Near-infrared analysis allows plant breeders and biorefiners to rapidly measure the composition of a biomass sample.
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Researchers at the United States Department of Agriculture’s Agricultural Research Service (USDA-ARS) have found that genetic, management, storage, and environmental factors affect the chemical composition of switchgrass samples. Using a database of 100 samples, they are constructing a robust near-infrared (NIR) calibration for switchgrass that can be used, ultimately, for other warm-season perennial grasses.
The initial NIR calibration for switchgrass appears to be accurate for measuring 23 plant properties, including cell wall components and soluble sugars. The final NIR calibration will be used for breeding improved bioenergy crop lines and will eventually be released to biorefiners to be used commercially in both thermochemical and biochemical conversion processes.
Knowledge of biomass composition is critical in order to breed improved bioenergy crops. This knowledge also enables biorefiners to rate the quality of biomass delivered to their factory gates, which bears directly on the feedstock’s performance and conversion efficiency in the processing facility.
Laborious wet chemistry methods precisely measure various carbohydrates, lignin, waxes, and other chemical properties. However, analysis time per sample is slow—on the order of weeks—and therefore impractical for characterizing thousands of samples for breeding purposes or for rating delivered biomass while a delivery truck waits to unload. The solution is to scan the samples with NIR, which analyzes a sample in seconds in a simple and nondestructive way.
By adapting wet chemistry methods, Bruce Dien and Victoria Nguyen of the USDA-ARS analyzed the chemical composition of more than 100 samples that were supplied by their colleagues Robert Mitchell, Michael Casler, and Kenneth Vogel. Akwasi Boateng of the USDA-ARS is processing an identical sample set for pyrolysis conversion to biofuel. Vogel and Boateng are also analyzing the samples for elemental constituents and forage quality measurements.
The data set, which builds upon previous research by Hans Jung, former USDA-ARS researcher, will eventually be analyzed to correlate chemical composition with pyrolysis results and to construct an NIR calibration by Robert Mitchell and Michael Casler.
Switchgrass composition varies widely, depending on genetics, management, and environmental factors. Knowledge of composition is important because it directly affects product conversion yields and the reaction conditions for optimal processing. NIR offers an accurate measurement of biomass samples within minutes.
A rapid and inexpensive method for analyzing chemical composition of switchgrass and other warm-season grasses will enable effective plant breeding of improved bioenergy crop lines. It will also help commercial biorefiners to efficiently and accurately grade delivered biomass right at the factory gate.
Contact Dr. Bruce Dien, lead scientist, Bioenergy Research Unit, ARS, Peoria, IL Bruce.Dien@ars.usda.gov, 309-681-6270
CenUSA Bioenergy is a coordinated research and education effort investigating the creation of a regional system in the Central US for producing advanced transportation fuels from perennial grasses on land that is either unsuitable or marginal for row crop production. In addition to producing advanced biofuels, the proposed system will improve the sustainability of existing cropping systems by reducing agricultural runoff of nutrients in soil and increasing carbon sequestration.