MIT Environmental Solutions Initiative (ESI) Hosts Global Conference on Mine Waste

Mining operations are estimated to produce 14.4 billion tonnes of tailings, or waste from mineral ore processing, per year, according to the Global Tailings Review. That is equal to the weight of 43,000 Empire State Buildings. 

At a low estimate, there are nearly 8,500 facilities worldwide that store this waste, usually in the form of slurries pumped into earth embankment dams. These facilities pose enormous environmental and social risks associated with potential structural instability or leakage. For example, two tailings dams collapsed in Brazil over the last decade, killing nearly 300 people and contaminating soil and waterways. As the world demands more metals and minerals for everything from electronic devices to the clean energy technologies used to power them, the amount of tailings produced each year will increase. 

This semester, the MIT Environmental Solutions Initiative (ESI) and faculty from the MIT School of Engineering, in collaboration with ICMM, convened the MIT Global Summit on Mine Tailings Innovation to consider technical advances that may help mitigate tailings hazards. 

Held over two days in late September, the hybrid event was oriented primarily toward exchanging ideas among and between engineers and tailings experts from the mining industry and universities. Speakers included eight MIT faculty and staff and 34 other representatives of diverse companies and organizations from around the world. More than 145 participants attended the event in person in Cambridge, Mass., while 100 tuned in virtually. Participants joined from 12 countries on six continents. 

“This conference represents a unique opportunity for researchers at MIT and beyond to understand key knowledge gaps that the mining industry faces, and share our innovative capacity to address them,” said Prof. Elsa Olivetti, Director of the MIT Climate Project’s Mission on Decarbonizing Energy and Industry.

Bryony Clear Hill, Director of Innovation at ICMM, echoed this sentiment. 

“A just and sustainable transition to a low carbon world requires collaboration and innovation,” she said. “The partnership between MIT and ICMM at the MIT Global Summit on Mine Tailings Innovation exemplifies the transformative power of collaboration in tackling one of the mining industry’s most pressing challenges: reducing tailings waste and reimagining its role in a sustainable future. The conference provided a unique platform to gather a diverse range of stakeholders – including practitioners, academics, and startups – to discuss both the need and opportunities to reduce, reuse, and reimagine tailings.”

The last three items were the key cross-cutting themes that emerged from the presentations and panel discussions.

Participants first explored opportunities to reduce the amount of tailings produced and the space taken up by their storage. For example, Luke Vollert, of Newmont Corporation, emphasized that being more precise at the mineral extraction phase through coarse particle flotation reduces the amount of unwanted material that eventually contributes to tailings. Other ways to reduce tailings volumes include smart shovels that reject low-grade ore and conveyor belts that then separate that ore further toward different processing streams. 

Several presenters indicated optimism for filter stacked tailings. This process removes most of the water from the tailings so that they do not need to be held in liquid form behind a dam. Kaci Jenkins, of Rio Tinto, noted that this reduces the amount of water used and the storage area of tailings. Phil Newman, from Anglo American, also noted that this storage method reduces the risk of dangerous failure of the facility. A key challenge to this process is that it is more expensive to produce dry tailings than wet tailings, so wide-scale adoption would require innovations and/or government regulation. 

A second key theme addressed by presenters was the potential to reuse tailings. Though presenters expressed some optimism that old tailings could be re-mined for ores that were passed over previously due to low grades or outdated technology, this practice is unlikely to reduce overall tailings production. However, several presenters noted that tailings themselves can be put to useful purposes. For example, Priscilla Nelson, of the Colorado School of Mines, noted that tailings can be used to meet some demand for sand, cement, ceramics, and even glass. Daniel Franks, from the University of Queensland, showed that producing ore sand, which can be upcycled into aggregates and other building materials for local uses, can replace demand for sand by more than 20 percent in Mexico, the Philippines, China, Peru, Ghana, and South Africa, and as much as 60 percent in Chile, while reducing equivalent volumes of tailings that would have to be stored indefinitely. 

Third, presenters throughout the conference looked for opportunities to reimagine tailings production and management. For example, Linda Figueroa, from the Colorado School of Mines, emphasized the important role of universities in researching tailings challenges and training the next generation of practitioners who will directly work on them in the industry. Other participants showed the potential for new methods to change the mineral extraction process. For example, MIT Prof. Antoine Allanore presented on the potential to use sulfur to more sustainably recover metal from ore deposits, while Prof. Yassine Taha, from the Mohammed VI Polytechnic University, envisioned the potential for mining and construction industries to work together to more efficiently meet material demands of the latter by using the waste of the former. 

Across these three themes, key gaps remain. For example, MIT Prof. Andrew Whittle noted that insufficient resources are invested in mine closure. This can result in tailings impoundments that pose threats to local populations and environments, and financial liabilities for companies. These observations indicate the need for companies to plan for the long-term management of their tailings from the outset of mining projects, which may in turn lead them to invest further in innovations to reduce tailings production. 

Another key gap is the role of community engagement in the design and management of tailings. Members of local communities often work at mining operations, but are also the most vulnerable to the environmental hazards of tailings. Yet more work is needed to understand and respond to community concerns around tailings. Industry and university researchers thus have an opportunity to train and involve communities more in decision-making about tailings design and management, and to participate in tailings monitoring. 

“This conference continues ESI’s commitment to addressing the inevitable expansion of mining for the minerals and metals needed for decarbonizing the world’s energy systems while considering the very real risk of social and environmental damage posed by that expansion,” said MIT ESI Director Prof. John E. Fernández. “The current state of mine tailings is representative of an attitude that we need to move beyond. We cannot be satisfied with the creation of dangerous and toxic landscapes because we did not deploy our creativity and ingenuity to think ahead of the problem we were creating. I am personally thrilled to know there are many people at universities and in the private sector committed to moving beyond business as usual in mining. Now let’s move forward with real improvements on the issue of the waste resulting from mining.”

Want more from the MIT Global Summit on Mine Tailings Innovation? View the full list of speakers and event agenda or check out select presentation videos and slides. 

The header image is courtesy of Rory Fisher.