Energy is a fundamental requirement for human existence.
Biodiesel is a renewable energy source that can be produced from
vegetable oil and animal fats. The choice of raw material is the main
factor in biodiesel application (fatty acid methyl and ethyl esters),
being more important than investment, operating costs or energy
consumption. At present, the main raw material for producing
biodiesel is edible vegetable oil. The price of the raw material is
higher than that of the final biodiesel product because the price of
feedstock-containing oil is a major component of the overall cost of
biodiesel, at 70e80% [1,2]. Efforts have been made to reduce the
costs of biodiesel by selecting cheap raw materials, improving
reaction conversion or simplifying the process to overcome these
disadvantages. A widely accepted development in this area is the
use of used and therefore inedible cooking oil to reduce the costs of
oil, the raw material of biodiesel [3e6]. Hence, inedible oils such as
jatropha, karanja, mahua, tobacco seed, linseed, rubber seed, neem
and soapnut may be significant sources for biodiesel production.