Abstract: A system for preparing gas mixtures for combustion, reducing emissions during combustion and treating and purifying resultant exhaust gas mixtures includes an exhaust gas scrubbing and condensing heat exchanger which cleans, cools and dries an exhaust gas mixture, a source of clean water which supplies clean water for heating and humidifying, a steam producer for converting clean water to steam, a steam boiler for increasing the energy of the steam and the energy of a fluid compound gas. An exhaust gas turbine, a steam turbine, and a fluid compound gas turbine all mounted on a common shaft are operative to convert energy in the exhaust gas mixture, the steam, and the fluid compound gas to mechanical energy on the common shaft. The system is particularly suited for use with an internal combustion engine.