Potential Biofeedstock: Sorghum
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| Sorghum. Photo Courtesy Peggy Greb, USDA Agricultural Research Service, Bugwood.org |
Sorghum is one of the world’s leading grain crops and is second only to corn in U.S. bioethanol production. In 2006, roughly 15% of the U.S. grain sorghum crop was used in ethanol production, generating the same yields per bushel of grain as corn. As sorghum produces more biomass than corn, it’s also a prime feedstock candidate for cellulosic ethanol production.
Although sorghum is thought to be primarily an annual plant, several related species are rhizomatous and perennial. Such a transition from an annual to a perennial has already occurred with sugarcane, which is a close cousin of sorghum and currently the leading crop for biomass production worldwide.
Other characteristics in sorghum’s favor are its low water (33% less than corn) and fertilizer requirements, tolerance to heat and drought, high biomass yield, and great genetic diversity. Furthermore, as a high energy capturing C4 crop, sorghum is well adaptive to many environmental extremes.
One trait of particular interest is the sweet sorghum trait, which results in the accumulation of fermentable sugars in the stem juices. Also of interest is the brown midrib trait, which changes the color and chemical composition of the vascular tissue, resulting in higher yields of fermentable sugars.
Applied genomics is expected to enhance these tendencies, as well as further increase sorghum’s tolerance to drought and other environmental conditions that limit productivity, especially on marginal land.
References
McCutchen, Bill. “Plant
Biotechnology’s Role in Feedstock Engineering: Positioning Sorghum
as an Energy Crop,” Texas A&M University. See also the Texas
A&M Agricultural and Engineering BioEnergy Alliance.
“Sorghum and Switchgrass in Biomass Ethanol Production,” National Sorghum Producers.
“Why
Sequence Sorghum?” Joint Genome Institute, U.S. Department of
Energy.
