Co-combustion performance and kinetic study of solid digestate with gasification biochar

Thermogravimetric (TG) analysis was carried out to evaluate the interactions and kinetics of char from biomass gasification, solid digestate and their blends under combustion condition. The gasification char was blended with solid digestate in the range of 10–90 wt% to analyze the co-combustion performance. Based on the thermal degradation experiments which were performed at three heating rates 5, 10, and 15 °C/min, the OFW model-free method was used to determine the activation energy, based on which the pre-exponential factor, the enthalpy, the Gibbs free energy and the entropy were also calculated to label the combustion process directly. Blending gasification char with solid digestate tends to reduce the activation energy, but the overall analysis of combustion, kinetic and thermodynamic parameters reveals the complexity of the degradation process of all blends. Results showed that the blending proportion of 50% was regarded as the optimum blend in according to the limitations of activation energy, comprehensive performance index and Gibbs free-energy.