No Free Lunch
Cleaner Air Can be Complicated
The air over western Wisconsin and places downwind will see fewer pollutants over the coming years, thanks to a major investment by Dairyland Power Cooperative and the customer-members it serves.
The La Crosse-based generation and transmission cooperative has budgeted more than $250 million over the next few years to install state-of-the-art emission controls at its two largest power plants. Control technologies put in place since the early 1970s have already been eliminating about 80 percent of the sulfur dioxide released in the coal combustion process. Part of the mercury and oxides of nitrogen emitted are also captured by the existing technologies; the new equipment is expected to do better. Though performance will vary over time and with different loads of coal, sulfur dioxide removal averaging about 90 percent over the course of a given year should be achievable. Mercury and nitrogen oxide capture will also improve.
Some of the new equipment is already in place. A fabric filter “baghouse” began capturing particulate emissions from the John P. Madgett plant at Alma in Buffalo County near the end of October. Another was installed at the Genoa 3 plant near Genoa, in Vernon County, earlier this year. With several months’ experience to help evaluate the performance of the equipment at Genoa, Dairyland officials say they’ve seen a dramatic reduction in fine ash emissions.
Obviously, that’s good news, but it’s not all that simple. The improved air quality technology leads straight to new challenges in other areas. One challenge that’s attracting attention right now is the additional complication the air quality improvements bring to a well-established program providing environmentally beneficial handling of power-plant byproducts, specifically, coal ash. The improvements being installed mean that eventually, much material that’s now being put to beneficial use will have to be disposed of in a landfill instead. One thing, as they say, leads to another.
Ashes to…Roads?
Dairyland Power Cooperative provides wholesale electricity to 25 distribution cooperatives and 19 municipal utilities in 62 counties spread across western Wisconsin, southeast Minnesota, northeast Iowa, and northwest Illinois. To run its generation equipment, Dairyland uses coal, natural gas, the power of wind and flowing water, methane harvested from landfills, and bacterial conversion of animal waste into combustible gas. But its most basic fuel is coal.
Coal provides almost exactly half of the nation’s electricity. Even with determined campaigns underway to banish it from the U.S. energy inventory, coal is still comparatively economical to use, but that’s not the only or even the primary reason for its dominance. The primary reason is that among the entire diverse portfolio of fuel sources used by Dairyland, coal is the only one that can be relied upon to produce energy on a very large scale all the time, every day, all year ’round.
And so, while it continues to nurture a program of renewable energy development that’s as aggressive as any in the nation for a utility of its size, Dairyland consumes a lot of coal—roughly three million tons annually in recent years—of predominantly low-sulfur Western coal. That leaves a lot of ash behind: From each ton of coal burned to produce electricity, approximately 5 percent, or 100 pounds of ash will remain.
But the ash isn’t useless. About 80 percent of the total is fly ash and of that amount, Dairyland has been recycling more than 80 percent. Light and powdery, fly ash is collected by electrostatic precipitators and makes a suitable additive to ready-mixed concrete, since the primary components of fly ash and cement are the same.
Much of the concrete used in Dairyland’s service area today is nearly one-third fly ash. With fly ash available at less than half the price of Portland cement, it’s a boon to taxpayers funding road, highway, and other infrastructure projects, making for concrete that’s not only more economical but stronger and less permeable as well.
The remaining ash byproduct, about 20 percent of the total, is called bottom ash. Dairyland markets almost two-thirds of this to be recycled as a substitute for crushed rock or sand in road construction and as an anti-skid material replacing sand or salt on winter roads.
The cooperative has been recycling far higher percentages of its fly ash than the roughly 30 percent recycled by U.S. utilities on average.
But the new environmental projects are expected to change that in a big way.
In addition to the filtering baghouses recently installed, Dairyland is in the engineering and design phase of three more changes. The sulfur dioxide reductions mentioned above will be accomplished by flue gas desulfurization systems or “scrubbers.” Activated carbon injection will remove most of the mercury that isn’t captured coincidentally by existing technologies, and new burners will be installed to improve combustion and cut back emissions of nitrogen oxides. At the Madgett plant, a selective catalytic reduction system will be installed to gain further reductions of nitrogen oxide emissions.
