Mercury in aging chemical plants could end up in and on the hands of gold miners
Cheryl Hogue, Chemical & Engineering News
28th May 2007
WILL TONS OF MERCURY now housed in eight U.S. chemical plants eventually get into the hands of poverty-stricken people panning for gold in developing countries and then into rivers and the air?
The U.S. government, led by the Environmental Protection Agency, is aware that the marketplace forces of supply and demand could make this scenario into a reality. With a goal of preventing that from happening, policy analysts now are studying how best to manage domestic stocks of the neurotoxic metal.
As a start, the government is examining national and worldwide supply and demand trends for mercury. These trends form a complicated web. It connects a handful of U.S. chemical plants, domestic recyclers that help prevent mercury pollution in the U.S., industrial gold mines in the U.S., Chinese production of a key plastic material, and impoverished communities in the developing world.
Driving these interconnections is the price of gold, which rose from $260 to $725 per ounce between 2001 and 2006, according to a recent report by the United Nations Environment Program (UNEP).
Pioneer Chemical Production
Eight plants in the U.S. use mercury cells to produce chlorine gas and caustic soda. As they close, thousands of tons of the metal are expected to be recovered and sold on the world market.
Those soaring values have fostered a gold rush as increasingly more impoverished people in developing countries have turned to small-scale gold mining for a livelihood. Millions of these miners rely on quicksilver to separate grains of gold from small bits of sand and rock in pans or other small-scale equipment. The technique—which yields a gold-mercury amalgam from which the gold can later be extracted by heating—is easy, effective, and generally, cheap.
An estimated 10 million to 15 million small-scale miners around the world use mercury, according to Michael T. Bender, executive director of the Mercury Policy Project, a group promoting the elimination or reduction of the use of, exposure to, and trade of mercury. Up to half of these miners have symptoms of mercury poisoning, he said.
International aid agencies and charitable groups are working with small-scale gold miners in developing countries to promote separation techniques that are not mercury-based and thus are safer from the standpoint of health and less damaging to the environment. But the use of mercury is more widespread than the reach of these efforts.
"In most countries, mercury is readily available and relatively inexpensive to miners," according to the UNEP report on mercury. "In some cases, it is given for free, contingent on the recovered gold being sold to the mercury provider."
This largely unregulated flow of mercury is polluting waterways, land, and the miners themselves in South America, Asia, and Africa, and not just at mining sites. To sell the gold, the miners need to extract it from their amalgam, which is often done by heating in open pans. This practice releases elemental mercury to the atmosphere, exposing people nearby to toxic fumes. UNEP estimates that small-scale gold mining releases between 650 and 1,000 metric tons of mercury per year, accounting for about a third of all mercury releases to the environment from human activities.
Use of mercury in small-scale mining appears to be highest in China, which releases 200 to 250 metric tons into the atmosphere per year, the UNEP report says. Indonesia comes in second, with 100 to 150 metric tons of releases. Brazil, Bolivia, Colombia, Ecuador, Ghana, Peru, the Philippines, Venezuela, Tanzania, and Zimbabwe each emit 10 to 30 metric tons per year.
SMALL-SCALE GOLD mining accounted for the largest single portion—1,000 metric tons, or about 30%—of global mercury demand in 2005, according to European Union figures. The world's second-largest user group-700 metric tons, or 20%-that year was manufacturers of vinyl chloride, which is a key monomeric building block for making polyvinyl chloride plastics.
China's vinyl chloride plants now consume about 600 metric tons of mercury per year, according to EPA. The Chinese facilities manufacture the monomer with an acetylene feedstock and a mercury catalyst. According to the Natural Resources Defense Council (NRDC), some mercury escapes to the atmosphere during the monomer production process.
China and the Kyrgyz Republic are the only two countries that still mine mercury. Much of the world's demand for mercury currently is supplied through recycling or as a by-product of mining for other metals. While demand for mercury is soaring in several developing countries for gold-mining purposes, it is declining dramatically in the U.S. and elsewhere in the industrialized world.
Between 1980 and 2001, U.S. mercury use fell from 2,225 to 271 metric tons per year, according to Maria J. Doa, director of EPA's National Program Chemicals Division. Accounting for this drop, she said at a stakeholder meeting on May 8, are limits on the amount of mercury in many types of batteries, elimination of mercury in paints, and closure or conversion of chemical plants that use mercury-containing electrolytic cells.
