Thermogravimetric investigation of spent shiitake substrate to solid biofuel

Abstract

The thermal behavior of the spent shiitake substrate (SSS) and its resulting biochar were evaluated as a means to minimize environmental problems related to the generation and disposal of spent mushroom substrate from mushroom cultivation activities. Analyzing biochars produced at 350°C (BC350) showed the highest energy potential due to a reduced amount of resulting ash and nitrogen, and larger amounts of carbon, hydrogen, fixed carbon, as well as a higher calorific value, gravimetric yield, and gravimetric yield factor. SSS and BC350 were used in thermogravimetric and kinetic analyses. Thermogravimetric analyses were performed at 10°C/min, 15°C/min, and 20°C/min heating rates in an oxidizing atmosphere. Conversion steps relating to water loss and degradation of hemicellulose, cellulose, and lignin were identified. The obtained activation energies were 110 and 136 kJ/ mol for the SSS and BC350, respectively, and were well within the range observed for other lignocellulosic materials. The pre-exponential factor, in the order of 108, indicated the presence of complex elements.