because milling can be performed before or after chemical pretreatment, recent studies
shows that milling after chemical pretreatment will significantly reduce: i) milling energy consumption, ii) reduce cost of solid liquid separation because the pretreated chips can be easily separated, iii) eliminate energy intensive mixing of pretreatment slurries, iv) liquid to solid ratio and v) did not result in the production of fermentation inhibitors (Zhu et al. 2010; Zhua et al. 2009).