Minergy - A Wisconsin Energy Corporation

Q. What is Minergy?
A. Minergy was created by Wisconsin Energy in 1993 to develop alternatives to landfilling ash generated by its utility subsidiary. Minergy has a plant and engineering office located in Neenah, Wis.
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Q. Why is Minergy involved with the Fox River?
A. Minergy has had a major operating facility located in the Fox Valley for several years. Minergy is also widely recognized as one of the leading experts in vitrification. If we can provide a local solution to the Fox River situation that has long-term environmental advantages, it is in the best interest of the state as a whole.

The company originally became involved in testing the processing of river sediment at the request of the Wisconsin Department of Natural Resources (WDNR). Because Minergy has a plant in Neenah that uses vitrification to process paper mill sludge, the WDNR asked the company if river sediment could be processed at the plant. After several tests, studies and evaluations, Minergy recommended Glass Furnace Technology (GFT) as the best way to process river sediment.
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Q. What happens to the PCBs in the GFT?
A. A glass furnace system would be capable of destroying or removing virtually all of the sediment contaminants. Glass furnaces operate at 2,600 to 2,900 degrees Fahrenheit. At this temperature, PCBs are destroyed.

The GFT has undergone an extensive review by the U.S. Environmental Protection Agency (EPA), which monitored a demonstration project operated round-the-clock for a one-week period, using PCB-contaminated sediment from the Fox River. The EPA's report showed that more than 99.999% of the PCBs were destroyed, in compliance with the EPA's "six nines destruction" rule. The EPA analysis also showed that no dioxins or other pollutants were created in the process.
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Q. Does the glass aggregate end-product contain PCBs?
A. The glass furnace system will destroy or remove virtually all of the sediment contaminants. In the EPA demonstration, more than 99.999% percent of PCBs were destroyed. Any remaining PCBs contained in the glass aggregate are lower than the concentrations found in the food of a typical American diet. Studies also showed that these PCBs were non-leachable and not bioavailable.
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Q. What happens to the metals contained in the river sediment?
A. Most metals are stabilized in the ceramic matrix of the glass aggregate. Any metals that pass through are captured in downstream pollution control equipment.
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Q. What happens to the mercury contained in the river sediment?
A. In the GFT process, mercury is captured in the carbon filtration system downstream of the pollution control equipment.
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Q. What happens to the lead contained in the river sediment?
A. In the GFT process, lead either is stabilized in the ceramic matrix of the Glass Aggregate or is captured in downstream pollution control equipment.
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Q. How does GFT work?
A. GFT is a relatively simple process that has been used for many years to melt minerals into glass. In this case, river sediment (which is composed primarily of minerals) will be substituted for sand and limestone, the traditional feedstock for clear glass production. The end result is a gravel-like byproduct called glass aggregate. The color will be black due to the mineral makeup of the sediment. (See Vitrification Process Diagram.)
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Q. Isn't this just incineration?
A. No. Incineration is defined as the burning of waste to reduce the volume of material that needs disposal. River sediment is made up mainly of minerals and, as a result, does not burn. Therefore, river sediment is not suitable for incineration or other combustion-based processing. In contrast, the glass furnace used in GFT vitrification uses heat to melt minerals into glass. This is important in processing river sediment, because its mineral component is an ideal feedstock for glassmaking in the GFT.

For more information on this subject, please see Minergy's document "The Differences Between Vitrification and Incineration."
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Q. Why can't you process the river sediment at the Minergy Neenah plant instead of building a new facility?
A. We ran a model at the Neenah plant based on processing river sediment and determined it would simply be too costly to use that facility. The model showed that it would be inefficient due to the large amount of additional energy required to handle river sediment at the plant.

