Efficient release of fermentable sugars from the complex biomass structure such as second-generation or third-generation feedstocks by an appropriate enzymatic hydrolysis needs a prior biomass fractionation. This process facilitates the exposure of more cellulose and hemicelluloses for enzymatic hydrolysis. This review focused on ‘green fractionation’ of biomass by applying the principles of green chemistry for bioethanol production. Besides, the recent technological achievements in applying these principles for the fractionation have been discussed. For green fractionation, energy delivery systems are referred to as microwave and ultrasound. Besides, green cellulose solvents, biomass-derived solvents, and supercritical carbon dioxide play an important role in green biomass fractionations. Furthermore, ball milling and biological treatment are significantly considered in this regard. These novel technologies are superior processes than conventional fractionation techniques in terms of energy and mostly environmental point of view
