Terra CO2 Technologies Ltd. thinks it has found a way for miners to use two major environmental impacts of mines to effectively cancel each other out.
The Vancouver company wants to treat mine waste waster using CO2 emissions from the mines themselves.
Since 2013, Terra has been working on the technology, which the company hopes will reduce a mine’s CO2 emissions while treating acid mine drainage.
Acid mine drainage is a naturally occurring phenomenon in mines as a result of the ore being exposed to water and oxygen.
The process Terra has been using to treat wastewater goes as follows: a basic solution runs through a CO2 absorption column, taking up the carbonate and turning it into what is essentially baking soda, Terra’s CEO Dylan Jones said.
The bicarbonate is then mixed with iron-rich wastewater in an environment deprived of oxygen.
That precipitates the iron into a solid form that can be then dried and later stacked.
“The CO2 can come from anywhere, (but) the best situation for economic efficiency would be from flue gas on site, maybe a diesel generator, a coal burning plant,” Jones said.
The reaction also creates pure sulphuric acid that can be sold.
“It’s more economical if there is a (mine) site near or close to a highway or rail to ship the acid to market,” Jones said.
Many mines in Canada and in the territory have to deal with acid mine drainage. A common treatment is to use lime.
But that requires bringing a lot of chemicals to mine sites.
It also creates a lot of caustic sludge that isn’t toxic but is “still not great for the environment,” Jones said.
“A big thing about our company is that we’re (also) focusing on … creating cleaner water as well as moving towards dry stack tailings,” he said.
Currently many mines use tailings ponds, where the tailings are flooded to avoid acid mine drainage.
But those tailings have to be kept behind a dam that can rupture. That happened at the Mount Polley mine in B.C. in 2014, flooding nearby ecosystems with large quantities of toxic sludge.
“It’s a huge environmental issue if (the tailing ponds) break and destroy local water systems or land,” Jones said.
In dry stack tailings piles, water is filtered out of the tailings, which are stored away from water sources that could create acid mine drainage.
Terra is not the only company recycling CO2 emissions. In January The Guardian reported that an industrial port in India was using a similar technique to turn CO2 from its coal-boiler into saleable baking soda.
The topic of acid mine drainage treatment itself has attracted a lot of research. Last August the News reported on research done in the Yukon to use carbon-based products, such as molasses and beer, to treat mine wastewater.
Terra’s technology could be used for abandoned and active mines alike.
But it won’t work with all mines, Jones said, because it depends on the chemistry of the tailings and the infrastructure available.
“It’s the chemistry of the tailings, it’s the availability of CO2 sources, of electricity to run the plant,” he said.
Terra claims its treatment technology can reduce water treatment costs by 25 per cent.
But that’s based on its lab work.
The company is now past the proof-of-concept stage, Jones said, when the technology is tested in a lab.
The next stage is to test it on mines. For now the company has selected a number of sites, including Lynn Lake, Manitoba, a town with large tailings ponds that are generating acid.
Jones hopes for commercialization by 2020, but more research and financing has to be done before that can happen.
The company is still in its infancy: in 2015 it separated from Strategic Metals Ltd., a company with a lot of mining claims in the Yukon.
It’s now 85 per cent owned by Strategic Metals.
The company hasn’t looked to the Yukon for its technology — yet.
“We’re a small operation,” Jones said. “We’re making sure we’re not overstretching ourselves.”
Contact Pierre Chauvin at firstname.lastname@example.org