July 2008, Work Truck - Feature
Industry Groups Address Expanding Biodiesel Use
By Richard Nelson
President Bush, in his 2007 State of the Union message, set a goal of reducing America’s gasoline consumption by 20 percent over the next 10 years. In early 2008, Congress passed the Energy Independence and Security Act (EISA), which mandated production of 36 billion gallons of renewable fuel in 2022, nearly five times the 2012 target of 7.5 billion gallons. Of this target, 500 million gallons of biomass-derived diesel (biodiesel) is required by 2009 and 1 billion gallons by 2012.
A renewable fuel for use in diesel (compression ignition) engines, biodiesel is derived from oils and fats and can be used with petroleum-based diesel fuel in existing diesel engines with little or no modification.
This fuel has many important attributes, such as a higher cetane level (refers to better combustion properties) and significant reductions in unburnt hydrocarbons, particulate matter, and carbon monoxide versus conventional diesel. With low sulfur and high lubricity even at very low (less than 2 percent) blends, biodiesel also has the highest energy balance of any alternate fuel at 3.5 to 1.
Biodiesel is defined technically as a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, designated B-100 and meeting the requirements of a national fuel specification, the American Society for Testing and Materials (ASTM) D6751.
Biodiesel Produced from Oil or Fats
Biodiesel can be produced from any oil or fat as well as waste greases. It is generally produced by a chemical process referred to as transesterification, which involves combining an oil or fat with an alcohol (generally methanol) and a catalyst to produce the biodiesel and glycerin, a byproduct. Figure 1 presents a diagram of the basic transesterification process. The notable elements in the process are that it removes glycerin from the oil and the vegetable oil or animal fat ingredient is not in a raw form.
Biodiesel can be produced from any oil or fat as well as waste greases. It is produced by a chemical process known as transesterification, which involves combining an oil or fat with an alcohol such as methanol and a catalyst to produce the biodiesel and glycerin, a byproduct.
Biodiesel that does not meet the chemical and physical parameters mandated by ASTM D6751 can cause significant problems with several engine components as well as problems with storage and handling. Table 1 presents information concerning the most important biodiesel production quality parameters and damages that could potentially occur to a compression ignition engine if they do not meet the ASTM D6751 specification.
