A method and system for CO2 capture from flue gas uses an absorber vessel in which a flue gas stream containing CO2 is contacted with an ammoniated solution to remove CO2 from the flue gas, and a regenerator vessel in which CO2 is released from the ammoniated solution. Parasitic energy consumption of the system can be reduced by adding to the ammoniated solution a promoter effective to enhance the formation of ammonium bicarbonate within the ammoniated solution. The amount of ammoniated solution recycled from the regenerator vessel to the absorber vessel is less than that which would be required using the ammoniated solution without the promoter for removal of the same amount of CO2 from the flue gas.