The federal government has set limits on airborne mercury generated by cement kilns, but they apply only to new or recently renovated plants and don’t require existing ones to make any significant changes.
Once fully in effect, the rules announced Monday will prevent between 1,300 pounds and 3,000 pounds of mercury nationwide from escaping into the atmosphere each year, the U.S. Environmental Protection Agency said. Mercury can damage nervous systems, cause developmental problems for children and pollute waters.
The nation’s 118 existing cement plants give off a combined 12,000 pounds of mercury, the EPA says, although that figure is based largely on company estimates that some state regulators say may be drastically understated.
Tests last year determined the Lafarge North America plant in Alpena, Mich., was emitting mercury at a rate that could produce 581 pounds annually, about 10 times more than previously reported. Other Michigan cement plants are located in Charlevoix and Dundee.
Cement and chlorine plants are the top producers of mercury in the U.S. manufacturing sector, said Marti Sinclair, chairwoman of the Sierra Club’s National Air Committee.
The EPA also set new limits on hydrocarbons - chemical compounds in fossil fuels - that it said would limit emissions by 1,100 tons while helping cut back on sulfur dioxide, another airborne pollutant.
Meeting the mercury and hydrocarbon requirements will cost about $5.4 million for each new kiln, the agency said.
Environmentalists said by giving older plants a pass instead of demanding upgrades, the new rule doesn’t comply with the Clean Air Act or federal court orders to set mercury standards for the cement industry.
"There’s this gigantic problem out there that isn’t getting fixed," said Jim Pew, a lawyer with the law firm Earthjustice in Washington, D.C. "What we’re really looking at here is an agency which thinks it’s completely above the law."
Earthjustice is considering its legal options, Pew said.
Keith Barnett, the EPA’s lead engineer for the rule, said: "We do believe we’ve satisfied the court ruling."
The Portland Cement Association, an industry group based in Skokie, Ill., said it was studying how the rule would affect cement companies.
"The industry will continue to conduct research to identify strategies for addressing mercury emissions and will share its findings with the EPA to ensure that industry standards are based on sound science and support our shared mission to protect human health and the environment," the group said.
Cement manufacturers bake raw materials such as limestone, clay, sand and iron ore in rotating kilns at temperatures up to 3,000 degrees Fahrenheit. Once cooled, the mixture is combined with gypsum.
Mercury comes from the ingredients and fuels used to heat the kilns, primarily coal.
The U.S. Court of Appeals for the District of Columbia Circuit told the EPA in 1999 to consider cement kiln emission standards for mercury, hydrogen chloride and hydrocarbons. After the agency failed to produce a mercury rule, Earthjustice won another court order in 2004.
Barnett said the EPA decided cement producers already met minimum requirements and that making them go further would force costly, disruptive changes in raw materials or fuels.
Many plants were built long ago in locations where there was abundant limestone, the chief ingredient in cement, Barnett said. "They can’t go out and find another limestone quarry somewhere" if the local supply has too much mercury, he said.
Pew said the EPA was legally required to set mercury limits based on those of the best performing kilns. "It would be up to the kiln owners to figure out how to match that," he said.
The only requirements of existing plants under the new rule are to make sure kilns operate properly and to avoid using kiln dust as a raw material if it contains excessive mercury.
The rule also prohibits making cement with fly ash from electric power plants that use certain emission controls likely to boost the ash’s mercury content. But those controls are still experimental, so the requirement again wouldn’t apply to existing cement producers.
State officials say the Lafarge plant’s mercury emissions jumped after it began using fly ash from a Canadian power generator in the 1990s.