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.