Page 77 - Advances in Eco-Fuels for a Sustainable Environment

54 Advances in Eco-Fuels for a Sustainable Environment

with little or no difficulty [14]. It was also reported that as the soybean methyl ester
ratio in the engine was being increased from 10% to 50%, the power, smoke intensity,
and CO and HC emissions decreased while the NO x emissions and fuel consumption
increased [15]. Aransiola et al. [16] also confirmed the decrease of CO and increase of
NO x with the use of Neem oil for biodiesel production.
Generally, vegetable oil has been classified as an edible oil (first generation) and
nonedible oil (second generation) [17]. A comprehensive review of the various veg-
etable oils is discussed. Similarly, the residual fats and oils of domestic, commercial,
and industrial processes is another source of feedstock [18]. The choice of oils or fats
for biodiesel production depends on both the process chemistry and economy and,
most importantly, the oil content of the feedstock. The oil content is of fundamental
significance and may likely become the competitive factor in the international
markets [11].
Free fatty acid (FFA) and fatty acid composition do influence biodiesel production
process selection and its final properties [11]. Oils with high FFA content decrease
biodiesel yield and increase production costs. Likewise, a high percentage of
mono-unsaturation in the fatty acid composition also determines the best oil for bio-
diesel production [19]. Extracting oil in the safest and most environmentally sustain-
able manner is of utmost concern globally [20]. Conventional methods of extracting
oil from oil feedstocks are the mechanical and chemical (solvent and aqueous extrac-
tion) methods. Other methods such as supercritical fluid extraction, enzymatic extrac-
tion, microwave extraction, and ultrasonic extraction are not yet fully commercialized
but are promising possibilities for the extraction of oil.
Only few studies in the literature have been able to review the feedstocks for bio-
diesel production and methods of extraction of oil. Therefore, this chapter reviews in
detail the prospects of different feedstocks to be used for biodiesel production,
methods of extraction, and production techniques and their challenges.

3.2 Feedstock prospects and their challenges

There have been various feedstocks employed in the production of biodiesel, includ-
ing edible oil, nonedible oil, and animal fats. These feedstocks will be discussed in this
section.

3.2.1 Prospects of edible oils for biodiesel production

Considerable research has been done on the utilization of several edible vegetable oils,
such as palm oil, palm kernel oil, soybean oil, sunflower oil, coconut oil, rapeseed
oil, groundnut oil, sesame seed oil, hazelnut kernel oil, almond kernel oil, olive kernel
oil, moringa oil, canola oil, cottonseed oil, corn oil, poppy seed oil, safflower seed oil,
walnut kernel oil, Chinese tallow tree oil, and bay laurel leaf oil, among others, for the
production of biodiesel. Currently, >95% of biodiesel production is from edible oil