Mercury emissions from power plants in 137 United Nations member countries could be subject to strict controls and reductions if an international treaty is signed by participating nations this October.
After wrapping up four years of complex negotiations to prepare a global instrument on mercury, governments of nations participating in the United Nations Environment Programme (UNEP) initiative on Jan. 19 agreed in Switzerland to the text of a legally binding instrument, which they called the “Minamata Convention on Mercury.” The text of the convention, named after the Japanese city where serious health damage occurred as a result of methyl mercury pollution in the mid-20th century, will be open for signature at the Diplomatic Conference in Japan, from Oct. 7 to 11, 2013. It will become legally binding once 50 countries have ratified and agreed to be bound by it.
The fifth session of UNEP’s Intergovernmental Negotiating Committee ended with governments including the U.S., European Union, China, and India agreeing to actions to reduce mercury emissions to the air from power plants and other sources, reduce the use of mercury in products and industrial processes, and address mercury supply and trade. The treaty would control mercury emissions and releases from large industrial facilities—including coal-fired power plants and industrial boilers, certain kinds of smelters (handling zinc and gold, for example), waste incineration, and cement clinker facilities.
It calls for the installation of “Best Available Technologies” for new power plants and facilities and would legally bind countries to implement plans that would bring emissions down from existing ones. The plans for existing sources would take into account “national circumstances, and the economic and technical feasibility, and affordability of the measures,” within 10 years after the accord is ratified.
The negotiations, which were held over five sessions between 2010 and 2013, had initially sought to set thresholds on the size of the plants or level of emissions to be controlled, but with countries disagreeing on these specifics until the final week, the nations agreed to defer that decision until the first meeting after the treaty has been ratified.
Among its key aspects, the treaty would ban by 2020 the export and import of a range of mercury-containing products, including batteries, certain types of compact fluorescent lamps, and soaps and cosmetics. And it would require countries to create strategies to reduce the amount of mercury used by artisanal and small-scale miners, requiring countries with legal small gold-mining operations to develop national plans within three years of the treaty’s enforcement to reduce or eliminate their use of mercury.
UNEP: World’s Mercury Emissions May Be Rising after Decline
UNEP says that worldwide mercury emissions likely peaked in the 1950s to 1970s and then declined because of reductions from Europe, Russia, and North America. Some indications show that emissions may be rising again, with increases from East Asia offsetting continuing reductions in Europe and North America, it warns.
According to the international institution’s “Global Mercury Assessment 2013,” a document that updates global releases and the environmental transport of mercury, an estimated 1,960 metric tons (mt) of mercury were emitted to the atmosphere in 2010 as a result of direct human activity. An updated inventory of emissions to air suggests that about 475 mt of mercury are emitted by coal combustion, compared with just 10 mt from combustion of other fossil fuels. More than 85% of the 475 mt estimated is attributable to emissions from coal burning for power generation and industrial uses.
But coal combustion isn’t the biggest source of the world’s mercury emissions, according to the report. It blames the informal sector of artisanal and small-scale gold mining for releasing a whopping 727 mt per year (mt/yr) to air. Artisanal gold miners, who often are poor, typically use mercury to create an amalgam separating gold from other materials, but they then have to separate the mercury from the gold. Though UNEP admits there are data gaps because collecting information about this sector is challenging owing to its widely dispersed and unregulated nature, it suggests the significant increase comes in large part from China, where the practice was banned in 1996.
|1. Quicksilver around the world. The United Nations Environment Programme (UNEP) estimates that global emissions of mercury to air from a variety of human activities in 2010 totaled 1,960 metric tons. This chart breaks down that total by region. The bulk of mercury emissions in South America and Sub-Saharan Africa were released by artisanal and small-scale gold mining practices, for which extensive data gaps exist, UNEP admits. Source: UNEP
|2. Anthropogenic mercury emissions by source. About 24% of the world’s anthropogenic emissions of mercury came from fossil fuel combustion in 2010—mostly from coal—though the widely varying mercury content of coal makes emissions estimates “highly uncertain,” UNEP says. Estimated emissions of mercury from artisanal and small-scale gold mining, the largest human-caused source, doubled those reported in 2005—owing partly to the high price of gold and increased emission estimates. Source: UNEP
Increases in Mercury Emissions from Power Plants Notable in Asia
The report notes that coal combustion for power generation for industrial purposes continues to increase—particularly in Asia. But it also points out that air pollution controls at some power plants and stringent regulations have reduced mercury emissions from coal plants, “and thus offset some part of the emissions arising from increased coal consumption.”