It’s important to remember that none of these pollutants currently exit the smokestacks unhindered. The Genoa and Madgett plants operate in compliance with air quality permits consistent with the control requirements of state and federal law. But once all of the new equipment is in operation, it will significantly reduce emissions below today’s controlled levels. It will also change the composition of the ash.
The ash will pick up contaminants that are expected to dramatically reduce the volume able to be recycled. Under present regulations, that means a lot more ash destined for landfills. Existing facilities including the La Crosse and Vernon County landfills were reviewed and found unsuitable: Neither is designed or permitted to accept the large volume of coal combustion byproducts that will be captured by the new scrubber systems.
Dairyland already has a landfill near Alma for disposal of ash from the Madgett plant. But that space needs to be preserved for the increased volumes anticipated when the new Madgett scrubber comes on line. Moreover, using that facility for unrecycled ash from Genoa 3 would mean hauling the material more than 80 miles by truck, an unattractive proposition from both economic and environmental perspectives. The bottom line is, the cooperative will need to develop a new facility. Two potential sites in Vernon County are being examined.
No Easy Way
Earlier this year, RMT, a Madison-based consulting firm that specializes in waste management engineering, performed a siting study for Dairyland. After reviewing the study through the summer, Dairyland directors voted in mid-August to go ahead with the project. The cooperative began contacting landowners, public officials, the media, and others and a public informational meeting was held in October.
Those were the first steps in a process that will be lengthy, because siting a landfill is never easy.
For instance, while it isn’t unusual to see parks and recreation areas developed on and around closed landfills, state regulations forbid siting a landfill within 1,000 feet of such an area unless it’s kept out of sight, screened by natural barriers or other means. That’s why no attempt was made by Dairyland to site a new ash containment facility on government-owned land.
The final word on whether either of the two potential Vernon County sites is eventually used belongs to the Wisconsin Department of Natural Resources. The DNR has permitting authority over such facilities and its regulatory review is expected to take years, not months.
Among Wisconsin’s stringent standards are requirements that material disposed of be compacted and totally contained within the walls of the facility, that storm water and precipitation be routed around it through ditches designed to control flow and minimize erosion, and that the material not be able to move beyond containment within the landfill walls.
From inside the landfill, groundwater will be protected by a collection system to capture precipitation that comes in contact with the stored material and also by a composite liner system. This would consist of clay or other low-permeability material in a layer up to four feet thick, covered with a geosynthetic clay liner and, in a third layer, a geomembrane liner.
The scrubber byproduct destined for landfill storage will be primarily calcium sulfite. Also present in lesser amounts will be calcium sulfate, calcium hydroxide (lime) and calcium carbonate. The fly ash, mainly oxides of aluminum, calcium, and iron as well as silica, will also contain oxides of various elements including arsenic, barium, cadmium, chromium, copper, lead, mercury, selenium, and zinc.
There is an old saying that it’s the dose that makes the poison. In strong concentrations, some of these elements are toxic. In weak concentrations, some of the same ones are essential nutrients. In any case, testing of the materials emitted by Genoa 3 indicates the byproducts resulting from operation of the new scrubber equipment won’t be toxic. Neither is the material classified as hazardous waste. According to Dairyland, fly ash, bottom ash, slag, and flue gas emission waste generated primarily from coal combustion are specifically classified by the Environmental Protection Agency as non-hazardous wastes.
The Cheery Closer
It almost goes without saying that a new landfill wouldn’t be high on anybody’s wish list for Vernon County or anyplace else. On the other hand, controlling larger percentages of the materials that are now partially captured by existing emissions equipment would seem like a good thing to do; a worthwhile trade. And someday when the landfill is full, closed, and covered over, it’s a pretty safe bet that it will remain fully in compliance with state regulations and invisible from the park someone might want to develop on top of it, making it less likely another landfill will be sited anywhere nearby.— Dave Hoopman
