Biodiesel from alligator fat reduces waste

"Conversion of animal fat to biodiesel has been around for some time, but the traditional biodiesel process generates significant quantities of solid waste," said Thomas Junk, Ph.D. "Our new method creates hardly any such residues." He also said that the new study concluded that using fat from such common sources as chicken, pork and beef could be much more practical for commercial implementation than from the limited amount available from alligators and could be just as effectively turned into biodiesel.

Junk, who is with the University of Louisiana at Lafayette, explained that in the earlier alligator fat study, they used a batch reactor, but switched to a flow reactor to process the fat in the new work. "We set up a flow reactor, and the reaction converting alligator fat to biodiesel happened within a few minutes," said Junk. "That's important for commercial manufacturing, where you want to produce as much fuel as quickly as possible." With batch reactors, reactions occur one-at-a-time in discrete batches. But in a flow reactor, the reactions run in a continuous stream.

He said that fuel produced from various animal fats is very similar to biodiesel manufactured by traditional, well-established methods, such as producing ethanol from corn. "So this approach is not really about a brand-new fuel, but the manufacture of a known type of fuel (biodiesel) using a more efficient, less wasteful process that largely eliminates solid-waste byproducts," he explained. This method does not require a catalyst, which creates a residue, he explained. Instead, they use "supercritical methanol," which is heated to pressures and temperatures high enough to take on properties in between those of a liquid and a gas.

Another advantage of the supercritical method is that the fat doesn't have to be extracted for the process to work, Junk said. It can be used in its raw form. Crude fat and methanol would be homogenized into a slurry (semiliquid mixture) and pumped into the system. This should be a straight-forward, simple process for a manufacturer, he added.

In the earlier study, Junk and the team noted that most of the 700 million gallons of biodiesel produced in the United States (2008 data) came from soybean oil. But there has been growing concern that using soybeans and other food crops for this purpose could raise food prices.

In searching for alternative biodiesel materials, they discovered that waste alligator fat, millions of pounds of which are thrown out every year, could also work. Their experiments showed that oil extracted from alligator fat can easily be converted into biodiesel. And now they plan to test other waste animal fats, such as those from chickens and cows. They predict that these fats also can be easily converted to biodiesel with the flow reactor system.

As a pilot project, the work was largely funded by the Departments of Chemistry and Chemical Engineering of the University of Louisiana at Lafayette.

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