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 10 g 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 7.96 g (79.6 wt.%), which is indicative of complete pyrolysis.

► Biomass samples were pyrolysed using microwave-induced plasma for 30 min.
► 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 1.3 g.
► Liquid, solid, gas mass ratio was found to be 66:20:13.