Materials Characterization Paper In Support of the Proposed Rulemaking: Identification of Nonhazardous Secondary Materials That Are Solid Waste Foundry Sand (used as ingredient in clinker manufacture)

March 18, 2010

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1. Definition of Foundry Sand

Foundry sand is an industrial material generate d by the metal-casting industry, which uses the sand to form a physical mold used in the produc tion of metal products. Two general types of sand are used in metal casting: clay-bonded sand (green sand); and chemically-bonded sand:

• Green sand is composed of naturally occurr ing materials that are blended together: high quality silica sand; bentonite clay as a binde r; a carbonaceous additive to improve the casting surface finish; and water. Due to the carbon content, green sand is actually black in color and adheres together due to th e clay and water content. Gr een sand molds comprise about 90 percent of the casting volume in the United States.

• Chemically-bonded sand does not employ a clay binder. Instead, chemi cal binders are used

to cause the sand to hol d its shape during the in troduction of the molten metal into the mold and the cooling of the casting. Chemically-bonded sand is generally light in color and coarser in texture than clay bonded sand, and accounts for only 10 percent of casting volume in the United States. Foundries use chemically-bonde d sand in core-making, where high strengths are necessary to withstand the he at of the molten metal (FIRSTb).

After multiple uses in castings, the sand becomes uns uitable for castings and is either disposed of in landfills or beneficially used in other applications, includi ng use as an ingredient in the manufacture of portland cement.

2. Annual Quantities of Foundry Sand Generated and Trends in Generation

(1) Sectors that generate foundry sand:

• The metal-casting industry, represente d by NAICS code 3115, is the sole generator of spent foundry sand.

(2) Quantities and prices of foundry sand generated:

• According to the American Foundry So ciety (AFS), a metal casting industry group, the metal-casting process generates 9.4 million tons of foundry sand annually (Oman, 2007).Foundry Sand

(3) Trends in generation of foundry sand:

• The generation of foundry sand generally tracks with the manufacture of cast metal products. Despite increased forei gn competition, the metal casting industry expects modest growth to continue. Sales of metal castings ar e expected to grow 14 percent over the next three years from $33 billion in 2005 to $37.7 billion in 2008 (Industrial Metal Casting).

3. Uses of Foundry Sand

(1) Ingredient uses of foundry sand:

• Spent foundry sand can be us ed in the manufacture of portland cement clinker. Most foundry sands are high in silica content and can serve as a potential

alternative silica source in portland cement clinker production. In addition, portland cement clinker production require s certain minerals, such as iron and aluminum oxides, both of which ar e found in many spent foundry sands (FIRSTa). Brass foundries create sands that can be hazardous under RCRA (if disposed of) due to metals content and, th erefore, are outside the scope of this report (EPA, 2002).

• According to the portland cement industry, foundry sand can be beneficially reused in the manufacturing of portla nd cement when it possesses the following properties: silica content of 80 percent, low alkali levels, and uniform particle size. In addition, large quantities of foundr y sands must be available for it to be used by Portland cement manufacturers (FIRSTa).

(2) Non-combustion uses of foundry sand:

• Spent foundry sand can be us ed as a substitute for vi rgin sand in road base, structural fill, flowable fill, soil amendm ent, or as the fine aggregate portion of concrete or hot-mix asphalt (FIRSTb). In addition, some sand can be used as a high-end additive to industrial materials, such as plastics, to provide specific textures and colors (Olenbush, 2006).

(3) Quantities of foundry sand landfilled:

• AFS estimates that in 2006, 6.8 million tons of foundry sand were disposed in landfills. This quantity includes sand us ed as a landfill daily cover (Oman, 2007).

(4) Quantities of foundry sand stockpiled/stored:

• The sources consulted for this paper did not provide avai lable information concerning whether significant quantities of foundry sand are stockpiled or stored.

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Exhibit 1: Overview of Generatio n and Use of Foundry Sand in 2007

Annual Quantity Used as Ingredient Annual Quantity

Generated Cement Kilns Other Annual Quantity

Landfilled Annual Quantity in

Other Uses Total Quantity Stockpiled Commodity

------------------------------------ Short T ons -----------------------------------

Foundry sand 9.4 million Undetermined None 6.8 million 2.6 million Undetermined

Sources : Oman, Alicia. American Foun dry Society (AFS), personal communication, 12/21/07. AFS, August 2007 , Foundry Industry Benchm arking Survey, accessed at: http://www.strategicgoals.org/benchmarking/foundryresults8-7.pdf

. Notes : Detailed quantitative data on the various beneficial use applications of foundry sand have not been well documented in the past. In an attempt to address this issue, AFS recently conduct ed a benchmark survey to collect information from the foundry industry on the specific quantities of spent foundry sand being beneficially used in different applications. The survey results indicate that none of the respondents are currently using foundry sand in clinker manufacture. According to the Portland Cement Association, however, foundry sand is being used by a number of North American cement kilns (FIRSTb).

