Mercury Controls Have Not Been Permanently Installed at Power Plants but Are Available for Purchase and Have Shown Promising Results in Field Tests

Power plants in the United States do not currently use mercury controls,  but some technologies are available for purchase and have shown  promising results in full-scale tests in power plants. These tests have  shown that mercury controls known as sorbent technologies—which  involve injection of a powdered material that binds to mercury in the  plant’s exhaust—have shown the greatest effectiveness in removing  mercury during tests at power plants. However, long-term test data are  limited because most of these tests have lasted less than 3 months. The coal-fired power  industry has not used mercury controls because, prior to EPA’s March 2005  rule, federal law had not required mercury emissions reductions at power  plants. EPA set the mercury emissions cap for 2010 based on a 50 percent  reduction from the 75 tons in coal. Mercury Control Costs Depend on a Variety of Factors, and Current Estimates Vary Widely

The estimated costs to install and operate mercury controls vary greatly  and depend on a number of site-specific factors, including the amount of  sorbent used (if any), the ability of existing air pollution controls to remove  mercury, and the type of coal burned. EPA and DOE have developed the  most comprehensive estimates available for mercury controls based on  modeling and data from a limited number of field tests, making them both  preliminary and uncertain. Regardless of the  exact costs of the controls, most of the stakeholders we contacted  generally expect the costs to decrease over time. As  noted above, EPA based its mercury reduction goals for 2010 to 2018 on  the level of control it expects plants will achieve with controls for these  other pollutants. Although the DOE and EPA estimates reflect different assumptions as  discussed above, we are providing the two agencies’ cost estimates for  achieving a 70 percent mercury reduction at a bituminous-fired coal power  plant under two scenarios (using an existing electrostatic precipitator and  installing a supplemental fabric filter) to provide a perspective on the costs  power plants could incur to install sorbent injection technologies. Alternatively, if this plant were to install  a supplemental fabric filter, the capital costs would increase to about  $28.3 million ($56.53 per kilowatt), and the operating and maintenance  costs would decrease to about $2.6 million annually ($0.74 per  megawatt-hour). In EPA’s rulemaking documents, the agency said that in light of  the more recent tests of chemically enhanced sorbents, their earlier  estimates likely overstated the actual costs power plants would incur. For a 500- megawatt plant operating at 80 percent capacity, this would equate to  $45 million to $60 million in capital costs and $6.0 million to $8.3 million  in annual operating and maintenance costs. According to EPA and DOE officials, the most recent test  results of injected sorbent technologies suggest that the cost of using these  technologies will be less than these agencies estimated in 2003, stemming  from advances in the sorbents. DOE reviewed the report and said that it generally agreed with  our findings. EPA’s Office of Air and Radiation and Office of Research and  Development provided technical comments, which we incorporated as  appropriate. Objectives, Scope, and Methodology

Congressional requesters asked us to (1) describe the use, availability, and  effectiveness of technologies to reduce mercury emissions at power plants;  and (2) identify the factors that influence the cost of these technologies and  report on available cost estimates. We did not independently test  these technologies. We also obtained  data on mercury emissions. EPA’s mercury rule requires mercury emissions monitoring and quarterly  reporting of mercury emissions data. Environmental Protection Agency. Department of Energy.
Why GAO Did This Study

In March 2005, the Environmental Protection Agency (EPA) issued a rule that will limit emissions of mercury--a toxic element that causes neurological problems--from coal-fired power plants, the nation's largest industrial source of mercury emissions. Under the rule, mercury emissions are to be reduced from a baseline of 48 tons per year to 38 tons in 2010 and to 15 tons in 2018. In the rule, EPA set the emissions target for 2010 based on the level of reductions achievable with technologies for controlling other pollutants--which also capture some mercury--because it believed emerging mercury controls had not been adequately demonstrated. EPA and the Department of Energy (DOE) coordinate research on mercury controls. In this context, GAO was asked to (1) describe the use, availability, and effectiveness of technologies to reduce mercury emissions at power plants; and (2) identify the factors that influence the cost of these technologies and report on available cost estimates. In completing our review, GAO did not independently test mercury controls. GAO provided the draft report to DOE and EPA for comment. DOE said that it generally agreed with our findings. EPA provided technical comments, which we incorporated as appropriate.

What GAO Found

Mercury controls have not been permanently installed at power plants because, prior to the March 2005 mercury rule, federal law had not required this industry to control mercury emissions; however, some technologies are available for purchase and have shown promising results in field tests. Overall, the most extensive tests have been conducted on technologies using sorbents--substances that bind to mercury when injected into a plant's exhaust. Tests of sorbents lasting from several hours to several months have yielded average mercury emission reductions of 30-95 percent, with results varying depending on the type of coal used and other factors, according to DOE and other stakeholders we surveyed. Further, the most recent tests have shown that the effectiveness of sorbents in removing mercury has improved over time. Nonetheless, long-term test data are limited because most tests at power plants during normal operations have lasted less than 3 months. The cost of mercury controls largely depends on several site-specific factors, such as the ability of existing air pollution controls to remove mercury. As a result, the available cost estimates vary widely. Based on modeling and data from a limited number of field tests, EPA and DOE have developed preliminary cost estimates for mercury control technologies, focusing on sorbents. For example, DOE estimated that using sorbent injection to achieve a 70-percent reduction in mercury emissions would cost a medium-sized power plant $984,000 in capital costs and $3.4 million in annual operating and maintenance costs. If this plant did not have an existing fabric filter and chose to install one--an option a plant might pursue to increase the efficiency of mercury removal and reduce related costs--capital costs would increase to about $28.3 million, while annual operating and maintenance costs would decrease to about $2.6 million. Most stakeholders generally expect costs to decrease as a market develops for the control technologies and as plants gain more experience using them. Furthermore, EPA officials said that recent tests of chemically enhanced sorbents lead the agency to believe that its earlier cost estimates likely overstated the actual cost power plants would incur.