data on the site—which EDF obtained through the Freedom of Information Act from a separate exposure assessment project conducted by EPA's Office of Policy— show that mobile and area sources are responsible for about 90% of the nation's hazardous air pollutants, Pease said. In light of that data's existence, Pease emphasized that EPA's new risk model will address only a small part of the picture of the sources of health risks from airborne toxics. The tool could be used as the basis for creating a more comprehensive tool, he said. Pease also faulted EPA for waffling about delivering the tool to the public, arguing that communities have wanted information about local health risks from TRI firms for years. Although Charles Pittinger, a principal scientist in Procter & Gamble Co.'s Environmental Sciences Department, said he was impressed with the scientific rigor of EPA's new relative risk assessment tool, he expressed concerns about its potential for misuse. (Pettinger is a new member of the SAB, and has seen the tool, but he did not review it for the board.) "Tools like this have the tendency to get out of the hands of their creators and into applications that either aren't appropriate, or not validated, or extrapolate beyond the limits of the data," he said. He cited the EPA data's presence on the EDF Web site as an example of what worries him, for the people viewing it may not understand the data's limits. Pease responded by saying that a number of business people who have accessed his Web site have thanked EDF for making the data available. The new EPA model is capable of performing estimates of human exposures from land, air, and water releases, Bouwes said. The initial version will only include information about air releases, however, because only the air data have been "groundtruthed" by comparing its results with data from site-specific modeling conducted in New York state. The air model correlated very well with that data, said Steve Hassur, senior chemist in
How does EPA's Risk-Screening Environmental Indicators model work?
OPPT's Industrial Chemistry Branch. At present, the model takesup to an hour to conduct a simulation, depending on the computing equipment, Bouwes said. The new tool will greatly reduce EPA's up-front costs for identifying areas of concern, such as where to target enforcement efforts. Bouwes said. Because it can show the cumulative expo-
sure of citizens to chemical releases from all nearby facilities, EPA expects to use it for analyzing environmental justice claims. It has already been used by the Department of Justice and the Office of Civil Rights, he said. Initially, EPA only plans to distribute the new software internally, Bouwes said, but he hopes that it will eventually be posted on the Internet. —KELLYN BETTS
Reducing mercury emissions in tandem with other pollutants cuts costs, EPA finds The difficult process of determining whether mercury emissions from electric power plants should be regulated may have received a boost from a new EPA report estimating that mercury control costs are 60% less than the agency reported in 1997. Released in March, Analysis of Emissions Reduction Options for the Electric Power Industry Report details the results of computerized analyses evaluating how to best cut emissions of the four most significant pollutants from the power industry: mercury, nitrogen oxides (NOJ, sulfur dioxide (S0 2 ), and carbon monoxide (CO). The report, which showed that it is far cheaper to reduce these emissions holistically, rather than reducing them individually, was the subject of ongoing talks between EPA and the power industry concerning how the industry might respond to upcoming regulations. However, the investor-owned utility sector, which
includes most large power companies, disagrees that the health studies support the need for mercury controls on power plants. The report was required under a settlement agreement to a lawsuit filed by the Natural Resources Defense Council because EPA had missed the deadline requiring a determination about whether mercury emissions at power plants should be controlled. The settlement agreement set a new deadline of December 2000; most of the hypothetical options in the report were developed with a compliance date of 2010. The cost estimates for controlling mercury are 60% lower than the $5 billion EPA estimated in its 1997 report to Congress, primarily because EPA's Office of Research and Development (ORD), in an ongoing effort to identify lowercost, reliable means to reduce mercury emissions, gathered new data on control technologies. Simply put, ORD staff found that coal-fired
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plants could reduce mercury emissions by 70%, (from an estimated base case of 47 tons to 14 tons) using activated carbon injection (ACI) followed by spray cooling and fabric filters, at a cost of $1.9 billion per year. If utilities operated under a cap and trade program, the control costs would drop to $1.7 billion, the analyses found. Under this program, each plant is allocated a specific level of emissions; plants that control below their allocations can sell their emissions, in the form of allowances, to another facility. Controlling for mercury alone would have little effect on reducing the other pollutants. However, by taking a broader view of control, the analysts found that adding ACI to a plant also controlling for S0 2 and CO can lower annual mercury emissions from 31 tons to 9 tons. Here is how: The modelers considered a range of potential S0 2 reductions, which went 40-55% beyond the requirements of the acid rain program and were designed to meet EPA's fine particulate (PM2 5) and visibility rules. Using flue gas desulfurization units or scrubbers, coal-fired plants could reduce S0 2 by 50%, mercury by 13%, NOx by 3%, and C0 2 by 2%, according to the model. To reduce CO, the modelers chose two options: by 2008, power companies would be assigned an emissions cap of 3% below 1990 emissions, then would cut emissions by switching to natural gas, with lower NO^ levels and 60% of the CO emissions per BTU when compared with coal. The remaining emission allowances would be purchased on the international market. Under this plan, mercury and NOx emissions would drop by 15% at a cost of $3 billion annually, including $2 billion to buy international emission credits. CO emissions would drop by 9%. The second scenario assumes energy efficiency programs have reduced demand in 2010 by about 15% below what the industry forecasted. The industry would convert some coal-fired plants to natural gas, and mercury emissions would drop by about 23%, the model shows.
