Catalytic decomposition of toluene (C6H5CH3) or benzene (C6H6) with inexpensive limonite ores, composed mainly of goethite (alpha-FeOOH), was examined using a vertical, cylindrical flow fixed-bed quartz reactor to develop a novel method of removing biomass-derived tar components. The unsupported limonite catalyst was active for the decomposition of 480 ppm of C6H5CH3 and 1700 ppm of C6H6 in 15 vol % H2O/45 vol % H-2/He, leading to C6H5CH3 and C6H6 conversions at 500 degrees C of nearly 100 and 97%, respectively. When the C6H5CH3 decomposition temperature was increased from 500 to 800 degrees C, the overall reaction path changed from demethylation to hydrocracking and then to steam reforming. A honeycomb-supported limonite catalyst also was effective and achieved nearly complete C6H5CH3 conversion at 600 degrees C. In addition, the honeycomb supported catalyst promoted C6H6 conversion of nearly 100% without carbon deposits at 700 degrees C in 15 vol % H2O/20 vol % H-2/26 vol % CO/20 vol % CO2/5 vol % CH4 that was designed to simulate raw fuel gas derived from biomass gasification. Powder X-ray diffraction (XRD) measurements after reaction at 700-800 degrees C revealed the presence of finely dispersed metallic iron (alpha-Fe), which is likely responsible for the high catalytic performance.