Each year, mining operations generate large volumes of mine waste, including tailings. According to the International Institute for Environment and Development’s (IIED) Mining, Minerals, and Sustainable Development Project (MMSD), there are approximately 3,500 active mining waste facilities worldwide, consisting of waste rock dumps and tailings impoundments. The estimated global generation of waste from the primary production of metal and minerals commodities is over 100 billion tonnes per year and is growing exponentially because of ever-lower ore grades.
To put that size into perspective, 1 billion tonnes of water would fill 400,000 Olympic-sized swimming pools. Imagine the number of pools that 100 billion tonnes of mine waste would fill! And, like water in a pool, the waste produced by metals and mineral processing facilities needs to be contained. How the mining industry manages its tailings is of critical importance to the safe and sustainable production of the world’s metals and minerals—and to the condition of our planet overall.
As responsible corporate citizens, we need to ensure that we are acting with transparency—engaging key stakeholders within the communities that we operate in, understanding their concerns, protecting their citizens, land, and livelihoods. It is imperative that we inform the communities about the technologies being used to deliver a safe facility—throughout operation and after closure. And, that we engage them at the outset of the process, establish trust and encourage their active involvement.
What are tailings?
Tailings are a common by-product of extracting valuable minerals and metals from mined ore. When leaving the plant, they usually take the form of a liquid slurry made of fine mineral particles, created as mined ore is crushed, ground, and processed. Typically stored in ponds―some of them stretching for hundreds of hectares—they’re called tailings because they represent the final, “tail-end” of the process.
Since the initial MMSD findings were published in 2002, the metals and minerals industry has been under tremendous pressure to improve its social, developmental, and environmental performance. In his 2011 book Waste, Geoffrey Blight poses that mine waste and their environmentally-acceptable storage constitute the largest waste problem on the planet. Accumulating for thousands of years, the rate of production of mine waste has accelerated in step with increases in the human population. Fortunately, keeping pace with the increase in population are the advancements made in technology to offer new and innovative solutions to this challenge.
There are a variety of new ways to manage tailings storage, from slurry containment to dry stacks. Identifying the most appropriate method of tailings storage is imperative to ensuring that the operation is safe and sustainable. Numerous factors must be considered at the outset, including the local topography, rainfall amounts, seismic activity, the type of mineral being mined, and proximity to populated areas. There is no one-size-fits-all solution—each tailings storage facility is unique because there are no tailings alike in the industry.
First and foremost, mine waste management facilities must be designed and managed with closure and expansions in mind from the onset. These facilities are required to perform well beyond mine closure, throughout changes in the environment, and after ore production has ceased. Yet, they must also be built with the flexibility to be reopened if the mine’s life gets extended. Critical thinking for the long-term is required. Extending the life of the mining complex can help cover the cost of its own closure. And, with hundreds of mines slated for closure in the next few years, the need for this expertise is imminent.
Competing factors such as cost, the environment, safety, and technical viability are at the forefront of thinking when today’s mining organizations invest in building new tailings systems, or in retrofitting existing ones. The process-water lock-up and increasing land take needed by conventional tailings management are pushing us to find more advanced systems. These new technologies offer significant benefits in terms of environmental sustainability, as well as worker and community safety. They’re designed to maximize water recovery and minimize our environmental footprint.
Mine waste management continues to be a primary issue for water management at mine sites, from flow to quality. Tailings dewatering technology has emerged in several formats over the past couple of decades as a promising option to mitigate this challenge. By dewatering tailings, waste materials can be produced at a higher solids content (with consistencies ranging from ultra-thickened to filtered cake) and constructed into a stack landform called a “dry stack.” The filtered tailings process reduces the volume of water and improves the stability of the facility.
Dewatered tailings are among the best available technologies for the industry today. But, it’s not a universal solution. Issues such as acid generation are also paramount drivers in determining the right solution. What it can do is help create a paradigm shift, where what’s perceived as useless mine waste today could be reused in the future with added value. With the potential for mine waste to be recycled into viable resources, it may lead us to see tailings as part of the solution for lower-grade and harder-to-reach resources.
In the IIED’s 2012 follow-up report to the MMSD project, they identified that progress has been made since the initial findings. There have been technical advances on water and waste metals toxicity, with accompanying regulations, and The International Council on Mining and Metals (ICMM) now has a toolkit to help plan for mine closure―with existing examples of good practice. Perhaps most importantly, global organizations are now working together to find solutions. The ICMM, the United Nations Environment Programme, and the Principles for Responsible Investment have co-convened a Global Tailings Review to establish an international standard. With a shared commitment to the adoption of global best practices on tailings storage facilities, this marks a step forward, beyond the national guidelines. The Global Tailings Review will evaluate current positive practices in the mining industry, and beyond, as well as review evidence and lessons learned from catastrophic failures.
As one of the largest producers of waste in the world, it’s incumbent on us, as an industry, to work together to find new ways to operate more sustainably. Technology gives us the tools; we must do our homework to determine the best solutions for each environment. Working with our clients, we must focus on all perspectives of stability―mineral processing, geotechnical, hydrotechnical, and geochemical―to determine the best combination of tools to address their particular challenges at their unique sites. By providing a holistic, integrated solution, we can help to mitigate the challenges of mine waste management.
To find out more about Hatch’s global tailings and mine waste management practices, click here.
