An investigation of the use of chemical equilibrium calculations to predict experimental measurements of the trace species K, Na, and Cl in a gasifier product stream was completed. The method applied two sequential equilibrium calculations. The first calculation used fuel and air data as input and was performed at the gasifier temperature (similar to 800 degrees C). A second calculation used the results of the first calculation as input and was performed at the temperature of the hot gas filter (similar to 700 degrees C). Equilibrium calculations based only on the fuel composition and air input data predicted potassium, sodium, and chlorine concentrations that were greater than measured experimental values. The equilibrium concentration of potassium, which is the alkali metal of particular interest in this study, was an order of magnitude larger than the experimental results (153 ppmw vs 28 ppmw). Including the mass of bed material used in the experiments as input to the equilibrium calculation reduced the predicted potassium concentration below the measured experimental value (2.2 ppmw vs 28 ppmw). The amount of bed material included in the equilibrium calculations was varied to identify a value (1.08% of the actual bed material mass equal to a 1-mu m-thick outer layer of the bed particles) where the predicted potassium concentration matched the experimental data. Using this value, equilibrium calculations were performed for five additional data sets, and the results were compared against available experimental measurements of potassium, sodium, and chlorine. Generally, the model calculations showed the same trends as the experimental data, with better agreement being observed for analytes that were present in greater abundance in the fuel. This indicates that, in addition to fuel and oxidizer inputs, a fraction of the bed material should be included in equilibrium calculations. This outer layer has an important role as a sink for inorganic species, thus impacting the gas-phase release of inorganic fuel elements in the fluidized-bed gasification of biomass.