As the mining sector looks to meet future growth in demand, experts forecast a dramatic increase in mining waste production through to 2050, due to lower ore grades processed with conventional approaches. Water use and tailings-related challenges have surfaced as water supply and quality are often stressed in many mining jurisdictions. The mining industry has recognised the risks associated with the storage of tailings and the absolute necessity of safety. It is acting to implement changes after catastrophic tailings dam failures at Mount Polley (Canada) in 2014, Samarco (Brazil) in 2015, and Brumadinho (Brazil) in 2019. The pressing issue for miners is how to address waste, treat it, and ultimately eliminate tailings.
Satish Rao and Grant Caffery present the following as a roadmap for mining companies that want to start the journey to zero waste and tailing optimisation:
- Optimise recovery: There are several opportunities to improve the recovery of valuable materials from tailings, either by repurposing for value – such as creating building materials, or reprocessing to extract value – such as rare earth elements. Dewatering of tailings can also help reclaim and recover water for further use, while improving safety.
- Eliminate waste: Early rejection of waste can unlock significant benefits – from requiring fewer inputs, to processing due to selectivity, and lower generation of waste. Precision mining through technological advancements such as directional drilling and keyhole mining can reduce the waste that is brought to the surface to be processed. Other methods include bulk ore sorting and ore upgrading. Dry processing technologies can further avoid and minimise the use of water, significantly lowering tailings production.
- Process everything: Value can be derived from the entire rock that has been extracted, and processing all of it, leaving little to no waste behind. Molten oxide electrolysis is an example of an emerging advancement, which can be used to convert all ore grades to high quality liquid metal using renewable electricity with a one step process. Supercritical fluids as solvents, and the use of microorganisms for extraction of minerals, are other options. The challenge with such approaches is to deliver value at scale, through cost effective means.
- Transform leaching: Heap leaching is widely used for certain commodities like copper for its simplicity and relatively lower cost in treating low-grade ores. It could help the economical recovery of copper from lower-grade ore, if challenges related to chalcopyrite leaching are effectively overcome. A range of innovations from novel oxidants, lixiviants, to other chemical and biological approaches are attempting to address the chalcopyrite passivation problem. If heap leaching can be transformed to achieve performance similar to the concentrator plants, in terms of cycle time and recoveries, it can provide a significant benefit of reducing water use, waste, and eliminating tailings.
- Recover through in-situ extraction: In-situ extraction removes valuable minerals directly from ore deposits without waste and tailings from conventional mining. This recovery can be achieved through drilling wells into the ore body, injecting a leaching solution to dissolve the target mineral, and pumping back to the surface for mineral extraction. However, several technical challenges to in-situ extraction exist, and the current regulatory landscape does not provide specific guidelines for in-situ extraction in many jurisdictions. These hurdles can further complicate obtaining operational permits.
The complete elimination of mine tailings can be a daunting task to consider as there is no silver bullet to eliminate waste and tailings, and challenges vary by commodity, deposit, geography, and operating legacy. However, the authors believe mining companies can develop a portfolio of initiatives based on the above approaches, to start providing value today, and address the risks and constraints of the future.
To read the full paper, visit: https://clareo.com/reimagining-tailings/