A system and method using fluidizing gas optionally augmented by oxygen for reducing nitrogen oxides present in a wide variety of waste materials. The system includes a single reaction vessel, or optionally multiple reaction vessels, providing multiple reaction bed zones in fluid communication. Reduction takes place quickly when steam or another fluidizing gas is injected into the reaction vessel or vessels. Reducing additives may be metered into the reaction vessel or vessels and/or provide energy input to facilitate reduction of nitrogen oxides to nitrogen. The oxygen, when used, allows for some oxidation of waste by-products and provides an additional offset for thermal requirements of operation.