The metalcasting industry prides itself on its recycling practices. Here’s a look at how metalcasters reduce waste, increase efficiency and operate responsibly.

Nicholas Leider, Associate Editor

(Click here to see the story as it appears in May/June's Metal Casting Design & Purchasing.)

Metalcasting—or, as many are fond of calling the industry, “the world’s original recycler”—has something of a messaging problem when it comes to environmentally sustainable practices. The old stereotype of a grimy, soot-filled foundry coughing smoke into the blue sky belies an important truth about metalcasting: The industry is conscious of reducing wastes, reducing costs and fulfilling a vital role in industrial sustainability.

The benefits can be both economic and environmental, but the industry struggles to emphasize its story of “sustainability,” just as it is becoming the latest buzzword. Those at the end of the supply chain are already asking about green initiatives and corporate responsibility, and metalcasters, if they aren’t already, will need to prepare an answer.

Additionally, buyers need to know a metalcasting facility has a plan to be in business for the foreseeable future. It’s about stability and risk management—the supply chain won’t break when a metalcaster operates as expected.

“There isn’t another industry, in terms of raw materials, that recycles as much as we do,” said Mike Lenahan, CEO of Resource Recovery Corporation, Coopersville, Mich., and president of AFS-FIRST (Foundry Industry Recycling Starts Today). “Look at the national average for household recycling. The numbers are between 22-30%. In addition to recycling foundry sand within the casting process, a foundry with a strong beneficial use program may be recycling as much as 95% of their discarded sands and slags. This eliminates the need for an end-user to mine virgin materials for their application. That’s incredible.

“On top of that, guess what they’re consuming as feed stock? They’re accepting somebody’s old washing machine or a 20-year-old engine block that’s otherwise useless and turning it into something brand new.”

Making the Most of Metal

Unsurprisingly, metal is a key component in metalcasting. To that end, the industry has become especially efficient in all phases of the manufacturing process, from purchasing scrap metal for recycling to producing castings that eventually can be reused.

Scrap Recycling: The metalcasting industry accepts huge amounts of scrap from other manufacturing industries. When a metal component reaches the end of its life, it can be scrapped and reused. Additionally, other manufacturing processes, like stamping, forging and machining, can produce usable scrap.

The environmental benefits and reduced pressure on landfills are obvious. But metalcasters also have an economic incentive to use what otherwise would be unwanted leftover material.

“You’d raise the price of the casting by 20-40% if you weren’t able to utilize the recycled material,” said Gene Muratore, metalcasting industry consultant. “Whatever you pay for those raw materials will affect the price of what you’re selling.”

According to the U.S. Environmental Protection Agency, recycling steel reduces air pollution by 86%, water use by 40%, water pollution by 97% and mining wastes by 97% in comparison to using virgin iron. Additionally, using scrap metal requires less energy, which can mean additional savings for the metalcaster.

Internal Reuse: Depending on a casting’s design, a significant amount of metal may be removed from the final casting. All gates, risers and runner bars will be separated from the casting before it’s ready to be shipped.

“The actual part that’s shipped to the customer, depending on the casting, may only be 30% of metal that is poured,” said Geoffrey Sigworth, GKS Engineering, Dunedin, Fla. “You have metal in runners, gates and risers. You will also produce scrap castings. All of this is remelted.”

Approximately 1% of the metal will be lost during the melting process in dross and slag. Depending on the casting, machining may result in metal loss. But for the large majority of casting operations, somewhere in the neighborhood of 95% of the as-cast part will eventually exit the metalcasting facility as the finished casting.

Costs are involved in processing and reusing metal, but the overall efficiency of the operation means that waste remains relatively small. Also, because metalcasters have been focused on maximizing metal usage for decades, internal recycling is approaching its peak.

“We’re pretty optimized now,” Muratore said. “There’s only so much you can do and the industry is already recycling and reusing a tremendous amount of material.”

In a typical melt, aluminum casting facilities use between 40-60% scrap from within the facility (gating, riserings, scrap castings, etc.), with the remaining aluminum coming from ingots that often contain a considerable amount of recycled material. In general, ferrous metalcasters use between 30-50% internal scrap and 40-50% scrap from external sources (including ferrous material from recycled cars, appliances, and scrap steel from other manufacturing operations etc.). Alloying elements, are then added to the melt to meet the specific chemistry requirements.

Recyclable Castings: Metalcasting facilities convert unwanted scrap metal into valuable castings with a variety of applications. Those components, once they are no longer needed, will become the scrap that may head to another metalcasting facility for a second or third life.

“Metal doesn’t have a memory,” said Sigworth. “It doesn’t know or care it was a casting yesterday.”

Reclaiming and Reusing Sand

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.

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.”

Energy: The Next Frontier?

Energy costs run between 5-7% of the average metalcasting facility’s operating budget. As much as 60% of that consumption occurs in melting operations. Unlike the highly optimized metal recycling processes, however, improved energy efficiency remains in the early stages of development for many metalcasters.

One trend that is beginning to take hold in the industry is waste heat recovery. For example, a facility’s engineers can modify the melting system to more efficiently use waste heat. If heat from a furnace otherwise escapes without purpose, it can be used to preheat the material for the next charge.

Historically, metalcasting facilities have received a single utility bill for electricity or gas usage. But specialized measuring systems are becoming more prevalent in the industry. Energy experts have developed sub-metering practices that place individual sub-meters on separate furnaces, compressors, bag house, etc. By measuring energy consumption on specific pieces of equipment, metalcasters can see exactly where the energy is used.

Brian Reinke, an energy consultant with TDI Energy Solutions, Lemont, Ill., identifies process improvement as another area of potential savings. For example, improving training procedures for those operating furnaces, air compressors and dust collectors, can lead to reductions in energy consumption.

“We routinely find significant energy savings opportunities for foundries, and many of them require little to no capital expense,” Reinke said. “People are especially interested when we discover ways to increase their throughput and save money on their utility bills at the same time. This provides both higher profit and the potential to produce more castings.”

In response to economic and environmental pressures, metalcasters will continue to look for ways to reduce consumption and waste. The larger idea—whether it’s called a sustainability program or green initiative—remains a plan for the future and an expectation of longevity.

“Really, [buyers] are looking for long-term planning instead of a focus on the short term,” Lenahan said. “What are metalcasters doing to retain talent? What are they doing to recycle industrial byproducts? What are they doing to maintain a positive reputation?”