What Are Tailings in Mining?

Imagine a mountain, rich with precious metals, being slowly chipped away in the pursuit of economic value. But as the valuable materials are extracted, what remains? This is where the story of tailings begins—a story not often told, but one that is critically important to the mining industry and the environment. Tailings are the leftover materials after the valuable part of the ore is separated during the mining process. They consist of crushed rock, chemicals, and water, forming a slurry that can present significant environmental challenges if not handled correctly.

Tailings might seem like a side issue when the focus is on gold, copper, or other valuable metals, but in reality, they are the centerpiece of some of the most complex environmental problems in the world of mining. The sheer volume of tailings produced is staggering, with modern mining operations generating millions of tons annually. These waste materials are often stored in vast tailings dams—large structures that contain the slurry, preventing it from contaminating nearby water sources or ecosystems.

But here’s the catch: these dams are not invulnerable. In fact, tailings dam failures have led to some of the most devastating environmental disasters in recent history, from the 2019 Brumadinho dam collapse in Brazil, which killed over 270 people, to smaller incidents worldwide that continue to impact ecosystems and local communities. Understanding the scope and risks of tailings management is not just a matter for engineers or policymakers; it’s a concern for all of us, as consumers and global citizens.

What exactly are tailings, and how are they produced? The process starts when raw ore is mined and transported to a mill or processing plant. Here, the ore is crushed and ground into fine particles. The valuable minerals are then separated from the waste rock through various processes, including flotation, magnetic separation, or chemical leaching. The leftover waste, composed of rock fragments, water, and chemicals, is what we call tailings.

This is where the real challenge begins: tailings management. The waste slurry is typically pumped into a tailings storage facility (TSF), often a dammed reservoir, where it is stored long-term. While this sounds like a simple enough solution, TSFs are notoriously difficult to manage. Their stability depends on numerous factors, including the design of the dam, the nature of the tailings, and external factors such as rainfall or seismic activity. When things go wrong, the consequences can be catastrophic.

Let’s break down the main components of tailings:

• Water: Tailings often contain significant amounts of water, used during the mining and separation processes. Managing this water is critical because it can contain harmful chemicals and heavy metals.
• Chemicals: In many mining processes, especially those involving gold and copper, chemicals such as cyanide and sulfuric acid are used to extract the valuable metals from the ore. Residual amounts of these chemicals often remain in the tailings, posing a potential environmental hazard.
• Solid Waste: The solid component of tailings consists of finely ground rock fragments. Depending on the ore being processed, these fragments may contain trace amounts of harmful substances like arsenic, mercury, or lead.

Why should we care about tailings? The importance of properly managing tailings goes beyond the immediate risks of dam failure. Poorly managed tailings can seep into groundwater, polluting drinking water supplies and harming local wildlife. In some cases, tailings dams are located near indigenous lands or communities that rely on agriculture and fishing, putting their livelihoods at risk.

One of the emerging solutions is the concept of “dry stacking,” where tailings are dried and compacted rather than stored in liquid form. This reduces the risk of dam failure, as there is no need for a large reservoir of potentially toxic liquid. While dry stacking is more expensive and requires more land, it is seen as a safer alternative in the long run.

What can be done to mitigate the risks? Modern mining companies are increasingly adopting new technologies and best practices to reduce the environmental impact of tailings. These include better dam designs, real-time monitoring systems, and the use of tailings as raw materials for construction or other industries. But there’s still much work to be done.

The global community, too, has a role to play. From investors pushing for more sustainable practices to governments enacting stricter regulations, there’s growing pressure on the mining industry to prioritize safety and environmental stewardship. After all, tailings may be the byproduct of mining, but their impact can last far longer than the life of the mine itself.

Looking at some real-world examples of tailings disasters gives us a sense of urgency:

• The Mount Polley disaster in Canada (2014): Over 25 million cubic meters of water and mine waste were released into local lakes and rivers after a tailings dam failure.
• The Bento Rodrigues dam disaster in Brazil (2015): Considered one of the worst environmental disasters in Brazilian history, the collapse of this tailings dam caused a flood of toxic mud, killing 19 people and devastating the Rio Doce river ecosystem.

These cases are not isolated; tailings dam failures continue to occur, even as technology advances. So why do these failures keep happening? One of the primary reasons is that tailings dams are often built using a method known as "upstream construction," where the dam is raised over time using the tailings themselves. While this is cheaper than other methods, it’s also less stable, particularly in areas prone to earthquakes or heavy rainfall.

There’s no one-size-fits-all solution to the tailings problem. Each mine presents unique challenges based on its location, the type of ore being processed, and local environmental factors. However, the growing awareness of the risks associated with tailings is pushing the industry towards more sustainable and responsible practices. Tailings management is no longer an afterthought; it’s a critical aspect of modern mining operations.

In conclusion, tailings are the unsung byproduct of the mining industry, but they demand our attention. From the physical waste left behind to the potential environmental disasters caused by mismanagement, tailings are a key part of the global conversation on sustainable mining. The future of mining will depend on how well the industry can adapt to the challenges posed by tailings, and whether it can do so in a way that protects both people and the planet.