Hydrochar derived from green waste by microwave hydrothermal carbonization.

Abstract Green waste (GW), rich in cellulose and hemicellulose, is a valuable resource. Developing alternative sustainable technologies to utilize GW is attracting increasing attention. In this study, microwave hydrothermal carbonization (MHTC) process parameters including holding temperature, holding time, and liquid-to-solid ratio were optimized by a response surface design to tailor the properties of hydrochar. The hydrochar characteristic was mainly evaluated by the calorific value. The results showed that the highest hydrochar calorific value (∼23.01 MJ kg−1) could be observed at a holding temperature of 190 °C, a holding time of 1 h and liquid-to-solid ratio of 8:1. Correspondingly, the hydrochar yield ranged from 50.40% to 76.80%. The economic evaluation of hydrochar was also done in this work. These results show that the GW-derived hydrochar warrants further investigations as a fuel source and as an adsorbent material. Graphical abstract Image 1 Highlights • Green waste was mainly transformed to hydrochar by microwave hydrothermal technology. • Hydrochar is a good fuel with high calorific value and considerable yield. • Microwave hydrothermal carbonization conditions were optimized. [ABSTRACT FROM AUTHOR]