Biodiesel refers to a diesel-equivalent, processed fuel derived from biological sources. It's a processed fuel that can be readily used in diesel-engine vehicles, which distinguishes biodiesel from the straight vegetable oils (SVO) or waste vegetable oils (WVO) used as fuels in some modified diesel vehicles. Biodiesel is biodegradable and non-toxic, and has significantly fewer emissions than petroleum-based diesel when burned.
Biodiesel functions in current diesel engines and can be distributed using today's infrastructure, but is generally more expensive to purchase than petroleum diesel. Biodiesel will degrade natural rubber gaskets and hoses in vehicles (mostly found in vehicles manufactured before 1992, most likely already replaced with synthetic rubber which is not effected by biodiesel).
Biodiesel is a light to dark yellow liquid with a viscosity similar to petrodiesel (diesel produced from petroleum). It can be used as an additive in formulations of diesel to increase the lubricity of pure Ultra-Low Sulfur Diesel (ULSD) fuel, although care must be taken to ensure that the biodiesel used does not increase the sulfur content of the mixture above 15 ppm. Much of the world uses a system known as the "B" factor to state the amount of biodiesel in any fuel mix, in contrast to the "BA" or "E" system used for ethanol mixes. For example, fuel containing 20% biodiesel is labeled B20. Pure biodiesel is referred to as B100.
Biodiesel's higher lubricity index compared to petrodiesel is an advantage and can contribute to longer fuel injector life. Biodiesel is a better solvent than petrodiesel and has been known to break down deposits of residue in the fuel lines of vehicles that have previously been run on petroleum. Fuel filters may become clogged with particulates if a quick transition to pure biodiesel is made, as biodiesel “cleans” the engine in the process. It is, therefore, recommended to change the fuel filter within 600-800 miles after first switching to a biodiesel blend.
Biodiesel is water-soluble and attracts moisture, which may be introduced during processing or by condensation in the storage facility. Contamination by water can cause the following problems:
