This may be the most versatile biofuel on the list. Along with being a staple food product from Asia to America, the soybean has been turned into everything from ink and crayons to fuel products [source: Scharlemann]. While corn is the most popular base stock for the ethanol that is blended with gasoline to fight smog, soybeans are the main source for the oil used to produce biodiesel.
To produce biodiesel using soy, manufacturers first press the oil from the beans. Soy's high oil content -- about 20 percent of the bean is usable oil -- makes it an ideal candidate for this process. Once the oil is extracted and filtered, it's mixed with a catalyst that removes its glycerin. The remaining oil can be poured directly into a diesel engine's gas tank.
Biodiesel has a number of benefits over petroleum diesel beyond its being a renewable resource. It burns cleaner, meaning biodiesel-powered engines produce less of the particulate matter that can cause smog and health problems.