Effect of Harvest Timing on the Quality of Switchgrass for Biofuel: Changes in Lignocellulose and Potential Energy Production.

Bioenergy is important in the United States to improve energy security and environmental integrity. There is a strong need to raise production of biofuels to cope with rising energy costs and the risk of global warming because of fossil fuel combustion. In 1991, the use of switchgrass for bioenergy was recommended by the U.S. Department of Energy. Switchgrass is a promising feedstock due to its high productivity, low input requirements and positive environmental effects. To produce ethanol from switchgrass, high levels of cellulose and low levels of lignin are ideal but these levels change during the growth of the plant.  Determination of the optimum date of harvest of switchgrass is therefore important to provide the best feedstock.  The objective of this study was to identify this optimum date by harvesting different switchgrass plants at multiple times from a one-cut system during the 2011 and 2012 growing seasons. Samples were analyzed for specific characteristics, such as lignocellulosic content that would affect the overall production and efficiency of ethanol from switchgrass. In general, cellulose and hemicellulose concentrations increased through July and then remained relatively constant from August to November while the lignin concentrations continued to increase during the entire growth period studied (June – November). Further results, including energy content and total carbon, and their implications for a specific optimal harvest date will be discussed.