Biodiesel is a combination of biologically derived components, typically including restaurant oils, vegetable oil, and/or animal fat, with a varied blend of petroleum diesel. Biodiesel in technical terms is a fuel comprised of mono-alkyl ester of a long chain of fatty acids that meets the American Society of Testing and Materials (ASTM) D6751 standards. Biodiesel that meets the 11 standard specifications of the ASTM D64751 can be run in an unmodified diesel engine, and if registered with the Environmental Protection Agency (EPA), can be legally sold and distributed in the United States. The international equivalent to ASTM D64751 is EN 14214. Biodiesel should not be confused with straight vegetable oil (SVO) systems, because SVOs require significant modifications to a diesel automobile that include a heat tank and a tank for the diesel.