Page 225 - Refining Biomass Residues for Sustainable Energy and Bioproducts

196 Refining Biomass Residues for Sustainable Energy and Bioproducts

In general, 10% of the crude glycerol is produced as a major byproduct during
the production of biodiesel (Chozhavendhan et al., 2016a; Pfromm et al., 2010).
The rise of biodiesel production leading to increased production of crude glycerol
with copious impurities has resulted in fallen prices for refined and crude glycerol
(Quispe et al., 2013). A fundamental question soon arises: what can be done with
the crude glycerol? or how could exploit the crude glycerol or convert the low-
value crude glycerol into value-added chemicals (Ardi et al., 2015)?
A biorefinery is a network of facilities, which integrates biomass conversion pro-
cesses and equipment to produce biofuels, energy, and chemicals from biomass or
from waste to wealth. The concept of biorefineries is applied to biofuel industries in
order to convert or utilize the crude glycerol for the production of 12 major platform
chemicals and that could be the major output of integrated biorefinery concept. This,
in turn, helps to improve economic feasibility and sustainable development of bio-
based industries (Chen et al., 2013; Cherubini, 2010; Cherubini and Ulgiati 2010).

9.1.1 Characteristics of crude glycerol

Biodiesel is generally produced by the transesterification reaction of triglycerides
(oils/fats) with alcohols in the presence of a catalyst. During this production process,
biodiesel is settled in the upper phase and the rest glycerol settles in the lower phase
due to the difference in densities and polarities (Tan et al., 2013). Glycerol obtained
from the biodiesel production process is known as crude glycerol and usually presents as
highly viscous, alkaline pH, anddarkbrown in color(Chozhavendhan et al., 2016b).
Crude glycerol comprises a mixture of compound usually consist of water, ash, soap,
methanol, etc. (Chozhavendhan et al., 2018b). The purity of glycerol may vary from
20% to 80% depending upon the raw material, catalytic process, and purification process.
Glycerol is available commercially in three different forms, namely, (1) crude
glycerol, (2) purified or refined glycerol, and (3) commercially synthesized glycerol
(Vivek et al., 2017). Glycerol is a versatile compound because of its unique physi-
cal and chemical properties. It is highly viscous, hygroscopic liquid with high boil-
ing point and more compatible with many compounds (Zhou et al., 2008). In
general, glycerol is capable of reacting with alcohol since chemically it is known as
trihydric alcohol. The three hydrophilic hydroxyl groups in glycerol are responsible
for its solubility in water and its hygroscopic nature. Therefore crude glycerol can
be directly fed as a substrate or feedstock for the production of high-value chemi-
cals, which increases the market value of glycerol and also helps the establishment
new employment offers for the new production plants for the conversion of glycerol
(Hu et al., 2012). It also finds its application in green refinery process as it is used
as a renewable source for biodegradable products (Ayoub and Abdullah, 2012).

9.2 The market scenario of glycerol

Glycerol is produced in two ways: natural glycerin (as a byproduct of soap
production or fatty acid methyl esters, such as biodiesel) and synthetic glycerol