Microwave Torrefaction of leucaena to Produce Biochar with High Fuel Ratio and Energy Return on Investment

Abstract

Abstract In this study, microwave torrefaction of leucaena was studied to find out the potential applications and energy usage benefit of this technique. Both maximum temperature and heating rate increased with increasing microwave power level. Processing time was also an important operational parameter, but its effect was weaker than that of microwave power level. The heating value of torrefied product was higher at higher power level and longer processing time, but the mass and energy yields were lower due to higher energy input and thus more severe reaction. Heating value was approximately 30 MJ/kg at a microwave power level of 250 W for 30 min processing time. The fuel ratio of torrefied leucaena was up to 3.7, which is much higher than that of bituminous coal and thus can be regarded as an alternative fuel to replace or co-fire with coal. The energy return on investment of microwave torrefaction of leucaena can be 1.4, 17, and 34 when handling capacities are 8, 100, and 200 g, respectively. Therefore, microwave torrefaction of leucaena is a promising technique, and it can be more competitive when it is scaled up.