Reburn with animal waste yield NO{sub x} reduction of the order of 70-80%, which is much higher than those previously reported in the literature for natural gas, coal and agricultural biomass as reburn fuels. Further, the NO{sub x} reduction is almost independent of stoichiometry from stoichiometric to upto 10% deficient air in reburn zone. As a first step towards understanding the reburn process in a boiler burner, a simplified zero-dimensional model has been developed for estimating the NO{sub x} reduction in the reburn process using simulated animal waste based biomass volatiles. However the first model does not include the gradual heat up of reburn fuel particle, pyrolysis and char combustion. Hence there is a need for more rigorous treatment of the model with animal waste as reburn fuel. To address this issue, an improved zero-dimensional model is being developed which can handle any solid reburn fuel, along with more detailed heterogeneous char reactions and homogeneous global reactions. The model on ''NO{sub x} Reduction for Reburn Process using Feedlot Biomass,'' incorporates; (a) mixing between reburn fuel and main-burner gases, (b) gradual heat-up of reburn fuel accompanied by pyrolysis, oxidation of volatiles and char oxidation, (c) fuel-bound nitrogen (FBN) pyrolysis, and FBN …