Biodiesel from Alligator Fat: A Comparison Between Supercritical and Conventional Transesterification Conditions

As the world expands and the population continues to rise, it is becoming more important to diversify where the world gets its energy from. Biodiesel as an alternative fuel source has been a steadily growing industry for years and offers a lot of promise. The traditional method for producing biodiesel is to mix some sort of vegetable or animal fat with a low molecular weight alcohol, as well as a NaOH catalyst, and react them in a batch reactor. After the reaction is complete the biodiesel, excess alcohol, filter cake, water, and glycerol must be separated. The alcohol can be reused, but the caustic catalyst cake must be disposed of properly and the conversion is only around 60%. An alternative method to this traditional process is doing the reaction via a supercritical process.

Research has been conducted using an autoclave to do a supercritical batch process with just raw alligator fat and methanol. The fat and methanol are mixed in the autoclave and it is put in a muffle furnace to react. Alligator fat is used as feedstock due to its availability in south Louisiana, but pork fat and beef fat have been used as well and it is thought that the process can translate well to any sort of triglyceride feed stock. Rendered oil can also be used in this process, which has a conversion of up to 95%. This process is advantageous because no solid waste is formed and no catalysts are required. Another process has been developed uses a supercritical flow reactor to produce biodiesel using an oil-methanol mixture. Oil is rendered from alligator fat and put in a mixer with methanol. An HPLC pump sends the emulsion through a small metal tube that is kept in a muffle furnace. The pressure is maintained by a high pressure valve on the end of the metal tube. The excess methanol can be flashed off and recycled. This process has shown promise and is currently being researched.