$500 Million Investment to Reduce Sulphur Dioxide and Mercury Emissions from AmerenUE’s Sioux Plant This environmental initiative—which will be completed years ahead of federal mandates — will enable AmerenUE to address the growing energy needs of our region with plants that meet or exceed federal environmental standards. AmerenUE’s Sioux plant in Missouri is installing scrubbers to comply, in advance, with the Clean Air Interstate Rule (CAIR), which mandates a major reduction in sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions on a regional scale by 2015 to help areas in the eastern U.S. achieve healthier air quality. The Sioux plant’s new scrubbers are scheduled to be in place by 2009. Overall, Ameren will spend $3.5 billion to $4.5 billion between 2006 and 2016 to retrofit our power plants with pollution control equipment.    The scrubbers will be capable of removing approximately 95 percent of the SO2 from the boiler flue gas when burning either low-sulfur or high-sulfur coals. Inside the scrubbers, the flue gas will be cooled and will react with a limestone slurry to convert the SO2 into a calcium sulfate solution, which will then be de-watered into a relatively dry gypsum byproduct. Depending on the type and purity of the salts in the gypsum, it could be used to make drywall or cement, used as fill, or stored in a disposal facility for possible later use.    In addition, Ameren and its subsidiaries are exploring renewable energy options—opportunities to use and create markets for combustion byproducts and processes to convert waste to energy.    Find more information in the Power On FAQs.