Fats Into Jet Fuel: NC State Develops Biofuels
Technology
Newswise — New biofuels technology developed by North Carolina State
University engineers has the potential to turn any fat source – vegetable oils, oils from animal fat and even oils from algae – into fuel to power jet airplanes.
The technology – called Centia™, derived from “crudus potentia,” or
“green power” in Latin – is “100 percent green,” as no petroleum-derived
products are added to the process. Centia™ can also be used to make additives
for cold-weather biodiesel fuels and holds the potential to fuel automobiles
that currently run on gasoline.
NC State received provisional patents to use the process to convert fats into
jet fuel or additives for cold-weather biodiesel fuels. The technology has been
licensed by Diversified Energy Corp., a privately held Arizona company
specializing in the development of advanced alternative and renewable energy
technologies and projects.
Dr. William Roberts, professor of mechanical and aerospace engineering and
director of the Applied Energy Research Laboratory at NC State, developed the
biofuels process with NC State’s Dr. Henry Lamb, associate professor of chemical
and biomolecular engineering; Dr. Larry Stikeleather, professor of biological
and agricultural engineering; and Tim Turner of Turner Engineering in Carrboro,
N.C.
Roberts says that besides being “100 percent green,” the new technology has
some key advantages over other biofuel projects.
“We can take virtually any lipid-based feedstock, or raw material with a fat
source – including what is perceived as low-quality feedstock like cooking
grease – and turn it into virtually any fuel,” Roberts says. “Using low-quality
feedstock is typically 30 percent less costly than using corn or canola oils to
make fuel. And we’re not competing directly with the food supply, like
ethanol-based fuels that are made from corn.”
The fuel created by the new process also burns cleaner, so it’s better for
the environment, Roberts says. There is no soot or particulate matter associated
with fuel from fats.
Further, Roberts says, the Centia™ process puts to use what other biodiesel
processes throw away. Converting feedstock into fuel produces a low-value
commodity – glycerol – as a by-product. Rather than discarding glycerol as waste
like most biodiesel plants do, the NC State engineers’ process burns glycerol
cleanly and efficiently to provide some of the process’ requisite high
temperatures.
“Instead of composting the glycerol as waste, we use it as an integral part
of the fuel-making process,” Roberts said.
It really does take a rocket scientist to make jet fuel, especially out of
oils or agricultural crops, Roberts says. The physical and chemical properties
of traditional biodiesel fuels – their combustion characteristics and viscosity,
for example – don’t match the stringent requirements required of jet fuels,
making biodiesel unacceptable for the task.
“Jet fuel travels at 25,000 to 35,000 feet where temperatures can reach 70
degrees below zero Fahrenheit, so it needs to flow better in cold temperatures,”
Roberts says.
The Centia™ process comprises four steps, Roberts explains. First, the
engineers use high temperatures and high water pressure to strip off the
so-called free fatty acids from the accumulated feedstock of oils and fats, or
triglycerides. Next, the engineers place the free fatty acids in a reactor to
perform the decarboxylation step; that is, carbon dioxide is taken off the free
fatty acids. Depending on the feedstock used, the scientists are left with
alkanes, or straight-chain hydrocarbons of either 15 or 17 carbon atoms.
“After these first two steps, which are always the same no matter which fuel
you want, we can make any fuel we want to make,” Roberts says. “In the last two
steps, we can change the recipe based on the fuel output desired.”
In the last two steps, the engineers break up the straight chains into
molecules with branches, making them more compact and changing their chemical
and physical characteristics. Jet fuel and biodiesel fuel require a mixture of
molecules with between 10 and 14 carbon atoms, while gasoline requires only
eight carbon atoms, so the engineers can control the process to elicit exactly
the type of fuel they desire.
Finally, the engineers make some other chemical tweaks to create the desired
fuel. Also, the glycerol by-product is burned off to provide heat for the
various processes involved.
“We produce one-and-a-half billion gallons of animal fats annually, which is
about half of the amount of vegetable oil produced yearly,” Roberts said.
“Animal fats are harder to work with, but cheaper. Last year, for the first time
ever, fuel costs in the aviation industry exceeded labor costs. We think the
aviation industry is keen on finding alternatives to petroleum-based jet
fuel.”