New Ground Ripe for Foundry Sands

Foundries, soil producers, private, state and federal agencies are forging relationships, markets and protocol for turning castaway sand into paydirt.

By Mollie Day

   The US foundry industry uses around 100 million tons of sand each year to produce metal castings. Although the sand is recycled inside the casting process, about 10 percent of the sand is discarded and potentially could be utilized in commercial soil blending operations. Currently only around a million tons of that sand is recycled; the remaining 8-12 million tons are landfilled, according to the US Environmental Protection Agency (USEPA).
   With the buzz of sustainability catching hold, relations are beginning to bloom between foundries and soil producers. Due to the infancy of the market, information sharing and policy have yet to get grounded. Federal and state agencies, private and public companies are sending roots into uncharted landscapes, and things appear to be coming up green.
   Spent foundry sand is generated in the metal casting process. Foundries purchase “virgin” sands to create casting molds, and the sand is reused repeatedly until heat and mechanical abrasion eventually render the sand unsuitable for use in casting molds. Spent foundry sand that is removed from the casting process is then either recycled or landfilled, at a large cost to the foundry.
   The recycling of this industry byproduct can save energy, reduce the environmental impacts of mining for virgin sand, and potentially reduce costs for both the producer and end user.
   Establishing spent foundry sand as a material source for soil blending is a high priority for the American Foundry Society (AFS), the nation’s lead metal casting association. Soil producers are stepping up for economic, environmental and conservation benefits.
   At the present, only a handful of states have the protocol in place to allow spent, but safe, industrial materials to be reused in commercial horticultural and agricultural applications. However, Dan Oman, chair of the AFS’s Beneficial Reuse Consortium, among many others, anticipates that other states may soon follow.
   The AFS is currently building a “critical” online database that will open channels of communication between the two industries. The web-based tool will allow soil producers to locate nearby foundries and review the quantities of available material. “Using the database, you’ll at least know where to start,” Oman says.
   A market that utilizes industrial byproduct for agriculture or horticultural purposes requires that stringent tests be conducted to ensure the safety of the materials. Oman anticipates that the database, forecast for completion before the end of 2009, coupled with forthcoming USDA reports and USEPA risk assessments, both expected to support the developing market, will clear the way for states to allow more reuse of spent foundry sand.
   Sand molds help to shape everything from simple tools to car parts. There are a number of different sands used in the foundry industry. Most common are natural silica sands (beach sand), along with specialty sands such as olivine (from magnesium silicate deposits) and chromite (from ore deposits) , Foundries typically acquire “virgin” sand through companies that mine from lakebeds and terrestrial environments.
   In the process of making the mold, the sand grains are bound, either chemically or with clay. Hollow molds may have a “core,” which is usually bound with synthetic resins. The external sand mold can be bound with water and clay, typically bentonite clay, which renders what’s commonly called “green sand.”
   Foundries produce castings by pouring molten metal into molds. The characteristics of residuals vary from foundry to foundry, and depend on the type of metal being poured (iron, steel, aluminum, brass or bronze), the type of casting process and the technology employed.
   It is standard foundry practice to reuse molding and core-making sands – up to 100 times. As the sand is recycled, the particles ultimately become too fine for the molding process, but remain a source of wealth for other industries. Spent foundry sand is typically non-hazardous, black in color, and contains a large quantity of fine particles (100 sieve size or less).

Elizabeth Olenbush whose work in matching supply and demand between foundry and soil producer says that the forthcoming "sustainable" market is good for the environment and it's an economically sound practice. Olenbush is the executive director of Foundry Industry Recycling Starts Today (FIRST), an industry consortium focused on market development for recycling of foundry institute byproducts.

