Plants' Cleanup May Create Side-Effect
Sunday, August 26, 2007; 2:20 PM
OMAHA, Neb. -- As the nation's coal-fired power plants work to create cleaner skies, they'll likely fill up landfills with millions more tons of potentially harmful ash.
More than one-third of the ash generated at the country's hundreds of coal-fired plants is now recycled _ mixed with cement to build highways or used to stabilize embankments, among other things.
But in a process being used increasingly across the nation, chemicals are injected into plants' emissions to capture airborne pollutants.
That, in turn, changes the composition of the ash and cuts its usefulness. It can't be used in cement, for example, because the interaction of the chemicals may keep the concrete from hardening.
That ash has to go somewhere _ so it usually ends up in landfills, along with the rest of the unusable waste.
"You're replacing an air problem with a land problem _ a disposal problem," said Bruce Dockter, a research engineer with the Energy and Environmental Research Center at the University of North Dakota.
Coal ash naturally contains arsenic and mercury, and if the elements leach into groundwater they can contaminate drinking supplies. The EPA says ash disposed of in landfills could pose significant risks when mismanaged, and there are gaps in state regulation.
And the chemicals added to clean up emissions _ such as ammonia, lime and calcium hydroxide _ make the ash worse, environmental groups say, because they take toxins such as mercury out of the air but leave higher levels of it in the ash.
The U.S. Environmental Protection Agency doesn't classify coal ash _ with or without the added chemicals _ as a hazardous waste, although many environmental groups say it should.
"As a general rule, anything you do to make the air emissions cleaner makes the ash more toxic," said Lisa Evans, an attorney with Earthjustice, a nonprofit environmental law firm.
More than 120 million tons of ash and other leftovers come from coal combustion each year in the United States, and more than 46 million tons are reused, according to the American Coal Ash Association.
Environmental groups encourage reuse of the ash because it keeps most of the waste out of landfills. And substituting ash for cement means less mining for the materials typically used to make cement _ consequently causing a drop in the amount of carbon dioxide that would be emitted by mining machinery.