Page 228 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Assessment of crude glycerol utilization for sustainable development of biorefineries 199

process of crude glycerol and purity level of glycerol reaches 95.5% with low
chemical cost and process adaptability (Stojkovic et al., 2014; Gerpen, 2005).
The change in concentration or electrical potential and hydrostatic pressure are
the driving force for the purification of crude glycerol through the membrane
separation process and attain the decent purification performance up to 99%. A
diverse group of membranes are employed for the purification process and the
main drawback with the process is fouling and durability of a membrane
(Hasheminejad et al., 2011).

9.3.3 Comparison of properties of crude and partially refined
and refined glycerol
Crude glycerol produced from different feedstocks has a different composition and
hence purification process is mandatory. Depending upon the usage and effects of
impurity, the purification process is carried out in profit measured by controlling
the purification cost. In most cases the presence of some contaminants is bearable
for the technical utilization of glycerol in the fermentation process. whereas high
purity of glycerol is required in the food and pharmaceutical sectors (Tan et al.,
2013). Hence physicochemical properties of crude, partially refined, and pure com-
mercial glycerol were compared and discussed in Table 9.1.

9.4 Applications

The excess amount of glycerol generated from the biodiesel industries has created a
glut in the market of glycerol. Glycerol is highly functionalized molecule when
compared with other hydrocarbons produced through the petrochemical process.
Thus glycerol can be considered as renewable building block for the biorefinery by

Table 9.1 Comparison of crude glycerol, partially refined and pure commercial glycerol
(Chozhavendhan et al., 2017).

Properties Crude Partially refined Commercial pure
glycerol glycerol glycerol
Color Dark brown Straw yellow Colorless
pH 9.6 5 6.7
3
Density (kg/m ) 1.29 1.23 6 0.2 1.25
Flash point ( C) 180 185 177

Fire point ( C) 211 214 204
Carbon residue (%) 18 12 11.25
Ash content (%) 11.26 0.14 Not applicable
Concentration (%) 10.43 42 44 95 99
Solubility with Miscible Miscible Miscible
water