One of the unfortunate consequences of mining is that the land that is left after all the minerals have been extracted is usually no longer fit for vegetative growth. For decades mining companies have tried to find ways to rehabilitate these tailings or mine dumps and regreen them. One possible solution came in the form of biosolids.
Vale, a Brazilian mining company, operates a mining site in Subury in Northern Ontario. Five years ago, it ran the Copper Cliff Tailings Project with environmental solutions company Terratec Environmental to use biosolids to reclaim lands lost to mining and since then it has seen very surprising positive results.
“We are doing this for two reasons: dust control and covering the area with vegetation for long-term closure plans,” said Glen Watson, superintendent of environment decommissioning and reclamation for Vale Canada.
The project has been so successful that they received the Water Environment Association of Ontario‘s 2018 Exemplary Biosolids Management Award for their efforts. “To win that award,” Watson said, “shows how important the project is, as well as how much their innovation is appreciated by the industry and environmental protection groups.”
This project began when Jeff Newman, director of business development, came to Vale with the idea of a pilot re-vegetation for Copper Cliff tailings. Before this, biosolids have never been used in mining reclamation.
This was significant because mine tailings are very difficult to vegetate given its lack of nutrients, its acidity as well as the sandy nature of the material. Watson explained that the type of biosolids needed were known as class B, which included treated sewage sludge. Typically, these were sent off to agricultural lands to act as fertilizer. During the winter months however, the biosolids are taken to landfills.
“The problem with that is they are sending otherwise good material for regreening to the landfill, and the amount of space available in landfills is limited,” Watson said. “This diverts biosolids away from landfills and they have a year-round use.”
To make the project work, Vale had to coordinate with the Ministry of Environment and Climate Change regulators for approval and work closely with the immediate community to ensure that smell and leakage were controlled. There was initially a concern about the hazards of shipping sewage into the area, but Vale and Terratec devised a way to develop a solution in-house.
The abundance of wood pallets left over from shipping are shredded and utilized as a carbon source instead of sending them off to be chipped or burned. The end result was a custom reclamation mix. The mix was monitored over several months. It was turned from time to time and fans were used to keep foul odours under control. Vale also enlisted the help of the City of Sudbury to contribute leaf and yard waste to add to their mix.
The result is a product that closely resembles common garden soil, which was then spread over the tailings. “It’s proving to be a very quick means to encourage vegetation growth,” he said.
To control the odor and dust, they utilized straw to cover the mix and seeds found in these straws promoted vegetation in the soil.
Vale’s success is only the beginning. There are a number of mining areas that for over 120 years or more have suffered from vegetation loss. The objective is to get the go signal from the province to use this apply this strategy to similar areas.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.