Grading Grasses on the Cheap

Researchers use near-infrared sensing to measure yield in switchgrass
By Holly Jessen | October 18, 2011

Using near-infrared sensing (NIRS) to predict ethanol yields for corn isn’t new. In a different twist, however, USDA Agricultural Research Service researchers figured out a way to use the same system to measure the potential of perennial grasses.

The real bonus is that grading grasses costs only about $5 a sample with NIRS. Compare that to $300 to $2,000 per sample using conventional analytical methods, which utilize chemistry laboratory tests on each plant component, from cell-wall sugars to starch and more. NIRS, on the other hand, uses wavelengths of reflected light to determine sample composition. “Instead of running weeks of analyses, a sample can be analyzed in less than 5 minutes using NIRS analyses,” geneticist Ken Vogel tells EPM. “The main cost is sample preparation which also has to be done for wet-lab or conventional analyses and equipment costs.”

Five USDA researchers, including Vogel, a University of Nebraska researcher, used NIRS to measure 20 components in switchgrass, such as cell-wall sugars, soluble sugars and lignin. That information was used to determine 13 traits, including how efficiently the sugars will be converted to ethanol. Hexoses, or six-carbon sugars, were used as the basis to predict actual ethanol yields. With improved conversion technologies, additional ethanol can be produced from pentose or five-carbon sugars, meaning the NIRS method can be used to estimate total potential yield if all sugars were converted to ethanol. “It will now be possible to determine the best switchgrass cultivars and management practices, Vogel says. “The technology can be expanded to other species but it will require additional comprehensive work.”

The NIRS equations developed in this study are already being used to develop new cultivars in breeding programs in Nebraska and Wisconsin. It could also be used to identify methods for growing grasses for the best ethanol yields. ARS and the Near Infrared Spectroscopy Consortium have a cooperative agreement to get the switchgrass composition calibrations out to other public and private laboratories researching switchgrass.  

—Holly Jessen