Mercury hasn't been mined as a primary commodity in the U.S. since 1990, Doa said, but the U.S. has significant privately held stocks of the metal. The largest pool of this mercury, according to EPA, is in eight chlor-alkali plants that employ an older industrial process that relies on the metal as a cathode to generate chlorine gas and sodium hydroxide from the electrolysis of a sodium chloride solution.
Of the eight U.S. mercury-cell plants, PPG Industries owns two, with facilities in Lake Charles, La., and New Martinsville, W.Va. Olin owns another two, in Charleston, Tenn., and Augusta, Ga. Others are Occidental Chemical, Muscle Shoals, Ala.; ERCO Worldwide (USA), Port Edwards, Wis.; Ashta Chemicals, Ashtabula, Ohio; and Pioneer, St. Gabriel, La.
These facilities together contain 2,368 metric tons of mercury, according to a 2005 report to EPA by the Chlorine Institute, a chemical industry group. In coming years, all these plants are expected to be shut down or converted to a process that does not use mercury, Doa said. Historically, mercury has been recovered from closed or converted chlor-alkali plants and sold on the commodity market, according to EPA. On the basis of today's prices on the world market, the mercury in those eight plants could fetch nearly $45 million.
Commodity mercury is bought and sold in steel flasks that are 4 inches in diameter and 12 inches high. Each one holds 76 lb of mercury. Twenty-nine flasks make up a metric ton of the liquid metal. According to the U.S. Geological Survey, the price of a flask of mercury has gone up from $155 in 2000 to approximately $650 now.
If mercury from closed or converted chlor-alkali plants reaches the international market, it probably ends up in the developing world and in small-scale gold mining operations, according to UNEP.
Some closures and conversions already are in the works. PPG is in the process of converting its Lake Charles facility to a membrane technology that does not use mercury. OxyChem announced last year that it will close its mercury-cell plant in 2008. ERCO Worldwide is considering the conversion of its Wisconsin chlor-alkali plant to a mercury-free process, according to a company spokesman.
Not For Sale: US Military and DOE Are Storing Mercury
As it crafts a policy for managing commodity-grade mercury, the U.S. government is concerned primarily with what it calls nonfederal sources of the metal.
The government owns more than half the country's supply of mercury. But its stockpiles are expected to remain in storage and off the world market, at least for now.
The military and the Department of Energy together own about 5,642 metric tons of stockpiled mercury. The liquid metal was used in the 1950s and '60s to produce enriched lithium for atomic weapons. It is also a component of some electrical switches, measuring devices, and button-cell batteries.
The military has 4,436 metric tons of mercury in storage, according the Defense National Stockpile Center. The center maintains 2,617 metric tons in Somerville, N.J.; 1,262 metric tons in Warren, Ohio; and 557 metric tons in New Haven, Ind. It plans to consolidate these holdings at the Hawthorne Army Depot in Nevada. The center stopped selling excess mercury in 1994, citing concerns about mercury's impact on the global environment.
DOE has 1,206 metric tons of mercury stockpiled in Oak Ridge, Tenn. In 2006, the department decided to store the metal rather than sell it.
The second-largest private U.S. source of mercury, after the chlor-alkali industry, is large-scale metal mining, especially for gold, silver, and copper, which produces mercury as a by-product, Doa said.
Joseph Pollara, chief environmental engineer of the Newmont Mining, explained that some ores of gold and other metals occur with the red mineral cinnabar, or mercury sulfide. When the ore is roasted, mercury is released, he said. At U.S. facilities, the quicksilver is captured in air pollution control equipment in the form of the mineral calomel, also known as mercurous chloride or dimercury dichloride.
ON AVERAGE, the U.S. produces about 255 metric tons of mercury per year, according to EPA. Some comes from the processing of calomel from mining operations, and some is recovered through the decommissioning of mercury cells at chlor-alkali plants or the processing of mercury-containing scrap, including thermometers and switches. Two U.S. facilities recover mercury and sell it on the world market, according to EPA.
As the U.S. government considers how it might manage nonfederal supplies of mercury in the face of a shifting global market for the troublesome element, it faces policy conundrums. It must determine whether or how it can continue to encourage domestic recycling and reclamation of the metal to prevent pollution at home while attempting to forestall releases of mercury elsewhere in the world. The government also is not eager to get into the mercury storage business, although the Departments of Defense and Energy have stockpiled the element for decades.
