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Paper sludge is is a clay-like material consisting of clays and short fibers. In the paper recycling process, waste paper is received and de-inked prior to recovery of the fiber. During the de-inking process fiber sludge is generated, which contains particles of ink and fibers too short to be converted to a finished paper product. In the past, paper sludge has typically been land filled. With landfill costs rising and the potential for ground water contamination from landfill operations, many environmentally conscious paper producers are recovering the energy from this waste stream. 1. Minergy Quick Facts:
Glass Aggregate What Minergy Does: The Minergy Fox Valley Aggregate Plant in Neenah, WI has developed an innovative technology to recycle paper sludge into a reusable product, glass aggregate. Paper sludge, delivered from paper mills, is a clay-like material consisting of clays and short fibers with a 60% moisture content when arriving at Minergy’s plant. The final product, glass aggregate, is a glass like substance (appears as small, ground-up, bits of glass) which is then used for various construction and industrial purposes. Glass Aggregate Uses: There are many beneficial uses for glass aggregate, while new uses are continually being developed. The majority of glass aggregate is bought and used as backfill. Another common use is for concrete. In this case, aggregate is ground into a fine powder giving the concrete a whiter color (versus darker fly ash, another common additive). Other uses include particles for sand blasting, particles in floor tiling, and roofing shingles. Environmental Benefits: By recycling paper sludge instead of placing it into a landfill, Minergy preserves 10 acres of green space per year. Steam produced during the glass aggregate process is transferred to a neighboring paper mill which has allowed the mill more efficient production and less emissions. Finally, the location of the plant saves sludge delivery trucks 450,000 miles of travel per year, enhancing air quality from less emissions.
On arrival, the sludge is approximately 60% moisture but as the sludge enters its next stage, the closed loop drying system, the moisture content is decreased to a dry 10%. Now, as a solid, it is conveyed to the glass furnace. The organic materials (wood fiber) within the sludge provide the high temperature (2600F) needed to melt the sludge into glass, also destroying the organic compounds contained within the sludge. At the same time, inorganic mineral components melt, and flow out of the furnace as liquid glass. During this melting process, any trace metals become contained and stabilized within the flowing glass. The liquid glass then quickly drains into a water bath system where it is cooled and the glass aggregate is formed 200 tons/day). Trucks, about 70 each week, then pick up the desired amount and take it for their various use. The aggregate can be crushed into smaller sizes (down to a powder) depending on its desired use (once leaving the plant the aggregate is typically no larger than a marble). Finally, steam that is generated, particularly in the furnace, is sold to P.H. Glatfelter, which has allowed them to shut down their older gas and oil-fired boilers (also contributing to a cleaner environment). Paper Mills Contributing Sludge to Minergy: There are numerous mills that have contributed paper sludge to Minergy since its production began in May 1998. Kimberly Clark’s plant in Munising, MI is willing to drive 5-hours (each way) to deliver a single truckload of paper sludge to Minergy. Other paper mills that are contributing sludge include: Fox River Paper, P.H. Glatfelter, SCA Tissue, Kimberly Clark (Marinette; Neenah; Whiting; Munising, MI), and Kerwin Paper. Mills that have contributed sludge in the past include: American Tissue, Appleton Paper, Gizmo-Tissue/Glatfelter, George Whiting, Gilbert Paper, Interlake Paper, Interlake Fiber, Menominee Paper, Ponderosa, U.S. Paper, and G.L. Pulp. Through November 2002, Minergy has received a total of 1,344,344.80 wet tons of sludge from all of the paper mills listed above. Companies that Purchase Glass Aggregate: There are three main companies that purchase glass aggregate from Minergy, those being Badger Mining, Badger Cement, and Warehouse Specialists. Badger Mining uses glass aggregate particularly for sandblasting. Glass Aggregate works particularly well for this because there are fewer health risks in comparison to sand due to less dust inhalation, and the aggregate is more angular than sand. Badger Cement uses glass aggregate in the form of a fine powder that is added to cement giving it a whiter color along with added strength