Parametric study of hydrothermal carbonization of waste biomass

Abstract

Bangladesh generates enormous amount of Municipal Solid Waste (MSW) daily, with Dhaka generating at least 5340 metric tons daily. At present, for the majority, Bangladesh practices open dumping of MSW. For a relatively small country like Bangladesh and with increasing amount of MSW, there is a scarcity of land for open dumping or landfilling. Among the valorization pathways, hydrothermal carbonization (HTC) may be considered to be relatively a more promising path for MSW processing due to its flexibility of han-dling high moisture containing feedstock. To carry out a parametric study on HTC of MSW, sampling was carried out at Dhaka North City Corporation’s Amin Bazar landfill which revealed that food waste constitutes 74.2% of MSW. For optimizing the HTC process, a parametric study at different reaction conditions was carried out on Municipal Solid Organic Waste (MSOW). The altered reac-tion parameters were temperature, residence time, and solid loading (water percentage). The optimum reaction condition for HTC was found to be at 275◦C, with a residence time of 20 minutes and a water loading of 90% (solid loading of 10%). At these condi¬tions, biocoal retained 82.7% of energy from parent MSOW with maximum solid yield of 78.2%. The higher heating value (HHV) of MSOW was found to be 10.9 MJ/Kg; the HHV of the obtained biocoal products ranged from 9.6 -14.9 MJ/Kg. Further charac¬terization of the biocoal was performed using Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDS). SEM images revealed the lack of pores on the biocoal surface. This might facilitate the surface reaction mechanism in any post-conversion scenario (i.e. combustion or gasification) of biocoal.