The report has been one of several reviewed during EPA's recent discussions with the power industry, including representatives from municipal facilities and independent power plants, to find ways to provide some certainty about the industry's regulatory future. A determination about possible mercury standards is only one requirement in the works; states may call for mercury controls if EPA declines to do so; emissions of fine particulates and NOx must be in place by 2003, although both rules have been challenged in court; S02 reductions may be necessary to meet the PM2 5 standard; and compliance with the Kyoto Protocol, if ever ratified by the Senate, would require CO reductions that are likely to fall on power plants.
Utilities are eager to discuss the future with EPA because they are concerned that a technological fix for one pollutant, for example, NO.,., may be the wrong choice later if a plant is required to reduce carbon dioxide (C02), said John Kinsman with the Edison Electric Institute, a lobbying organization. A few utilities are conducting pilot projects to see how they can reduce several pollutants at once. With funding from the Department of Energy, EPA, and the Electric Power Research Institute, a few power companies are experimenting with ACI combined with various sorbents to see if they can reduce two or more pollutants at once. —CATHERINE M. COONEY
ACI + hydrated lime = 90% mercury reduction? The state-of-the-art multipollutant control technologies in pilot-stage development at Public Service Electric and Gas's (PSE&G's) coal-fired plants may be what the industry needs as it moves into the 21st century. The projects, supported by EPA, the Department of Energy, and the power industry's Palo Alto, Calif.-based Electric Power Research Institute, could have significant implications for the industry if new mercury or air toxic standards are issued. Engineers at PSE&G's Mercer plant, located in Trenton, N.J., are testing a 20-foot-high circulating fluidized bed (CFB) pilot unit installed adjacent to the coal-fired boiler. In operation, a minor fraction of flue gas captured from the boiler is passed though the CFB. There, fly ash entrained in the diverted gas builds up and circulates through the unit at 1000 cubic feet per minute. Contaminant mercury in the circulating gas collides with and sticks to the ash, and both are captured when the flue gas is returned through a huge duct from the fluidized bed into the unit's electrostatic precipitator (ESP). A fairly common technology for controlling particulates, the ESP unit electronically charges the ash, forcing it to stick to thousands of hanging metal plates in the precipitator. The "cleaned" flue gas then continues through another duct and is pushed out the boiler's stack. Use of the CFB has resulted in mercury emissions reductions of 50%, said Paul Feldman, with Environmental Elements Corp. in Baltimore, Md., which conceived of and designed the Mercer pilot. If an activated carbon sorbent is simultaneously injected into the fluidized bed, mercury emissions can be reduced by 90%. Also, reductions of sulfur dioxides and hydrogen chloride as high as 75-95% were achieved when hydrated lime sorbents were added, Feldman said. These pilots, which have been in place for two years, are still highly experimental and are being run on small power plants, PSE&G's engineers noted. PSE&G's Mercer project is one of a few pilots under way at utilities to concurrently reduce multiple pollutants, said Charles Sedman of EPA's National Risk Management Research Laboratory. New Century Energies (formerly Public Service of Colorado), in Denver, Colo., and Southern Company, in Atlanta, Ga., have pilots aimed at reducing more than one pollutant, Sedman said.
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