Executive Summary

Biodiesel is a renewable, biodegradable, alternative fuel or fuel additive used in diesel engines or fuel oil generators. It can be used in its pure form or it can be mixed with a petroleum-based diesel (distillate). Biodiesel is usually described based on its concentration in distillate diesel fuel as B100 (pure biodiesel - 0% distillate diesel & 100% biodiesel), B20 (80% distillate diesel & 20% biodiesel) or B2 (98% distillate diesel & 2% biodiesel). Biodiesel can be made from a variety of biological products, including animal fats and virgin and recycled vegetable oils and even certain yeasts and molds. The majority of biodiesel production and consumption is in Europe, but biodiesel is in the early stages of development in the U.S. and Canada.

Biodiesel is composed of monoalkyl esters (most commonly referred to as methyl/ethyl esters), which is a long chain of fatty acids and a methyl or ethyl alcohol. The ester based biological products, which have had their viscosity reduced using a process called transesterification, produces biodiesel and glycerin (thick component of vegetable oil). Glycerol or glycerin is the primary byproduct of methyl ester production. Biodiesel is biodegradable, non-toxic, and usually free of sulfur and aromatics. Originally biodiesel was considered a by-product of glycerin soap production.

The primary process of making biodiesel, referred to above, is chemistry called transesterification. At a simple level, you take 10 parts oil, 1 part methyl or ethyl alcohol, (methanol is most commonly used), and 1/10th part catalyst, (most commonly a base catalyst like sodium hydroxide), and combine them under a certain pressure and temperature. From this you get about 10 parts biodiesel and 1 part crude glycerin. The figure below describes the basic transesterification reaction.

The most important factor in creating methyl esters is the oil feedstock. The oil feedstock accounts for 20% - 80% of the cost of production (on average). The reason for the cost variation is the wide range of possible feedstock materials. If a plant intended to use the cheapest input, trap grease, the feedstock can be very cheap ranging from $-0.05 to $0.05 per pound. The challenge with this feedstock is quality and composition of the oil. Trap grease is a dirty, smelly waste product of food preparation. It would be a cheap input, but would entail additional equipment, (acid esterification), processing costs, processing steps, and different conversions. The ability to make regular quantities of biodiesel that could meet quality standards is unlikely.

The other extreme is using very clean refined oil, also called refined, bleached and deodorized (RBD) oil. In this case, the oil cost is high, ($0.255 per pound on average), but transesterification is the only activity that needs to be done to create a clean and consistent biodiesel and glycerin byproduct. One of the key characteristics that affect the type of processing of the oils into methyl esters, is the percentage of triglycerides. This is the predominant structure of most fats and oils. Triglycerides are a combination of 3 fatty acid chains combined with a glycerol backbone. These fatty acid chains are combinations of carbon and hydrogen atoms. The number of carbons and the type bonds typically describes the difference between different fatty acids. To learn more about the biodiesel industry and the factors that drive the success of these plants, click here to register