Page 461 - Advances in Eco-Fuels for a Sustainable Environment

414 Advances in Eco-Fuels for a Sustainable Environment

be utilized as fuel. In this manner, manufacturing biodiesel from nonedible oils is an
effective method to overcome all the related issues with edible oils [7]. In any case,
the capability of converting nonedible oil into biodiesel must be well analyzed. This
is on the grounds that the chemical and physical properties of biodiesel obtained from
any feedstock should comply with the limits of ASTM specifications for biodiesel fuels.

15.3.3 Production process
The crude vegetable oil or animal fat has higher free fatty acid (FFA) content and its
viscosity is higher as well. The conversion of crude vegetable oil or animal fat into
biodiesel can be achieved through a three-stage transesterification process. The main
constituent of raw oils obtained from animal fats is triacylglycerol, which is highly
viscous as compared to diesel. This is because of the presence of three long-chain fatty
acids in triacylglycerol, and this higher viscosity makes it unusable in diesel engines.
To reduce the viscosity, transesterification reactions on the triacylgycerol are carried
out to convert it into esters by converting each fat oil molecule into one molecule of
glycerine and three molecules of ester. Separation of glycerine from the ester produces
biodiesel. The separated glycerine is a valuable raw material in the soapmaking and
food industries. The transesterification process is used to obtain the biodiesel and the
KOH catalyst is added to a beaker containing a mixture of animal fats and methanol.
A heater is used to heat the beaker to 70°C and the mixture is continuously stirred for a
period of 6h. Now, the blend is collected in a beaker where it is separated into AFME
and glycerine. This separation is due to the difference in density between the glycerine
and methyl ester; the glycerine is denser and settles at the bottom of the beaker. The
separation process takes 4h and the upper layer is the AFME. Fig. 15.5 shows the tech-
niques of production of biodiesel from various sources of biomass, this also emphasis
on various conversion techniques that exist in their production process. Figs. 15.6 and
15.7 show the detailed transesterification process where vegetable oil is converted into
biodiesel.
Various properties such as viscosity, density, cetane numbers, and flash point mea-
surements of six oil methyl esters are listed in Table 15.2. It is generally observed that
the viscosity of the crude biodiesel is higher than that of diesel. This makes the bio-
diesel more viscous than diesel. It is important to control the fuel viscosity with
acceptable limits to avoid deleterious effects on the fuel injection system. Flash point
of a fuel is the temperature at which it will ignite when exposed to a flame. The higher
the flash point of a fuel, the safer it is to transport. Biodiesel has a flash point that is
intermediate between that of diesel and crude biodiesel, so it is safer to transport the
biodiesel than it is to transport diesel. The cetane number of a fuel is an indicator of its
ignition characteristics. Ignition properties are better if the cetane number is higher. It
affects various engine performance parameters such as combustion stability, noise,
and drivability and emission characteristics such as HC and CO. It is also observed
that generally biodiesel has a higher cetane number than neat diesel, which results
in a higher combustion efficiency. From the table it’s clear that the viscosity for all
the oils is higher and it can be reduced by blending with diesel or higher alcohols.
Upon transesterification, the viscosity, density, and flash point values of the methyl
esters decrease significantly.