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In the U.S. corn is by far the largest carbohydrate source used to produce ethanol. But for a wide range of reasons, scientists are looking at alternative feedstocks. Sorghum has been identified as a promising candidate both in the U.S. and in the developing world.

Dr. Bob Avant, program manager for the Texas Agricultural Experiment Station's bioenergy initiative, stands in front of tall sorghum being bred for biofuel production in College Station. Pictured front are hybrid sorghum varieties used in conventional cross-pollination with tall sorghum. The research effort is led by Dr. Bill Rooney, Experiment Station plant scientist. Credit: Texas Agricultural Experiment Station, photo by Jerrold Summerlin.

The tropical grass species narrowly related to sugar cane is robust, needs relatively small amounts of water and is being bred to become drought-tolerant and more sugar-rich. It can be grown and processed following a model that resembles the highly successful sugarcane ethanol industry in Brazil.

Dr. Bill Rooney, a Texas Agricultural Experiment Station researcher, is one of the scientists who hopes to contribute to this new vision by producing a high-tonnage and sugar-rich variety that could soon be used for bioenergy. His test field at the College Station shows a sorghum crop towering 12-feet high.

Sorghum as a source of biofuels had some of the U.S. top scientists at the recently held Great Plains Sorghum Conference enthusiastic about its future. The good thing is that the farmers who will have to grow the crop have joined the scientists in their optimism. If modeled after the sugarcane industry, a tall sorghum variety producing 20-plus tons to the acre transported to a processing plant within a 40-mile radius would economically viable [50 tons per hectare and a radius of 65 km]. The sugarcane industry has been doing this for a long time. What we're not saying is switchgrass or corn isn't a viable crop, but if we can grow sorghum, it's worth giving a serious look. We believe this paradigm is happening and will happen. - Dr. Bill McCutchen, deputy associate director of the Experiment Station of Texas

Sorghum can play a pivotal role in the biofuel future because the crop needs far less water than corn while producing more biomass. But like corn, it can fit into first generation starch and sugar based conversions as well as in next-generation cellulosic ethanol pathways. And as in the Brazilian model, in a first instance, ethanol can be produced from the sugar of the crop, while its biomass residues (bagasse) could be used as a solid biomass feedstock for the production of green power at the conversion plant.

Sugar and Water

Dr. Rooney's research has focused on improving sorghum as a bioenergy feedstock. The sorghum breeding program in College Station changed about four years ago, he told a group of researchers at the conference. On the side, they began working on bioenergy and sweet sorghums. It's meanwhile evolved into a project that has consumed a good portion of time.

Like sugarcane, sorghum can be converted into ethanol with relative ease. The tall sorghum trials in College Station boast superior genes from hybrid sorghums. Specifically, Rooney is evaluating the sorghum's sugar content. He wants to develop a high-sugar hybrid, but this means he needs have to have high levels of sugar on both sides of the parent.

Using cross-pollination of selected hybrid varieties, Rooney will soon establish a superior, high-yielding plant variety commercially viable for biofuel production. He's also attempting to include genetic traits that withstand periods of drought:

The tall sorghum trials are also being conducted in Weslaco and Lubbock. Another component of the research is harvesting. Rooney and other scientists are evaluating composition and yield both for animal feed and ethanol production, he said. One of the things they are looking at is to see how long can you leave the crop in the field.

Sugarcane model

The state of Texas is positioned to help meet the challenge of producing 1 billion tons of biomass needed to replace 30 percent of the America's petroleum, says Dr. Bill McCutchen, deputy associate director of the state's Experiment Station. Texas already is one of the largest biomass producers in the nation.

Using plant cellulose from Texas crops, such as sorghum, not only "has incredible potential, but also big potential for by-products", McCutchen told the conference.

According to McCutchen, sorghum produces more biomass than corn, using 33 percent less water. He thinks sorghum may have been overlooked as a potential biomass product.

If modeled after the sugarcane industry, a tall sorghum variety producing 20-plus tons to the acre transported to a processing plant within a 40-mile radius would economically viable [50 tons per hectare and a radius of 65 km].

The sugarcane industry has been doing this for a long time, McCutchen says. "What we're not saying is switchgrass or corn isn't a viable crop, but if we can grow sorghum, it's worth giving a serious look. We believe this paradigm is happening and will happen."

But how to incorporate these crops into an existing portfolio of feedstock crops and other cash commodities in Texas is a challenge that lies ahead. "One of the things we envision is we want to be able to grow dedicated biomass crops for fuel within a diverse system," he added.

The design of sorghum is being aided by the U.S. Department of Energy's sorghum genome sequencing project and technology platforms developed by funding from the National Science Foundation. Acquiring fundamental knowledge about optimal sorghum biomass and biofuels design will aid in developing related biofuels crops such as corn, sugarcane, and switchgrass.

 

References:
Texas A&M University System Agriculture Program: Sorghum Producers Optimistic About Biofuel Potential - July 26, 2007.

Texas Agricultural Experiment Station: Designing Sorghum for the U.S. Biofuels Industry [*.pdf].

Bioenergy and biofuels research at the Texas Agricultural Experiment Station.

Source:
http://news.mongabay.com/bioenergy/2007/07/researchers-and-producers-optimistic.html