CASTING INNOVATIONS Supply Chain Grows Greener With Use of Metalcasting Byproducts
Metalcasting is one of the oldest methods of recycling, with a few mil- lennia 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 facili- ties in Wisconsin, Indiana and Tennes- see. Te 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 byprod- uct from Waupaca Foundry contains sodium bentonite, properly hydrated and compacted sand can achieve a low hydraulic conductivity, which is the pri-
mary 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. Te 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. com- pacted 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. Te 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. Te select foundry byproduct mate-
rial met state and federal regulatory design standards and retained the de- sired 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. Te Wisconsin Department of Natural Resources approved the plan modification in May 2014. Tis will equate to saving more than 100,000 cubic yards of clay and keep more than 80,000 cubic yards of foundry byprod- uct from a landfill. Te 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. Fur- thermore, this project shows how metalcasters are working to ensure the entire supply chain is as green as possible. Successfully using metalcast- ing byproducts replaces native clay soils with what formerly had been a waste product. Additionally, second- ary environmental impacts related to soil excavation, hauling and borrow area reclamation are reduced.
Tis 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.
Visit
www.waupacafoundry.com and
www.trcsolutions.com for more information.
After 2.5 years, both liners appeared intact, without deterioration, cracking or preferential flow paths.
The project included two test pads that monitored how foundry by-product performed as a landfill liner. 74 | MODERN CASTING March 2015
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