Mercury can harm fetuses and cause neurological  disorders in children, resulting in, among other things, impaired cognitive  abilities. Substantial Mercury Reductions Have Been Achieved Using Sorbent Injection Technology at 14 Plants and in Many DOE Tests

Power plants using sorbent injection systems—either commercially  deployed or tested by DOE and industry—have achieved substantial  mercury reductions with the three main types of coal and on boiler  configurations that exist at nearly three-fourths of U.S. coal-fired power  plants. Nonetheless, some plants  already achieve substantial mercury emissions reductions with existing  control devices for other pollutants. Data from power plants show that these  boilers have achieved, on average, reductions in mercury emissions of  about 90 percent. Further, when the  results of 50 tests of sorbent injection systems at power plants conducted  primarily as part of DOE’s or EPRI’s mercury control research and  development programs are factored in, mercury reductions of at least 90  percent have been achieved at boiler configurations used at nearly three- fourths of coal-fired power boilers nationally. Plant officials told us, for example, that they chose to  install fabric filters to assist with mercury control for 10 of the sorbent  injection systems currently deployed—but that some of the devices were  installed primarily to comply with other air pollution control requirements. The successful deployments of sorbent injection technologies at power  plants occurred around the time DOE concluded, on the basis of its tests,  that these technologies were ready for commercial deployment. Some Plants May Require Alternative Strategies to Achieve Significant Mercury Reductions

While sorbent injection technology has been shown to be effective with all  coal types and on boiler configurations that currently exist at more than  three-fourths of U.S. coal-fired power plants, DOE tests show that some  plants may not be able to achieve mercury reductions of 90 percent or  more with sorbent injection systems alone. Mercury Control Technologies Are Often Relatively Inexpensive, but Costs Depend Largely on How Plants Comply with Requirements for Reducing Other Pollutants

The cost to meet current regulatory requirements for mercury reductions  has varied depending in large part on decisions regarding compliance with  other pollution reduction requirements. The costs of purchasing and installing sorbent injection systems and  monitoring equipment have averaged about $3.6 million for the 14 coal- fired boilers that use sorbent injection systems alone to reduce mercury  emissions. Information on  detailed average costs to purchase and install sorbent injection systems  and monitoring equipment, with and without fabric filters, is provided in  appendix V.
Regarding operating costs, plant managers said that annual operating costs  associated with sorbent injection systems consist almost entirely of the  cost of the sorbent itself. Most sorbents increase the carbon content of fly ash, which may  render it unsuitable for some commercial uses. Advances in sorbent technologies that have reduced costs at some plants  also offer the potential to preserve the market value of fly ash. Decisions EPA Faces on Key Regulatory Issues Will Have Implications for the Effectiveness of Its Mercury Emission Standard for Coal- Fired Power Plants and the Availability of Monitoring Data

EPA’s decisions on key regulatory issues will impact the overall stringency  of its MACT standard regulating mercury emissions. Specifically, the data  EPA decides to use will affect (1) the mercury emission reductions  calculated for “best performers,” from which a proposed emission limit is  derived; (2) whether EPA will establish varying standards for the three  coal types; and (3) how EPA’s standard will take into account varying  operating conditions. Each of these issues will affect the stringency of the  MACT standard the agency proposes. Current Data from Commercial Deployments and DOE Tests Could Be Used in Determining Whether to Support a More Stringent Standard for Mercury Emissions from Power Plants Than Was Last Proposed by EPA

Obtaining data on mercury emissions and identifying the “best  performers”—defined as the 12 percent of coal-fired power plant boilers  with the lowest mercury emissions—is a critical initial step in the  development of a MACT standard regulating mercury emissions. Before a federal agency can collect data from 10 or more nongovernmental  parties, such as power plants, it must obtain approval from the Office of  Management and Budget (OMB) for the information collection request. EPA and DOE provided  technical comments, which we incorporated as appropriate. Appendix I: Objectives, Scope, and Methodology

