The federal government is encouraging farmers to spread a chalky waste from coal-fired power plants on their fields to loosen and fertilize soil even as it considers regulating coal wastes for the first time.
The material is produced by power plant "scrubbers" that remove acid rain causing sulfur dioxide from plant emissions. A synthetic form of the mineral gypsum, it also contains mercury, arsenic, lead and other heavy metals.
The U.S. Environmental Protection Agency says those toxic metals occur in only tiny amounts that pose no threat to crops, surface water or humans. But some environmentalists say too little is known about how the material affects crops, and ultimately human health, for the government to suggest that farmers use it on their land.
"Basically this is a leap into the unknown," said Jeff Ruch, executive director of Public Employees for Environmental Responsibility. "This stuff has materials in it that we're trying to prevent entering the environment from coal-fired power plants and then to turn around and smear it across ag lands raises some real questions."
With coal wastes piling up around the coal-fired plants that produce half the nation's power, the EPA and U.S. Department of Agriculture began promoting what they call the wastes' "beneficial uses" during the Bush administration.
Part of that push is to expand use of synthetic gypsum _ a whitish, calcium-rich material known as flue gas desulfurization gypsum, or FGD gypsum.
The Obama administration has continued promoting FGD gypsum's use in farming even as it drafts a coal waste rule in response to a spill from a coal ash pond near Knoxville, Tenn., one year ago Tuesday. Ash and water flooded 300 acres, damaging homes and killing fish in nearby rivers. The cleanup is expected to cost about $1 billion.
The EPA is expected to announce its proposals for regulation early next year, setting the first federal standards for storage and disposal of coal wastes.
EPA officials declined to talk about the agency's promotion of FGD gypsum before then and wouldn't say whether the draft rule would cover it.
Instead, the agency released a statement saying the heavy metals in the material are far less than the amount considered a threat to human health. Field studies have shown that mercury, the main heavy metal of concern because it can damage development of the human nervous system, doesn't accumulate in crops or run off fields in surface water at "significant" levels, it said.
"EPA believes that the use of FGD gypsum in agriculture is safe in appropriate soil and hydrogeologic conditions," the statement said.
Eric Schaeffer, executive director of the Environmental Integrity Project, which advocates for more effective enforcement of environmental laws, said he's not overly worried about FGD gypsum's use on fields because research shows it contains only tiny amounts of heavy metals. But he said federal limits on the amounts of heavy metals in FGD gypsum sold to farmers would help allay concerns.
"That would give them assurance that they've got clean FGD gypsum," he said. "The farmers don't want to get a bad batch."
Since the EPA/USDA partnership began in 2001, farmers' use of the material has more than tripled, from about 78,000 tons spread on fields in 2002 to nearly 279,000 tons last year, according to the American Coal Ash Association, a utility industry group.
About half of the 17.7 million tons of FGD gypsum produced in the U.S. last year was used to make drywall, said Thomas Adams, the association's executive director. But he said it's important to find new uses for it and other coal wastes because the nation is likely to remain reliant on coal-fired power plants for decades to come.
"If we can find safe ways to recycle those materials, we're a lot better off doing that then we are creating a whole bunch of new landfills," Adams said.
Darrell Norton, a USDA soil scientist, said a predecessor of FGD gypsum produced about 25 years ago often had high levels of heavy metals because it had been mixed with coal fly ash. But FGD gypsum has no fly ash and is "environmentally clean," he said.
FGD gypsum is widely used in the South as a less expensive alternative to mined gypsum, said Glen Harris, a soil scientist at the University of Georgia in Tifton, Ga. Farmers in states such as Georgia, Alabama and the Carolinas have long spread mined gypsum on their fields, where its calcium spurs the growth of peanuts.
Clay McDaniel, 47, who farms about 4,000 acres of peanuts and corn near the southern Georgia town of Newton, has used synthetic gypsum on his peanut fields for more than 20 years. He and other farmers call both FGD and mined gypsum "land plaster." He said he's never worried about the safety of the synthetic version.
"If we buy a chemical that's toxic, it's got a skull and crossbones on it," he said. "But this does not come with any such warning. It's just a calcium source."