Abstract: NOx emissions from an internal combustion engine fueled by a gaseous hydrocarbon fuel can be reduced by catalytically producing a hydrogen and carbon monoxide fuel gas stream from the gaseous hydrocarbon fuel and a portion of the hot exhaust gas from the internal combustion engine. Furthermore, ammonia is also produced catalytically by reacting a portion of the hydrogen produced with ambient nitrogen present in the exhaust gas. The ammonia produced is used in connection with a selective catalytic reduction reactor to treat the remaining hot exhaust gas produced from the internal combustion engine, resulting in a treated exhaust gas stream having near-zero NOx emissions.