Wet oxidation is a pretreatment technology using water and air or oxygen to fractionate biomass at temper­atures above 120 °C. A clear advantage of wet oxidation, in particular in combination with alkali, is the relatively mild temperature and the limited formation of fermenta­tion inhibitors (e. g. furan aldehydes and phenolalde — hydes) (Klinke et al., 2002). Wet oxidation facilitates the separation of cellulose after the majority of hemicellu — loses and lignin has been solubilized. The amount of lignin removed after pretreatment ranges from 50% to 70% depending on the type of biomass pretreated and the conditions used. The solid material after wet oxida­tion displayed a higher enzymatic convertability than the remaining solid material after steam explosion (Mar­tin et al., 2008). Wet oxidation is effective in pretreating a variety of biomass such as wheat straw, corn stover, sug­arcane bagasse, cassava, peanuts, rye, canola, faba beans, and reed (Brodeur et al., 2011; Martin et al., 2008). Wet oxidation can be combined with other pretreatment methods to further increase the yield of sugars after enzymatic hydrolysis. Combining wet oxidation with alkaline pretreatment has been shown to reduce the for­mation of by-products, thereby decreasing inhibition. In combination with steam explosion, in a process called wet explosion, the biomass undergoes not only the chem­ical reaction described above but also physical rupture. The advantages to combining wet oxidation with steam explosion includes the ability to process larger particle sizes and to operate at higher substrate loadings, up to 50% substrate (Brodeur et al., 2011).