LUBBOCK — Sweet sorghum is grown in the U.S. for cooking and as livestock feed. But the tall plant also has a juicier benefit.
A sugary sap inside the plant's stalk, which can grow as tall as 12 feet, can be turned into a potent biofuel, and experts and companies are studying its potential with hopes that farmers will want to plant more of it.
Ethanol made from the stalk's juice has four times the energy yield of the corn-based ethanol, which is already in the marketplace, unlike sweet sorghum. It produces about eight units of energy for every unit of energy used in its production. That's about the same as sugarcane but four times more than for corn.
"I think it can be a piece of the puzzle" as a biofuel crop, said Danielle Bellmer, executive secretary of the Sweet Sorghum Ethanol Association and an Oklahoma State University researcher studying ways to improve stalk pressing and fermentation methods. "The real issue is it's just not a well-known crop."
Currently about 10 million tons of the grain from the tops of the sweet sorghum stalks are harvested in the U.S., the world's leading grower, but most of the sugar from the stalks goes to make syrup that many people pour on biscuits, for cooking and to feed animals.
However, Global Renewable Energy, LLC has planted two 20-acre plots to conduct tests with an eye toward using the plant for ethanol production.
"The purpose of those are obviously the testing, but we want to bring farmers and investors out," said Ray Coniglio, a spokesman for the Sebastian, Fla.-based company.
Growers in South Texas and South Florida can get two crops a year because of the tropic-like weather. The crop, though, can be grown as far north as Canada. It grows in dry conditions and tolerates heat well.
In Texas and Florida, the second crop doesn't need to be planted; it sprouts from the first harvest, a happening called "ratooning."
"We've found the contents are as good as the first crop," Coniglio said.
Sweet sorghum also spares the environment. Less fertilizer is needed than with corn and as a result there is less water contamination, Coniglio said.
Sweet sorghum differs from grain sorghum, which is grown on about 100 million acres worldwide. Sweet sorghum could be grown on about half of those.
If drought hits, the plant goes dormant temporarily and will begin to grow again when rain comes.
"I think it will add more ethanol to the market," said Morris Bitzer, the executive secretary of the National Sweet Sorghum Producers and Processors Association, which has 500 members in 38 states.
The cost to transport the plant's bulky stalks to a processing plant, although fermentation equipment could change that. The freshly pressed juice must be processed right away, either by beginning the fermentation (into ethanol) or concentrating the sugar to stabilize it, or refrigeration, Bellmer said in an e-mail.
Distillation, which involves removing the water and concentrating the ethanol, occurs after the juice has been fermented to ethanol, she wrote.
Crushed stalks are called bagasse and when compacted into small blocks can be fed to cattle, according to the International Crops Research Institute for the Semi-Arid Tropics, a nonprofit organization that does agricultural research to aid poor dry-land farmers.
The crop has caught the eye of the U.S. Agriculture Department, which along with Texas A&M University is sponsoring a conference on its use as a biofuel in Houston in August.
"I'm excited that they recognize that there are more feedstocks than just corn and switchgrass," Oklahoma State's Bellmer said.
In developing countries across Africa and in India, the grain is also used as food — to make a porridge and a flat bread — though its taste is rather bland, experts said.
"It's basically like their main staple starch," said Mark Winslow, who works with the international institute. Sweet sorghum in those countries that's turned into ethanol is allowing money that used to go overseas to buy oil to remain in rural economies.
Curtis Congleton, a sweet sorghum grower in Versailles, Ky., started growing sweet sorghum in 2000. He had grown tobacco but that industry was "on kind of unstable territory," so he began growing sweet sorghum for syrup on a couple of acres.
The 49-year-old farmer said he's open-minded about other value the plant can provide him.
"Who knows?" he said. "It's interesting about the juice in turning it into fuel."
