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Turning nonfood crops into biofuel

May 5, 2008 10:30 AM, By Rick Bogren
LSU AgCenter

Processing nonfood crops to produce biofuels and value-added chemicals can provide Louisiana with another vehicle for economic growth, according to LSU AgCenter officials.

“We think Louisiana is a unique place to grow plants for biofuel because of our long growing season and land currently not in cultivation,” said David Boethel, vice chancellor for research in the LSU AgCenter. “In addition, we have the infrastructure in the state to handle large quantities of biomass.”

The LSU AgCenter, particularly through its Audubon Sugar Institute, has been a leader in developing the biorefinery concept, which envisions sugarcane mills as sites that produce fuel, value-added chemicals and steam and electric power, Boethel said.

Sugars from corn, sugarcane and similar sources are converted to ethanol by fermentation, said Donal Day, a researcher at the LSU AgCenter’s Audubon Sugar Institute. LSU AgCenter researchers are looking to other products, such as sugarcane residue, called bagasse, and other vegetative materials that can be converted to sugars and then fermented into ethanol.

The non-food part of plants that can be converted to fuel — primarily ethanol — is cellulose. Cellulose is a polymer chain carbohydrate that can be converted to a form of sugar through a process called hydrolysis. After that, the material can be converted to ethanol through fermentation.

With the right plant and at the right price, Louisiana’s non-producing land could be used to raise biofuel feedstocks without interfering with food production.

Day said the Audubon Sugar Institute’s approach is to develop new technologies that can be integrated into existing sugar mills and take advantage of capital investments, which sit idle most of the year because the sugar-processing season is only about three months long.

He said the LSU AgCenter is evaluating a range of crops to harvest at different times of the year to allow mills to operate year-round. That is in addition to sugarcane, mills could process sweet sorghum and miscanthus, a grass with properties to produce ethanol.

They also could process energy cane, which has been under development at the LSU AgCenter’s Sugar Research Station in St. Gabriel and at the U.S. Department of Agriculture’s Sugar Research Unit in Houma, La., through sugar mills to remove the sugars. Then the remainder would be handled similar to bagasse.

The LSU AgCenter and its USDA and American Sugar Cane League partners released three high-fiber sugarcane plants for biofuel applications in 2007.

“High-fiber canes have the potential for biofuel applications,” said Kenneth Gravois, LSU AgCenter sugarcane breeder and resident coordinator at the AgCenter’s Sugar Research Station in St. Gabriel.

Sweet sorghum is similar to corn but doesn’t produce any grain. The stalks and leaves can be handled in ways similar to sugarcane, with the juice pressed out for fermentation into ethanol and the remainder handled similar to bagasse.

Miscanthus grass is a fourth candidate for ethanol production in Louisiana, Day said. “We could extend mill operations from three months to 12 months a year by using a range of feedstocks for biofuels that can be processed in a sugar mill.

“The technology is there for producing cellulosic ethanol. But it’s not yet on a commercial scale. It depends on economics.”

Although ethanol can be manufactured from sugar, as they do in Brazil, the cost of sugar in the United States makes the practice prohibitive, because sugarcane growers cannot produce sugar cheaply enough to be competitive with other ethanol feedstocks, said Mike Salassi, an economist with the LSU AgCenter.

Salassi conducted a study in 2006 funded by the Office of the Chief Economist in the USDA’s Office of Energy Policy and New Uses to evaluate the economic feasibility of producing ethanol from sugar feedstocks in the United States.

His study concluded cellulosic conversion of biomass into ethanol offers the potential for a wide variety of feedstocks.

From an economics standpoint, a biofuel facility that uses these nonfood feedstocks must pay a grower enough to assure the supply can be available and sustainable, Salassi said. “Whatever crop it is, we have to pay growers a price to cover their costs.”

Biofuel crops may be more dependent on petroleum markets than on traditional commodity markets. Growers would have to understand that the prices they would receive for feedstocks depend on the costs of energy, not the costs of grains.

Salassi said the LSU AgCenter’s role in biomass research is threefold — first, to research the process of converting biomass to fuel; then, to research the production and cultural practices of growing these alternate crops; and finally, to research the costs of producing these nontraditional crops to assure growers can earn reasonable returns on their investments.

This year, for example, LSU AgCenter researchers are planting trial fields of sweet sorghum to learn how to grow the crop profitably. They’ll then pass gathered information on to growers should a market materialize for sweet sorghum as an energy feedstock.