due to increased mineral content, glass aggregate is also much cheaper relative to other pozzolanic materials. Finally, Warehouse Specialists, primarily uses Minergy products for backfill applications and base layers prior to the spread of concrete. Unlike other granular such as screenings, gravel, or sand, no water is required to get maximum compaction and the glass aggregates do not absorb water and hence do not freeze making it an ideal product for winter use and construction. Future Applications/Possibilities: The use of glass aggregate is an expanding market. Minergy is hopeful that their aggregate product will be able to be applied to asphalt in long lasting cold-patch applications as well as chip-seal (for oil spills). Minergy is also working on applying their glass aggregate technology to PCB contaminated sludge, a major pollutant contaminating the Fox River in Northeastern WI and the Upper Hudson River Basin in New York. The process would remain relatively similar to that of paper sludge, but only with PCB contaminated sludge from the River bottoms. The operation plants would be designed so that they could be built and then easily disassembled to move to another contaminant location. GranTek, a subsidiary of Kadant Inc., produces biodegradable absorbing granules from papermaking by-products (sludge) that are marketed and sold as Biodac agricultural carriers, Gran-sorb oil and grease absorbents, and PaPurr cat box fillers. Ideally located in Wisconsin, the number one paper sludge producing state, GranTek receives all of its sludge from its neighboring paper mill, Georgia Pacific, in Green Bay. GranTek processes approximately 200 to 250 dry tons of paper sludge a day, processing approximately 10 dry tons per hour. If not for GranTek, the mill has two other options, either landfill the waste or incineration, neither option is economically or environmentally friendly. GranTek does not charge Georgia Pacific to take their sludge making it a win-win situation for both parties. The paper sludge that is received at GranTek arrives with approximately a 60% moisture content. The facility never keeps the received sludge for more than 24 hours to minimize the amount of bacterial build up. GranTek then dries the sludge, granulates it to the specific size that is needed, and is then dried once again for a final moisture content of approximately 3%. The process is completely clean, the only substance released from the smoke stack is steam and there are absolutely no by-products created in the process. Biodak is a granulated product that is mixed with seed (particularly very light weight seed) to give the seed added weight. This extra weight is beneficial when it comes time to spread the seed. It prevents the seed from being washed away by rain or irrigation as well as the seed from being blown away for accurate application during the speeding process. Biodak is also sent to specific companies where pesticides or herbicides are added. In this case, when the granule gets wet it begins to breakdown and release the particular substance that it was treated with. This reduces chemical runoff and helps to add stability to soft soils. Gran-sorb is an industrial absorbent made from 100% recycled paper waste. It absorbs oils, solvents, lubricants, coolants, water and most other non-aggressive liquids on contact. Gran-sorb is virtually dust free, leaves no stains, cleans up quickly and easily, and is safe for disposal by incineration. PaPurr is cat litter made from paper instead of the typical clay particle. The advantages of this, to begin with, is that there is a lot less dust. Since paper is biodegradable, it is safe to dispose of by either incineration or flushing. PaPurr contains only non-toxic ingredients, with naturally occurring oils for odor control and is colored with food-grade dyes. The product can be purchased at local retailers such as Target or Pet Smart. Most of the GranTek’s product is manufactured for agriculture purposes, approximately 90%; while 5% is for cat litter, and the remaining 5% is for industrial absorbent. The main purchasers of GranTek products are Scotts, BASF, and Bayer. References
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Minergy's
Glass Aggregate Process:
Each day about 60
truckloads deliver sludge to Minergy’s Glass Aggregate Plant where it is
deposited into the receiving building (a total of 1,200 wet tons). Although a
strong odor is present in this building,, it is contained by a 1500-hp odor
control air duct system which eliminates virtually all fumes from escaping (the
air is moved into the furnace ductwork and is used as furnace intake air). If
the receiving building is full, Minergy has storage for 3000 wet tons of sludge.