Earth's tiniest miners help environment

Similar to some International Space Station experiments for mining in space, the University of Waterloo in Southern Ontario has been using microorganisms as an environmentally friendly means of breaking down tailings here on Earth, reclaiming critical resources and cleaning up the leftovers of yesteryear at the same time.

A common byproduct of mining, tailings are typically fine-grained waste material left after extracting a target ore mineral. Stored in various media such as ponds, piles, or dams, decades of mining have left trillions of metric tons of waste material globally, with the mining industry being estimated to produce more than 172 billion metric tons each year.

The hazards and risks of such storage often come from the volume of liquid stored in dams or ponds and the toxicity of the process with which the material is broken down – acid leaching.

Over time, mining practices have evolved to become more efficient, but the climate crisis and rising demand for critical minerals require the development of new recovery and reclamation technologies.

Old tailings have been found to contain higher amounts of critical minerals that can be extracted with the help of various practices, many of which minimally affect the environment; hydrometallurgy, solvometallurgy, and electrometallurgy, to name a few.

Yet scientists seeking to tap into the near-infinite resources that exist outside Earth's atmosphere understand these processes aren't going to be immediately available in the vacuum of space. Costs, location, and just straight technology to mine the planets and asteroids are decades, if not centuries, away.

Thus, a brilliant and simple solution in the form of life's most basic organisms was devised.

Read the complete story of the ISS microbial experimentation at Microbes mine metals, make soil on ISS in the November 18, 2020 edition of Metal Tech News.

"We can take tailings that were produced in the past and recover more resources from those waste materials and, in doing so, also reduce the risk of residual metals entering into local waterways or groundwater," said Jenine McCutcheon, assistant professor in the Department of Earth and Environmental Sciences at University of Waterloo.

Using a bioleaching process involving microbes, the tiny microorganisms can break down ore, releasing any valuable metals that weren't fully recovered in an eco-friendly way that is also much faster than natural biogeochemical weathering processes.

In addition to improving resource recovery, the microbes also capture carbon dioxide from the air and store it within the mine tailings as new minerals. This process would aid in offsetting some of the emissions released while the mine is active and help stabilize the tailings themselves.

"This technique makes better use of current and past mine sites," McCutcheon said. "Rethinking how future mine sites are designed in order to integrate this process could result in mines that are carbon neutral from the get-go rather than thinking about carbon storage as an add-on at the end."

If applied to an entire mine, microbial mineral carbonation could offset more than 30% of a new mine site's annual greenhouse gas emissions. Additionally, this microbial-driven technique would unlock the value of historical mine tailings that are otherwise considered industrial waste.

McCutcheon further believes that the microbial-driven processes could help industry move toward carbon-neutral or carbon-negative mining. However, industry engagement is critical to move this technology toward large-scale deployment.

"This technology is a potential game-changer in the fight against climate change, and the mining industry has a unique opportunity to play a significant role in the future of green energy," the assistant professor added.