(580d) Biochar from Agricultural Waste Via Microwave-Driven Pyrolysis

In view of obtaining biochar for agriculture usage via pyrolysis, two different heat treatments – microwaves (MWP) and conventional electrical (CEP) heating were investigated and compared. The chosen biomass waste was poplar (Populus alba). MWP pyrolysis was carried out using 2.45 GHz microwaves generated by a semiconductor generator (0-200 W) in a TE01 monomode cavity, while CEP was carried out in a custom-made lab-scale tubular batch reactor electrically heated placed in a commercial NABERTHERM oven. Although the temperature evolution vs. time was not possible in MWP above 240ºC (max. temperature of the fibre optic built-in the experimental set-up), the influence of the microwave power & residence time and the energy/gram of treated biomass were recorded and used for the evaluation. In CEP the influence of pyrolysis temperature (300-800ºC) vs. the characteristics of biochar was evaluated. To determine how heating method affects the properties of biochars and consequently their possible utilization, physical, chemical, thermal, porosity and EDX analysis were carried out for all biochars and for the corresponding feedstock. The experimental study was focused on the comparison of heating method vs. biochar yield distribution, elemental composition, pH, high heating value (HHV), surface area, porosity and morphology. In relation to the microwave heating, the evaluation of the process economics vs. application of the obtained biochar is attempted.