When it comes to developing a biofuel industry based on sugar-producing crops such as sweet sorghum, Arizona – and much of the desert Southwest – has what it takes.

Sunlight enables crops to grow year-round, and fields in the Southwest thrive during the wintery off-seasons experienced by colder parts of the country. For example, 95 percent of the U.S.' homegrown winter vegetables come from Yuma County in western Arizona. "Nowhere else can grow vegetables during that time of the year," said Mark Riley.

The extended growing season of the Southwest provides a niche to produce biofuel crops off-sequence from when other parts of the country are growing corn, said Riley. Biofuels could not only provide an ecological source of fuel for the future, but also could create a sustainable industry for Arizona and the desert Southwest.

Said Ray: "We're looking at rural development. If you have a little industry in this area, you need people to run the processing plant. That means jobs. That means bringing money back into these communities. It's always a much bigger picture for what we're looking at in the long run."

While crops in Arizona may benefit from comparatively mild winters, they must be able to contend with the lack of water that goes hand in hand with the warmer climate. And perhaps none is better suited to grow well in arid environments than sweet sorghum.

Master's student Tania Martinez-Cruz is conducting research on the four varieties of sorghum planted at Red Rock Agricultural Research Center.

"In addition to looking at the maturation rates of different varieties, she's looking at the water requirements as well and the main thrust of her study is to see how much water each variety requires and how well it responds to stress," said Slack.

"By stressing the plant we had no negative effect on the amount or quality of the sugar. Significantly reducing the amount of water didn't reduce the yield. At the campus agricultural center, we irrigate with treated sewage effluent as well, and there's no negative effects."

Since sweet sorghum is not intended for human consumption, it can be irrigated with treated wastewater, which saves on both water usage and fertilizers, as it provides many of the nutrients the crop needs.

Of course, the harvest is not without setbacks. "We are typically getting in our harvest now a brix reading of 15-18, which means 15-18 percent is sugar," said Slack. "When they convert the starch in corn into sugar, which they have to do before they can refine it, they have brix of 25-30."

"We're learning that maybe we're not growing it quite right, and maybe we're not harvesting at quite the right time," said Slack. "We've learned quite a lot this year."

And all learning is progress. The scientists already are refining their plans for next year's experimental sorghum harvest.

"We would like to have one or more varieties that would allow us to have staggered planting and staggered harvest dates," said Slack. "The juice doesn't keep very well; we can't store it. So we'd like to be able to harvest it directly and continuously provide it to the energy plant over time without storing it."

The sorghum harvest is part of a multidisciplinary effort at the UA to develop sustainable biofuel crops for Arizona and the desert Southwest. The sorghum-harvesting project is funded by the U.S. Department of Energy and Martinez-Cruz's research is funded by the Cecil H. Miller, Jr. Families endowment.

"The goal of the project, of all these projects, is to have a commercial product," said Ray. "The end goal is to give back to folks who have given to us through funding and in other ways."

UA biofuels research is funded by the U.S. Department of Agriculture's Agricultural Research Service, the U.S. Department of Energy, the Sun Grant Initiative from the U.S. Departments of Energy, Transportation and Agriculture and the UA's College of Agriculture and Life Sciences.