As a non-traditional heating way, microwave irradiation (MWI) has long been used for lignocellulose
pretreatment with the advent of commercial microwave oven since the 1970s. MWI pretreatment using
MWI as heating source is similar to other pretreatment methods. Although MWI pretreatment solves
some problems caused by other pretreatment methods, such as low heating rate and thermal efficiency,
uneven heating, it brings some new challenges such as reaction vessel selection and pretreatment process
design. Over 30 years of development, researchers have achieved good pretreatment performance with
MWI which has been applied gradually from laboratory scale to pilot-scale. It should be noted that
MWI pretreatment is facing some problems: high cost of pretreatment, short of large-scale equipment,
the non-thermal effects in pretreatment is still controversial. If MWI pretreatment reaction mechanism
could be further clarified and large-scale industrialized reactor be designed, MWI pretreatment might
be widely used in biorefinery.