Alfalfa may be an
alternative source –
but not anytime soon
Scientists predict that filling your gas tank with fuel made from alfalfa will become a reality, but not in the near future.
“I think it's feasible to happen in the next 20 years,” says JoAnn Lamb, USDA-ARS plant geneticist based in St. Paul, MN. “We need alternative fuels and we need perennial crops in the landscape, especially in at-risk topographies.”
“Alfalfa shows tremendous promise,” says Joe Bouton, director of the Forage Improvement Division of the Samuel Roberts Noble Foundation, Ardmore, OK. “It could be burned to make synthetic gas or fermented to make cellulosic ethanol.”
Cellulosic ethanol would be made from crop residues, switchgrass, alfalfa and other fibrous plants. While making ethanol from the starches and sugars in corn grain is a simple fermentation process, cellulose would first be treated with heat or acid.
“There isn't an efficient, large-scale means for doing that, but it's edging closer,” says Bouton, who toured Iogen's pilot-scale cellulosic ethanol plant in Toronto a few years ago. “I saw wheat straw going in the front end and ethanol coming out the back.”
A recent U.S. Department of Energy and USDA report predicts that, by 2030, a billion tons/year of biomass could produce enough cellulosic ethanol to replace 30% of the current U.S. consumption of petroleum. The report says perennial crops would account for about 377 million tons of that annual requirement.
Alfalfa could help meet those goals, experts say. “Once the production of cellulosic ethanol is commercialized, one or two crops won't be able to carry the load because the need for biomass will be so great,” says David Miller, Pioneer Hi-Bred International's alfalfa research director.
The crop's stable infrastructure also enhances its biofuel potential, says Beth Nelson, president of the National Alfalfa and Forage Alliance.
“Alfalfa's grown in about every state from a wide selection of varie-ties, and there's a trucking network in place to haul it,” says Nelson. “In contrast, switchgrass isn't really a commercial crop yet, so it doesn't have that built-in infrastructure.”
But paying growers good prices for alfalfa destined for ethanol production will be a big challenge, say the researchers. “Initially, cellulosic ethanol plants will probably rely on readily available, low-cost crop residues that cost about two-thirds less than alfalfa,” says Bouton.
“If alfalfa could be stratified into components — the leaves for high-value meal and the stems for fuel — growers should recognize enough value to make it worth their while,” he adds. “If co-products such as high-value, natural compounds that benefit human health are simultaneously extracted from the leaf material, this allows the economics of using alfalfa for fuel to work even better.”
While ethanol from alfalfa won't happen anytime soon, the crop has a very important role to play today in cutting our country's petroleum dependency.
“As the ethanol industry has taken off, the number of acres planted to corn has increased tremendously, but so has the price of nitrogen fertilizer,” says Bouton. “I think more row-crop farmers will add alfalfa to their crop rotations because it fixes its own nitrogen and adds organic matter to the soil.”
Scientists Are Developing Varieties For Fuel
Researchers have been working for years to improve varieties for cellulosic ethanol production.
In St. Paul, MN, USDA-ARS plant geneticist JoAnn Lamb and her colleague, dairy scientist Hans Jung, have been studying alfalfa as a bioenergy crop since the early 1990s. They've developed two experimental varieties with large, lodging-resistant stems. In small-plot trials, the varieties have been grown for longer periods between harvests without lodging, giving them time to accumulate more biomass.
“Research suggests that ethanol yield/acre could double because these experimental alfalfas produce twice as much stem when managed for cellulosic ethanol, with no reduction in leaf yield,” says Lamb.
Scientists at the Samuel Roberts Noble Foundation, Ardmore, OK, are collaborating with Forage Genetics International to change alfalfa's lignin content. Low lignin would be preferred for cellulosic ethanol production, while high amounts may fit best for gasification, says Joe Bouton, director of Noble's Forage Improvement Division.