A gas generator is provided with a combustion chamber into which oxygen and a hydrogen containing fuel are directed for combustion therein. The gas generator also includes water inlets and an outlet for a steam and CO2 mixture generated within the gas generator. The steam and CO2 mixture can be used for various different processes, with some such processes resulting in recirculation of water from the processor back to the water inlets of the gas generator. In one process a hydrocarbon containing subterranean space is accessed by a well and the steam and CO2 mixture is directed into the well to enhance removability of hydrocarbons within the subterranean space. Fluids are then removed from the subterranean space include hydrocarbons and water, with a portion of the hydrocarbons then removed in a separator/recovery step. The resulting hydrocarbon removal system can operate with no polluting emissions and with no water requirements.