Environ. Sci. Technol. 2010, 44, 7994–7995
China Needs to Control Mercury Emissions from Municipal Solid Waste (MSW) Incineration
RHONDA SAUNDERS
H E F A C H E N G * ,†,‡ YUANAN HU§ State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China, Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94025, United States, and Education Program for Gifted Youth, Stanford University, Stanford, California 94025, United States
Because of its toxic, persistent, and bioaccumulative nature, mercury is a significant public health and environmental problem. Elemental mercury is generally the predominant form of mercury (∼95%) in the atmosphere, with natural (e.g., volcanoes and weathering of rocks) and anthropogenic sources (e.g., coal combustion and metal smelting) contributing approximately equally to the total atmospheric budget of vapor-phase mercury (1). Because elemental mercury has a long atmospheric residence time (0.5-2 years) (2), it is a
* Corresponding author phone: (+86) 20 8529-0175; fax: (+86) 20 8529-0706; e-mail:
[email protected]. † Chinese Academy of Sciences. ‡ Department of Civil and Environmental Engineering, Stanford University. § Education Program for Gifted Youth, Stanford University. 7994
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problem with global reach. Governments from around the world have begun negotiating a global legally binding instrument on mercury since June 2010, with the goal of completing the negotiations by 2013. China has the largest anthropogenic mercury emissions (∼700 tonnes/year) and is responsible for approximately a quarter of the global emissions (3). The limited data available indicate mercury pollution occurs in various environmental media (soils, air, surface water, and plants) in China, and the major mercury exposure pathways are consumption of contaminated fish for residents living in coastal cities and inhalation in areas with severe atmospheric mercury pollution (4). It is imperative for China to make vigorous efforts in reducing mercury emissions to protect the health of its citizens, to prepare for compliance with the upcoming international treaty, and to support global efforts of mercury reduction. Among the mercury source categories, emissions from incineration of municipal solid waste (MSW) experienced the fastest growth, from 0.6 tonne in 1995 to 10.4 tonnes in 2003 (3), due to the rapid expansion of MSW incineration industry in China (5). Incineration is increasingly replacing landfilling as the preferred MSW management option in China (5). Mercury-containing products that end their life cycle in MSW, such as batteries and fluorescent lamps, release mercury upon combustion. Globally, waste disposal, primarily from incineration, contributes to ∼8% of the total anthropogenic mercury emissions (1). In China, MSW incineration is not a major source of anthropogenic mercury emissions (1.5% in 2003) yet (3), primarily because of the dominance of metal smelting and coal combustion, and the infancy state of the incineration industry. Nonetheless, as the leading sector in mercury emission growth (3), MSW incineration should be considered a high priority source in China’s mercury control strategy. Atmospheric mercury emissions from MSW incinerators depend on the mercury input from the waste, the incineration technology, and the flue gas cleaning system. Figure 1 illustrates the speciation and atmospheric transport of mercury released from MSW incineration. Although postcombustion emission control can be effective at limiting the atmospheric emissions, it is not necessarily the optimum solution. Effective mercury emission control can be achieved by limiting and preventing mercury from entering incinerators, through both source separation and source reduction measures. Additionally, air pollution control equipment can limit the escape of mercury with the flue gas, while a stringent emission standard and a strong monitoring capacity can ensure the reduction in mercury emissions. Significant control of mercury emissions from MSW incineration can be achieved by limiting the amount of mercury entering incinerators. It is important to establish laws, standards, and regulations that prohibit or restrict mercury-containing products and manage them throughout their life cycles. In addition, China should actively develop and support programs on collection and replacement of mercury-containing devices from households, such as thermometers, batteries, and fluorescent lamps. Effective mea10.1021/es1030917
2010 American Chemical Society
Published on Web 10/01/2010
