Pyrolysis kinetics and thermodynamic parameters of macroalgae Cladophora glomerata based on multi-step devolatilization to assess its bioenergy potential

Cladophora biomass, through pyrolysis, has great potential for utilization in bioenergy applications and biochar formation. Here, we performed a detailed kinetic and thermodynamic evaluation of the slow pyrolysis of Cladophora glomerata. The pyrolysis was performed in a thermogravimetric analyzer using non-oxidative inert conditions of nitrogen gas at a temperature range of 25–800 °C under three low heating rates (5, 10, and 20 °C min⁻¹). In the pyrolysis of C. glomerata, three different stages were observed, showing the complex nature of its biomass. The kinetics were obtained through isoconversional methods, where the average activation energies were in the range of 159.5–169.5 kJ mol⁻¹, 221–239 kJ mol⁻¹, and 157–168 kJ mol⁻¹ for stages 1, 2, and 3, respectively, each with a coefficient of determination (R²) above 0.9. The average values of change in enthalpy (ΔH) were 155.36 kJ mol⁻¹, 217.83 kJ mol⁻¹, and 150.08 kJ mol⁻¹ for stages 1, 2, and 3, respectively, while the average values of change in Gibb’s free energy (ΔG) were 169.81 kJ mol⁻¹, 179.90 kJ mol⁻¹, and 273.42 kJ mol⁻¹ for stages 1, 2, and 3, respectively. Thermodynamic analysis of the slow pyrolysis of C. glomerata shows that it is an endothermic, non-spontaneous process that proceeds in the direction of producing bioenergy.