Biodiesel is a substance much like petroleum-based diesel, except it is made from plant-based sources such as microalgae and coconuts instead of petroleum. While biodiesel can occur naturally under specific circumstances, these circumstances are rare and can take years. A biodiesel reactor shortens the amount of time and makes the process semi-automated or fully automated so commercial amounts of biodiesel can be created. There are two main types of biodiesel reactor units: shear and ultrasonic. Both work on biodiesel in different ways, but both lead to the creation of large amounts of biodiesel with little work on the part of the reactor operator.
All biodiesel starts out as a plant-based feedstock. Some feedstocks include microalgae, coconuts and used or virgin vegetable oils. A biodiesel reactor then works on the feedstock to cause a chemical reaction called transesterification. In this process, the feedstock is separated into two substances: glycerin and methyl esters.
Glycerin is a byproduct of the process and is a sweet alcohol. After production, glycerin is normally used by other industries to create moisturizers or soaps, so the glycerin is not wasted or thrown away. The other substance, methyl ester, is the chemical name for biodiesel. At this stage the biodiesel is refined further to create other biofuels, mixed with petroleum diesel to create a diesel blend that offers both sustainability and usability in cold temperatures, or is used immediately without the blend or extra processing.
An ultrasonic biodiesel reactor uses ultrasonic waves to make biodiesel feedstock bubble. The bubbles are produced and collapse because of the ultrasonic waves, causing a reaction from heat and pressure that makes the feedstock transesterificate. An ultrasonic biodiesel reactor is normally used for large or commercial needs, because these units have a hard time creating smaller amounts of biodiesel. These units also tend to require less work from operators and run at a more automatic pace than shear reactors.
A shear biodiesel reactor is used in laboratories that need small amounts of biodiesel for testing, can be used in a home by a qualified person, and can also be ramped up for commercial use. These units use heat and reduce the droplet size of the biodiesel feedstock to cause transesterification. Biodiesel usually takes from 30 minutes to four hours to make, depending on the unit. These units require more work from operators, but the unit itself is more versatile about creating different yields and works better with solid feedstock than ultrasonic biodiesel reactor units do.