An overview on pretreatment processes for an effective conversion of lignocellulosic biomass into bioethanol

Abstract Nowadays, the dependence on fossil fuels is creating a particular instability in the global market. Moreover, waste management in urban areas is becoming a real problem. Different research groups all over the world are dealing with the resolution of both problems, using agricultural and urban wastes as an initial feedstock for the production of various fuels. In particular, using bioethanol turns out to be one of the most promising for two reasons: firstly, it is characterized by chemical–physical properties similar to gasoline (i.e., octane number, evaporation enthalpy, etc.); and secondly, it is easy to obtain fermentation processes from simple sugars. The problem of waste disposal strongly depends on lignocellulosic substrates, being lignin not easily fermentable like cellulose. Therefore, it became necessary to eliminate/separate it from the starting organic matrix. Pretreatments are used to separate the lignin and part of the hemicellulose from the starting matrix. This crucial point, for the transformation of lignocellulosic biomass into ethanol, is the most expensive process. For this reason, different types of pretreatments have been developed to find the most promising one, to be used in the industrial field, in terms of the total amount converted from an economic point of view. This chapter is an overview of the most widespread pretreatment types, highlighting advantages/disadvantages for each methodology.