U.S. scientists develop drought tolerant sorghum for biofuels

In order to diversify the portfolio of crops grown for the production of biomass and biofuels, scientists at the Texas A&M University's Agricultural Experiment Station (TAES) are breeding a drought tolerant sorghum that may yield between 37 and 50 tons of dry biomass per hectare (15 to 20 tons per acre).

The U.S. has the technical potential to produce about 1.3 billion tons of lignocellulosic biomass that could supply 30 percent or more of the U.S. transportation fuel requirements. But in order to turn this technical potential into real production, new crops are needed and so-called 'second generation' conversion technologies must become competitive. These technologies include the transformation of lignocellulosic biomass into liquids via biochemical and thermochemical processes. Such methods have the promise of converting all of the plant material - not just the grain as is the case with the first generation - into biofuels or directly into electricity.

A drought-tolerant sorghum cultivar is seen as one of the most promising biomass crops to this end. The United States currencly grows approximately 20 million acres of the plant which could provide 25 percent of the country's long-term goal for biofuels. The prospects for accelerated development of sorghum as a premier source of biofuels are excellent.

Sorghum is a highly diverse grass species originating from Africa and Asia, where it is grown on a large scale, often by subsistence farmers in semi-arid regions such as the Sahel. In the U.S. it is currently grown for grain and forage.

But a team of agricultural research centers, including the Institute for Plant Genomics, the USDA Agricultural Research Service and the Texas Agricultural Experiment Station is designing [*.pdf] a sorghum for high sugar and cellulosic biomass production for ethanol and other biofuels. 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/biofuels design will aid in developing related biofuels crops such as corn, sugarcane, and switchgrass.

The research process adopted includes the following steps:

• Sorghum genetic resources will be screened for sources of improved yield and biomass composition (sugar content, cellulose, hemicellulose, lignin) optimal for biofuels production.
• Sorghum germplasm, traits and genes that improve biomass yield, bioenergy composition, and drought tolerance will be identified and pyramided into cultivars and elite hybrids.
• Advanced material will be tested to identify cultivars that have optimal biomass-to-biofuels conversion properties and agronomic production parameters.
• Logistical approaches will be optimized for the harvest and transport of sorghum to facilities for biofuels and bioenergy production.
• Production of high yielding, drought-stress tolerant sorghum bioenergy cultivars and hybrids specifically engineered to meet the needs of the U.S. biofuels industry
• Generate information and technology useful for improving corn, sugarcane, switchgrass, and other grass species for biofuels production

Rapid breeding
The breeding process of the new sorghum lines is part of a conventional breeding program and does not involve genetic engineering. In a conventional breeding program, parent plants are selected for specific traits, then cross-pollinated with other varieties to strengthen those desired traits. The process is repeated over several growing seasons until the plant with the desired traits breeds true:
bioenergy :: biofuels :: energy :: sustainability :: sorghum :: ethanol :: cellulose :: biomass :: plant breeding ::

Agronomists have essentially used these same breeding techniques for centuries, and all modern cultivars, from improved landscape plants to row crops, have been developed this way. The process is painstaking, and the development of a new variety takes from 8 to 10 years or longer. Much of that time is spent just identifying which parent plants carry the gene that is responsible for the desired trait.

However, plant geneticists at the Norman E. Borlaug Center for Southern Crop Improvement are helping by applying the latest techniques to map the chromosomes of the sorghums. Using these genetic maps, the plant breeders hope to bypass many of the field trials to identify parent plants with the desired traits. With this technique, they expect they can cut the time it takes to further develop high-tonnage sorghum by more than half. As a result, it a drought-tolerant sorghum is expected to be ready for farmers in a few years rather than a decade.

The Texas Agricultural Experiment Station’s sorghum biofuels design team brings together expertise in production systems, breeding, genetics, and genomics that will accelerate developing advanced sorghum bioenergy cultivars for the Texas and U.S. biofuels industry.

Sorghum elsewhere
Outside the U.S., sorghum has been of interest to the bioenergy community for quite a while. In Europe the crop is being improved with the aim to use it as a dedicated feedstock for the production of biogas. German researchers from the University of Applied Sciences in Bingen (South-West Germany), have been collecting and planting 160 different sorghum varieties from Africa and Asia in two test fields. Already in 2005, the agricultural extension services of the state of Rheinland-Pfalz did the same with two promising varieties and in Bingen, Emmelshausen and Herxheim near Landau, another 20 different sorghum species were grown in experimental plots. The goal of this research is to study whether the crop can be made to adapt to the dry but relatively warm climate of South-West Germany, where it can be grown on land less suitable for maize, the major biogas crop in the country.

Likewise, the North Sea Bioenergy partnership, a project to stimulate the use of bioenergy in Belgium, the Netherlands, Scandinavia and the Eastern part of the UK, is experimenting with both sorghum and sudangrass hybrids for the production of biogas. Experiments involving co-digestion of the hybrids with manure in anaerobic fermenters have been encouraging (one hectare of the crop results in around 4000 liters of petro-diesel equivalent biogas).

Most importantly, the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) has launched a pro-poor biofuels initiative, linking small farmers of drylands of the developing countries with the global biofuel revolution via a newly developed cultivar of sweet sorghum that yields unprecedented levels of ethanol. The crop meets the main needs of the dryland farmers - they do not require much water, can withstand environmental stress, are not that expensive to cultivate and allow a stream of products (grain, stalks, sugar) that makes it possible for farmers to combine food and fuel production (earlier post).

More information:
Texas Agricultural Experiment Station - Bioenergy Initiative: Designing Sorghum for the U.S. Biofuels Industry [*.pdf] May 21, 2007.

Bioenergy initiatives at Texas A & M University.

Check Biotech: Texas A&M team to add a 'grain of common sense' to biofuel optimism - May 21, 2007.

Norman E. Borlaug Center for Southern Crop Improvement website.