The Many Lives of Copper
The Many Lives of Copper
It’s all around you, but in many cases, you may not be aware of its presence. The coins jingling in your pocket may contain it, and it’s part of the circuit board in your cellphone. You’ll find it in your home’s wiring, and the pipes that deliver water, and the motor that powers the refrigerator. You might see it on your neighbor’s roof, and if she plays the saxophone, you can hear it, too.
What is this ubiquitous material? It’s copper: periodic symbol Cu from the Latin cuprum, a reference to the island of Cyprus, a major source of the metal in Roman times. Its atomic number is 29 and it is extremely ductile, a superb conductor of heat and electricity, and used in a wide array of familiar, everyday applications.
The recent installation of Copper Development Association (CDA) vice president Andrew G. Kireta Jr. as 2020 chair of the ASTM International board of directors provides the opportunity to take a closer look at the work of the committee on copper and copper alloys (B05) and its newest subcommittee on recycling (B05.08).
A Long History
Copper is a remarkable metal. It is second only to silver as an electrical conductor and is an excellent thermal conductor as well. Its surface is inherently antimicrobial, and its malleability allows it to be shaped into a variety of forms. Aesthetically speaking, copper is one of just three metals (gold and cesium are the others) that is not silver or gray in color. Its pinkish-gold hue is instantly recognizable.
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The use of copper dates back millennia. The oldest example, an ingot (block) found in what is now northern Iraq, dates to 8700 B.C. However, copper really came of age with the dawn of the Industrial Revolution as a key component of electrical systems and electric motors, transformers, and generators.
“Over 50% of all copper is used in electrical systems and components,” says Kireta, who notes that copper wire and cable, and copper and copper alloy sheet and strip for electrical connections make up the largest portion of this end use.
Kireta cites other critical applications in which copper is a key constituent, including tube, pipe, and fittings that transport clean water, medical and fuel gases, and HVAC (heating, ventilation, and air conditioning) refrigerants. In addition, “Brass, bronze, and other alloy rods, bars, and shapes are the base materials for a wide variety of machined parts. It’s used in valves, bearings, and other components in plumbing systems, builders’ hardware, automotive parts, and electrical and electronic devices,” he says.
Speaking of devices, the explosive growth of cell phone and computer technology, as well as more widespread implementation of renewable energy systems and the maturation of the electric vehicle industry, has created an unprecedented appetite for copper. In fact, per capita use of the metal has roughly doubled over the last 50 years, according to the CDA.
The Evolution of Copper Standards
ASTM International has been an important voice in the development of copper-related standards for more than 100 years. Although the B05 copper committee was established in 1928, several core copper-related standards actually date back further, to a time when the metal fell under the purview of the ASTM committee on nonferrous metals and alloys (B02). For example, the specification for high conductivity tough pitch copper refinery shapes (B5) was first approved in 1911, and most recently updated in 2016.
Copper tubing ready to be shipped for use in plumbing, HVAC systems, and much more.
B05 currently comprises seven technical subcommittees that cover the production and use of copper and copper alloy semi-fabricated products, including plate, sheet, and strip; rod, bar, and wire; pipe and tube; and castings and ingots (for remelting). Six additional subcommittees address such areas as terminology and strategic planning.
“Much of the work of the committee is focused on maintenance of existing standards to reflect changes in test procedures, methods, and equipment,” Kireta says.
Charles Blanton, chair of the copper and copper alloys committee, explains that historically, a lot of their work has been prescriptive in nature. “You have a minimum or maximum wall thickness and you must adhere to that spec. However, we are looking at performance-based standards, which will allow alternative copper wall thicknesses,” says Blanton, vice president of environmental health and safety for Mueller Industries, a multinational copper manufacturer headquartered in Tennessee.
One such standard was developed by the tube and pipe subcommittee (B05.04) and first published in 2016. The standard specification for seamless copper tube for linesets (B1003) established performance-based requirements for the tubing used to connect the indoor evaporator coil and outside condenser coil in air conditioning and heat pump systems. Previously, there were no standards or code requirements governing the properties of this tubing.
Blanton notes that while the copper committee as a whole has traditionally concentrated on performance and usage, the newest technical subcommittee on recycled materials (B05.08) will explore issues related to the recycling of copper. Its scope was approved in April 2019, and the inaugural meeting of the subcommittee’s 19 members (with more expected to join) took place in October 2019. Though its work is just beginning, the subcommittee’s importance to an even more sustainable future for copper products is clear.
The Value of Scrap
According to chair Adam Estelle, the CDA’s director for rod and bar and B05.08 chair, the genesis of the recycling subcommittee can be found in discussions on scrap copper and copper alloys that took place among his organization’s members. “We were seeing issues in the brass space,” he explains. “Folks who were making brass products were running into some issues with cross-contamination of scrap from different alloy compositions. It was pretty hard for them, and getting harder in some cases, to be able to keep these different compositions separate in recycling.”
The fact that these issues were not unique to the brass world, and that they were bedeviling many companies that incorporated scrap into their copper and copper alloy products, soon became apparent to Estelle and his colleagues.
“Many companies are using their own internal standards to specify acceptable conditions for the scrap they purchase for remelting,” Estelle says, adding that before the creation of subcommittee B05.08, the committee addressed recycling issues on a piecemeal basis. “Maybe there’d be a short paragraph or a footnote that would get inserted into one of the broader product specifications in B05. In some cases that was effective, but we realized that with the larger issues, you can’t just jam that into another product spec.”
