Sioux is a two-unit, 986-megawatt coal-fired power plant. Construction of the Sioux scrubbers cost approximately $600 million. Scrubbers are emission reduction systems that remove more than 95% of a plant’s sulfur dioxide emissions and reduce emissions of mercury and particulate matter.

How a Scrubber Works
As hot flue gas passes through each scrubber, a slurry of crushed limestone and water is sprayed into it. The limestone in the slurry reacts with sulfur dioxide in the flue gas, creating synthetic gypsum - an inert material that will be captured and stored in a new landfill on plant property. Some plants that generate this type of gypsum send it to be used in the manufacture of wallboard or as a soil amendment.

Waste Management at Sioux Energy Center
The utility waste management facility at Sioux provides long-term or permanent storage of the gypsum generated from the removal of sulfur from the coal combustion gas. An expansion of the facility will allow the long-term dry management of fly and bottom ash. The management facility has been built to address the local hydrogeological setting and it is designed in accordance with State regulations to minimize potential for environmental impact. The material deposited is an inorganic, non-hazardous waste.