January 25, 2008
Ken Silverstein
EnergyBiz Insider
Editor-in-Chief
Burning coal creates a sensitive waste that could ultimately become a beneficial byproduct used in building materials and cement.
Coal waste actually falls under the guidelines set for non-municipal, non-hazardous waste. The rules governing its disposal are vague, allowing the substance to be regulated by the state that establishes the appropriate rules for each site. At present, most such waste is buried in landfills. But promising technologies are emerging that allow it to be converted into other, more useful products.
The improvement of control efficiencies and the integration of various gasification technologies either already have or will have the ability to reduce emissions from coal powered electric generation. However, the byproducts of the coal combustion process, such as fly ash and bottom ash, and emissions control byproducts, such as scrubber sludge, are still an outstanding issue. Critics say that those byproducts create a nasty pollutant that leaches into the groundwater when they are buried.
Routine coal plant operations are estimated to produce annually about 28 million tons of fly ash and bottom ash, according to the U.S. Department of Energy. A small fraction of that is now used to make concrete, asphalt or masonry blocks, although the potential to create far more is on the horizon. "By seeking alternative uses for these waste materials, we are showing how innovation is a key to environmental stewardship," says Secretary of Energy Sam Bodman. "Materials that once were discarded are now going into construction projects, not landfills."
Older sub-critical pulverized coal-fired operations are less efficient than the newer super-critical units. Because they operate at higher temperatures and pressures, those higher efficiency boilers will burn 20 percent less coal. Less coal means less carbon dioxide and other harmful emissions. Considering the tonnage of coal burned each year, those improvements could have a dramatic effect on the environment.
Sithe Global has a 1,500 megawatt project in Northern New Mexico that it says will use a super-critical coal facility that will effectively manage coal combustion byproducts. The so-called Desert Rock project will use a scrubber system to cut more than 98 percent of the sulfur dioxide emissions and generate a subsequent byproduct known as synthetic gypsum. This gypsum is used primarily in the production of drywall. It is also used as an additive to high strength cement, an agricultural supplement and a raw material for the production of common chalks used in schools.
Desert Rock says that its super-critical boilers will not just produce fewer emissions than other types of coal plants in the United States but that it will also use 80 percent less water than conventional cooling towers. The facility will be located next to the mouth of the mine, it adds, thereby reducing transportation risks and costs.
"Desert Rock is obtaining the necessary approvals to bury all coal combustion byproducts back into the coal mine from which it is obtained," says Nathan Plagens, vice president for the Desert Rock project. "However, it is our goal to contract the removal of all byproducts from the plant to a company that can use them."
Better Ideas
The controversies surrounding coal combustion byproducts are not new. In fact, in 2000 the Environmental Protection Agency determined there would be a need for national regulations to deal with such "waste," saying that it could pose serious health effects and that viable pollution controls may be currently lacking.
Just recently, the non-profit group Environment Maryland issued a report that said that technicians sampled 80 acres near a dumpsite that is used by Constellation Energy and discovered fly ash residue "everywhere." While the Maryland Department of the Environment has issued fines and ordered clean ups, environmentalists have said the site needs to be permanently closed.
To avert federal regulations, utilities have clamped down on themselves while the states have enacted more rules. For their part, utilities are now placing so-called synthetic liners in their ponds to help prevent leakage. In the case of Constellation, it stopped using the dump site last September and says that it is submitting a plan to clean up the mess.
"The dust results in this study are disturbing because the samples were taken a month after Constellation's dumping was temporarily stopped," says Tim Berkoff, of Crofton First, a local community organization. "It seems like it's everywhere in the surrounding neighborhoods."
That hazard, though, gives rise to the possibilities of re-using coal waste. The Energy Department is underwriting $7.2 million of a $19.6 million conversion process in which a Pennsylvania-based company will turn 430 tons of the stuff into building materials. Power plant designer Universal Aggregates took an existing 240-megawatt Birchwood Power Facility and re-shaped it so that it could make soft pellets from ash. It then sold the pellets to Versalite Sales for use in the making of concrete blocks. In the past, Birchwood has had to pay to bury 100,000 tons of ash in the county landfill.
Similarly, Colorado-based Sky Ute Sand and Gravel uses fly ash to replace cement in concrete. It says that not only is it cheaper than cement but it also increases the quality of the concrete. The company, which has been in business for six years, has projects all over New Mexico and the western slope of Colorado.
"These are all materials that are the result of burning coal, which has its environmental disadvantages," says Rodney Zubrod, vice president of Sky Ute. "Meantime, the production of cement has the same environmental consequences. The more materials you can use from 'necessary evils,' the more you are lessening the impact on the environment and the overall carbon dioxide emissions."
Without question, utilities need to better handle coal combustion byproducts. The dissention created by burying them in landfills, however, could give way to the promise of re-using such waste to make practical products. If that technology expands, it would be good for coal and good for the environment.
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