Science & Technology, Canada (Commonwealth Union) – Mining is a significant industrial activity that involves extracting minerals and metals from the earth’s crust. The process of mining, however, generates large quantities of waste, which can have severe environmental and health impacts. Mining waste can be in the form of solid or liquid waste, and it contains a range of contaminants such as heavy metals and acids that can pollute the soil, water, and air.
One of the primary sources of mining waste is the extraction of metal ores, which typically involves crushing and grinding the rocks to separate the valuable minerals from the rest of the rock. This process generates a significant amount of waste rock, which is usually dumped in large piles known as tailings. These tailings can take up vast areas of land and can remain a significant environmental hazard for decades or even centuries.
Mining waste also includes process water, which is used in various stages of mining to separate minerals from ore. This water often contains toxic substances such as cyanide and mercury, which can have harmful effects on aquatic life and human health if they are released into rivers or groundwater.
Scientists have produced a new mining method that applies microbes to recover metals and retain carbon from the waste formed during the mining process. Bringing about this method of reusing mining waste, known as tailings, has the ability to transform the mining industry and form a greener and more environmentally friendly future according to researchers.
Tailings are the waste materials that remain after the extraction and processing of minerals from ore in mining operations. They consist of a mixture of finely ground rock particles, water, and residual chemicals used in the extraction process. Tailings are typically stored in large impoundments called tailings dams or ponds, where they settle and separate into layers based on their density.
The composition of tailings can vary depending on the type of mineral being extracted and the specific extraction methods employed. They may contain a variety of minerals, trace elements, heavy metals, and chemical reagents used in the extraction process. The size of the particles in tailings can range from fine silt-like particles to larger gravel-sized particles.
Tailings occur as a result of mining, which are the fine-grained waste products left after the extraction of the target ore mineral, that is stacked and stored. This procedure is known as dry-stack tailing.
As the years have gone by the mining practices have adjusted and resulted in greater efficiency. However, the climate concern and increasing need for critical minerals have required the formation of new ore removal and technology for processing.
The old tailings consist of increased amounts of critical minerals with the ability to be extracted with the assistance of microbes via bioleaching. The microbes assist in breaking down the ore, sending out any valuable metals that were not completely recovered in an environmentally friendly manner that is much quicker than natural biogeochemical weathering methods.
“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,” explained Dr. Jenine McCutcheon, who is an assistant professor in the Department of Earth and Environmental Sciences, University of Waterloo.
Together with enhancing resource recovery, the microbes gather CO2 from the air and retain it inside the mine tailings as new minerals. This method helps in offsetting certain emissions released during the time the mine was active and assists in stabilizing the tailings according to researchers.
They further indicated that microbial mineral carbonation may offset over 30% of a mine site’s greenhouse gas emissions each year if implemented to the complete mine.
