A Theoretical Investigation of the Thermodynamic Limits of Efficiency for Integrated Biomass Gasification and Solid Oxide Fuel Cell Power Generation Systems Under Nigerian Feedstock Conditions

The theoretical maximum efficiency achievable by integrated biomass gasification and solid oxide fuel cell systems represents an incompletely explored frontier in thermodynamics, and the specific constraints imposed by Nigeria's diverse biomass feedstock compositions, including agricultural residues from the six geopolitical zones, introduce important boundary conditions that have not been incorporated into existing theoretical treatments of the topic. This research conducts a rigorous theoretical investigation of the thermodynamic limits of conversion efficiency for integrated systems combining downdraft and fluidised bed gasification of representative Nigerian biomass feedstocks with solid oxide fuel cells using equilibrium and non-equilibrium thermodynamic methods. A generalised exergy-based theoretical framework for maximum attainable system efficiency as a function of feedstock thermochemical properties, gasification temperature, fuel cell operating conditions, and heat integration strategy is developed and systematically analysed. Pinch analysis theory is extended to incorporate electrochemical reaction networks within the composite curve formalism, establishing new theoretical bounds for heat recovery integration in gasification-fuel cell systems. The theoretical framework is applied to twelve biomass feedstock compositions representative of rice husk, sugarcane bagasse, sawdust, groundnut shells, and municipal organic waste from the six geopolitical zones. Findings demonstrate that the theoretical efficiency ceiling varies from 52 to 67 percent across feedstock compositions on a lower heating value basis, with gasification temperature and feedstock ash composition as the dominant parameters. The work constitutes an original contribution to energy conversion theory with specific relevance to sustainable power generation in Nigeria. Keywords: thermodynamic limits, biomass gasification, solid oxide fuel cell, exergy analysis, Nigerian feedstocks.