One of the reasons biodiesel fuel is so helpful to the environment one of the qualities that makes it so extraordinary is its fast rate of biodegradation. The word biodegradation means a substance's chemical breakdown resulting from whatever is present in the environment. A material that is highly biodegradable, therefore, is one that will break down quickly into elements that can be reused within a natural environment; and thus it will renew and replenish that environment. In the case of biodiesel fuel, the methyl esters that make up this substance break down in any natural environment quickly and completely. Even biodiesel hybrids show relatively high rates of biodegradation. In fact, when biodiesel is mixed with petroleum, the presence of that biodiesel makes the petroleum biodegrade at least three times faster than it would on its own.

Indeed, the rate of biodegradability of biodiesel fuel has even taken some scientists and environmentalists by surprise. Consider, for instance, the landmark study that the University of Idaho in Moscow, Idaho, conducted in 1995. The study was called Toxicology, Biodegradability, and Environmental Benefits of Biodiesel. And in their report the researchers at the University of Idaho noted that after leaving biodiesel in an aqueous solution for twenty-eight days, ninety-five percent of this biofuel was gone completely degraded. By contrast, after leaving the same amount of diesel fuel in an aqueous solution exactly the same as the first aqueous solution, only forty percent of the diesel fuel had degraded. This is an enormous difference. In fact, the rate of biodiesel fuel's biodegradability is the same as the rate of table sugar, perhaps even a little bit higher and think about how fast table sugar can dissolve in water!

The flip side of biodiesel's fast rate of degradation is that, if it is exposed to oxygen while it is being stored, it can start to break down chemically fairly quickly (this is known as oxidative degradation) and thus it will not be usable. Therefore, if you owned a large commercial operation and had a large supply of biodiesel on hand, and that supply were to be exposed to the air because its containers were not airtight, then you could potentially lose a lot of money's worth of fuel. However, you can get your biofuel treated so that it won't break down quite as quickly when it's oxidized. Also, scientists and chemical engineers are working on ways they can alter the chemical makeup of biodiesel so it won't have such a fast rate of oxidative biodegradation. These alterations may include the creation of special chemical additives.

One last point here: the degradation rate of biodiesel makes it perfect for using on the water, for if it spills it will dissipate and break down quickly, and thus not cause damage to a marine ecosystem. In fact, this kind of fuel would be perfect for boaters of all kinds.