Holistic Thermoenergetic Assessment of Biomass Boilers: An Integrated Static, Dynamic, and Emergy Framework

The evaluation of biomass boilers using partial approaches limits system understanding, because energy, exergy, dynamic, and emergy analyses describe complementary, but not equivalent, dimensions of thermo-industrial performance. In response to this gap, an integrated methodological framework is proposed to analyze two representative steam generator technologies in the sugar industry, fueled with ternary mixtures of sugarcane bagasse, Agricultural Crop Residues (ACR), and Dichrostachys cinerea, with the aim of identifying robust operating windows from a simultaneously thermal, exergetic, transient, and sustainability perspective. The methodology combines: (i) a direct and indirect steady-state model to quantify thermal losses and efficiency; (ii) an exergy model to assess conversion quality; (iii) a two-node coupled transient dynamic model capable of representing the differentiated response of the combustion zone and the water/steam system to moisture perturbations; and (iv) an emergy model to estimate the overall sustainability of the process. The results show that the effective moisture content of the mixture is the dominant control variable, since it determines the lower heating value on a wet basis, the specific fuel consumption, the main thermal loss, and the dynamic stability of the system. In the transient domain, a +5% step perturbation in moisture generates drops of 11.14–12.20 °C and 17.76–19.39 °C in furnace temperature for G1 and G2, respectively, while the steam response is damped to 1.03–1.14 °C and 2.39–2.65 °C. Likewise, moisture explains the magnitude of the response with coefficients of determination above 0.99, and the sensitivity analysis identifies the controller time constant, the thermal mass of the water/steam system, and the emissivity as the most influential parameters. Overall, the proposed framework makes it possible to go beyond isolated efficiency assessment and move toward a holistic characterization of biomass boiler performance under technically plausible ternary mixtures. Although the proposed methodological framework is transferable to other biomass combustion contexts, the numerical results—including optimal compositional zones, emergy indicators, and dynamic sensitivity coefficients—are specific to the Cuban sugar industry conditions, adopted transformities, and the biomass types evaluated herein.