This study extends the application and validation of the Gibbs Free Energy Gradient Method (GMM) for modelling gasification processes, focusing on scaling up from pilot to commercial operations. The model simulates syngas production using poplar wood and olive pomace briquettes under various gasification conditions. Experimental data from a downdraft gasifier were employed to refine the model parameters, achieving accurate predictions of syngas composition with an average error below 8%. Sensitivity analyses highlight the impact of operating conditions, particularly temperature and air flow rates, on the syngas calorific value, hydrogen yield, and energy efficiency. These results emphasize the potential of biomass residues, such as olive pomace, for sustainable energy production in a circular economy context. The findings demonstrate the robustness of the GMM for predicting gasification performance and offer practical guidance for scaling up biomass-to-energy systems while optimizing efficiency and reducing waste.