Page 136 - Advances in Eco-Fuels for a Sustainable Environment

Prospective ecofuel feedstocks for sustainable production 107

of around 90% of waste fryer grease to its corresponding methyl esters has been
obtained via the two-stage method for a methanol to oil molar ratio of 6:1 at a reaction
temperature of 25°C in a reaction time of 30min using 1% (wt of oil) KOH catalyst.
Some of the properties displayed by methyl esters of waste fryer grease include a kine-
2
matic viscosity of 4.68mm /s, an acid value of 0.5mgKOH/g, a calorific value of
37.27MJ/kg, a cloud point of 1°C, and a pour point of 3°C [61]. The fatty acid pro-
file of grease is presented in Table 4.3.

4.2.5 Animal fats as feedstock

Tallow from cattle processing, lard and white choice grease from pig processing, and
poultry fat from chicken, turkey, and other bird processing are the main animal fats.
The fish processing plant generates fish oil, which can also be used as a viable feed-
stock for the production of biodiesel [62]. The fatty acid profiles of some animal fat
feedstocks are presented in Table 4.3.

4.2.5.1 Fish oil as feedstock

Fish is a good source of nutrients such as proteins, vitamins, minerals, and lipids. The
fish flesh is mainly composed of lipids such as phospholipids, triacylglycerols (TAG),
and sterols, their byproducts in minor quantities, and small amounts of glycolipids and
sulfolipids. The lipid content in the fish varies depending on the type of fish and its
range varies from 0.3 to 45wt% [63]. According to the studies, the fish muscle forms
the basis of the lipids. The lipid storage sites in fish are the subcutaneous tissues, the
belly flap, the muscle tissue, the liver, the mesenteric tissue, and the head [64].
A significant amount of oil-rich waste is generated by the fish processing industry,
which can be used for biodiesel production. Fish heads, viscera, bones, trimming,
tails, fins, and skins mixed with wastewater will be present in the effluents from
the fish processing industry [62]. Fish oil has omega-3 polyunsaturated fatty acids
such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Hence, it
is recommended for a healthy diet. Due to the high free fatty acid content and oxida-
tion products, the refining of fish oil from fish waste would result in a low yield. Fish
oil can be blended with other oils that are stable and can be used for the production of
biodiesel [65]. The polyunsaturated fatty acids are present at levels between 10% and
25% [66]. The fatty acid profile of fish oil shows that it contains various fatty acids
such as myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid,
arachidonic acid, eicosapentaenoic acid, and docosapentaenoic acid [67]. Sharma
et al. [68] found that around 98% conversion of waste fish oil to its corresponding
methyl esters has been obtained for a methanol to oil molar ratio of 12:1 in a reaction
time of 120min at a reaction temperature of 55°C and using 2% (wt of oil) KOH cat-
alyst. Some of the fuel properties displayed by marine fish oil biodiesel include a kine-
matic viscosity of 4.4 at 70°C and 7.2 at 40°C, an acid number of 1.17mgKOH/g, a
cetane index of 50.9, a calorific value of 41.37MJ/kg, and a flash point of 103°C [69].