Although gasoline is the fuel of choice for the American automobile, diesel is the fuel of choice for moving freight — whether by truck, train or ship.

And while the primary source for diesel is from petroleum, the fuel can be made from both plant and animal sources, according to experts in the LSU AgCenter.

“We have many sources of feedstocks for biodiesel,” said Gary Breitenbeck, a researcher in the LSU AgCenter’s School of Plant, Environmental and Soil Sciences.

The current source for most biodiesel produced in the United States today is soybean oil, Breitenbeck said.

“Soybean oil was at one time more of a byproduct,” he said. “The primary product was meal for feeding livestock. But as demand changed, the oil became the primary product and meal became secondary.”

Breitenbeck said the source for biodiesel can come from many waste streams, including used cooking oil and fats from animal processing.

Biodiesel is most commonly made by chemically altering animal fats or vegetable oil through the use of a catalyst and an alcohol during a process called transesterification, said Bill Carney with the LSU AgCenter’s Callegari Environmental Center.

“Biodiesel is actually a methyl ester from a chemical standpoint,” Carney said. And it’s different from ethanol, which is made by converting plant sugars through a fermentation process.

“Biodiesel is 10 times more biodegradable than sugar and 10 times less toxic than table salt,” Carney said.

“Biodiesel has exceptional lubricating qualities for engines,” he added. “And as little as 2 to 3 percent biodiesel mixed with petrodiesel increases lubricity and creates less soot, which is better for air quality.

“It’s a good product. It’s a safe product. It’s better for the environment,” Carney said.

One gallon of vegetable oil yields 1 gallon of biodiesel, and 50 gallons of biodiesel also produce 12 gallons of glycerin, which has many uses, including making soap.

“Any fat — or lipid — can be transformed into diesel,” Breitenbeck said. “But in order to produce enough diesel to serve the market, we have to produce crops dedicated to diesel production.”

While soybean oil is currently the feedstock of choice, Breitenbeck said researchers are looking for alternative crops that will produce more oil per acre and not compete with crops used for human consumption.

“We’re looking at alternative oilseed crops for Louisiana,” Breitenbeck said, pointing to such plants as sunflowers and rapeseed — the basic parent of canola — which are currently grown in other parts of the United States.

But LSU AgCenter researchers are looking for nonfood plants better-adapted to Louisiana growing conditions.

“The vast majority of Louisiana agricultural land is fallowed during the winter,” Breitenbeck said. “This fallow land could be used to grow cover crops that can solve several production problems — including nematodes and hardpans — and also produce an oilseed crop.”

One such plant, the plant scientist says, is wild radish — a tuber that can break up a hardpan, provide forage for animals and produce oil seed.

“The crop matures in 80 days from planting, is cold-tolerant and can be grown without interfering with normal crop rotations,” Breitenbeck said. “It’s not an earth-shattering oilseed crop. It produces no meal but can be viewed as an organic fertilizer.”

Breitenbeck points to improved water quality, soil conservation and improved hunting by providing feed and shelter for animals as additional benefits from the wild radish.

Three other crops that could provide feedstock for biodiesel are perennial — pecan, jatropha and Chinese tallow tree.

Although pecans are grown for the consumer market, many are unsuitable for sale as food, Breitenbeck said. These nuts could be harvested as feedstock for biodiesel, producing as much as 500 to 600 gallons per acre.

Another crop is jatropha, a tropical plant that is resistant to drought and pests and produces seeds containing up to 40 percent oil, he said.

“It can’t take a bad freeze and needs dry roots,” Breitenbeck said. “But it produces seed in about two years.”

Breitenbeck said he believes jatropha is suited for former citrus land that is too saline for growing citrus trees. To find out how well jatropha can stand up to south Louisiana winters and wet conditions, he’s planted some in Baton Rouge for evaluation.

The third crop with potential for producing biodiesel is the Chinese tallow tree — an invasive species that’s difficult to manage, Breitenbeck said. The tallow tree is a wetland plant that likes wet soils, especially in early spring, making it ideal for south Louisiana.

“No oilseed crop is adapted to south Louisiana or the Southeast in general with greater potential to produce quality biodiesel and other industrial materials than the Chinese tallow tree,” Breitenbeck said.

He said in their natural environment, exceptional tallow trees can yield in excess of 1,000 gallons of biodiesel per acre compared to 40 to 50 gallons of biodiesel from an acre of soybeans. Most naturalized trees, however, yield only a few pounds of seed — or none at all.

“Since World War II, the Chinese have developed it into a commodity of major importance,” Breitenbeck said of the tallow tree.

“Traditionally, tallow yielded soap, candles, dye and ink,” he added. “There is nothing that compares.”

Within five years, newly planted trees can begin producing seeds that contain two oils, Breitenbeck said.

“This tree can be grown on marginal land and therefore would not compete with food production for limited cropland,” he said.

Currently, naturalized stands of the tallow tree occupy tens of thousands of acres throughout Louisiana, the LSU AgCenter plant scientist said. Converting these lands to commercial production of the tallow tree as a feedstock for biodiesel offers many potential benefits.

Perhaps the greatest deterrent to commercialization of the tallow tree lies in its potential for “invasiveness,” Breitenbeck said. “The tallow tree has both strong supporters and detractors, and discussion of its possible use as a bioenergy crop can quickly lead to heated debate.”

Breitenbeck said be believes Chinese tallow trees can be moved into commercial production as a biodiesel feedstock within the next few years.

“We have to demonstrate that within a few years you can make more money with Chinese tallow than with soybeans,” Breitenbeck said. “Tallow trees should thrive on marginal land that now is used for producing pulpwood or marginal grazing for cattle.”

e-mail:rbogren@agcenter.lsu.edu