A power plant and method of operation are provided. The power plant comprises at least one main air compressor and at least one gas turbine assembly. Each gas turbine assembly comprises a turbine combustor for mixing a compressed ambient gas with a recirculated low oxygen content gas flow and a fuel stream to form a combustible mixture for burning to form the recirculated low oxygen content gas flow. A turbine is arranged to be driven by the recirculated low oxygen content gas flow from the turbine combustor. The assembly includes a recirculation loop for recirculating the recirculated low oxygen content gas flow from the turbine to a turbine compressor and a gas flow extraction stream for extracting a portion of the recirculated low oxygen content gas flow for delivery to a carbon monoxide catalyst unit. A portion of the compressed ambient gas is directed to the carbon monoxide catalyst unit.