Biodiesel is a term coined to refer to the converted vegetable oils that can be utilized in a diesel engine. It originally referred a very specific kind of fuel that was made from palm oil in Brazil. As it gained in popularity, the name grew to include any form of diesel fuel that was derived from a vegetable oil. The energy capacity for biodiesel is remarkably static across a wide range of foodsources.
The first experimentation towards using vegetable oil as a fuel source was done in the 1850’s. unsurprisingly; they were not created for use in an engine at that point, but rather as a potential “what if” curiosity. The curiosity was fleeting, and vegetable oil receded from the consciousness of inventors for several decades.
It came back after the turn of the century, when a number of inventors began to tinker with the idea of running an automobile on vegetable oil. One of these inventors went by the name of Rudolph Diesel. As you may have surmised, he was the father of the diesel engine. He found that his engine could be successfully run on vegetable oil, but never truly tackled the logistical problems that came with vegetable oil.
The next breakthrough brought about the first fuel that could correctly be called biodiesel. In 1937 a Belgian inventor and professor filed for a patent on a process that transformed vegetable oils for use as fuel. This transformation was accomplished with ethanol, and the alcohol methanol was also outlined in the patent submission. This process was the beginning of the conversion that we use today to create biodiesel.
The conversion itself is relatively easy to understand. First the vegetable oil must be purified of any latent acids within it. To do this, it is titrated with a base until the point of equilibrium is reached. Once the acid has all been neutralized, it remains to separate it from the rest of the oil before processing. Thankfully the material will stratify on its own, allowing a skimmer to remove the waste.
Once the oil has been purified it needs to be made into a more viscous liquid with a higher energy density. To accomplish this, it is pressurized and heated, and then mixed with alcohol, normally methanol. There are long carbon chains, called R chains, in both methanol and in vegetable oils. The chains differ slightly in composition, and the goal of the biodiesel conversion is to foster an exchange of these chains between the two liquids.
This exchange results in two by products, a completed biodiesel compound, and glycerol. Glycerol, which is also known colloquially as glycerine has a variety of commercial uses, but current production leaves it in an unrefined form, which lowers its marketability. However, biodiesel is still cheaper in many areas than petrodiesel, and this trend is expected to continue as advances in process are made. Biodiesel is one of the renewable energy sources that allows us to keep existing infrastructure, such as the diesel engines in cars and trucks, as well as fueling stations that are already in place. This is the opposite of technologies such as electric cars, that will require re-equipping our infrastructure to deal with them.