a preferred method for determining changes in the temperature of the waste stream is to directly monitor it with one or more thermocouples energy content may also change due to a change in the waste stream 39 s physical state for example if the stream comprises liquid water at its boiling point and the stream is passed through a hot heat exchanger the energy content of the stream will increase and at least a portion of the water in the waste stream will become water vapor changes in the state e g liquid to gas of the waste stream may be monitored through a combination of composition analysis pressure temperature measurement and the use process knowledge in the combined feed forward feedback method if the energy content e has increased u03b4e gt 0 then the firebox temperature fig1 is lowered by u03b4b u03b4b is a function of u03b4e u03b4b f 7 u03b4e once the firebox temperature is lowered by u03b4b the control method turns to the feedback method again and analyzes the co emission rate or u03b4co at 32 once the co emissions are at the target rate the control method then turns to the combined feed forward feedback method and analyzes.