The main problem associated with the use of straight vegetable
oils (SVOs) is their viscosity which has to be decreased down to
make them usable in engine. This is done mainly with help of
transesterification reaction. Table 3 enlists the key properties of
different vegetable oils and their comparison with petroleum diesel.
Table 3explains the various fuel properties of different nonedible oils. The table shows that the kinematic viscosity of oil is
quite high and to make it comparable to diesel, therefore oil is
converted to biodiesel. In addition to it, feedstocks like waste
cooking oil, jatropha, polanga, rice bran oil and chicken fat have
very higher acid value/FFA content thus need two step acid–base
transesterification process for biodiesel production. Calorific value
for the vegetable oil feedstocks is found to be less than that of
petroleum diesel. On the other hand Flash point of oils is superior
to diesel thus making biodiesel safer for storage. Similarly, other
properties are comparable to that of diesel