This appendix details the methods we used to examine (1) the mercury  reductions that have been achieved by existing mercury control  technologies and the extent to which they are being used at coal-fired  power plants, (2) the costs associated with mercury control technologies  currently in use, and (3) key issues the Environmental Protection Agency  (EPA) faces in developing a new regulation for mercury emissions from  coal-fired power plants.
Why GAO Did This Study

The 491 U.S. coal-fired power plants are the largest unregulated industrial source of mercury emissions nationwide, annually emitting about 48 tons of mercury--a toxic element that poses health threats, including neurological disorders in children. In 2000, the Environmental Protection Agency (EPA) determined that mercury emissions from these sources should be regulated, but the agency has not set a maximum achievable control technology (MACT) standard, as the Clean Air Act requires. Some power plants, however, must reduce mercury emissions to comply with state regulations or consent decrees. After managing a long-term mercury control research and development program, the Department of Energy (DOE) reported in 2008 that systems that inject sorbents--powdery substances to which mercury binds--into the exhaust from boilers of coal-fired power plants were ready for commercial deployment. Tests of sorbent injection systems, the most mature mercury control technology, were conducted on a variety of coal types and boiler configurations--that is, on boilers using different air pollution control devices. In this context, GAO was asked to examine (1) reductions achieved by mercury control technologies and the extent of their use at power plants, (2) the cost of mercury control technologies, and (3) key issues EPA faces in regulating mercury emissions from power plants. GAO obtained data from power plants operating sorbent injection systems. EPA and DOE provided technical comments, which we incorporated as appropriate.

What GAO Found

Commercial deployments and 50 DOE and industry tests of sorbent injection systems have achieved, on average, 90 percent reductions in mercury emissions. These systems are being used on 25 boilers at 14 coal-fired plants, enabling them to meet state or other mercury emission requirements--generally 80 percent to 90 percent reductions. The effectiveness of sorbent injection is largely affected by coal type and boiler configuration. Importantly, the substantial mercury reductions using these systems commercially and in tests were achieved with all three main types of coal and on boiler configurations that exist at nearly three-fourths of U.S. coal-fired power plants. While sorbent injection has been shown to be widely effective, DOE tests suggest that other strategies, such as blending coals or using other technologies, may be needed to achieve substantial reductions at some plants. Finally, some plants already achieve substantial mercury reductions with existing controls designed for other pollutants. The cost of the mercury control technologies in use at power plants has varied, depending in large part on decisions regarding compliance with other pollution reduction requirements. The costs of purchasing and installing sorbent injection systems and monitoring equipment have averaged about $3.6 million for the 14 coal-fired boilers operating sorbent systems alone to meet state requirements. This cost is a fraction of the cost of other pollution control devices. When plants also installed a fabric filter device primarily to assist the sorbent injection system in mercury reduction, the average cost of $16 million is still relatively low compared with that of other air pollution control devices. Annual operating costs of sorbent injection systems, which often consist almost entirely of the cost of the sorbent itself, have been, on average, about $675,000. In addition, some plants have incurred other costs, primarily due to lost sales of a coal combustion byproduct--fly ash--that plants have sold for commercial use. The carbon in sorbents can render fly ash unusable for certain purposes. Advances in sorbent technologies that have reduced sorbent costs at some plants offer the potential to preserve the market value of fly ash. EPA's decisions on key regulatory issues will have implications for the effectiveness of its mercury emissions standard. In particular, the data EPA decides to use will impact (1) the emissions reductions it starts with in developing its regulation, (2) whether it will establish varying standards for the three main coal types, and (3) how the standard will take into account a full range of operating conditions at the plants. These issues can affect the stringency of the MACT standard EPA proposes. For example, if EPA uses data from its 1999 power plant survey as the basis for its mercury standard, the standard could be less stringent than what has been broadly demonstrated in recent commercial deployments and DOE tests of sorbent injection systems at power plants. On July 2, 2009, EPA announced that it would seek approval from the Office of Management and Budget to conduct an information collection request to update existing emissions data, among other things, from power plants.