Characterization and pyrolysis kinetics study of hydrochar derived from turfgrass (Zoysia matrella) using hydrothermal carbonization

The use of grass for bioenergy is being promoted to provide energy security. This study investigated turfgrass (Zoysia matrella) treatment using the hydrothermal carbonization (HTC) process prior to pyrolysis. The treatment conditions consisted of temperatures of 180, 200, or 220 ^∘C for 30 min. The pyrolysis of turfgrass and its hydrochar was investigated at heating rates of 5, 10, 20, or 40 ^∘C min^− 1 using thermogravimetric analysis. The experimental data were used to calculate kinetic parameters using the isoconversional models of Kissenger-Akahira-Sunose (KAS) and FlynnWall-Ozawa (FWO). The HTC process improved the H/C and O/C atomic ratios and the heating value of hydrochar derived from raw turfgrass. The average activation energies calculated for turfgrass using the KAS and FWO models for raw turfgrass were 168 and 178 kJ mol^− 1, respectively, whereas the average activation energies for the turfgrass hydrochars were lower for both models. The differences in behavior between turfgrass and its hydrochar pyrolysis could have been due to the higher degree of carbonization obtained using HTC.