In This Issue
Winter Bridge on Frontiers of Engineering
December 15, 2023 Volume 53 Issue 4
This issue features articles by 2023 US Frontiers of Engineering symposium participants. The articles cover pressing global issues including resilience and security in the information ecosystem, engineered quantum systems, complex systems in the context of health care, and mining and mineral resource production.

Mining and Sustainability Matching Stewardship with the Circular Economy to Meet Societal Demands

Wednesday, December 13, 2023

Author: Joshua Werner

To keep up with the ever-expanding societal demand for metals, responsible stewardship in mining and the circular economy are essential.

The United States is coming to terms with the existential need for a sustainable and secure supply of critical materials. We are facing the challenge of satisfy­ing the increasing demand for metals in society while ensuring sustainability and responsible stewardship of the planet’s natural resources. ­Inextricably linked to this challenge are the quantity and preparation of qualified personnel. To evaluate this complex ecosystem, this article examines this problem from a first-principles approach, exploring the mass balance issue of increasing demand for metals through mining and the recovery and recycling of metals to maintain them in the ecosystem. Also discussed is the need for technological development and changes in societal norms and technical barriers to ensure the success of the circular economy. By providing a practical approach, this article aims to offer valuable insights into the importance of responsible stewardship in mining and the potential of the circular economy to enable the ever-expanding societal demand for metals.

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Mass Balance and the Circular Economy

The cause of the recent interest in critical materials and minerals can be found in figure 1, which shows the fundamental mass balance equation and a representation of the circular economy. With regard to the sourcing of raw ­materials, only mining (primary) or recycling (secondary) sources represent feasible means of introducing raw materials into the circular economy. The ­recovery of ­materials after use is critical to maximizing value, either through reuse, remanufacturing, or ­recycling. Those ­materials not subject to recovery are refused back into the biosphere. The recovery of true end-of-life materials is subject to the economic and technological barriers to extracting value from waste through recycling. It is often more cost-­effective to dispose of something than to recycle it. These materials are often low grade, ­highly ­heterogenous, and more complex than the ores they replace.

As a case study, copper illustrates the complexity of this issue. The world population has increased from about 2.5 billion in 1950 to slightly over 8 billion in 2022. In the same period, copper utilization rose from about 1.2 kg per person to about 3.3 kg (The World ­Copper Factbook 2023). Not only is the population increasing, but the consumption per person is also increasing. In considering both the per capita use and population, the quantity of required copper has increased by 880% from 1950 to 2022. It becomes clear from the mass balance equation shown in figure 1 that it is impossible to recycle our way into prosperity. The circular economy requires mining to prime the system. This is further compounded by the fact that the ten-year recycling input rate for copper is about 31% (The World Copper Factbook 2023). Thus, the problem is twofold: insertion into and loss prevention in the circular economy. Similar statistics are found across other critical materials, for which demand is driven in large measure by the dependence of our technologies on them and our ever-increasing appetite. Such an example of technology-driven demand can be found in comparing a conventional car, which requires 23 kg of copper, to a battery electric vehicle, which requires approximately 83 kg of copper (The World Copper Factbook 2023).

The Straight and Narrow Path

This leads to a paradox that might be termed the “straight and narrow path.” It is as though the mining industry ­travels a road bounded by two competing forces. On the one hand, you have what society requires, often termed the “social license to operate.” This can be described as the sum of all the societal forces acting on the mine. It ranges from regulatory requirements to politics and community approbation. It includes intangibles such as reputation and goodwill. It is the permissions and expectations that society places upon the mine to allow its commencement and continued operation. On the other hand, you have what society demands, manifested by the market price for materials. Ever present are the competing market forces of environmental sustainability pitched against metals demand, causing the pendulum to swing.

