Slow Pyrolysis Kinetics of Two Herbaceous Feedstock: Effect of Milling, Source, and Heating Rate

Kinetic models for pyrolysis of switchgrass and tall fescue were obtained using thermogravimetric analysis and a newly proposed parameter-extraction methodology. The optimization strategy demonstrates the use of the Akaike information criterion for the statistical identification of the number of distinct processes and a robust global search method. The effects of sample mass, heating rates, particle size, and crystallinity index on the kinetic parameters of each feedstock were considered. For whole biomass particles, the kinetic parameters of the cellulose component was found to be similar to that of pure microcrystalline cellulose. Further particle size reduction through extensive milling reduced the activation energy of cellulose by 48%. X-ray diffraction indicated that the cellulose fraction of highly milled whole biomass becomes largely amorphous and that the amorphization of the cellulose, not the particle size reduction, is likely responsible for the decrease in activation energy.