Project turns coal waste into valuable building material

Working under a $7.2 million U.S. Department of Energy (DOE) cooperative agreement, a Western Pennsylvania-based company recently converted 430 tons of coal combustion by-products (CCB) into valuable building material. In doing so, the company took a major step forward in reducing significant plant operating costs while taking a strong environmental initiative. Routine coal plant operations result in an estimated 28 million tons of the byproducts each year being placed in landfills. With the new procedure, that waste could be turned into useful products.

"By seeking alternative uses for these waste materials, we are showing how innovation is key to environmental stewardship," Secretary of Energy Samuel W. Bodman said. "Materials that once were discarded are now going into construction projects, not landfills."

Universal Aggregates LLC, of Bridgeville, Pa., sold the highly marketable lightweight aggregate material to Versalite Sales Inc., of Midlothian, Va., for use in manufacturing concrete block. In February, Universal Aggregates followed up its initial success by producing and selling an additional 305 tons to the same company. Universal Aggregates completed the design and construction of its plant in the latter months of 2004 to manufacture the aggregate from CCBs generated on-site at Birchwood Power Partners' Birchwood Power Facility in King George, Va.

In past years, the Birchwood plant has had to pay the costs of having more than 100,000 tons of ash disposed in a county landfill. With the construction of its plant, Universal Aggregates has saved Birchwood operators the landfill costs. Although the cost of landfilling can vary considerably, estimates place the operating and maintenance costs at $2-$4 per ton and capital costs at an additional $8-$17 per ton. Weighing the 28 million tons of waste produced annually against those costs demonstrates the benefit of recycling to power plant operators.

At present, approximately 30 percent of the 28 million tons is reused from so-called "wet scrubbers." Currently, 21 U.S. coal-fired power plants use spray dryer systems to reduce the emission of sulfur pollutants into the atmosphere. With that number of plants, estimates place the potential for aggregate material at two billion tons annually, thereby filling a large need for concrete and asphalt paving material, as well as masonry blocks.

In the Universal Aggregates plant, operators produce a granular material by blending ash from the spray dryer with other solid admixtures. The resulting material is shaped in an "extruder," machinery that forces the material through a die and forms it into wet, green, pellets. After these soft pellets are cured and hardened, they are crushed, screened for size, and stockpiled for sale as manufactured aggregates.

Following its first-ever shipment of aggregate, Universal Aggregates expects to produce about 167,000 tons of the material each year at its plant. The company operated the plant at about 30 percent capacity when it produced its initial 220 tons of aggregate.

That initial success comes just 30 months after signing the cooperative agreement calling for DOE to provide $7.2 million of the project's $19.6 million cost to build the aggregate plant. Universal Aggregates had tested its technology at a six-ton per hour pilot plant located at CONSOL Energy Inc. in South Park, Pa. Universal Aggregates began as a joint venture between CONSOL and SynAggs, LLC, of Pittsburgh, Pa. P.J. Dick, West Mifflin, Pa., served as the engineering and construction contractor of the Virginia plant.

This article originally appeared in the 04/01/2005 issue of Environmental Protection.

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