A range of plant oils have been used to create renewable fuel, with canola, palm and soybean as some of the most commonly used options. Fuel produced from these sources, called biodiesel, offers better miles per gallon than regular gasoline, but fewer miles per gallon than the petroleum-based diesel fuels currently available. Pure biodiesel's fuel economy and power is about 10 percent lower than that of petroleum diesel. Biodiesel/petroleum blends are more efficient, but still about 2 percent less than the pure petroleum variety [source: U.S. Department of Energy]. The canola plant, which is part of the mustard family, produces seeds with high oil content -- about 40 percent -- and is a frequently used feedstock for fuel, particularly in the United States and Canada. Palm oil, which is produced in large quantities in Malaysia and Indonesia, may be a good choice from an economic perspective, but has raised concerns about its negative environmental effects. Biodiesel presents many of the same problems as ethanol, including displacement of food crops and increased greenhouse gas emissions as a result of transforming natural areas into biofuel croplands [source: The Nature Conservancy].