Moreover, biochar shows good microwave heat absorbency, storing and transferring heat effectively. The temperature profile of three different sizes of biochar was investigated to examine the efficiency of biochar in heat absorption from microwave radiation. It was found that the powder form of biochar showed a higher heat transfer rate of 40 °C/min and a low cooling rate of 7.5 °C/min. The presented results are useful for evaluating the application of biochar as a promising medium for heat storage systems.