Biodiesel, or methyl esters*, is composed of mono-alkyl esters of long chain fatty acids that comes from vegetable oils or animal fats. To truely be labelled as biodiesel it must first meet the requirements of ASTM D 6751, and then it may be called B100. Biodiesel can also be blended with normal petroleum diesel to form a biodiesel blend. Biodiesel blends are labelled BXX where XX tells you the percentage of biodiesel mixed into normal diesel. The Environmental Protection Agency has registered biodiesel as both a fuel and an additive for this reason.When biodiesel is made you produce two products from the animal fats or vegetable oils, methyl esters and glycerin. This process, which is a chemical reaction brought about by alcohols, is called transesterfication. The methyl esters become the biodiesel you use, and the the byproduct is glycerin. Glycerin is used in things like soap, lotions, prevent freezing in hydraulic jacks, dynamite (though glycerin is not explosive by itself), and other things. Biodiesel is not the same thing as straight vegetable oil (SVO). Biodiesel has to meet the strict industry specifiacations of ASTM D 6751, and is the only alternative fuel to have completed the health effects testing of the 1990 Clean Air Act Amendments. Biodiesel can generally be run successfully in any diesel engine with little to no modifications. Diesel vehicles can run on SVO but generally modifications have to be done first to insure proper performance. There are many kits sold that allow SVO to be run on specific vehicles and universal kits that can be made to run on any diesel.

There are many benefits to running biodiesel. Biodiesel is better for the environment because it generates lower emissions than petroleum based diesel. Biodiesel has lower hydrocarbon (HC) and particulate matter (PM) emissions than regular diesel. It also has a greater lubricity which means less friction and heat that the engine is subjected too. One of the greatest benefits of using biodiesel is that it is a domestically renewable product. Most biodiesel is made from soybeans, but can come from all kinds of vegetables farmed here in the U.S. This obviously means less dependence on foreign suppliers for oil, and its great for the economy.This chart from the EPA that shows the average biodiesel emissions compared to conventional petroleum biodiesel.

As you can see with pure biodiesel the sulfur emissions are essentially gone. Sulfur oxides and sulfates are some of the major components of acid rain. The tests also show the substantial reductions of unburned hydrocarbons, carbon monoxide, and particulate matter. Hydrocarbons have been identified as ozone forming. Carbon monoxide is a poisonous gas. Particulate matter has been shown to be a human health hazard when inhaled. Polycyclic Aromatic Hydrocarbons and nitrated PAH’s have been identified as potential cancer causing agents.

The question everyone asks is “Will biodiesel hurt my engine?”. Essentially the answer is “No”. There are, however, things you have to take into account when running biodiesel. Biodiesel has a solvent effect. When biodiesel is run it can basically clean your engine out which means in the beginning it may knock deposits loose, and you may have to change your fuel filter more often. The other concern is if you have an older diesel engine it may have rubber seals(most newer diesel do not use rubber seals). The aforementioned solvent effect of biodiesel can cause these rubber seals to wear out and deteriorate quicker.

For more information on biodiesel please visit The National Biodiesel Board

* methyl esters is what is seen most, but almost any alkyl group can be used to make biodiesel.