Page 137 - Advances in Eco-Fuels for a Sustainable Environment

108 Advances in Eco-Fuels for a Sustainable Environment

4.2.5.2 Chicken fat as feedstock

Chicken fat is produced from poultry waste or rendering of chicken feathers. Around
2%–12% of fat can be extracted from a feather meal [62]. Chicken fat contains pri-
mary fatty acids such as oleic acid (40.9wt%), palmitic acid (20.9wt%), and linoleic
acid (20.5wt%). The unsaturated fatty acid content in chicken fat is high, as a result of
which the corresponding methyl esters display poor oxidative stability [17]. As per
Alptekin and Canakci [70], a methyl ester yield of 87.4% has been obtained from
chicken fats for a methanol to fat ratio of 40:1 in a reaction time of 80min at a reaction
temperature of 60°C and using 20% sulfuric acid. The kinematic viscosity of chicken
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fat at 40°C is 59.20mm /s and the acid value is 26.89mgKOH/g [70].

4.2.5.3 Lard as feedstock
The rendered form of pig fat is lard. For rendering pig fat, either the wet or dry process
can be used. In wet rendering, the pig fat is first steamed or boiled in water at a high
temperature and the lard is skimmed off from the surface because it is insoluble in
water or it is separated by an industrial centrifuge. If the fat is exposed in a pan or
oven to high heat in the absence of water, then it is the dry rendering process. The
product obtained from both rendering processes is different. Wet rendering yields
product that has a neutral flavor, lighter color, and higher smoke point whereas dry
rendering products have a brown color and lower smoke point [62]. Pork lard has a
relatively high saturated fatty acid content. Oleic acid (44.7wt%), palmitic acid
(26.4wt%), linoleic acid (12.7wt%), and stearic acid (12.1wt%) are the primary fatty
acids present in pork lard [17]. According to the work carried out by Lee et al. [71],
<80% methyl esters from lard have been obtained but after removal of free fatty acids,
the maximum conversion of 96% has been obtained for a methanol to lard molar ratio
of 3:1 in a reaction time of 24–48h using a lipase catalyst.

4.2.5.4 Tallow as feedstock
When the slaughterhouse byproducts are subjected to rendering, they get converted to
tallow. In tallow, about 50% of fatty acids are saturated fatty acids. Tallow is rich in
palmitic acid and stearic acid, as a result of which it is solid at room temperature and
has a high viscosity and melting point. There are two forms of tallow-edible and non-
edible forms. The edible form of tallow has low free fatty acid (FFA) content and can
be easily converted to biodiesel, thus forming a viable feedstock for the production of
biodiesel. The nonedible form of tallow has high FFA content and the conversion
of the tallow to biodiesel involves expensive procedures [62]. The fatty acids present
in tallow are myristic acid (3–6wt%), palmitic acid (24–32wt%), stearic acid
(20–25wt%), oleic acid (37–43wt%), and linoleic acid (2–3wt%) [12]. Fadhil [72]
stated that the maximum conversion of 91% has been obtained from tallow at a
reaction temperature of 60°C in a reaction time of 60min for methanol to tallow molar
ratio of 6:1 and using 0.5% KOH catalyst. Some of the properties of methyl esters of
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tallow include a kinematic viscosity of 4.36mm /s, an acid value of 35mgKOH/g,
a cloud point of 15°C, and a pour point of 11°C [72].