Nowhere can these juxtapositions be observed more clearly than in the examples of mining around ­Yellowstone National Park. By way of background, in the ’90s the Clinton administration spearheaded agreements for federal lands to ban mining in the area. Although successful, this still left the opportunity of mining private lands. Just this year, a creative solution was announced where environmental groups block a gold mine by purchasing it (Grandoni 2023). The societal value of preservation was leveraged against market forces to reach an economic solution. However, this does not fundamentally resolve the problem of “if not here, then where?” Much like a dammed river, an eventual outlet for pent-up demand will be found and sometimes in locales where economic forces outweigh ethics and environmental considerations.

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Ecosystem Realities

To evaluate the interplay among primary metals sources, over 100 “customer discovery” interviews in the mining and recycling space were done as a part of the NSF I-Corps entrepreneurial training program. Its purpose is to determine, through direct consultation with potential customers, the reality of the need and to provide concrete evidence that the proposed solutions to those needs are in fact valid. The realities of the recycling ecosystem are shown in the ecosystem map below (figure 2), which represents the copper recycling ecosystem. This figure was created after interviewing suppliers such as e-waste processors, sorters, shredders, and wire choppers. Also included were companies specializing in smelting and the customers for produced semifinished goods. It depicts a simplified representation of the interdependent material flows.

The results were surprising. The industry is multi­faceted and appears to be going through a ­period of consolidation, from various regional and familial ­entities to larger corporations. A key finding was the distillation of what appear to be six fundamental competitive ­advantages: 1) access to supply (also known as book of business), 2) logistics, 3) solution value to customers (such as IT asset destruction and recovery [ITAD/ITAR]), 4) ­asymmetry of information, 5) technology and/or process, and 5) access to capital. Of note is the asymmetry of information, where a competitive advantage exists due to having privileged or proprietary information. In our interviews, this opacity was fascinating as a key competitive advantage of the ecosystem. The economic realities of low-cost overseas solutions combined with modernization costs led to a period, from 2002 to 2023, in which there existed no smelters (a mixed-metal ­pyrometallurgical process) in the United States capable of processing secondary materials. Even though primary material smelters exist in the United States, not all smelters can handle the same feed material form factor. Further, the downstream customers can seamlessly alternate between mined and recycled materials.

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A Path Forward

In view of the interplay between primary and secondary materials, often the answer to current problems is technological progress. At the University of Kentucky ­Mining Engineering Department, several unique ­projects have been launched addressing sustainability in the circular economy and in mining. One of these, sponsored by the NSF, is titled “SMaRT (Sustainable Materials and ­Recovery Technologies) for E-waste” and aims to use a novel and green technology to recover copper and precious metals from e-wastes in an environmentally friendly and closed-loop fashion, as shown in figure 3. In like manner, a first-of-its-kind heap leach pad for coal refuse was established to study the feasibility of recovering rare earth elements (REEs) via heap and tank leaching utilizing the bio-oxidation of pyrite (see figure 4).

Conclusions and a Call to Action

As we look to the future in addressing how we will meet our growing consumption of materials while balancing ecological sustainability, it is clear that this is a truly multi­disciplinary endeavor. From a mass balance perspective, we cannot recycle our way to prosperity. A true ­solution will require the balance of exploration, production, and sustainability. It will require the very best that we, as engineers, have to offer. Yet persistent is the problem of too few to fill so great a demand. It may be said of the industry, to quote Winston Churchill, “Never has so much been owed by so many to so few.” The opportunities are immense, the challenges are real, and the “straight and narrow path” becomes increasingly tenuous. So, the call comes. It calls to me. It is calling to you. Come bring the best you have. Join us, and together we will meet this challenge. Let us walk this long road together.


Grandoni D. 2023. Environmentalists aim to block gold mine near Yellowstone—by buying it. The Washington Post, May 11.

Jawahir IS, Bradley R. 2016. Technological elements of circular economy and the principles of 6R-based closed-loop material flow in sustainable manufacturing. Procedia CIRP 40:103–108.

The World Copper Factbook. 2023. International Copper Study Group. Online at

About the Author:Joshua Werner is assistant professor, Department of Mining Engineering, College of Engineering, University of Kentucky.