Kathleen Davis, Associate Editor
In December the Environmental Protection Agency (EPA) called for regulation of mercury emissions from coal-fired utility boilers. While the timeline for regulation stretches to full compliance in 2007 (with testing of control and measurement technology already underway), the future of mercury emissions regulations remains shrouded by unanswered questions: Will mercury be regulated as a lump unit or broken down into elemental or oxidized? Will a universal sorbent be found for the varying mercury content in different types of coal? Will the addition of a wet scrubber be enough to capture mercury along with other pollutants? How much will compliance with these regulations cost?
But the question that elicits the most grumbling from power generators remains centered firmly on proof.
Seeking the source
It seems there’s a gap in the chain of cause and effect, a gap big enough to push a power plant through. While no one is disputing that mercury is one of the emissions that a coal-fired plant exudes (the EPA gives the U.S. average for power plants between 45 and 48 tons annually), whether it is being absorbed into land and water and eventually tracing a methylmercury path into fish (where it can affect the human body on excessive ingestion), remains unproven.
“That’s where the hole in the knowledge is,” said Mike Durham, president of ADA Environmental Solutions (ADA-ES). “They have been analyzing fish and measuring fish. And those measurements are real and increasing. But we don’t know exactly what happens.”
“[Scientists] are not really sure of the correlation,” stated John Pavlish, Senior Research Manager for the Energy and Environmental Research Center at the University of North Dakota. Pointing out that the Center had proposed a study to connect those dots a few years ago, Pavlish lamented its ultimate death, mostly due to complications and cost.
“Personally, I would have preferred to see the project carried out,” he added. “It would have given everyone a better understanding about whether [methylmercury] is really coming from the electric utility sector.”
Pavlish separates the issue into two particular camps: those who see power plants as the biggest mercury polluters and those who want to know for sure that mercury from power generators is the source of methylmercury before running up such a large tab for an industry already struggling to comply with regulations for other emissions, such as NOx.
While one camp is focusing on EPA numbers (that power plants account for approximately 13 to 26 percent of total airborne mercury emissions in the U.S.), Pavlish notes that “utilities want to know the linkage.”
Durham agrees. “If you look at it from the purely scientific aspect, you would say, ‘Well, we shouldn’t do anything because we really don’t know what’s happening,'” he stated. “From a regulatory perspective, however, once waste incinerators were controlled, the coal-fired utility boiler pops into the lead. So they’re coming at it from a different point of view.”
Making peace with the future
Proof in hand or no proof in hand, the EPA is going forward with mercury regulations. All power generators can do now is examine three factors: available technology, the cost of that technology, and whether they can navigate the pothole-laden road to compliance.
EPA estimates about the cost of compliance range from $2 to $5 billion per year. ADA-ES, who is currently one of two companies (the other is Babcock & Wilcox) working with the Department of Energy’s (DOE) National Energy Technology Institute on mercury control technologies, predicts that much of that sum will be borne by power plants that burn low-sulfur coal and use particle collection devices instead of wet scrubbers (which have been found to remove oxidized mercury as well, to an extent). In fact, ADA-ES estimates that a 90 percent mercury reduction at a 500 MW power plant could cost as much as $5 million a year, but no one knows for sure.
“No one has ever done full-scale measurements,” Durham pointed out. “That’s what our program is for, to gather data on levels of control and cost.”
As ADA-ES attempts to find mercury solutions that juggle both finances and accuracy-a balance that’s not an easy one to maintain-they’ll be working with four plants to focus on control technology based upon injecting chemical sorbents into the flue gas. The sorbents would then be collected in existing particulate control equipment further down the line. However, Pavlish points out the Center has also been working on the development of a universal sorbent along similar lines, but has yet to mix the right recipe.
In fact, control technologies for mercury emissions remains a hit-and-miss experiment, much like the attempt to directly link power plant emissions to methylmercury in fish.
It seems the scientific side of this issue has more questions than answers. While traditional emission controls like wet scrubbers have been found to remove a percentage of oxidized mercury, if the make-up of the coal mix is slightly different (Powder River Basin, or PRB, coal vs. an eastern version for example), the plant could be producing elemental mercury, which will not be removed by that wet scrubber.
“I see a real need-a real serious technology development need-for utilities that are burning PRB fuels, or i.e. low sulfur or low chlorine fuels, because conventional technologies-at least with the data we have-in general will not work for removing [elemental] mercury, and as the data suggests, the emissions are going to be almost twice as high as compared to eastern fuels,” Pavlish commented.
Both Pavlish and Durham cited cases where the fly ash itself (generated through combustion) is able to absorb up to 90 percent of the mercury-so that some plants give off very little mercury from their process, even without the benefit of downstream control technology.
“We can’t explain it, but if you’re one of those lucky few, your units are already doing a really good job of removing mercury,” he said.
Pavlish added that both the known and unknown factors about mercury point out “the need to assess what your emissions are and how well the control technologies you have in place are working.”
A starting point
The EPA decision has essentially killed one issue and created another: It’s now obvious that both financial and scientific focus will be on control technology rather than proving causality. However, weighing the benefits of technologies while those technologies are still being explored leaves the possibility of inadvertent-yet still costly-failure all too apparent.
Both Durham and Pavlish agree that use of conventional systems will likely be the first wave in the battle against mercury, but they certainly will not be the last.
“What you could see happening is a favor towards utilities putting in scrubbers now-not just to control SO2, but to also control mercury,” Pavlish stated.
“We’re looking at the idea of co-control,” Durham said, citing technologies that may be used to capture more than one pollutant. “Instead of looking just at mercury, you need to develop a wider strategy. Combination is going to be cheaper than going after individual solutions by themselves.”
One of the chosen few in the ADA-ES study is Alabama Power, a subsidiary of Southern Company. Their Gaston plant is slated to test ADA-ES’ transportable mercury control technology within this first quarter of 2001.
Durham points out that ADA-ES goal is breaking down and examining the expense of varying sorbent applications. Their four test sites will be attempting to iron out the details, to answer all those questions that the EPA’s decision to regulate has created.
“We are going to try to develop accurate cost data: If you have an ESP (an electrostatic precipitator) and you’re burning a subbituminous coal, how much is it going to cost you in sorbent? If you’ve got a fabric filter, how much is it going to cost you? And, what is the true cost of mercury control?”
However, at press time, no technology manages to cover all the mercury bases, leaving the concept of “mercury control” a rather large area to keep under the thumb. Pavlish played with the analogy that perhaps the industry’s timeline for regulations is a bit like “putting the cart before the horse.”
“It’s almost impossible to say, ‘This technology will work across the board.’ It won’t,” Pavlish added.
Durham, president of ADA-ES, can be reached via phone at 303-734-1727, and Pavlish, senior research manager with the Energy and Environmental Research Center at the University of North Dakota can be reached at 701-777-5268.