Page 22 - Lignocellulosic Biomass to Liquid Biofuels

Fundamentals of lignocellulosic biomass 3

Nevertheless, LCB is considered as the most promising raw material
for the renewable biofuel production as it is readily available, low cost,
and environment friendly.
Before in-depth discussion of processes for the production of biofuels,
this chapter is intended to give some fundamentals of LCB. It also incor-
porates the concept of LCB biorefinery to produce fuels and chemicals.

1.2 Components of lignocellulosic biomass
The main components of LCB are cellulose, hemicellulose, and lignin
(Table 1.1). Other minor parts are ash and extractive components.
Cellulose molecules are arranged in regular bundles, forming crystal-
line regions, or in random geometry forming amorphous regions.
Microfibrils of cellulose polymers are linked by hydrogen and van der
Waals bonds and are protected by hemicellulose and lignin.
Carbohydrates, which are the main component of cellulose and
hemicellulose, make up for about 70% of the dry weight of lignocellulose
biomass and represent the feedstock for nearly all of the most promising
bio-based building blocks and chemical intermediates, whatever the con-
version technology (biological or thermochemical) adopted. Lignin is
another important constituent of lignocellulose biomass making up for
about 25% of its weight and is by far the most important natural resource
of aromatics, beside a good solid biofuel.
Lignocellulose can play a vital role in the energy sector as different
forms of energy products can be obtained from LCB, such as solid (bri-
quettes), liquid (bioethanol and biodiesel), and gas (biogas and bio-H 2 ).

1.2.1 Cellulose

Cellulose is an organic compound composed of polysaccharides,
which consists of a straight chain of D-glucose molecules linked
through β-(1-4) glycosidic bonds with the formula (C 6 H 10 O 5 ) n .Itis

Table 1.1 Major components of various lignocellulosic materials [3,6,7].
Raw material Cellulose (%) Hemicellulose (%) Lignin (%)
Energy crops 21 54 5 30 5 10
Grasses 25 40 25 50 10 30
Softwoods 45 50 25 35 25 35
Hardwoods 45 55 24 40 18 25