Title: Sustainable Mining: Innovative Solutions for Environmental Remediation and Resource Recovery
By Julie Leibach
For the past two decades, researchers with the University of Arizona Superfund Research Program (SRP) Center have been studying human exposures to mining waste and how to improve site remediation in the Southwest. Funded by NIEHS, the team is also exploring ways to meet future mineral demands by mining an unconventional source: the waste itself.
“If you think about it, the green economy will rely on electrification, which is batteries, which is mining,” said Raina Maier, Ph.D., SRP Center director. “The question is, how can we do it with the least impact on the earth and on neighboring communities?”
Mineral mining generates the largest waste stream on the planet. That refuse takes two primary forms: piles of rock removed when digging for ore, and tailings – pulverized rock left over from mineral extraction.
Of more than 150 billion metric tons of rock mined each year, the industry produces around 85 billion metric tons of waste rock and tailings, according to a 2022 United Nations (UN) report. For perspective, that amount of waste roughly equals the weight of 257,000 Empire State buildings.
Those numbers do not account for the remains of abandoned, or legacy, mines. On federal lands, at least 22,500 legacy hardrock mine features – such as toxic waste piles – could be environmental hazards, the U.S. Government Accountability Office reported in 2020. Thousands more legacy mines exist globally, according to the Encyclopedia of Environmental Health.
Addressing Environmental and Health Risks
In 2011, with SRP funding, Maier co-founded the Center for Environmentally Sustainable Mining (CESM), as a bridge between researchers and mining companies. The focus is on developing more sustainable methods to satisfy growing mineral demand in the U.S. A couple years later, CESM formed a research cooperative, now primarily funded by the mining industry, as an opportunity for mining companies to participate in research.
Legacy and active mines pose various risks to environmental and human health. Tailings can contain compounds called iron sulfides that, upon contact with air, undergo a chemical reaction that forms acid – a process hastened by soil bacteria. Fish and their predators are at risk of metal exposure, as well as humans who rely on those waterways for food, irrigation, and recreation.
“Many abandoned sites were mined a long time ago, when technology was cruder and left more metal, like arsenic, lead, zinc, and cadmium, in the tailings,” Maier explained. “As wind erodes barren mines, people living nearby can be exposed to these metals.”
Several years ago, the University of Arizona SRP Center studied exposures of children living near the defunct Iron King Mine and Humboldt Smelter, a designated Superfund site. The researchers found that, in many participating homes, arsenic levels in drinking water, yard soil, and indoor dust were above recommended levels. Exposure to arsenic has been linked to various health issues, including cancer and diabetes.
Sustainable Remediation Practices
On January 25, 2019, a tailings storage facility in Brumadinho, Brazil, collapsed, unleashing over 3 million gallons of mining waste that killed more than 250 people. The disaster sparked an international effort to develop a global industry standard on tailings management, released in 2020. In striving for “zero harm to people and the environment,” the standard reflects a growing trend toward environmental, social, and governance (ESG) investing.
For legacy tailings, a standard remediation practice in the U.S. is “cap and plant,” which involves placing a soil cover over the tailings to control dust and encourage plant growth. Maier’s team is studying how to optimize the process, as mines typically have low revegetation success rates.
Maier and colleagues also helped pioneer another technology for mine sites called phytostabilization, which entails adding nutrients directly into tailings to transform the waste into a plant-supporting medium. This approach could be an alternative to cap and plant, which requires substantial resources to implement.
Resource Recovery and Innovation
Given the growing demand for elements, Maier’s team is exploring alternative mining strategies. Instead of traditional rock crushing, she envisions mining liquid waste for recovery of rare earth elements.
She sees metal-binding molecules produced by bacteria as a promising alternative to traditional mining methods. As a co-founder of GlycoSurf, a company supported by an NIEHS Small Business Innovation Research Grant, Maier has patented technologies that harness microbial power for various applications, including mining.
“We can’t live without mining,” she said. “But I think there’s a lot of interest now in approaching it in a more sustainable manner.”
Conclusion
In conclusion, the University of Arizona SRP Center is at the forefront of sustainable mining practices, addressing environmental remediation and resource recovery in the mining industry. Through innovative research and collaboration with mining companies, they are working towards a more sustainable future for mineral extraction. By implementing sustainable remediation practices and exploring alternative mining strategies, the team is paving the way for a greener and more environmentally conscious approach to mining. Engage with their ongoing research and initiatives to support the transition towards a more sustainable mining industry.
