Kinetic and thermodynamic study of finger millet straw pyrolysis through thermogravimetric analysis

Pyrolysis kinetics of finger millet straw (FMS) was studied using a thermogravimetric analyzer under N2 environment. Physico-chemical characteristics of FMS were comparable with the established pyrolysis feedstocks. FMS thermally decomposed in three stages: drying, active pyrolysis, and char formation resulting in 70.37% overall weight loss. Average activation energy determined by Friedman and Starink methods was 177.80 and 172.18 kJ mol-1, respectively. Frequency factor was found to be in the range of 108 to 1029. Reaction pathway followed diffusion, nucleation, and order-based mechanisms. The pyrolysis of FMS was characterized by empirical modeling and predicted well with model adequacy of 97.55%. Thermodynamic parameters (Delta G and Delta H) revealed the non-spontaneous and endothermic nature of FMS pyrolysis. The biochar obtained at multiple heating rates were characterized for its physicochemical, functional, and morphological characteristics. The kinetic and thermodynamic analyses illustrate the feasibility of exploiting finger millet straw as a pyrolysis feedstock to derive biofuels.

Automated summary

The pyrolysis kinetics of finger millet straw was studied using a thermogravimetric analyzer under N2 environment, with the average activation energy determined to be around 177.80 kJ mol-1. The empirical modeling of the pyrolysis process showed a high model adequacy of 97.55%, indicating the feasibility of exploiting finger millet straw as a pyrolysis feedstock for deriving biofuels.