A combustion system and method for operating a combustion system, such as a furnace or boiler. The method includes providing a burner system having one or more burner elements configured to combust solid fuel and one or more oxygen providing devices configured to introduce oxygen into the near burner zone of one or more burner flames. A sensor is provided and arranged and disposed to measure a flame parameter in the near burner zone of the burner flame associated with one or more the burner elements. The flame parameter is measured with the sensor and an oxygen flow is determined in response to the measured flame parameter. Oxygen flow is introduced to one or more locations in the combustion system with the one or more oxygen providing devices.