New ground ripe for foundry sands

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Courtesy of Security Shredding & Storage News

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.”

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