A review of biochar prepared by microwave-assisted pyrolysis of organic wastes

Biochar is widely used in various fields due to its good physical and chemical properties. The biochar prepared by microwave-assisted pyrolysis is affected by reaction parameters. This study reviews biochar preparation by microwave-assisted pyrolysis of organic wastes. The effects of reaction temperature, microwave power, microwave absorbent and the other parameters on the properties and yields of biochar produced from microwave-assisted pyrolysis of organic wastes were covered. And the application of biochar in different fields was also detailed. The results show that higher reaction temperature and microwave power mainly reduce the biochar yield produced from microwave-assisted pyrolysis, but promote the formation of its porous structure. Higher microwave absorbent load reduces the biochar yield, but increases the high heating value. The best reaction parameters corresponding to the maximum biochar yield were 300 °C (90 wt% for biosolid biochar), 600 W (94 wt% for palm oil empty fruit bunch biochar), and 50% load of coconut shell-based activated carbon (microwave absorbent) (78.98 wt% for horse manure biochar), respectively. The reaction parameters should be selected reasonably according to the specific objectives during the preparation of biochar by microwave-assisted pyrolysis.