Copper mine tailings — the leftover rocks, water and chemicals of the mining process — are produced at a very high rate during excavation from mining activity. The displaced material sits idly and is harmful to the environment as it releases particulate matter emissions and leaches acid, heavy metals and even toxic and radioactive material to its surroundings and groundwater.

A team of five graduating students from the School for Engineering of Matter, Transport and Energy in the Ira A. Fulton Schools of Engineering at Arizona State University worked together on finding a solution that would repurpose 1,000 tons of copper mine tailings per day as their final capstone project.

The team of five chemical engineering graduating students knew they wanted to engineer a process to convert mine tailings into a valuable product and investigated many options. One approach would be to extract certain compounds from the tailings and utilize them in other production pathways.

“Unlike extraction where only select portions of the tailings are used, our approach would utilize the mine tailings in totality, incorporating all of the waste into a product and generating no solid byproduct/waste of its own,” says Dylan Ellis, “We felt this solution would fully capture the concept of closing the loop on a circular economy.”

The solution they came up with was to utilize the tailings as a whole in the production of concrete. Concrete will continue to be a high-demand material for a variety of purposes.

“Prior research has shown that using mine tailings a substitute for aggregate components in the making of concrete is not only feasible, but increases the strength of concrete without introducing risks related to the leaching of harmful compounds,” says Ellis. “This project will enable a more sustainable pathway for concrete production and for mining operations.”

The capstone project team of Ellis, Adam Martin, Trevor Ciha, Xavier Bonelli and Sean Innes presented their idea at the virtual WERC Environmental Design Competition hosted by New Mexico State University after learning about the competition from Lecturers Jared Schoepf and David Taylor, the advisors for their senior capstone course.

The faculty advisors selected problem statements for the capstone class from real competition problem statements as ideas for the class to pursue. The team of five students was excited to apply their coursework to a meaningful competition where they won a Judges Choice Award.

“Personally, my favorite part of the experience has been working with my amazing teammates,” says Ellis. “It was incredible to work toward solutions for a real-world problem, and even more incredible to grow in this capacity alongside excellent fellow students and friends.”

In the competition, the team had the opportunity to discuss their project and receive feedback from a judging panel of professional engineers.

“I learned a lot in discussions with the judges and felt more confident in myself as an engineer as a result,” says Ellis. “Winning a Judges Choice Award was the cherry on top at the end of the experience.”

While this particular team of students will not be pursuing this project in the future, they have laid the groundwork for those that follow them.

“We hope our current research toward mine tailing reutilization in concrete is advanced,” says Ellis. “Our goal is for future ASU students to take advantage of the excellent opportunity provided by the WERC Environmental Design Competition.”