Countries showing improvements include the U.S., where coal generators are rushing to meet the initial April 2015 compliance deadline for the Environmental Protection Agency’s (EPA’s) December 2011–promulgated Mercury and Air Toxics Standards (MATS). An agency Information Collection Request (ICR) from 2010 suggests that electric generating units emitted about 29 mt of mercury that year, but it extrapolates from a 2005 finding (because the ICR did not cover total U.S. anthropogenic emissions) that 53 mt of the nation’s total 105 mt of mercury emissions came from electric generating units.
This claim—that power plants were responsible for 50% of mercury released in the country—was repeated in documents justifying the EPA’s 2011-finalized MATS rule. The agency admitted, however, that power plants will emit 27 mt of mercury in 2016 even if MATS is not enforced, constituting 42% of the nation’s total of 64 mt of anthropogenic mercury emissions.
Meanwhile, UNEP explains the decrease from 53 mt in 2005 to 29 mt in 2010 in U.S. mercury emissions from coal plants as largely attributable to “new regulations that have resulted in changes in the sources of the coal that is burned in large power plants and the installation of mercury controls as well as controls on sulphur dioxide and particulates that have the co-benefit of further reducing mercury emissions.”
Anthropogenic mercury emissions from Asian power plants—particularly in China—are also expected to decrease because “many of the new coal-fired power plants have state-of-the-art pollution controls installed,” the report foresees. Stationary combustion of all fuels in Asia emitted about 622 mt per year, constituting about 64% of the region’s total. According to the report, China and India dominate the region’s emission inventories, but a handful of Southeast Asian countries also contribute significantly to the total.
In 2005, China’s total mercury emissions from its power plants totaled about 108.6 mt. That number had fallen by 34 mt in 2008 with the enactment of mandates limiting sulfur dioxide emissions, which resulted in the installation of flue gas desufurization (FGD) technologies and the shutdown of smaller, inefficient units. A UNEP technical briefing document also claims that by 2008, more than 95% of China’s myriad coal-fired power plants had installed electrostatic precipitators, and by 2009, 71% (about 460 GW) had installed FGD.
India’s mercury issues, on the other hand, are much more complex, suggests Dr. Lesley Sloss, who leads efforts by the International Energy Agency’s Clean Coal Centre to track and analyze the world’s mercury emissions. She says in an October 2012 study (funded by the U.S. State Department) that in the South Asian nation (which relied on high-mercury indigenous coal for about 70% of its heat and power production in 2007), coal combustion currently releases mercury emissions of about 40 mt/yr. By 2016, these emissions are expected to rise to 106 mt/yr and to more than 148 mt/yr by 2021. New laws could curb this output, Sloss notes, but the likelihood of nationwide mandates to curb mercury emissions “are small.”
Indian coal is low in sulfur, and sulfur dioxide emission limits have not been a priority—though a law exists that would require new coal plants over 500 MW to provide space on site to allow for the installation of FGD technology in the future. And India does not have nitrogen oxide emission limits, though emission limits introduced in 1981 have prompted many plants to be retrofitted with particulate control systems, mostly electrostatic precipitators.
Compared to India, several Southeast Asian countries have installed, or are installing some of the most advanced combustion and pollution control systems available, Sloss says. About 80% of Indonesia’s 10 GW of coal-fired capacity has sulfur control systems in place, for example. And in Thailand, where coal use is expected to increase by a factor of four by 2021, most coal plants have installed FGD and de-NOx systems.
“In many countries, mercury control is assumed to be expensive—this misconception needs to be corrected with demonstrations of cost-effective mercury control options at real plants in Southeast Asia,” Sloss concludes. UNEP has produced an interactive process optimization guidance document (POG) that should help plant operators understand and maximize mercury reduction on a plant-by-plant basis, tools that along with expert workshops should be promoted throughout coal-heavy Southeast Asia, she recommends.
—Sonal Patel is POWER’s senior writer