The Neenah plant processes paper mill sludge that has a high fuel value. River sediment, on the other hand, is made up primarily of minerals that have very little fuel value. Therefore, processing river sediment in Neenah would require the use of more fuel, making it too costly. A facility built to process river sediment would be designed to melt the mineral content of the sediment instead of trying to burn it.
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Q. The Minergy plant in Neenah generates steam used by area paper mills. How will the steam be used from the river sediment facility?
A. The Neenah plant was designed to process materials that have significant fuel value. As a result, the plant supplies steam to a local paper mill. GFT is designed specifically for melting river sediment that has very little fuel value. A plant processing river sediment would generate only enough steam to dry the incoming sediment.
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Q. How big is a GFT facility? Will it compare to the size of the Neenah Minergy plant?
A. The size of a GFT facility to process river sediment would depend on the parameters of the cleanup plan. We would expect a "base case" design to be about 80,000 square feet, or roughly the footprint of a large grocery store.
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Q. What kind of evaluation has been done on the GFT for river sediment?
A. The EPA has performed a complete, independent study of the technology, specifically using Fox River sediment samples. A demonstration scale test using a pilot melter was conducted. Every input, output and multiple mid-process points were monitored. Samples were taken over a seven-day test, with sampling performed 20 hours per day. In addition, a certified toxicologist reviewed the results from the perspective of the Glass Aggregate product.

A summary of the results is listed below:

1) PCB

a) Met the "six nines" criterion for stack basis Destruction Removal Efficiency
b) Treatment efficiency was 99.999488%

2) Dioxin

a) No 2,3,7,8 TCDD was detected in the stack either before or after the carbon filter
b) Greater than 99.9% removal of dioxins/furans both before and after the carbon filter

3) Mercury

a) No mercury was detected after the carbon filter
b) Removal efficiency was greater than 99.9%

4) Glass Aggregate

a) Leach test showed no-detect or no significant levels of any test parameter
b) PCB mass was less than that found in U.S. food supply and was not bioavailable
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Q. Are the EPA test results available for public review?
A. The EPA is in the process of finishing the final report. We would expect it will be available when it is complete.
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Q. By how much does GFT reduce the volume of the sediment processed?
A. It takes approximately 3.5 cubic yards of sediment to be dredged to result in 1 ton of glass aggregate.
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Q. What is glass aggregate?
A. Glass Aggregate is made up of the sand and clays contained in sediment that have been melted at high temperatures then quickly cooled. The gravel-like material is black in color due to the small amount of iron contained in the sediment.
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Q. Is the glass aggregate environmentally sound? Will we have to worry about leaching problems in the future?
A. Glass aggregate is environmentally sound. Again, the glass furnace system would be capable of destroying or removing virtually all of the sediment contaminants. Minergy produces a similar glass aggregate at its facility in Neenah. The material is so inert that the WDNR has exempted the glass aggregate produced at Minergy's Neenah plant — and any glass aggregate produced from river sediment — from all regulation and allowed it to be marketed as a product.

The EPA tested the aggregate using two different methods to see if contaminants would leach. The following trace metals were tested (in addition to PCBs): arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver and zinc. All test results were below the detection limits.
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Q. What can you do with the glass aggregate?
A. The glass aggregate byproduct of the GFT is an inert product that is sold to construction companies. It is inert and nonleachable — features that construction companies find favorable. The gravel-like material can be used in its raw form as asphalt road making, filler for building foundations, or ceramic floor tile. Some companies use similar glasses for sand-blasting grit and as roofing shingle granules. For many years, Minergy Neenah's glass aggregate has been finely ground and used as a cement in concrete.
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Q. How much will this cost?
A. GFT is a cost-effective way to process river sediment. Cost estimates have shown that a long-term sediment melter project would have average costs that are competitive with or, in some cases, less than landfilling. The final cost depends on the size of the plant and how many months per year it operates.

The base case option studied for the Fox River is a project that would be able to process 500 to 600 tons of sediment per day. The project would cost $32 million to build, employ 25 people and have annual operating costs of $6.2 million. A 15-year financial analysis on these numbers results in an average cost of $36 per ton of sediment. This cost is competitive with or less than the alternative costs of many landfills. Any revenue derived from the sale of the final glass aggregate product would reduce this number even further.
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Q. Haven't other thermal treatment tests on river sediment been shown to be expensive?
A. Yes. Prior to using GFT specifically, other thermal treatment tests did not use the right process for river sediment. These tests used a burning process on a nonburnable feedstock (river sediment). This resulted in high auxiliary fuel costs. River sediment consists of minerals that do not burn. GFT relies on a melting process that is more appropriate for river sediment.

Attempts have been made to process river sediment in incinerators. Because the sediment does not burn, the incinerators required large amounts of fuel and did not provide any reduction in landfilling. As a result, attempting to incinerate sediment has been very expensive and not cost-effective.
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