innovations CASTING


Green Use of Metalcasting Byproducts M


etalcasting is one of the oldest methods of recycling, with a few millennia worth of experi- ence, but today’s industry still battles outsiders’ preconceptions about dirt, grime and pollution. A recent project from one of the world’s largest


producers of iron castings highlights eff orts from metalcasters to further contribute to a greener supply chain. Waupaca Foundry Inc., Waupaca, Wis., worked with TRC


Companies Inc., Lowell, Ma., and Madison, Wis., to develop a means to reuse metalcasting byproducts from Waupaca’s six facilities in Wisconsin, Indiana and Tennessee. T e goal of the three-year project was to establish a way to use spent foundry sand as landfi ll liner, which could lead to a number of signifi - cant benefi ts: • Increased volume of benefi cially use materials. • Reduced landfi ll construction costs. • Extended life of their landfi lls. • Reduced environmental impact. • Improved sustainability of their operations. Waupaca Foundry produces iron castings via the green


sand casting process. Byproducts not destined for benefi cial reuse historically have been considered wastes and disposed in nonhazardous landfi lls. Because green sand byproduct from Waupaca contains sodium bentonite, properly hydrated and compacted foundry 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 completed construction of two


test pads to evaluate the long-term performance of com- pacted foundry byproduct as a landfi ll liner. T e side-by-side 20-ft. x 25-ft. test pads included one with a 3-ft. compacted select clay liner and the other with a 3-ft. compacted select foundry byproduct liner (a mixture of casting sand and dust), each overlain with 2-feet of foundry sand by-product waste material and underlain with a lysimeter, a device that collects liquids released at the base of the test pad. T e lysimeters were monitored on a monthly basis for a 2.5-year period. T e test pads were exposed to over two full changes of seasons in Wisconsin, meaning the materials experienced harsh freeze- thaw conditions. At the end of the monitoring period, the test pads were


carefully exhumed and samples were collected for testing. Both the liners appeared intact, without visible signs of deterioration


or cracking or preferential fl ow paths in the select foundry by- product barrier layer. T e select foundry byproduct material met strict Wiscon-


sin EPA regulatory design standards and retained the desired engineering properties. Waupaca Foundry submitted a modifi ed plan with an alternative liner system for the remaining 13 acres of their landfi ll using a 4-ft.-thick foundry byproduct layer with a geomembrane layer. In 2014, the Wisconsin Department of Natural Resources approved the plan modifi cation., which will equate to saving 100,000 cubic yards of clay and stopping 80,000 cubic yards of foundry byproduct from going to a landfi ll. T e use of foundry byproduct as low-hydraulic conductivity


barrier eliminates the need and cost to import clay soil, maxi- mizes airspace capacity and extends the working life of the landfi ll. 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 reclamation are reduced.  T is article is written by Douglas Genthe, TRC Companies Inc., and Bryant Esch, Waupaca Foundry, based on their presentation


at the 2014 Global Waste Management Symposium. Visit trcsolutions.com or waupacafoundry.com for more information.


The project included two test pads to monitor the liner made of foundry byproduct.


Jan/Feb 2015 | METAL CASTING DESIGN & PURCHASING | 47


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