Biomass pretreatment: Separation of cellulose, hemicellulose and lignin. Existing technologies and perspectives

Biomass pretreatment represents a fundamental step which reduces the recalcitrance of the lignocellulosic material adopting many different approaches (physical, physico-chemical and chemical, biochemical) which have been summarized and discussed in this chapter. Many examples provide evidence that the choice of the proper pretreatment is strictly related to the characteristics of the starting material and to the downstream use of the pretreated material itself. Moreover, in recent years, the evaluation of environmental, economic and energetic aspects plays a fundamental role for the choice of the pretreatment or of combined pretreatments. The development of more and more green pretreatment processes, in terms of adoption of cheap, easy recyclable, renewable solvents (as the emerging deep eutectic solvents which potentially represent a valuable improvement compared to ionic liquids), reduction of energy consumption (as observed for the adoption of instant controlled pressure-drop pretreatment as an alternative to steam explosion) and the proper integration of tailored process options are discussed.