Thermal decomposition aspects and kinetics of pyrolysis of garlic stalk

Agricultural crop residues are at the center stage of biomass utilization in view of their huge potential in the production of bio-oil and in turn bio-based chemicals. The present investigation aims to study comprehensive physico-chemical characteristics, thermal decomposition behavior, and kinetics of pyrolysis of garlic stalk using thermogravimetric analyzer at four heating rates (5, 10, 15, and 20°C/min). High volatile matter (71.2%) together high carbon (43.1%) content indicates prospective potential of garlic stalk for deriving bioenergy from pyrolysis process. Thermogravimetric analysis showed that the major mass loss in the form of devolatilization of volatile matter in garlic stalk was found to occur in the temperature range of 220 to 420°C. Model-free (FWO and KAS) and model-based (Coats-Redfern) methods were used to determine the kinetic parameters. The activation energy (94.54 kJ/mol) obtained from FWO was found to be in very good agreement with activation energy (95.11 kJ/mol) obtained from KAS method, which substantiates reliability of the obtained results. Further, Coats-Redfern method was used to determine the pre-exponential factor using the activation energy obtained from KAS and FWO methods. The experimental data for pyrolysis of garlic stalk was found to fit best with the contracting volume model (G3) from among various models.