LEON G. SCHUMACHER
University of Missouri, Columbia Columbia, Missouri, United States
JON VAN GERPEN
Iowa State University Ames, Iowa, United States
BRIAN ADAMS
University of Missouri, Columbia Columbia, Missouri, United States
olefin Any unsaturated hydrocarbon containing one or more pairs of carbon atoms linked by a double bond. triglyceride A naturally occurring ester formed from glycerol and one to three fatty acids. Triglycerides are the main constituent of vegetable and animal derived fats and oils.
The United States depends heavily on imported oil to fuel its transportation infrastructure. The use of alternative fuel derived from plant oils was examined by researchers in the mid-1970s to determine if internal combustion engines could be fueled from sources other than petroleum. The initial research on pure vegetable oils as a replacement for petroleum diesel fuel was met with mostly negative results. Researchers determined that transesterification of these plant – and animal-derived oils reduced the viscosity of the oil without any other significant changes to the oil. Since the new fuel was bio-derived and was used to fuel a diesel engine, the name ‘‘biodiesel’’ was selected to refer to the new fuel. This article focuses more specifically on how biodiesel fuel was developed, its chemical and physical properties, advantages, disadvantages, and how biodiesel is used and stored. The article concludes by reviewing the economic issues associated with its use.
1. BIODIESEL FUELS AND THEIR ORIGINS
1.1 What Is Biodiesel?
Biodiesel is made from a number of feedstocks including vegetable oil, tallow, lard, and waste
cooking oils (yellow grease). ‘‘Biodiesel is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats which conform to American Society of Testing Materials (ASTM D5453) International specifications for use in diesel engines.’’ Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. Feedstocks can be transes – terified to make biodiesel using an alcohol that has been mixed with a catalyst such as potassium hydroxide or sodium hydroxide. The most commonly used alcohol for transesterification is methanol. Methanol reacts easily and is less expensive to use than most other alcohols.
Soybean derived biodiesel is the most commonly used biodiesel in the United States. The most commonly used feedstock for biodiesel production in Europe is rapeseed. Biodiesel is biodegradable, nontoxic, and essentially free of sulfur and aromatics. Biodiesel is considered a renewable resource due to the fact that it is derived from products that can be grown and produced domestically.
