The emission of NOx and-N2O were studied experimentally in a fluidized bed biomass combustor. To investigate effectively the influence of different parameters on the NOx formation with a limited number of experiments, an orthogonal experimental design was adapted. Four biomass fuels, three NOx-repressing additives, four bed materials, and four alkali-capturing additives were tested in a temperature range of 670-900 degreesC and at two pressure levels, 1.0 and 1.5 MPa. The NO,,repressing additive was added to repress the formation of NOx and N2O and the alkali-capturing additive was added to prevent the bed from agglomeration. In the present study it was found that it was not possible to minimize both NO (NOx) and N2O with the same combination of parameters. Instead, either NO formation or N2O formation has to be minimized. The results also showed that the NOx-repressing additives were active in repressing NOx and N2O, except for NH4HCO3. The optimal combination of the parameters investigated in the present study for minimizing the emissions were: sawdust, bone ash, mullite, and urea for NO minimizations, and straw, bone ash, clay, and Na2CO3 for N2O minimizations.