In collaboration with researchers at the Colorado School of Mines, the University of Heidelberg and the Technical University of Denmark, we studied the formation of pollutant in nitrogen enriched diffusion flames. During combustion of coal and biomass fuels, fuel-bound nitrogen compounds are volatized and released with combustable gas, potentially leading to enhanced NO_x formation. Laboratory experiments at the Technical University of Denmark are being used to study this phenomena. In the experiment ammonia is added to an inflow methane stream to model the effects of fuel-bound nitrogen. The figure depicts computed axisymmetric temperature and nitric oxide (NO) profiles, typical of the experimental setup. To simulate the experiment computationally, we incorporate a set of detailed methane mechanisms descibing the nitrogen chemistry, and NO formation in particular. These comprehensive mechanisms contain as many as 65 chemical species and 447 fundamental reactions. The NO production, measured in ppm of flue gas, are plotted below in blue as a function of ammonia (NH₃) concentrations in the fuel. The experimental setup used for obtaining diagnostics for the steady flame is depicted to the right of the plot. The individual data points on the plot represent our simulation results using standard and a modified version of GRI-3.0, and an alternative mechanism under development at the Technical University of Denmark. This work has been published in Combustion Flame, and is available on the CCSE Publications page.