Characterization of Switchgrass, Cellulose, Hemicellulose and Lignin for Thermochemical Conversions

There is much interest in using switchgrass as a potential biomass feedstock to produce energy and fuels. Thermochemical conversions, such as gasification and pyrolysis, are efficient ways of converting switchgrass into energy and fuels. The goal of this study was to investigate reaction kinetics and volatiles evolved during thermo-chemical conversion of switchgrass under nitrogen and air conditions, and contributions of cellulose, hemicellulose and lignin components. To accomplish this, a thermogravimetric analyzer (TGA) coupled with a Fourier Transform Infrared Spectrometer (FTIR) was used. Weight loss kinetics and gas evolution profile of switchgrass, and its components (cellulose, hemicellulose and lignin) were analyzed under inert and oxidizing conditions at heating rate of 50 degrees C min(-1). Significant weight loss of switchgrass occurred in the temperature range of 220 to 420 degrees C in nitrogen atmosphere and 220 to 390 degrees C in air atmosphere depending on heating rate. The weight loss of the components occurred in different temperature ranges and also the reactivity of each component was different from one other. Among the components, cellulose decomposed sharply in narrow temperature range with the highest mass loss; whereas lignin decomposed in a wide temperature range with the lowest mass loss. The gases CO2, CO and CH4 were identified as major end products during switchgrass decomposition in inert condition. As compared to lignin, cellulose and hemicellulose decomposition yielded higher CO and CO2. However, most of the CH4 yield was due to lignin decomposition in inert condition.