WPS actively recycles its coal ash. At one time, most of this ash would have been landfilled.

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What is ash?
Ash is a by-product of coal combustion. Two types of ash are produced by burning coal at power plants: fly ash and bottom ash. Both ashes are also known as coal combustion residuals.
  • Fly ash - a very fine powder material that is carried with the stack gases. It is collected by electrostatic precipitators or a baghouse before it exits the stack. It has cementitious and/or pozzolanic properties, which makes it useful in concrete and geotechnical construction applications.
  • Bottom ash - much coarser than fly ash. It is an almost sand-like material that is sluiced from the bottom of the boilers.
  • SDA ash - a combination of two materials. One material is fly ash. The other is flue gas desulfurization (FGD) condensate from a semi-dry spray dryer absorber (SDA) air pollution control system. These systems capture sulfur dioxide emissions.

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How much ash does WPS produce?
WPS purchases coal from the Powder River Basin in Wyoming. This type of coal contains about 5% ash.
  • The Pulliam Power Plant burns 600,000 tons of coal each year. The burned coal produces 30,000 tons of fly ash and 6,000 tons of bottom ash.
  • The Weston Power Plant burns 3.7 million tons of coal each year. The burned coal produces 60,000-70,000 tons of fly ash, 130,000-135,000 tons of FGD ash and 55,000-60,000 tons of bottom ash.

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Are there beneficial reuses for ash?
Yes. Ash is used as a replacement for Portland cement in concrete applications. When used this way it actually makes the concrete stronger than if fly ash were not added to the mix.

Structural fill projects use ash in place of general fill. An example would be using ash to build a highway embankment. Bottom ash and fly ash can be used in these types of projects. This way, less virgin material needs to be trucked from other places. Structural fill projects incorporate special features to ensure environmental protection. Depending on the material and type of project, these features range from sloping and covering with clay and asphalt to fully lined projects with leachate collection systems.

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What regulations address beneficial reuses?
In Wisconsin, the beneficial reuse of coal combustion residuals is regulated as a solid waste by the Wisconsin Department of Natural Resources (WDNR). It is regulated under the NR 538 rule. Under this rule, ash producers sample and analyze their ash regularly. This is known as ash characterization. It determines the appropriate category of reuse and disposal methods.

NR 538 saves time for both regulators and by-product generators by describing when and how coal combustion residuals can be used in a project. The public also benefits from NR 538. This is because NR 538 determines when public notices are needed and sets a standard for how the notices are published.

NR 538 has also simplified the reporting requirements for ash used as cement replacement. Before the rule, ash producers were required to complete chemical analysis of ash used in cement each year. However, this use has proven to be safe and effective over the years. In turn, the yearly chemical analysis requirement has been removed under NR 538.

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What beneficial reuses has WPS pursued?
Both the Pulliam and Weston power plants produce and sell a high quality fly ash. Ash with these qualities can be used to replace 30% or more of Portland cement. Other beneficial reuse applications we have used or are considering are:
  • Structural fill (highway embankments)
  • Subbase fill (under paved highways)
  • Roller compacted concrete
  • Permeable base for paving projects
  • Stabilizer for in-place asphalt recycling
  • Soil cement compacted for an interior floor surface
  • Soil stabilization
  • Bottom ash may be used as daily cover in public and private landfills or as an additive in making asphalt
  • Mineral fillers in asphalt processes
  • Full depth reclamation

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How does WPS develop beneficial reuses?
WPS has formed relationships with organizations that can use the material. Ash sales to the construction industry are organized through Lafarge North America. It is the #1 worldwide leader in cementitious materials.

Since 1986 we've partnered with Wisconsin Department of Transportation (WDOT) District 3 to place ash in highway embankments. The first project was Highway 41 and County F. 55,000 tons were placed into the County F project. Since then, we have done projects on Highways 441, 45 and 76. By the end of 2009, over 1.3 million tons of ash was placed in WDOT projects.

Ash has also been used for road construction in the central Wisconsin area. Ash was used in the WDOT District 4 Hwy 29 project. We are always looking for opportunities to work together on projects where ash is a good structural fit.

We've also worked with the Central Wisconsin Airport to extend their east-west safety way. This project used more than 675,000 tons over the course of several years. Making the safety way longer increased safety for travelers.

Not only do we reuse our own ash, we help local paper mills by reusing their ash. Coal ash from less efficient fluidized bed boilers that are operated by local mills is reburned in our boilers. This reduces the volume of solid waste for disposal or reuse.

In the past we have helped the University of Wisconsin - Milwaukee Center for By-Products Utilization (CBU) and the Electric Power Research Institute (EPRI) with several research and development projects.

Additionally we have used ash in several of our own projects:
  • We used fly ash as roller compacted concrete in a paved surface around a portion of the Pulliam Plant.
  • We used ash in a paving project at our Green Bay warehouse. But, instead of a surface application, it was used as a permeable base course The parking area has an asphalt top surface over the fly ash that was produced at Pulliam.
  • The Weston 4 site is an example of structural fill. The plant was built on a pad of fly ash effectively reducing the cost of building.
  • Roadways at the Weston site were constructed with soil stabilization technology. In this process ash is added to the soil to create a more durable and stable surface for roadway construction. A more stable surface increases the life of the asphalt.

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Why does WPS continue to look for new uses?
WPS has a long history of using ash in traditional beneficial reuses. We look for new uses because:
  • Coal-fired power plants will always create ash.
  • It is good environmental stewardship. Ash that is not beneficially reused would be a waste product. As a waste product it would be destined for a landfill. Beneficial reuse keeps more space available for other wastes to be placed into landfill and reduces the need to build new landfills.
  • Beneficial reuse encourages new markets to develop. Full depth reclamation and soil stabilization are examples of markets that continue to grow.
  • Reuse keeps costs lower for our customers.

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Who do I contact for more information on coal ash?
For more information on coal ash, please contact:

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WEC Energy Group