The application of chemical looping combustion (CLC) to solid fuels for the purpose of electric power generation from coal is the focus of research at the Center for Applied Energy Research (CAER), University of Kentucky, Lexington, KY. One important aspect for the use of CLC for solid fuels is the effect of ash on the capacity and reactivity of the oxygen carrier (OC). Four different coal-derived fly ashes obtained from electric power plants were used to study the effect of the ash on the ability of an OC to oxidize the carbon in a beneficiated gasification coal char containing 58.9% carbon. The four coal ashes were obtained from the following sources representing different coal ranks: sub-bituminous (Bulgaria), bituminous (China), Texas lignite (U.SA), and Powder River Basin sub-bituminous (U.S.A.). The OC was 50% Fe2O3 on an Al2O3 support. The OC was made by freeze granulation (FG) at the CAER Mixtures of char/OC/ash with increasing ash contents to 75% were tested in a thermal analyzer coupled to a mass spectrometer (TGMS) system at 950 degrees C and a purge of argon for 5 h. Carbon determinations before and after heating were used to calculate the amount of carbon removed from the char by the OC as an indication of the oxygen-transfer capacity of the OC. Reduction reaction rates were determined from the differential of the weight loss curves from the TG. The lignite ash had a beneficial effect on the ability of OC to oxidize carbon, but all other ashes were detrimental and reduced the ability of the OC to remove carbon from the mixtures. Low concentrations of ash increased reduction rates, but a concentration of 75% significantly slowed the rate. This study indicated that consideration will have to be given for each type of ash generated from different coal sources for the successful application of CLC to solid fuels.