Biodiesel is the product of the reaction between an Alcohol and a Triglyceride. Common sources of Triglycerides are Animal fats and Vegetable oils. The manufacturing process for Biodiesel is generally referred to as Transesterification. Currently Biodiesel producers generate Glycerol that is 80-85% pure and commands pricing in the range of $80-120/ton.
Triglycerides are composed of a mixture of saturated, monounsaturated and polyunsaturated components designated as R1, R2 and R3 and attached to the Glycerol backbone. The composition of R1, R2 and R3 and their relative % in the Triglyceride determines the solidification temperature of the Biodiesel.
Biodiesel is commonly described as FAME (Fatty Acid Methyl Ester) with an added numeral indicating its cold flow specification. The Transesterification of Triglycerides is most commonly carried out using Caustic based catalysts at moderate temperatures. The primary reason for the process is to reduce the viscosity of the Triglyceride to one closely matching that of fossil diesel. All vegetable oils and animal fats are suitable candidates for conversion to Biodiesel.
The most commonly processed feedstock's include Tallow, Soybean oil, Canola/oilseed Rape, Palm oil, Coconut oil, Sunflower oil and Camelina oil. New sources of oil under development include Jatropa oil, Honge oil and Algae oil. Waste cooking oil, Tallow and Poultry fat for Biodiesel production require an added processing stage to reduce the Free Fatty Acid (FFA) content.
While pricing is a primary consideration for the Biodiesel manufacturer, the choice of vegetable oil also determines the gel/cold flow characteristics of the Biodiesel. Biodiesel manufactured from Soybean and Canola oil have low melting points whereas Palm oil and Tallow have high melting points. Blending of various oils and fats is common and provides a commercial balance of Biofuel properties and price..