Another way to produce bioethanol is using cellulosic materials. Examples of cellulosic materials are bagasse, straw, paper, cardboard, wood and materials of plant cellulosic fibers such hemp, giant reed, eucalyptus tree and Miscanthus. Cellulosic resources are immensely widespread and found abundantly everywhere. These cellulosic materials have the potential to be used for the production of bioethanol since they are not commonly used in the human food chain and exist in large amounts. Moreover, these materials are inexpensive as compared to the sugar and starchy feedstocks and preferably used for bioethanol production. Cellulosic materials are called lignocelluloses because they are composed of lignin, cellulose and hemicelluloses (Kahn et al., 2011).

The cellulosic residue more reported in Table 3.3 for ethanol production is sugarcane bagasse (Dawson and Boopathy, 2007; Santos et al., 2012; Wu et al., 2011; Buaban et al., 2010). This can be explained because of the great use of its juice for sugar ethylic fermentation
and the residue is generated just in the alcohol manufac­ture (Santos et al., 2012). Furthermore, the quantity of this waste available is very great and its direct combus­tion is not the best economical way to use this resource (Wu et al., 2011). The hydrolysis process more employed for saccharification of the bagasse is enzymatic. This is because of the inefficiency of acid hydrolysis in a very complex matrix. Moreover many studies are trying SSF, which can reduce one step of the process.

The agricultural wastes (apart from sugarcane) are studied much for the ethanol production. This is because they are present around the world (comes from diverse agricultural crops). Thus these residues can mean the energetic independence of many countries. Rice plant (Kitamoto et al., 2011) and Lycoris radiata Herbert (Liu et al., 2012) are examples of how much singular are the wastes that the researches are using to produce biofuels. Similarly to sugarcane, Talebnia et al. (2010) have tested SSF and SHF of wheat straw, and obtained good results in the two cases. In Table 3.3 it is possible to see that pretreatment (physical or chemical) is usually necessary, and this is a difficulty in this production.