The present study systematically investigated the combustion characteristics of spent mushroom substrate (SMS) using TG-MS (thermogravimetric/mass spectrometry) and TG-FTIR (thermogravimetric/Fourier transform infrared spectrometry) under five heating rates. The physicochemical characteristics and combustion index pointed to SMS as a promising biofuel for power generation. The high correlation coefficient of the fitting plots and similar activation energy calculated by various methods indicated that four suitable iso-conversional methods were used. The activation energy varied from 130.06 to 192.95 kJ/mol with a mean value of 171.49 kJ/ mol using Flynn-Wall-Ozawa and decreased with the increased conversion degree. The most common emissions peaked at the range of 200-400 degrees C corresponding to volatile combustion stage, except for CO2, NO2 and NO. The peak CO2 emission occurred at 439.11 degrees C mainly due to the combustion of fixed carbon.