Traditional methods of minimising NOx emissions from thermal processes including incinerators have included post-combustion treatment technologies in the form of catalytic and non-catalytic ammonia or urea injection. These processes are effective in reducing nitrogen oxides but emit by-products which require further treatment and disposal. The major source of NOx from municipal waste incinerators is the nitrogen in the fuel due to the relatively lower flame temperatures. Computational fluid dynamics (CFD) simulations using FLUENT code conducted to simulate and predict gaseous flow patterns within full-scale incinerator plant showed that the thermal and prompt NOx is about 60 ppm at approximately 10% O-2 at the exit from the radiation shaft. The measured value on the plant was approximately 350 ppm at a similar O-2 level, confirming the significance of fuel NOx emitted from the bed. Further reduction of NOx emission from Municipal Solid Waste (MSW) incinerator plants can be achieved by optimising the grate combustion process. Detailed experiments with simulated waste were successfully carried out in a small-scale laboratory combustion rig. The results obtained from the tests demonstrated that up to 90% reduction in NOx emission from the burning bed of solid waste can be achieved by increasing the thickness of the char layer above the pyrolysis front where NOx is produced. Existing grates already achieve an undetermined fraction of this capability. This paper presents the work carried out in order to develop a cheap, reliable and most efficient strategy for the reduction of NOx emission at the source of formation in an incinerator.