4. Management and Combustion processes for Foundry Sand

(1) Types of units using foundry sand:

• When used in clinker manufacture, f oundry sand is fed into cement kilns with

other raw material feed. No other co mbustion applications appear to use significant quantities of f oundry sand as an input.

(2) Sourcing of foundry sand:

• In some cases, cement manufacturers obtain foundry sand through direct agreements with foundries, most of which are located in certai n states, including Illinois, Wisconsin, Michigan, Ohio, and Pennsylvania (Turner Fairbank Highway Research Center ). Some foundries mark et their spent sand through a third-party or a cooperative instead of selling direct ly to the end-user. The majority of foundries are small businesses that gene rate small quantities of spent foundry sand. Through arrangements with multiple foundries, cooperative brokers/third party processors may be able to provide sufficient and consistent amounts of spent foundry sand to support the need of cement ki lns. If a cement kiln uses a third party broker, the broker will pay the foundry for the foundry sand, but in some cases the kiln purchases the sand dire ctly from the foundry (Lenahan, 2007).

(3) Processing of foundry sand:

• Foundry sand used in portland cement ma nufacturing must be separated from other foundry by-products thr ough a series of screens (FIRSTa). The oversized material that does not pass the screens is termed "core butt" and consists of

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chunks and grains of coarse sand a nd scrap metal (FIRSTb). Most portland cement plants also require that core butts be ground to a uniform grain size (FIRSTa). Vibrating screens and a ball mill are used to further separate the components of this stream and to crus h the oversized chunks of sand. Through use of a magnetic separator, meta l in the stream is removed.

(4) State status of foundry sand use as ingredient:

• At this stage, we have not identified any states that have specifically given beneficial use designation to the use of foundry sand in clinker manufacture, or that prohibit use of foundry sand in c linker, but we have not performed an exhaustive investigation of st ate activities and regulations.

5. Foundry Sand Composition and Impacts

(1) Composition of foundry sand:

• Spent foundry sand consists primarily of si lica sand, coated with a thin film of burnt carbon, residual binder (bentonite, sea coal, resins) and dust (Turner Fairbank Highway Research Center). Sp ent foundry sand may also contain heavy metals and phenols that are absorbed by the sand during the molding process and casting operations. Phenols are formed through high-temperature thermal decomposition and rearrangement of or ganic binders during the metal pouring process. The presence of heavy metals is greater in foundry sands generated from nonferrous foundries. Spent foundry sand from brass or bronze foundries, in particular, may contain high concentrations of cadmium, lead, copper, nickel, and zinc (Turner Fairbank Highw ay Research Center).

(2) Impacts of foundry sand use:

• In clinker manufacture, foundry sand partia lly offsets the need for virgin silica, iron, and alumina sources. Thus, using foundry sand in the cement kiln can reduce the unit consumption of virgin feed stock materials and related emissions.

• The specific lifecycle impacts of foundry sand use as a raw material in clinker production are not evaluated here because of uncertainties in lifecycle scenario development. For example, it is difficu lt to determine the replacement ratio between foundry sand and other raw feed materials in clinker production. Thus, the correct quantity of material to be modeled is unclear. In addition, foundry sand may substitute for a variety of virgin raw materials as well as other secondary materials (e.g., blast furnace slag, CCPs, cement kiln dust, etc.); the choice of material often depends on location-specific factors such as the proximity of material sources to the cement kiln and relative availability of different materials. Avoided upstream impacts depend heavily on the specific material being displaced in the lifecycle scenario.

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References

American Foundry Society (AFS), About Metal Casting , accessed at: http://www.afsinc.org/content/view/62/122/

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American Foundry Society (AFS). August 2007. “Foundry Industry Benchmarking Survey: Industry Practices Regarding the Disposal and Beneficial Reuse of Foundry Sand – Results and Analysis.” Accessed at: http://www.strategicgoals.org/ benchmarking/foundry.html

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Foundry Industry Recycling Stars Today (FIRSTa), Foundry Sand in Portland Cement Manufacturing , accessed at: http://www.foundryrecycling.org/TechnicalApplications/ManufacturedProducts/PortlandCement/tabid/173/ Default.aspx

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Foundry Industry Recycling Stars Today (FIRSTb), What is Recycled Foundry Sand? , accessed at: http://www.foundryrecyc ling.org/Home/WhatisRecycledFoundrySand/tabid/294/Default.aspx

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Industrial Metal Casting, “Casting Industry,” accessed at: http://www.industrialmetalcasting.com/castingindustry.html

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Lenahan, Mike. Resource Recovery Corporation, personal communication, April 27, 2007.

Olenbush, Elizabeth. FIRST, personal communication, April 2006.

Oman, Alicia. American Foun dry Society (AFS), personal communication, 12/21/07.

Turner Fairbank Highway Research Center and the Federal Highway Administration, User Guidelines for Waste and Byproduct Materials in Pavement Construction , accessed at: http://www.tfhrc.gov/hnr20/recycle/waste/begin.htm

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US EPA, Beneficial Reuse of Foundry Sand: A Review of State Practices and Regulations , December 2002.

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