Page 209 - Lignocellulosic Biomass to Liquid Biofuels

172 Lignocellulosic Biomass to Liquid Biofuels

Figure 5.1 Schematic illustration of lignocellulosic biomass materials’ biorefinery
pathway.

extractives, and ash. Table 5.1 summarizes the percentage of cellulose,
hemicellulose, and lignin content present in the various lignocellulosic
biomass materials or feedstocks.

5.3 Pretreatment of lignocellulosic biomass feedstocks
The low-cost, highly abundant, renewable, eco-friendly, and carbon-rich
lignocellulosic biomass sources are the most promising feedstocks for the
production of biobutanol and other compounds. The conversion of bio-
mass materials or feedstocks into fermentable energy-rich sugar moieties is
carried out through pretreatment processes, that is, by opening of the bio-
mass structure and releasing the sugar moieties from cellulose and hemi-
celluloses [75,76]. There are four types of pretreatment processes, which
are well studied; (1) physical, (2) chemical, (3) physicochemical, and (4)
biological or enzymatic pretreatment technologies (Fig. 5.2). The main
aim of the preceding pretreatment technologies is to improve the
fermentable sugar moieties and degrade other inhibitory compounds. The
main advantages and disadvantages of various pretreatment processes are
summarized in Table 5.2.
The physical pretreatment method is the key stage for lignocellulosic
biomass processing; in this stage, the lignocellulosic biomass is reduced
into a suitable powder form for better approachability of enzymes/
microbes during hydrolysis process. Also, the size-reduced biomass materi-
als help decrease the crystalline nature of celluloses, that is, to increase the
biomass product yields. This pretreatment method includes milling or
grinding, extrusion, microwave and ultrasonication processes; such meth-
ods are widely utilized for opening the structure of lignocellulosic