Thermal conversion behaviors and products of spent mushroom substrate in CO2 and N2 atmospheres: Kinetic, thermodynamic, TG and Py-GC/MS analyses

Abstract This study aims at characterizing pyrolysis/gasification behaviors and products of spent mushroom substrate (SMS) in the CO 2 and N 2 atmospheres. The major decomposition stages occurred between 200 and 600 °C with the mass losses of 60.4 and 61.5% at 20 °C/min in the CO 2 and N 2 atmospheres, respectively. The maximum mass loss rate grew with the increased heating rate, while DTG curves shifted toward a higher temperature. Volatiles were released easier in the N 2 than CO 2 atmosphere with a higher comprehensive devolatilization index and decomposition rate. At above 750 °C, the char gasification in the CO 2 atmosphere resulted in a significant mass loss as well as a less char yield. Average activation energies by the Flynn-Wall-Ozawa method were estimated at 212 and 214 kJ/mol in the CO 2 and N 2 atmospheres, respectively. The higher thermodynamic parameters in the N 2 than CO 2 atmosphere indicated the higher reactivity of the pyrolysis in the N 2 atmosphere. The reaction mechanisms of the volatiles decomposition were best described by g ( α ) = (1- α ) −1 -1 (R2 model) in the range of 200–370 °C in both atmospheres. The major pyrolysis products at 800 °C were identified using Py-GC/MS and composed mostly of aromatic compounds such as toluene and x-methyl-naphthalenes.