How Is Mining Waste Recycled?
February 25, 2016
Mining waste comes in many forms and varies from harmless to highly hazardous.
Much of it has little or no economic value but the mining industry is making an effort to find new uses for waste to reduce environmental impacts. And with the prices of commodities moving up and down by large amounts, what may be waste today can suddenly become a valuable resource tomorrow.
Here’s a quick look at what happens to some of the leftovers of mining and resource extraction.
How We Recycle The Big Stuff
Rock and soil need to be moved to gain access to the coal, metal ores or other materials of interest. In some situations, it may be possible to sell rock and soil for a range of purposes as it is usually set aside for rehabilitation of the mine site after mining ceases. It’s used to contour the site and fill in some of the holes, and after re-vegetation the site may be restored to something close to its pre-mining condition.
Recycling The Smaller Stuff
Tailings are the finely ground rock left over after mineral processing and they are mostly stored as a watery mix in tailing dams. Despite big improvements in the construction of tailings dams, they can fail, often with disastrous consequences. Some mines reduce this risk by ‘thickening’ the tailings. They can then be mixed with cement to produce construction materials or backfilled into underground mines.
Waste rock and tailings may still contain a low concentration of the target material such as copper or gold and may be reprocessed if the price of the metal rises to a point where it becomes economic to do so.
Slags are are the non-metallic components left over from metal smelting. They are largely environmentally safe and are increasingly being used in making concrete and in road construction.
Metal smelting can also produce large amounts of sulphur dioxide, the cause of acid rain. Sulphur dioxide can be captured and converted to sulphuric acid, a major industrial chemical.
There are many other types of mining waste, from airborne dust and gasses to clays and sludge. Efforts to find better mine waste management solutions are seeing these materials made into a range of products including bricks, tiles and glass or used in agro-forestry, for soil improvement and in construction.
Unfortunately, many resources are mixed with poisonous materials such as cadmium, arsenic and mercury. With some contaminants the waste needs to be treated as hazardous and provision made for their safe, long-term storage.
In the case of mercury there is a better solution. Mercury is a by-product of most resource extraction activities and is most commonly associated with gold, oil and gas. During processing it is trapped in beds of catalyst that concentrate the mercury into a manageable volume. It is then recycled using a distillation process. Mercury has many uses, one being in the manufacture of dental amalgam.
More Recycling, Less Mining Waste
We are all dependent on the products of mining, from the copper that carries our electricity to the steel in our cars. However, as a major global industry, the impacts of mining are significant. So while it’s great to see industry take positive steps to find new uses for mining waste, we can all play a role in reducing the total volume of that waste. The more people recycle metals, plastics and glass, the more we reduce the need to extract virgin materials and the less mining waste that needs to be produced in the first place.
If you need to recycle mercury, contact us on 1300 32 62 92 or fill out the form below to discuss your requirements with one of our mercury recycling specialists.