Pyrolysis kinetics of wildland vegetation using model-fitting methods

Slow-heating pyrolysis experiments of 14 plant species native to forests in the southern United States were conducted in a TGA to find the kinetic parameters for slow pyrolysis of all live and air-dried plant samples. Kinetic coefficients were determined from the data using model-fitting methods, resulting in single kinetic parameters for the entire pyrolysis process which can be used by wildland fire modelers. The model forms explored here are a simple one-step model and single and multiple reaction distributed activation energy (DAE) models. The mass loss and derivative mass loss data were fitted simultaneously at heating rates of 10, 20, and 30 °C min⁻¹ to find kinetic parameters for these model forms. The multiple-reaction DAE model gave the best fit to the pyrolysis data at multiple heating rates when multiple peaks were observed. The multiple pyrolysis peaks were attributed to decomposition of hemicellulose, cellulose, and lignin, based on literature observations for biomass. The order of activation energies for pyrolysis of all plant species indicated that hemicellulose and extractives decompose more readily than cellulose and finally lignin.