Safe solution for dangerous mine waste puts UBC researcher in running for $20-million prize

Acid mine drainage happens when mine waste, especially ‘fool’s gold,’ is exposed to water and air. Photo: Annelieke B, Flickr CC.

UBC mineralogist Lee Groat wants to combine two common yet dangerous byproducts of mining — acidic drainage and carbon dioxide emissions — to make one stable byproduct that won’t hurt the environment.

Groat is working with Terra CO2 Technologies Ltd. to make mining operations cleaner. Their idea and its potential impact have landed them in the semi-finals of the $20-million NRG Cosia Carbon XPrize competition. The competition encourages the development of technologies that convert carbon dioxide emissions into useful products.

How does your proposed technique improve current methods for containing acid mine drainage?

Mining operations treat acid drainage by adding lime, which forms a sludge that has to be contained. Often it is stored in a tailings pond which has to be lined with a geotextile so the lime sludge doesn’t seep into the ground. But this geotextile can wear down over the years and release toxins into the environment.

We are working to create a solid product that would be non-toxic and inert, making permanent storage possible without environmental issues. Mining companies could save money by not building tailing ponds and the sludge wouldn’t leak into the environment. Plus, our method isolates carbon, which would have gone into the atmosphere.

How are these waste products created in the mining process?

When elements are extracted from the earth, a common waste product is an iron-sulfide mineral called pyrite, you likely know it as ‘fool’s gold.’ If it’s exposed to water and air, it breaks down and forms sulphuric acid. Obviously, you don’t want sulphuric acid seeping into rivers because it hurts wildlife.

We’re also working with carbon dioxide. Doug Eaton, CEO of Terra’s parent company, noticed that many mining operations in Canada are in remote locations, far from the electrical grid. The mines need electricity so they burn fossil fuels, generally diesel or liquefied natural gas. He wondered if we could capture some of those carbon dioxide emissions and do something useful with them.

How will your idea remove these two waste products?

First we’re attempting to capture carbon dioxide gases in the lab and make it into a bicarbonate solution like an antacid. Then we take the iron-sulfate from the acid mine drainage and react it with the bicarbonate solution. This chemical process produces iron carbonate which is a gel that over a period of a few hours hardens into a rusty red solid, made up of tiny spheres. When it is in the gel form I imagine it could be made into bricks, pellets, etc. In the end, we hope to have a solid, stable product that can be stored more safely.

"Mining companies could save money by not building tailing ponds and the sludge wouldn’t leak into the environment. Plus, our method isolates carbon, which would have gone into the atmosphere."