The Use of Microwave Pyrolysis for Biomass Processing

The method of processing biomass of various kinds by microwave-assisted pyrolysis has been presented. The fast pyrolysis process, characterized by rapid heating of the feedstock in the absence of oxygen and rapid cooling of the volatile intermediate reaction products, is one of attractive liquid biofuel production methods. However, the pyrolysis still requires improvements as regards the process yield, quality of liquid biofuel products, and energy efficiency of the process as a whole. The microwave pyrolysis is a promising attempt to solve these problems thanks to the fast and efficient feedstock heating through the effect of “microwave dielectric heating”. Before proceeding to the main topic of this paper, the conventional pyrolysis has been characterized. At such a technology, the thermal energy necessary to heat the feedstock is transmitted from the surface into the depth, which is rather a slow process. This has been followed by a presentation of the microwave pyrolysis, where the microwave radiation causes fast and productive bulk heating of the material having been finely ground (the material should be susceptible to the action of microwaves). Moreover, a review of materials used as microwave radiation absorbers, biomass types, and methods of biomass preparation for the process, as well as qualitative and quantitative characteristics of the pyrolysis products obtained, i.e. raw bio-oil, which should be subjected to further processing, and synthesis gas (“syngas”) have been provided.