Mercury can harm fetuses and cause neurological  disorders in children, resulting in, among other things, impaired cognitive  abilities. As a result, DOE now has comprehensive information on the  effectiveness of sorbent injection systems using all coal types at a wide  variety of boiler configurations. Substantial Mercury Reductions Have Been Achieved Using Sorbent Injection Technology at 14 Plants and in Many DOE Tests, but Some Plants May Require Alternative Strategies to Achieve Comparable Results

The managers of 14 coal-fired power plants reported to us they currently  operate sorbent injection systems on 25 boilers to meet the mercury  emission reduction requirements of 4 states and several consent decrees  and construction permits. Preliminary data 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. 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. Other plants may also be able to  achieve high mercury reduction with their existing pollution control  devices. While sorbent injection technology has been shown to be effective with all  coal types and on boiler configurations 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. Finally, mercury controls have  been tested on about 90 percent of the boiler configurations at coal-fired  power plants. 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. For example, while sorbent  injection systems alone have been installed on most boilers that must meet  mercury reduction requirements—at a fraction of the cost of other  pollution control devices—fabric filters have also been installed on some  boilers to assist in mercury capture or to comply with particulate matter  requirements, according to plant officials we interviewed. 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 (see table 1). 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. For the 18 boilers with sorbent injection systems for which power plants  provided sorbent cost data, the average annualized cost of sorbent was  $674,000. 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 mercury emissions limit. 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. In addition, the format of the standard—whether it limits  the mercury content of coal being burned (an input standard) or of  emissions from the stack (an output standard)—may affect the stringency  of the MACT standard the agency proposes. Current Data from Commercial Deployments and DOE Tests Could Be Used 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 for mercury. The 1999 data do not reflect the significant  and widespread mercury reductions achieved by sorbent injection  systems. Other strategies, including  blending coal and using other technologies, exist for the small number of  plants with configuration types that were not able to achieve significant  mercury emissions reductions with sorbent injection alone.
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 laws 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. This testimony provides preliminary data from GAO's ongoing work on (1) reductions achieved by mercury control technologies and the extent of their use at coal-fired power plants, (2) the cost of mercury control technologies in use at these plants, and (3) key issues EPA faces in regulating mercury emissions from power plants. GAO obtained data from power plants operating sorbent injection systems.

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 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, sorbent injection has not been tested on a small number of boiler configurations, some of which achieve high mercury removal with other pollution control devices. 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 $640,000. 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. For example, 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. Data from EPA's 1999 power plant survey do not reflect commercial deployments or DOE tests of sorbent injection systems and could support a standard well below what has recently been broadly achieved. Moreover, the time frame for proposing the standard may be compressed because of a pending lawsuit. On July 2, 2009, EPA announced that it planned to conduct an information collection request to update existing emission data, among other things, from power plants.