Two new studies, each independent of the other, point to sweet and biomass sorghum, and sweet sorghum juice sugars, as potential dark horses in the search for better and more cost-effective methods and materials of biofuel production.
Last month, a collaborative study found a significant increase in ethanol production from a combination of sweet sorghum juice and corn mash. Sorghum Checkoff announced the results of a benchmark study that was conducted in collaboration with the National Corn-To-Ethanol Research Center at Southern Illinois University-Edwardsville.
The study evaluated the effects of various amounts of sweet sorghum juice in corn mash on ethanol yield under conditions that are similar to those used in the fuel ethanol industry. Sorghum sugar juice was successfully used as a replacement for process water in the study, demonstrating the potential for a corn ethanol plant to increase production above nameplate capacity by incorporating sweet sorghum juice sugars.
In the second study, it was determined sweet and biomass sorghum would meet the need for next-generation biofuels that would be environmentally sustainable, easily adopted by producers and could take advantage of existing agricultural infrastructure.
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Scientists from Purdue, the University of Nebraska-Lincoln, University of Illinois and Cornell University conducted the study. In a report published in the journal Biofuels, Bioproducts & Biorefining, researchers believe sorghum, a grain crop similar to corn, could benefit from the rail system, grain elevators and corn ethanol processing facilities already in place.
"The Midwest is uniquely poised to get the biorefining industry going on cellulose," reports Nick Carpita, a Purdue professor of botany and plant pathology. "As we move to different fuels beyond ethanol, the ethanol plants of today are equipped to take advantage of new bioenergy crops."
According to a study report, scientists say sorghum should be a larger part of a national bioenergy plan. Cliff Weil, a Purdue professor of agronomy, said some types of sorghum would require fewer inputs and could be grown on marginal lands.
"In the near future, we need a feedstock that is not corn," Weil reported in the report. "Sweet and biomass sorghum meet all the criteria. They use less nitrogen, grow well and grow where other things don't grow."
Researchers say one of the many advantages of sorghum production as an energy crop is it would minimize inputs such as nitrogen. Carpita said corn, which has been bred to produce a maximum amount of seed, requires a lot of nitrogen. But sorghum could be genetically developed in a way that maximizes cellulose, minimizes seeds and, and subsequently minimizes inputs.
"If you're just producing biomass and not seed, you don't need as much nitrogen," Carpita said.
Fits in rotation
Farmers may also be more willing to grow sorghum he says, a crop they're familiar with, because it is an annual, compared with perennials such as switchgrass or Miscanthus, that would take up a field for a decade or longer.
According to a report published this week in Science Daily, sorghum would fit in a normal crop rotation with food crops rather than tying up valuable cropland.
"If we're talking about planting switchgrass, that's a 15-year commitment," said Nathan Mosier, a Purdue associate professor of agricultural and biological engineering. "You can't switch annually based on the economy or other factors."
Researchers say an added benefit to bringing sorghum back as a biofuel crop would be that it could have a positive economic impact on poorer rural areas of the country.
In the first study, sweet sorghum juice was used as a replacement for process water. The researchers found that adding sweet sorghum juice to corn mash significantly improves the ethanol yield without requiring additional nutrient or yeast inputs.
Results showed that with 50 percent sweet sorghum juice, a 12 percent increase in ethanol yield versus control can be expected without any increase in viscosity, without requiring additional enzymes and without overwhelming the yeast with too much sugar in the system.
The theoretical yield could be as high as 23 percent above the control if all the water were substituted with sorghum juice.