Coal often contains sulfur (S) as an impurity that is released as gaseous SO2 during combustion, and SO2 is one of six primary air pollutants monitored by the EPA. The U.S. Clean Air Act limits sulfur...

Coal often contains sulfur (S) as an impurity that is released as gaseous SO2 during combustion, and SO2 is one of six primary air pollutants monitored by the EPA. The U.S. Clean Air Act limits sulfur emissions from large coalfired boilers to 0.54 kilograms (1.2 pounds) of sulfur per million Btus (British thermal units) of heat generated. (1 metric ton = 1,000 kilograms = 2,200 pounds = 1.1 ton; 1 kilogram = 2.2 pounds.)

If all of the sulfur in the coal is released to the atmosphere during combustion, what is the maximum percentage of sulfur that the coal can contain and still allow the utility to meet the standards of the Clean Air Act?