Microwave torrefaction technology in biochar production: A review.

Torrefaction is a thermochemical process in an inert or limited oxygen environment where biomass is slowly heated to a specified temperature range. The art of torrefaction has caught the attention of power industries to produce biochar and coal substitute from biomass. In recent years, there has been an increasing interest in torrefaction technology. The main difference between technologies is the reactor design and the heating mode. These parameters influence the product quality of torrefied biomass. Microwave torrefaction is one of the available technologies that recently received considerable attention due to some advantages. Along with this growth, there is increasing concern over comparing microwave torrefaction with conventional ones. So far, there has been little discussion about the technical comparison of reactor design of microwave torrefaction itself. This paper will review the research conducted on the microwave design of biomass torrefaction. The use of microwave as an apparatus for torrefaction process reported is mainly dominated by domestic microwave oven followed by the single-mode microwave oven, non-modified microwave oven and only a few studies of large-scale microwave reactor. Each type of microwave reactor design determines mass yield, energy density, and energy yield as quality parameters of torrefied biomass. The findings should contribute to the field of a microwave as an apparatus for torrefaction technology. [ABSTRACT FROM AUTHOR]