Spectral Characterization of Switchgrass for Biomass Energy and Biofuel Quality.

Switchgrass (Panicum virgatum L.) a native, perennial, warm-season C₄ grass, is a potential renewable biomass energy crop for the Northern Great Plains regions, including North Dakota.  Switchgrass biomass can be burned directly to generate electricity or heat space, or can be converted into biofuel products.  When grown for energy purposes switchgrass management practices must take into account both, biomass production and biofuel quality.  Monitoring switchgrass and acquiring information about its growth throughout the growing season is important to optimize crop management; either it is to assess yield quality and quantity, to take crop management decision according to the limitation of the system (water vs. fertilizer, harvest time, etc), or to get information on energy quality. There is a need to characterize switchgrass spectral signature throughout a cultural cycle, to analyze switchgrass seasonal patterns, and to investigate the potential of remote sensing data to estimate some important switchgrass variables for biomass production and bioenergy purpose. 

The goal of this study was to characterize switchgrass spectral signature throughout the growing season. Switchgrass spectra were collected using a hand spectroradiometer (ASD-FieldSpec Pro) on a weekly basis at the site of 3 experimental switchgrass plots of the North Dakota State University, Fargo, ND, with three Nitrogen (N) treatments, one by plot: 0 kg/ha, 75 kg/ha, 150 kg/ha.  Significant differences between the three N treatments for switchgrass reflectance were observed throughout the growing season.  Various hyperspectral vegetation indices, such Simple Ration and NDVI, Cellulose Absorption Index, Normalized Difference Lignin Index, and Normalized Difference Nitrogen Index were examined.  The potential use of spectral information to characterize switchgrass biomass with suitable quality for use with advance technologies for biomass combustion or biochemical conversion is discussed.