The realization that standalone specifications and standards were badly needed spurred Estelle and other industry stakeholders to consider scrap copper in a different light. “Let’s start thinking of scrap as a valuable product, a commodity that’s bought and sold by different parties and is an important part of the industry,” Estelle says. “We think there is an opportunity to find some common ground and develop new standards that benefit both producers and users of scrap. From a standardization perspective, it made sense to carve out a separate space to handle specific issues related to scrap and recycling, rather than trying to address them indirectly in the product standards.”
Many of the challenges with copper recycling can be traced to one of its greatest strengths: the ability to combine with other elements to create alloys designed to meet the particular demands of various end uses. These alloys include the brasses (copper and zinc), bronzes (copper and tin), copper nickels, and many other specialty alloy families. Currently, there are approximately 800 copper alloys with unique chemistries registered in the Unified Numbering System (UNS). (The UNS was developed in 1974 to uniformly number commercial metals and alloys in the United States. The system is administered jointly by SAE International and ASTM International.)
“In each of these categories, major and minor alloying elements are added to copper to improve specific properties such as strength, corrosion resistance, formability, and machinability,” Kireta says.
Ironically, copper’s very versatility creates challenges for recycling. Although copper can be recycled again and again with almost no loss of its beneficial properties, separating different alloys within the waste stream prior to recycling is difficult, especially for end-of-life or post-consumer scrap. And the introduction of new alloying elements such as bismuth, silicon, and selenium adds further complexity to recycling efforts.
Setting up the recycling subcommittee was an important first step. As Estelle points out, “Our top priority is to protect the technical and economic viability of the copper and copper alloy scrap stream. We’re going to do that by developing specifications, test methods, practices, and guides related to recycled or reclaimed copper and copper alloy materials intended to produce new products via direct remelting, fire-refining, and smelting and refining.”
Smoothing the kinks out of the copper recycling process presents two major challenges: distinguishing among multiple distinct alloy families that can and cannot be recycled together, and dealing with increasingly complicated product designs that make it difficult to recover the copper when those products enter the waste stream.
“Over the years, the recycling stream has become more complex, and as a result we’re facing new technical challenges,” Estelle says. “Many copper alloys look identical and are difficult to separate with conventional techniques like manual sorting or handheld analyzers, and as we continue to add more and more elements and different compositions to our recycling stream, not all of those play nice with each other when you recycle them. So it’s really our challenge to help figure out how to create closed-loop recycling systems and make sure that the incompatible alloy compositions are not co-mingled in the scrap stream. But it’s a lot easier said than done from a practical standpoint.”
Another challenge is bimetallic products like copper-clad aluminum wire and cable, which can be difficult to detect. Featuring an aluminum core protected by a solid copper sheath, such products offer reduced weight and lower costs compared to a pure copper alternative. The problem occurs when it’s time to recycle.
“When all that gets ripped out of a building, it’s typically cut into short lengths called wire chops that companies throw into the furnace to remelt,” Estelle says. “It looks like copper on the outside, but there’s an aluminum core. It’s very, very difficult to spot that, and you throw that in, and even in small concentrations, you can really have some big issues in remelting.”
One question, Estelle explains, is whether the subcommittee can develop a consistent methodology to obtain representative samples when inspecting different types of scrap for the presence of contaminants. “If we have a reproducible method that you can use to better detect deleterious impurities and avoid putting them in the furnace, it makes sense to try to write that up and get that out in a standard way,” he says.
The Promise of Sustainability
In one very important respect, copper already has a huge advantage in terms of a more sustainable future: its nearly infinite ability to be recycled. Incredibly, 75 percent of all copper produced since the year 1900 is still in use today. It may not be in its original product form, but the metal lives on as a recycled component of other copper products and may have been recycled several times already.
“On average, copper products produced today contain 35% post-consumer recycled content, and nearly 10 million tons of copper are recycled each year,” Kireta says. “This not only reduces the demand for newly mined copper but saves both energy and carbon dioxide emissions.”
The recent addition of two new copper rod alloys — UNS C11020 and C11025 — to the standard specification for copper rod for electrical purposes (B49) illustrates advancements in the use of recycled content to make new copper products. The alloys are made mostly from post-industrial and post-consumer recycled content, which is turned into copper rod, a product that typically has been fabricated from virgin, refined copper alloys.
In Kireta’s view, one significant issue facing the copper industry is less about the metal itself and more about the people who dig it out of the ground. “Because copper mining is concentrated in underdeveloped or developing regions, mining sustainability must consider more than responsible use of the metal and focus more on responsible sourcing to account for local human, economic, labor, and environmental stewardship factors, and ensure that resource development is a productive force for the local population,” he says.
While new sustainability initiatives may start at the mine, Kireta believes such efforts must involve a comprehensive, cradle-to-cradle mindset. “It means more than focusing on the sustainability of mining,” he notes. “It means being a good steward of copper as a material all the way through its lifecycle from mine, to semi-product fabrication, to final product manufacture, through the product’s installation and use, and finally through end-of-life recovery, reuse, or recycling.”
The members of the copper committee and its new recycling subcommittee are working hard to support these sustainability efforts. The new subcommittee and the industry’s focus on sustainability go hand-in-hand with their continued work with and active participation on the ASTM sustainability committee (E60), further advancing an agenda that includes improving product transparency and finding new ways to enhance copper’s profile in terms of environmental impacts, energy and resource consumption, and waste creation and reuse.
Jack Maxwell is a freelance writer based in Westmont, New Jersey.