Pyrolysis kinetics, thermodynamics, and reaction performance of wheat straw and water hyacinth using TGA-DTG analysis: Bioenergy potential in Ethiopia

The kinetics and thermodynamics of biomass pyrolysis are crucial for its design, optimization, and industrial application. In this study, proximate analysis, together with higher heating value (HHV) and kinetic and thermodynamic studies of water hyacinth (WH) and wheat straw (WS) pyrolysis were performed. Nonisothermal thermogravimetric analysis (TGA) at heating rates of 15, 20, and 25 degrees C min-1 were employed to investigate their pyrolysis kinetics experimentally. Detailed results from the proximate analysis and HHV measurements for both biomasses were documented and analyzed. Iso-conversional kinetic analysis revealed that the effective activation energy varied significantly with the reacted fraction. For WS, the average activation energy values were 63.67 kJ mol-1 and 45.74 kJ mol-1 based on the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, respectively. For WH, the corresponding values were 118.58 kJ mol-1 and 114.09 kJ mol-1.The Coats-Redfern model demonstrated that the TGA data obtained in an inert environment were best described by a second-order reaction mechanism and the 'D3c' three-way diffusion model. Thermodynamic analysis indicated that the pyrolysis of WH and WS is not spontaneous and requires external energy input for thermal decomposition. Both processes were identified as endothermic, with reactivity increasing as pyrolysis advanced.The comprehensive pyrolysis index (CPI) increased with higher heating rates, suggesting that elevated heating rates were more favorable for the pyrolysis of these biomasses. These findings contribute to a better understanding of the reaction mechanisms and highlight the potential of WH and WS for bioenergy production.