Thermal degradation and kinetic behaviour of hybrid solid fuels derived from corncob and African birch wood

Abstract The development of solid fuels from biomass is critical for achieving sustainable and affordable energy security, with woody biomass offering advantages such as relatively high energy content. However, the overexploitation of woody resources raises sustainability and environmental concerns. Therefore, this study investigated the thermal degradation and kinetic behaviour of hybrid solid fuels derived from corncob and African birch wood (ABW). Corncob and ABW samples were collected, sorted, and pulverised, after which their higher heating values (HHVs) and ash content were determined using standard analytical methods. An optimal blend was designed using Minitab 19 mixture design, and its thermal degradation was assessed through thermogravimetric analysis (TGA). Kinetic analyses were performed using the Ozawa–Flynn–Wall, Starink, Kissinger–Akahira–Sunose, and Tang models. Results showed that the HHVs of raw corncob and ABW were 14.21 MJ/kg and 17.80 MJ/kg, with ash contents of 3.46% and 1.52%, respectively. The optimal blend ratio of corncob to ABW (3:22) exhibited an HHV of 16.82 MJ/kg and an ash content of 2.0%. Kinetic analysis revealed activation energy values ranging from 194.22, 197.12, 208.09 and 226.17 kJ/mol for the Tang, Starink, Kissinger–Akahira–Sunose, and Ozawa–Flynn–Wall models. These findings suggest that the developed hybrid solid fuels possess favourable characteristics and can be utilised for process heating in both domestic and industrial applications, thereby reducing reliance on raw wood and supporting sustainable energy transition.