Experimental analysis of biomass pyrolysis using microwave-induced plasma

Energy-from-waste, a process that converts high calorific wastes to energy, has posed a possible renewable energy route, in addition to reducing waste volumes being sent to landfill. One technology that is effective at near complete organic–inorganic dissociation is plasma gasification. However, a precursor to generating this plasma is to create an electrical arc by a large DC current, which is highly energy intensive. This study, however, examines a novel method of producing plasma by microwaves, which is much more energy efficient. To test its suitability in waste and biomass treatment, three 10g triplicate waste wood (biomass) samples was pyrolysed using microwave-induced plasma in a lab-based reactor. The resultant gas was siphoned from the reactor exhaust pipe and characterised using a Gasmet DX400 FTIR analyser. To determine the proportion of gas flow between the siphon tube and exhaust, a mass balance model of the system was constructed. After applying the appropriate correction factor, the mean mass ratio of liquid, solid, and gas was found to be 66:20:13. The start and final masses were recorded and compared with literature values. Mean mass loss was determined to be 7.96g (79.6 wt.%), which is indicative of complete pyrolysis. ► Biomass samples were pyrolysed using microwave-induced plasma for 30min. ► Mean mass reduction post-treatment was found to be 79.6%. ► A gas flow model was constructed to validate flow rates and process dynamics. ► Resultant gas of samples was analysed and the mean mass detected was 1.3g. ► Liquid, solid, gas mass ratio was found to be 66:20:13.