Investigating Kinetic and Thermodynamic Parameters in the Pyrolysis of Sheep Manure Using Thermogravimetric Analysis

The kinetics of the pyrolysis process of sheep manure were investigated using Thermogravimetric Analysis in this work. It was heated at 30^°C to 900 °C with a heating rate of 10 °C/min. There are two stages of mass degradation, namely dehydration and devolatilisation. The temperature of the dehydration stage is 30–140 °C while the devolatilisation stage is 210–900 °C. However, mass degradation decreases at temperature >500 °C until it reaches 900 °C. It indicates that most of the volatile matter has disappeared at this temperature. The devolatilisation stage includes the decomposition of hemicellulose and cellulose (210 °C–900 °C) and lignin (>590 °C). The calculated activation energy from Friedman's non-conversional method is 21.32 kJ/mol, and Coats-Redfern is 26.20 kJ/mol. At the same time, the frequency factor value is 9.94×10¹⁸ 1/s for Friedman and 3.42×10¹⁸ 1/s for the Coats-Redfern method, indicating that sheep manure's pyrolysis process is a complicated phenomenon. The estimated activation energy value is then used to calculate thermodynamic properties, e.g., Gibbs free energy, enthalpy, and entropy.