Biodiesel Production

Petroleum diesel has a big value for fulfilling the energy demand of in different sector such as industrial engines and vehicle engine applications. In recent years the oil seeds and particularly non edible oil seeds found significant tri acyl glycerides or triglycerides compound which on processing become equivalent to petroleum diesel. In this reaction, the fatty acids of the triglycerides are converted to the corresponding ester, which is called Fatty Acid Alkyl Ester (FAAE). This FAAE is commonly known as biodiesel.

The oils obtained from the above said substrates cannot be used as a fuel directly because of some impurities it posses such as free fatty acids, sterols, phospholipids, water, odour etc. To overcome these problems there are some chemical modifications are required like transesterification, pyrolysis and emulsification.

Table: Substrate used for biodiesel production

Among these, the transesterification is the key and foremost important step to produce the cleaner and environmentally safe fuel from vegetable oils. Transesterification or alcoholysis is the displacement of alcohol from an ester by another in a process similar to hydrolysis, except than alcohol is used instead of water. This process has been widely used to reduce the high viscosity of triglycerides. If methanol is used in this process it is called methanolysis. It is one of the reversible reactions and proceeds essentially by mixing the reactants. However, the presence of a catalyst (a strong acid or base) accelerates the conversion.

A wide range of lipid containing substrate such as vegetable oils, algal lipids, and animal fats are used for biodiesel production now a day, but commonly oil seed plants used as feedstock to produce biodiesel. In recent years, selected algae species were also studied for cultivating as a biodiesel feedstock. Critical challenges are still exist in cost-effective cultivation of algae, in energy-efficient harvest of algal biomass, and in effectual algal oil extraction.