Sweet sorghum is a sturdy grass grown in the United States for livestock forage and for sugar for making syrup and molasses. But several attributes make it uniquely suited as a bioenergy crop in the Southeast.

It is drought tolerant; adapts to diverse growing conditions; has low nitrogen fertilizer requirements; produces abundant biomass; can be rotated with cotton and peanuts; and is compatible with equipment used to harvest, transport, and mill sugarcane.

It also contains soluble sugar that can be fermented directly into biofuel.

The fiber (or bagasse) that remains after the sugar juice is extracted can be burned to generate electrical power — a strategy that South American sugarcane-producing countries are expanding.

"Sweet sorghum has the potential to augment biofuel and electricity production from cultivated sugarcane and lengthen the season for bioenergy production," says plant geneticist Jeff Pedersen, a former ARS scientist who was based in Lincoln, Neb., and collaborated on sweet sorghum studies for the Southeastern region before he retired in 2011.

In Tifton, Anderson and other researchers are trying to identify desirable sweet sorghum genes and understand their functions so they can improve on commercial varieties. The researchers selected 117 sweet sorghum genotypes from the ARS sorghum germplasm collection in Griffin, Ga., where sorghum seeds from around the world are kept. 

They tested the genotypes for 2 years, evaluating their ability to mature quickly and resist fall armyworm and anthracnose, a common fungal disease.

 The results are providing much-needed guidance to a growing biofuel industry, showing that sweet sorghum has tremendous potential as a biofuel crop for Southeast growers.

The work also boosts efforts among breeders by identifying sorghum varieties that will make good candidates for developing future high-seed-yielding hybrid varieties. 

For all of sweet sorghum's bioenergy promise, there's still much work to be done, says Pedersen.

In his estimation, sweet sorghum's long-term future as a bioenergy crop hinges on the ability of the seed industry to rapidly generate and deliver new elite hybrids — using dwarf seed-parent lines — that produce high yields of seed.

Besides enabling laboratory and field research, having sufficient seed stocks "is going to be essential to getting the bioenergy industry going," says Pedersen.

The sweet sorghum improvement research work is one of several examples of work being done by researchers in Tifton to produce market-ready biofuel feedstocks.

Environmental concerns are also a high priority being addressed by the Southeast Watershed Research Laboratory, in Tifton. "The lab is looking at potential effects on water quality, runoff, water-use efficiency, and carbon-nitrogen pools in soils and plant tissue as biomass feedstock species are incorporated into Southeast agricultural systems," Anderson says.

For additional information go to http://www.ars.usda.gov/is/AR/archive/sep12/biofuels0912.htm.