Biodiesel is an alternative fuel produced from renewable resources such as plant oils, animal fats, used cooking oil, and new sources such as algae. Biodiesel contains no petroleum, but can be combined in any quantity with petroleum diesel to create a biodiesel blend. Biodiesel blends can be used in most "compression-ignition" (diesel) engines with little or no modifcations. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics (the "diesel" odor). (Biodiesel is not raw vegetable oil.).