In order to compare potential oxygen carriers for the iG-CLC with coal a methodology was developed from results obtained in a batch fluidized reactor. The methodology is based on the solids inventory in the fuel reactor. The solids inventory values will be used for comparison purposes among different materials rather than for design purposes. In a companion paper, experiments with different types of Fe-based oxygen carriers were presented. Based on these experimental results, the present paper proposes two theoretical approaches for a fast evaluation of different materials as potential oxygen carriers for the iG-CLC process with different fuels. The methodology is focused on the study of the gasification of the char generated in the process after the devolatilization of the corresponding solid fuel and the subsequent combustion of the gasification products. Considering the results of carbon capture and combustion efficiency, the adequacy of the material can be evaluated. Four different Fe-based materials are tested in this work: ilmenite, bauxite waste, a mineral based on hematite, and a synthetic material. Based on the results obtained, the bauxite waste and the hematite mineral present the best performance for iG-CLC. As a rough estimation, an inventory around 1600 kg/MWth will be needed using any of the above materials to achieve carbon captures above 0.93 and combustion efficiencies of 0.99 at 1000 degrees C.