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Supply chain grows greener with use of metalcasting byproducts.

Metalcasting is one of the oldest methods of recycling, with a few millennia worth of experience. A recent project from one of the world's largest producers of iron castings highlights efforts from metalcasters to further contribute to a greener supply chain.

Waupaca Foundry Inc., Waupaca, Wis., worked with TRC Companies Inc., headquartered in Lowell, Mass., and locally in Madison, Wis., to develop a means to reuse metalcasting byproducts from Waupaca's six facilities in Wisconsin, Indiana and Tennessee. The goal of the three-year project was to establish a way to use spent foundry sand as landfill liner, which could lead to a number of significant benefits, such as:

* Increased volume of beneficially used materials.

* Reduced landfill construction costs.

* Extended life of their landfills.

* Reduced environmental impact.

* Improved sustainability of their operations.

In the green sand casting process, byproducts not destined for beneficial use historically have been considered wastes by the industry and regulatory community and disposed in landfills. Because green foundry sand byproduct from Waupaca Foundry contains sodium bentonite, properly hydrated and compacted sand can achieve a low hydraulic conductivity, which is the primary characteristic needed for a barrier layer material to contain liquids.

In early 2011, Waupaca Foundry completed construction of test pads to evaluate the long-term performance of compacted foundry byproduct as a landfill liner. The two 20-ft. x 25-ft. test pads included one consisting of a 3-ft. compacted select clay liner and the second consisting of a 3-ft. compacted select foundry byproduct liner (a mixture of casting sand and dust), each overlain with 2-feet of foundry sand byproduct waste material and underlain with a lysimeter, a device that collects liquids released at the base of the test pad. The lysimeters were monitored on a monthly basis for 2.5 years, with the pads exposed to two full changes of seasons including harsh freeze-thaw conditions.

At the end of the monitoring period, the test pads were carefully exhumed for visual observation, and samples were collected for laboratory testing. Both the select foundry byproduct and select clay liners appeared intact, without visible signs of deterioration, cracking or preferential flow paths in the select foundry byproduct barrier layer.

The select foundry byproduct material met state and federal regulatory design standards and retained the desired engineering properties. Waupaca Foundry submitted a modified plan with an alternative liner system for the remaining 13 acres of its landfill using a 4-ft-thick compacted select foundry byproduct layer with a geomembrane layer. The Wisconsin Department of Natural Resources approved the plan modification in May 2014. This will equate to saving more than 100,000 cubic yards of clay and keep more than 80,000 cubic yards of foundry byproduct from a landfill.

The use of foundry byproduct as low-hydraulic conductivity barrier construction eliminates the need and cost to import clay soil, maximizes airspace capacity and extends the working life of the landfill. Furthermore, this project shows how metalcasters are working to ensure the entire supply chain is as green as possible. Successfully using metalcasting byproducts replaces native clay soils with what formerly had been a waste product. Additionally, secondary environmental impacts related to soil excavation, hauling and borrow area reclamation are reduced.

This article is written by Douglas Genthe, Principal Solid Waste Management and Geotechnical Engineering Services, TRC Companies Inc., and Bryant Esch, Environmental Coordinator, Waupaca Foundry, based on their presentation at the 2014 Global Waste Management Symposium in June 2014.

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Comment:Supply chain grows greener with use of metalcasting byproducts.(CASTING INNOVATIONS)
Author:Genthe, Douglas; Esch, Bryant
Publication:Modern Casting
Geographic Code:1U3WI
Date:Mar 1, 2015
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