Physicochemical properties and combustion kinetics of food waste derived hydrochars

Abstract

In this work, simulated food waste (15% white bread, 15% palm dates (without seeds), 5% boiled egg (without shells), 20% spent tea leaves, 20% spent coffee ground, and 25% banana peel in parts weight) was subjected to hydrothermal carbonization (HTC) at 180, 200 and 220 °C for 120 min. The mass yield and energy yield of the resultant hydrochars viz. HTC180, HTC200, and HTC220 were 69.46, 68.50, 65.35% and 88.91, 87.68, 84.30%, respectively. Among the hydrochars produced, HTC220 had the highest heating value (HHV: 23.61 MJ/kg), while the food waste had a HHV of 18.17 MJ/kg. Activation energy for the combustion of food waste and HTC220 was determined by modelling the thermogravimetric data using the Arrhenius equation and was found to be in the range of 29.98 to 33.51 kJ/mol and 16.52 to 25.47 kJ/mol, respectively. The densification ratio for the three hydrochar samples varied slightly (1.28–1.29). The results indicate that the hydrochar produced from food waste could be a potential to substitute coal combustion.