A char-supported iron catalyst was investigated as a catalyst for destructing the NOx precursors (e.g. HCN and NH3) during the catalytic steam reforming of tar derived from the pyrolysis of mallee bark and leaf. It was found that the H-form char as a catalyst exhibited little activity for destructing NOx precursors even at high temperature, while on the contrary NOx precursors were decomposed efficiently on the char-supported iron catalyst during the steam reforming process. The activities of the char-supported iron catalyst for decomposing NOx precursors were indifferent for the gasification of bark and leaf. More importantly, the hydrolysis of HCN and the decomposition of NH3 are consecutive reactions during the catalytic steam reforming of biomass tar/volatiles. A majority of HCN was hydrolysed and converted to NH3 on the char-supported iron catalyst, where NH3 can be further decomposed to N-2 when it has enough contact time with the catalyst during the steam reforming process. (C) 2013 Elsevier Ltd. All rights reserved.