Meanwhile, the EU, home of dozens of aging mercury-cell chlor-alkali plants, is already moving to reduce the flow of mercury to world markets. Earlier this month, the Environment Committee of the EU Parliament called for a ban on exports of mercury starting Dec. 1, 2010, and proposed that the 12,000 metric tons of mercury in European chlor-alkali plants be stored in a shuttered mercury mine in Spain. In addition to elemental mercury, the committee wants to ban EU exports of cinnabar, calomel, and compounds with a mercury concentration above 5% by weight. A decision on that matter is anticipated in coming months.
Representatives of the chlorine, mining, and recycling industries as well as environmentalists and academics provided a variety of perspectives on what to do about mercury at EPA's stakeholder meeting. David Lennett, a senior adviser to NRDC on mercury policy, recommended that the U.S. government restrict exports of mercury and create a domestic storage facility for excess amounts of the metal. Art Dungan, president of the Chlorine Institute, added that any potential U.S. export ban must be predicated on a policy of what to do with excess mercury supply.
"We ought to keep it here," Lennett said. If domestic mercury supplies leave the U.S., mercury is likely to be released and end up tainting fish eaten by people around the world, he said. Doa noted that EPA is interested in exploring the possibility of storing mercury, but not having the federal government take possession of it.
It is unlikely that any private entity would store the metal without compensation, said Edward J. Balistreri, an assistant professor of economics and business at the Colorado School of Mines. "The federal government seems like the appropriate party" for carrying out this task, he concluded.
One possible way to move forward, Lennett suggested, would be to fund a government-owned storage facility for excess mercury through a tax on the use of mercury. This would put the burden on those who benefit from mercury-containing products rather than on taxpayers at large, he said. In response to that proposal, the Chlorine Institute's Dungan said a use tax might work for new mercury-containing products but would not help for older products and processes.
The mercury problem even shows up in one the most touted energy-efficiency success stories: compact fluorescent bulbs. A ban on U.S. exports of mercury could discourage the recycling of spent fluorescent and other light bulbs that contain the metal, said Raymond Graczyk, president of Northeast Lamp Recycling. The Connecticut firm processes defunct mercury-containing light bulbs from industrial complexes, hospitals, and other large-scale users of such bulbs.
In 1994, it cost between 80 and 90 cents to recycle a mercury-containing lamp, Graczyk said. The cost is now about 24 cents each. If a ban on mercury exports makes the recycling price rise to above $1.00 per bulb, "people will go back to trashing them" and mercury contamination will increase, he said.
Trying to manage the metal using a U.S. export ban would raise the price of mercury on the world market and depress it domestically, Balistreri said. Higher world prices would have the undesirable effect of making mercury mining economically attractive in the rest of the world, he said.
Countering that likelihood, however, Pollara pointed out that the International Council on Mining & Metals, a coalition of 15 of the world's largest mining companies, has committed to not opening new mercury mines. Pollara chairs the council's mercury working group.
Instead of mining the metal, China will generally buy elemental mercury on the world market when the price is less than $500 to $600 per flask, said Bruce Lawrence, president and owner of Bethlehem Apparatus of Hellertown, Pa. When the price rises higher than those figures, China tends to resume mining, said Lawrence, whose company for more than 30 years has recovered and purified mercury from waste, scrap, and chlor-alkali plants for resale.
As an incentive against mercury mining by China, the U.S. might offer to sell some of its excess mercury to the country, suggested Glenn Miller, professor of natural resources and environmental sciences at the University of Nevada, Reno.
With China's demand for mercury catalysts in the manufacture of vinyl chloride and with demand from small-scale gold mining in the developing world driving up the price of mercury, Dungan said, Miller's proposition could prove expensive.
Instead of banning exports, Balistreri said, the U.S. government could take a more economically efficient action by purchasing mercury on the world market at the lowest price available and then storing it. He suggested a tax on mercury exports to fund the purchases.
EPA will hold more public meetings on mercury in the coming months, said James Gulliford, the agency's assistant administrator for prevention, pesticides, and toxic substances. These will focus on the sources of mercury in the U.S., options for managing the metal, and the possibility of long-term storage. The agency will use the input as it drafts a report on managing the metal.
Bureaucratic goals aside, the issue that EPA and the U.S. government must ultimately resolve is whether poverty-stricken people in Asia, Africa, and South America who eke out a living mining gold will get mercury cheaply from growing excess supplies in the U.S.