Coal waste converted

Universal Aggregates recently converted 430 tons of coal combustion by-products (CCB) into valuable building materials.

Working under a $7.2 million US Department of Energy co-operative agreement, a Western Pennsylvania-based company recently converted 430 tons of coal combustion by-products (CCB), the solid residues generated by coal-burning electric utilities, into valuable building materials.

“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, of Bridgeville, Pennsylvania, sold the lightweight aggregate material to Versalite Sales, of Midlothian, Virginia, 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, Virginia.

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. 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. According to the DOE, weighing the 28 million tons of waste produced annually against those costs demonstrates the benefit of recycling to power plant operators.

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 30 months after signing the co-operative agreement calling for DOE to provide $7.2 million of the project’s $19.6 million cost to build the aggregate plant.