Abstract: Provided is a system for enhancing combustion in a kiln, including a kiln combustion chamber disposed within the kiln, the kiln combustion chamber having an atmosphere therein; a main burner for heating the atmosphere; a calciner assembly for providing a substance to be heated into the kiln combustion chamber; a precalciner including a precalciner combustion chamber disposed within the precalciner for receiving a biomass fuel for combustion in the precalciner combustion chamber, the precalciner combustion chamber in communication with the kiln combustion chamber; and a precalciner oxygen injector in fluid communication with the precalciner combustion chamber for providing a first oxygen stream into the biomass fuel for the combustion. A related apparatus and method for enhancing combustion with oxygen and biomass fuel are also provided.