   “The big thing here is that everybody is moving in the direction, as a nation, of how to produce products more sustainably” Olenbush asks. Foundry sand is a good example because the material is reused many times inside the foundry. “This is a real opportunity for commercial soil blenders to make money,” Olenbush continues, referring to the edge that a recycled material can give to bids for LEED certified projects.
   Olenbush is the executive director of Foundry Industry Recycling Starts Today (FIRST), an industry consortium focused on market development for recycling of foundry industry byproducts. Olenbush says, that prior to embarking on the journey, FIRST asked the USDA to look into the future of spent foundry sand in soil blending.
   “We wanted to know if it would work in high volume soil operations and if it is safe,” says Olenbush. The USDA is presently collaborating with the EPA in the final stages of concluding the work.
   Dr. Rob Dungan is a soil microbiologist and the project manager of the USDA-ARS Foundry Sand Initiative. He’s also the lead author of the forthcoming foundry sand characterization and beneficial use guideline, which is currently undergoing EPA review. “I’m very excited to see it out there,” says Dungan. “With this document more states will open the market for spent foundry sands to be put to beneficial use.”
   Dungan recommends spent foundry sand as a good candidate for use in manufactured soil, especially if it can be used to replace virgin aggregate. “That way you wouldn’t have to mine as much from lake beds, you conserve natural resources, reduce carbon footprint, greenhouse gasses, and they make really good blends,” says Dungan.
   The Foundry Sand Initiative, a federally mandated research program, began in 2002 to specifically address agricultural and horticultural use of spent foundry sands while determining if the sand can be safely used in the environment. In cooperation with Ohio State, Pennsylvania and Purdue Universities and FIRST, the USDA-ARS Foundry Sand Initiative has conducted extensive scientific experiments to assess the fate and transport of trace contaminants, and the human health and ecological risks posed by those contaminants when using spent foundry sand in manufactured soils.
   Dungan emphasizes that “not all foundry sand is created equal” when applied to commercial and homespun gardens. “We’re talking about specifically “molding sands” and “green sands,” Dungan specifies.
   What are the risks associated with using spent foundry sand and how do they stack up next to, say, adding manure to soils? “The overall gist is, you add anything to a soil, you’re going to have an impact,” says Dungan. “You’re changing the environment – it doesn’t necessarily mean negative.”
   Through his work Dungan concludes that when certain spent foundry sand was added to soil there were changes in the microbial community, but those changes “were similar to, or the same as,” when he added native silica sand (beach sand). He also found that earthworm survivability was high in samples of spent foundry sand compared to samples of clean silica blends.
   “We’re recommending iron, steel and aluminum are generally the three [foundry sands] that look really good for beneficial use,” says Dungan.
   On the other hand, studies show that spent sand from brass foundries is frequently not good to use in many commercial applications. Brass foundry sand tends to have high copper and zinc, which can cause problems. Olivine sand that has high nickel can also be an issue and is probably not good to use in manufactured soil, according to Dungan.
   Through the Foundry Sand Initiative the USDA’s focus was on looking for metal concentrations and xenobiotics (organic compounds) in spent sand. “So far, research reveals that sands from iron, steel and aluminum foundries contain very low metal concentrations, very similar and lower to what you find in native soils,” says Dungan.
   The same goes for the xenobiotics and other potential threats. “Organic phenolic compounds, PAH’s, dioxins,. . . they [the tested sands] all contain very, very low concentrations of these compounds,” says Dungan. From a risk standpoint, Dungan confirms that, so far, it appears spent foundry sand from properly maintained and tested sources would pose little risk in the environment, even cumulatively.
   What’s Dungan’s advise to soil producers who want to use spent foundry sands in a state that permits the use of post-industrial process materials?
   “I’m encouraging a soil producer to go to the foundry and develop an arrangement,” says Dungan. “Don’t be afraid to call a foundry and ask to come look at the product. If it’s a clean material – if there isn’t other waste in the sand, take a bucket or two back and experiment with it.”
   Sharon Barnes of Barnes Nursery in Huron, Ohio, experiments with more than just buckets of foundry sand. The company is fortunate to be located in a state that has protocol for being able to use the industry byproduct. Barnes’ company uses their own carefully crafted blend of composted food and yard waste as a building block for blending manufactured soil with spent foundry sand.
