Scientists develop technique to repurpose harmful mining waste into nutrient-rich soil

With more of the world's industries increasing their rate of manufacturing at an alarming pace, mines across the world have to work twice as much to keep up with the demand. Mining leaves behind a waste material called tailings. These often contain harmful substances and heavy metals that are harmful to the environment. According to Canadian Light Source, there are over 1800 tailing storage facilities in the world. But this is not enough considering the massive scale at which the waste is being generated.

A tailings dam collapsed in Brazil in 2019 and approximately 300 people drowned in the harmful waste. Thankfully, a team of researchers from the University of Queensland has come up with a method to convert these tailings into healthy soil. The team used the synchrotron at the University of Saskatchewan to identify the conversion process. Longbin Huang, a professor at the University of Queensland, said, "We have basically taken engineering solutions into the context of natural soil formation from rocks because tailing has some useful minerals common to natural rocks." 

He further added that it was not economically or environmentally viable to store tailings for long periods. According to him, their findings could result in saving money by utilizing the tailings for something useful and helping the environment as well. He said, "Tailings have no biologically friendly properties for growing plants. Roots and water cannot penetrate them, and soluble salts and metals in tailings can kill plants and soil microbes."

Huang added that waiting for nature to break down the material would take a long time. They essentially discovered a solution to speed up the process of tailings becoming natural soil. Their findings have been published in the Environmental Science & Technology journal. He spoke on the process, saying, "We can convert these colossal volumes of biologically hostile tailings into growth media similar to natural soil by developing soil structure that will enable biological activity of microbes and plants, basically establishing a natural ecosystem."

The newfound process is done by fostering certain microbes to develop in tailings that were carried over from plant mulch originating from agricultural waste and urban green waste. Once these microbes come in, they consume the organics and minerals that are present in tailings, fundamentally changing them into the material that constitutes healthy soil. He explained, "You have microbially active surfaces in soil crumbs that develop a porosity in compacted tailings that allows the gas, water, roots and microbes to survive, just like in arable soil. Therefore, the dead mineral matrix of tailings becomes a soil-like media that will enable plants to grow."

The process, which takes up to 12 months to happen, can be used to revive soil that had initially been damaged by over-farming or climate change. The light from the synchrotron allowed the research team to clearly see the detailed mechanism of the tailings turning into healthy soil. He talked about its use, saying, "The facility access and the expert inputs of the beamline staff were critical to enable us to collect quality data and therefore to have reliable scientific evidence."

The research team has also managed to finish a field trial coupled with an elaborate greenhouse trial by utilizing the revitalized tailings to grow plants. Reflecting on their achievement, he said, "We are confident that it works. The maize and sorghum love it. The technology is usable now. Someone just needs to use it at mine sites." They hope that their findings can minimize the harmful effects that arise out of mining activities.