• Open Access

Torrefaction/biochar production by microwave and conventional slow pyrolysis – comparison of energy properties


Correspondence: Mark Gronnow, tel. + 441 904 567 821, fax + 441 904 322 705, e-mail: mark.gronnow@york.ac.uk


The energy efficiency of torrefaction/pyrolysis of biomass to fuel/biochar was studied using conventional (slow) and microwave (low temperature) pyrolysis. Conventional pyrolysis is approximately three times as energy efficient as microwave pyrolysis, in terms of the energy required to process a unit of feedstock. However, this is more than compensated for by the higher energy content of the condensable and gaseous coproducts from microwave pyrolysis, as these can be utilized to generate the electricity required to drive the process. It is proposed that the most efficient method of torrefaction/biochar production is a combination of conventional heating with ‘catalytic’ amount of microwave irradiation.