   With the curiosity of a soil scientist and the wisdom of a gardener, Barnes explains, that “the sand is a subculture all by itself. Some sand is sharp, that acts differently from a rounded grain in that it’ll lock together and give you less permeability than the round ones,” says Barnes.
   Indeed it’s not just the shape but also the size that matters. Sand ranges from course (1-2 mm), to very fine (.05-.1 mm) grains. “When you’re looking at foundry sand you have to know what particle size it falls in and its angularity,” says Barnes, who takes a lab-based approach to her craft.
   Barnes says that for soil producers, a keystone to being able to utilize spent foundry sand is proximity to the foundry. “You have to be in a market range where it’s going to be cost effective to truck the product,” says Barnes.
   Equal in importance to logistics, is the existence of a marketplace that provides a reliable place for foundries to deliver the sand. Barnes says it’s her experience that foundries aren’t trying to get rid of their waste; they’re interested in quality assurance. “They want to know about it; it’s a partnership. They want to know that it’s going to be screened and used properly,” says Barnes.
   Dr Rick Stehouwer of Penn State University chimes in that the budding market still requires some necessary nurturing from interested parties. Stehouwer ran a series of test plots with spent foundry sand for the USDA-ARS initiative. When the plots turned up successful he became a matchmaker between two pairs of foundry and soil producers in Pennsylvania, where there is a protocol in place for the industry byproduct.
   Stehouwer reports that in each on-going case there have been issues to work out that don’t have anything to do with the foundry sand or a blended soil product, but that are common in the young reuse and recycling markets. These nuts and bolts issues include: hauling, storage space, delivery times and scheduling. “Each company is on a learning curve,” says Stehouwer.
   Stehouwer continues to facilitate market relations between the newlyweds. “Hopefully we’ll get them to start marketing some product and hopefully the next group will have an easier time at it,” says Stehouwer.
   More than one seasoned company does exist, as does seasoned advice. Kurtz Bros. Inc, is a leading commercial landscape supplycompany with retail operations, soil & mulch manufacturing, C & D and organic waste-to-reuse operations throughout Ohio. Kurtz Bros. pioneered the use of spent foundry sand as an ingredient in manufactured topsoil 25 years ago. Six million-tons of foundry sand later, company president John Kurtz offers, “It isn’t just how the sand is used, it’s how the foundry does housecleaning. They could be throwing paper cups or gloves in the bin that they throw spent sand in, which can add to costs.”
   Kurtz Bros. secured approval from Ohio’s EPA to utilize the sand from Ford Motor Company in “unrestricted” soil blends in 1996. “It’s because Ford is so uniform and so clean and they don’t change their process,” says Kurtz.
   Kurtz adds that a secondary challenge Kurtz Bros. has encountered in its use of foundry sand is resistance from folks who look at the material as competitive, and from folks “who are set in their ways,” Kurtz says. In the end, many companies warm up to recycled foundry sand because the product can cut costs and because it can enhance a bid for a LEED certified job, says Kurtz.
   The best quality sand for soil producers to consider is one that meets all test requirements and one that has not been used often enough to destroy the integrity, according to the experts. As the sand is used over and over in the casting process eventually it becomes dust. Dust doesn’t improve the quality of the materials.
   Once obtained, sand should be screened, and then matched with the right base of organic matter with the proper pH. “We use [foundry sand] in soil blends at generally not more than 15-20% of a blend, just because my soils generally don’t need more than that,” says Barnes.
   Soil producers agree that spent foundry sands are currently being blending to specification, based on sieve sizes and texture class, both of which can be ranked by a lab, a method many agree on. “Then you know what you’re selling,” says Barnes. “Not all foundry sands are the same,” she reminds.
   According to FIRST’s Olenbush, one of the most outwardly enthusiastic proponents of the emerging market, the message needs to be: “contact our industry for more information” through (www.foundryrecycling.org) or the AFS (www.afsinc.org). Additionally, soil producers who want to increase the likelihood of the permissible market and protocol should contact their state regulatory agency, let them know the information is coming out and that the potential end market is being cast.