The catalytic combustion of gasified biomasses over Mn-substituted hexaaluminates with high thermal stability is addressed. Combustion activity tests of the main fuel components, i.e. CO, H-2, C2H4 and CH4, have been performed, and the effects of H2O and CO2 on the fuel combustion have been investigated. The reactivity of NH3 in the catalytic combustion has also been studied in view of its potential source of undesired fuel-NOx. Lab-scale data have been preliminarily scaled up through mathematical modeling.