Complying with various state (and expected federal) requirements governing mercury removal from the stack gas of coal-fired power plants has usually been achieved by adding an expensive activated carbon injection system. Now there is another alternative: a catalyst that features higher. mercury oxidization activity than conventional catalysts while maintaining the same SO(2) to SO(3) conversion activity-and all at a lower operating cost. Full-scale installations are under way at several Southern Company plants that burn a variety of coals.