Biodiesel used for automobiles as a fuel with standards of American Society for Testing and Materials (ASTM) D6751. As per the standards, it should have properties with values ranging of specific gravity 0.88g/ml, pour point -15 to 16 centigrade, flash point 100 to 170 centigrade, cetane number 48-60 and weight basis of sulphur 0.05%, carbon 77%, oxygen 11% and hydrogen 12%. Biodiesel is produced in two ways either by transesterification process or by esterification method. If the raw material is a triglyceride than transesterification is used and if free fatty acids are the starting materials than esterification process is selected. Lipids are the source of these raw materials that are present in plants and animals.
While processing the triglyceride methyl ester is produced which is a biodiesel, along with it a byproduct called glycerol is produced. This glycerol cannot be used as a fuel like biodiesel. So this became as feedstock for producing other chemical product because its quantity of production is same as biodiesel. As per the stoichiometry for a mole of methyl ester, one mole of glycerol is obtained as a byproduct.
Similarly, in the process of production of biodiesel by transesterification of cooking oil the product and by-product quality vary based on the catalyst used. For example, natural solid catalysts like rice husk or eggshell powder. The oil structure cracking and its conversion highly depends on the activity of alkali metals.
One of the important products obtained from glycerol is acetol. The process of dehydration obtains acetol from by-product glycerol. By hydrogenation of acetol, an important consumer product called propylene glycol (C3H8O2) is obtained. Propylene glycol contributes in producing a product in food, cosmetics, and domestic solutions. The product that is obtained from the byproduct of biodiesel process will cut down the consumption of fossil petrol crude. Propylene glycol is used for making soaps, lubricants, sanitizers, lotions, shampoos, lipsticks, automotive anti freezers, soft drink preservatives and many more. Thus, a by-product of biodiesel process turns to environmental friendly because almost many consumer goods are segregated to the green technology sector. The lesser the fossil crude is used the faster we save our planet. Obviously, many consumer products can be manufactured as biodegradable with propylene glycol obtained from glycerol.
Lot of research work is under its way to improve the process design and obtain optimized condition to run the process. One of the technologies like catalytic reactive distillation brought promising result so that it can be implemented in the large production of chemical product from the byproduct of biodiesel process industries.
Microbial bio-oils, glycerol carbonate, and glycerol acetyl esters are also the promising products formed from glycerin. Due to its production in large scale, it becomes a cheap feedstock for other petrochemical industries.
Crude glycerin is gasified to produce synthesis gas or hydrogen gas at moderate temperatures.
Seed cake after extracting the oil is solid material left over is mostly non-edible due to chemical treatments. The cake contains botanical active ingredients that can be used for making mosquito and pest repellents.