FIGURE 1. Schematic illustration of emissions and atmospheric transport of mercury from MSW incineration. Emissions of mercury from waste incinerators are approximately 10-20% Hg0 and 75-85% Hg2+ (2), some of which condense and adsorb on the surface of fly ash particles as the flue gas cools, forming particulate mercury (Hgp). sures have been taken at reducing mercury contents in batteries and establishing relevant recycling programs in China, whereas little attention has been paid to the disposal of fluorescent lamps (containing up to 10 mg mercury each). Besides the wastes, mercury content of coal, which is widely used as a supplementary fuel (up to 20%) in MSW incineration in China (5), should be effectively reduced (e.g., via coalwashing). Attention should also be paid to mercury source reduction in MSW management practices. Environmentally sound collection, recycling, and disposal of mercury-containing products and wastes are crucial for reducing the mercury content of MSW. Operators of MSW incinerators should be properly trained to identify and divert mercury-containing wastes. Meanwhile, community outreach and public education programs on the health and environmental risks of mercury, the use of nonmercury alternatives, proper disposal of mercury-containing products, and ways to reduce mercury release to the environment are key to substantial mercury reduction in MSW. MSW incinerators in China were built according to different criteria until the establishment of the national standards on pollutant emissions in 2001 (5). Furthermore, the Chinese emission standard on mercury (0.2 mg/m3) is much weaker than those in Europe and the United States (0.05-0.08 mg/m3) (5). A more stringent mercury emission standard from MSW incineration should be developed to halt or even reverse the increasing trend of mercury release from this source category. Existing MSW incineration facilities without mercury control devices should be retrofitted, and advanced flue gas cleaning technologies for mercury removal should be required for new facilities. Meanwhile, financial and technical support should be provided to help the industry develop and implement efficient mercury control technologies. As environmental laws and regulations are often poorly enforced in China, it is also important to develop an effective administrative mechanism for MSW incineration and a strong monitoring capacity to verify the compliance of MSW
incineration facilities regarding emissions of mercury and other pollutants. Finally, pollution prevention is a far better strategy than reducing and controlling the release of pollutants after their generation. Reduction and elimination of the mercury contents in consumer products by the manufacturers is the ultimate solution to mercury problems in MSW management. The flow of mercury to MSW can be stopped by using safe alternative technologies and products and banning the production, trade, and consumption of mercury-containing products. The Administrative Measure on the Control of Pollution Caused by Electronic Information Products (aka China RoHS) enacted on March 1, 2007 restricted 6 groups of hazardous chemicals, including mercury, in a wide variety of products. Besides such legislative work, China should promote mercury-free products and provide incentives to manufacturers to develop alternatives to mercury-containing products and nonmercury production processes. These efforts will significantly cut the mercury contents in consumer goods and thus the mercury input to wastes.
Literature Cited (1) Pirrone, N.; Cinnirella, S.; Feng, X.; Finkelman, R. B.; Friedli, H. R.; Leaner, J.; Mason, R.; Mukherjee, A. B.; Stracher, G. B.; Streets, D. G.; Telmer, K. Global mercury emissions to the atmosphere from anthropogenic and natural sources. Atmos. Chem. Phys. Discuss. 2010, 10 (2), 4719–4752. (2) Carpi, A. Mercury from combustion sources: A review of the chemical species emitted and their transport in the atmosphere. Water, Air Soil Pollut. 1997, 98 (3-4), 241–245. (3) Wu, Y.; Wang, S.; Streets, D. G.; Hao, J.; Chan, M.; Jiang, J. Trends in anthropogenic mercury emissions in China from 1995 to 2003. Environ. Sci. Technol. 2006, 40 (17), 5312–5318. (4) Zhang, L.; Wong, M. H. Environmental mercury contamination in China: Sources and impacts. Environ. Int. 2007, 33 (1), 108– 121. (5) Cheng, H.; Hu, Y. Municipal solid waste (MSW) as a renewable source of energy: Current and future practices in China. Bioresour. Technol. 2010, 101 (11), 3816–3824.
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