One of the biggest human uses of fuel is in transportation, where billions of gallons are used each day around the world. Enter biodiesel, a renewable and clean-burning diesel alternative fuel that can run in diesel engines without any problems. There are also blends of biodiesel and regular diesel that reduce impact while still maintaining some use of diesel. But how exactly does this biodiesel get manufactured?

The Manufacturing Process

To understand the process of manufacturing biodiesel, we first have to understand what components biodiesel is actually made from. There are two primary parts to biodiesel: vegetable oil or animal fat and low molecular weight alcohols. Low molecular weight alcohols include ethanol and methanol. Ethanol is generally used more (and you will see more biodiesel advertised as “containing ethanol”) due to its low cost, but methanol provides greater yield from the chemical reactions. 

The primary oils are vegetable oils and animal fats. The most common oil used to produce biodiesel is virgin oil feedstock, an oil from soybean and rapeseeds. Vegetable oils that have been used can be recycled into biodiesel production, and animal fats can as well. A growing portion of biodiesel production and research is in using algae as a source for oils, as growing algae does not need land that would otherwise be used for agriculture. There are other interesting areas currently under research for oil production, such as using sewage for extraction of the fatty acids necessary for the chemical reactions.

Manufacturing biodiesel from these oils and alcohols actually relies almost entirely on some well-known organic chemistry reactions. The two chemical reactions are esterification and transesterification. Both of these involve exchanging groups of atoms from esters (the fats or oils in this case) and alcohols (methanol or ethanol). This reaction is catalyzed with some sort of base, and the resulting products are methyl esters and glycerin. Methyl esters are long chains of fatty acids, and are the technical names for a variety of biodiesels. Glycerin may sound familiar as well, as it is an extremely valuable byproduct that can be found in soap and other health products.

Of course, many of the oils used for production are not very clean. For example, recycled vegetable oil that has been used prior can include pieces of other plant matter or even phospholipids (the molecules that make up cell membranes). Therefore, the oils must go through a pretreatment refinement process to take out any impurities. Water is also removed due to its potential reaction during the catalysis that can lead to salt production. 

Once pretreatment is finished, the alcohols and oils are ready to be processed together to create the biodiesel. But where and how does this occur? There are quite a few methods already developed, and there are still more currently under development. Each production method has its pros and cons.

Batch Mixing Method

Batch mixing biodiesel is the most common method used to produce this alternative fuel, as it uses standardized types of mixers that drastically lower production times and volumes in comparison to earlier methods. In essence, this method lowers the droplet size of oils and alcohols, allowing for a more homogeneous mixture. This is done using precisely calculated industrial mixers that produce the proper amount of shear to reach the desire viscosity of the product. The more homogenous mixture means that the reaction can take place faster, as individual oil and alcohol molecules are allowed in closer proximity to each other than would normally be possible. This process does need a base to catalyze the reaction, however.

Biodiesel production is gaining more and more prominence in mainstream energy, as petroleum becomes more expensive and the world begins to focus on renewable fuel sources. The field seems extremely promising, and many scientists are dedicating their work toward making production even faster and more efficient. The methods covered are just some of the most common in the United States, but there will absolutely be more innovations in the field within the coming years.