A combustion modification method that uses the fuel to reduce NOx emissions. About 10-20 % (energy) of the fuel- the reburn fuel- is added above the main combustion zone, to form a fuel-rich zone where NO is partially reduced to N2 and other nitrogenous species (HCN, NH3). After the reburn zone, additional air is supplied to complete the combustion. In this burnout stage, the remaining fixed-nitrogen species (NO, HCN and NH3) are converted back to NO and/or to N2.