Biofuels and Co-Products Out of Hemicelluloses

Abstract

Second generation biofuels are based on the utilisation of non-edible feedstock for the production either of ethanol to be inserted in the gasoline pool or of biodiesel to be insert‐ ed in the diesel pool. Ethanol is usually produced out of fermentation of C6 sugars (al‐ though other approaches does exist, see [1]) and the latter came, in first generation ethanol, from starch. In second-generation ethanol, the source of carbohydrate considered is usually cellulose, which, in turns, is obtained from lignocellulosic biomass. Recent work by Lavoieet al. [2] have depicted an overview of many types of lignocellulosic biomass and in most cases, cellulose, although a major component, is not the only one and is ac‐ companied by lignin, hemicelluloses, extractives and, in case of agricultural biomass, pro‐ teins. High grade biomass (as wood chips, sugar cane or even corn) are usually very expensive (more than 100 USD/tonne) because, in most part, of the important demand re‐ lated to those feedstock in industries and this is why cellulosic ethanol is more than often related to residual biomass. The latter includes but is not limited to residual forest and ag‐ ricultural biomass as well as energy crops. In all cases, although the feedstock is rather in‐ expensive (60-80 USD/tonne), it is composed of many different tissues (leaves, bark, wood, stems, etc.) making its transformation rather complex [3]. Industrialisation of second-gen‐ eration biofuel requires specific pre-treatment that should be as versatile as efficient in or‐ der to cope with the economy of scale that has to be implemented in order to make such conversion economical.