Excerpt from the May/June 2015 issue of Metal Casting Design & Purchasing.
Foundry sand, which is used by 60% of metalcasters to make molds and cores in a variety of metalcasting processes, represents a significant industrial byproduct. Unlike metal, which has been recycled for centuries, foundry sand has become a target of reclamation and recycling efforts in the last 20-30 years. Due to increasing regulatory control and disposal costs, metalcasters have reduced the amount of sand headed to landfills.
Green sand can be reclaimed and reused an average of eight times for molds.
Reclaiming and Reusing Sand
The industry discards between 5-8 million tons of sand no longer suitable for making quality castings annually. However, according to a recent industry study, prior to being discarded, the average sand grain is reclaimed and reused by the metalcaster an average of eight times.
Additionally, approximately 30% of foundry sands are reused in non-landfill applications. These uses include geotechnical fills, road sub-base, embankment construction, aggregate in asphalt, soil additives and replacement for silica in cement. Despite the advancement of recycling initiatives into higher-end recycling, it is not necessarily a revenue-generating endeavor. Processing costs to get the material to “product quality” typically consume any margin in the sale price of the material. However, the advantage of minimizing disposal costs, in addition to the environmental benefits, makes this approach more preferred to disposal.
“Sand as a raw material for construction applications is typically not a high dollar expense for contractors,” Lenahan said. “It doesn’t generate quite as much excitement as we would hope sometimes. However, if you can reduce the transportation costs for an end-user and provide a quality material that meets a specification they already have, you may be on to something. Transportation costs continue to play a huge role in the ability to recycle materials. A contractor may be interested in utilizing a recycled material but transportation costs can take that material right out of the discussion.”
Beneficial use of discarded sand, according to EPA estimates, is saving more than 202 billion BTUs per year and reducing CO2 emissions by 20,000 tons. While foundry sand has been used in a variety of applications after leaving the casting operation, government regulation can be an obstacle to maximizing its non-landfill use.
EPA has determined a vast majority of foundry sands are considered non-hazardous solid wastes. Individual states, however, retain regulatory authority over the materials, even when they are comparable in physical and chemical nature to non-regulated materials.
“It’s been a challenge to convince regulatory agencies that many of these materials do not belong in landfills and should be recycled,” Lenahan said.
Though regulations can prove cumbersome, the general public has become more amendable to reusing an industrial byproduct. Metalcasters have also marketed the material better to potential partners.
“We’ve got a good, uniform product,” Lenahan said. “Foundry sand producers provide uniform materials with tight tolerances. As a result, sands that are discarded benefit from some of those same tight controls.”.
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