Hydrochar derived from green waste by microwave hydrothermal carbonization

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 (similar to 23.01 MJ kg(-1)) could be observed at a holding temperature of 190 degrees 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. (C) 2018 Elsevier Ltd. All rights reserved.