From extraction to sequestration: miners chart a course towards net-negative emissions

A UNEP 2017 report states in no uncertain terms that limiting global warming to well below 2 degrees Celsius requires achieving net-negative emissions. This means that globally, according to the Intergovernmental Panel on Climate Change (IPCC), more than 10 billion tonnes (gigatons) of CO₂ need to be removed from the atmosphere every year towards the end of this century. 

This means that more CO₂ needs to be captured and stored than is emitted, making effective approaches for capturing and utilising or permanently storing carbon to achieve net-negative emissions, more urgent than ever.

However, according to IEA analysis, while momentum has increased in recent years with new carbon capture and storage (CCS) as well as carbon capture, utilisation and storage (CCUS) – where carbon is not just permanently stored but utilised further to create new products or revenue streams – facilities coming onstream, the combined effort still falls short of the global target required for net zero emissions by 2050. 

This implies that while energy efficiency, renewable energy and electrification are all central pillars to lowering emissions, according to the IEA, deep emissions reductions require an entire portfolio of technologies that include measures to effectively capture and use or store remaining carbon emissions.

Mine tailings: low hanging fruit for carbon capture innovations

The mining industry, which is historically less associated with carbon capture, has been entering the arena in recent years, and, as it turns out, stands uniquely positioned in the CCS and CCUS space. 

Unlike other sectors, where economic viability remains a challenge, the mining industry inherently produces vast quantities of tailings which are generally considered waste materials. 

However, especially ultramafic wastes – those produced from calcium- and magnesium-rich rock in which diamonds, along with metals such as nickel, platinum, and palladium are found – have shown to be highly reactive with CO_2.

When exposed to air and rainwater, new carbon-based minerals, or carbonates, are formed. These rocks are among the most stable on Earth and can safely lock away carbon for thousands of years. 

The breaking-up of rock during the mining process greatly enhances the reactivity of tailings by increasing the surface area of the material. Technological innovations now being tested have shown potential to accelerate this natural process to transform, what typically takes thousands of years, into a matter of months or even days. 

The potential impact is mind boggling. According to an article published in Science, about 419 million tonnes (Mt) of ultramafic and mafic wastes are produced annually by the mining industry. These wastes could be used to lock up 175Mt per year (Mt/y) of atmospheric CO₂ . 

If wastes from aluminum, iron, steel, and cement production are added, the total could be brought up to 310Mt/y or more, and estimates go up to 4 gigatonnes of trapped CO₂ per year. Basalt rock powder generated by coal production could sequester another 2 gigatonnes per year, the article stated. 

If these numbers line up, alkaline wastes from mining operations have the potential to provide more than half of the negative emissions that the IPCC called for, putting the mining sector center stage in this hugely relevant global endeavor to avert a climate crisis.

Research to tap this potential is well underway. Over the past decade, research undertaken at the BRIMM Bradshaw Research Institute for Minerals and Mining at the University of British Columbia (UBC), has identified several key areas where innovations could accelerate the direct capture of CO₂ from the atmosphere, and boost mineralisation from CO₂-rich (10-100%) gas streams at rates commensurate with mine greenhouse gas (GHG) emissions. 

Some mine operators could capitalise upon existing infrastructure and resources, making carbon capture technologies a comparatively low-cost option, not only in becoming net zero, but even carbon negative in the foreseeable future. Moreover, exposing these wastes to atmospheric CO₂ would make tailings storage safer by solidifying them. 

In this article, we’ll highlight some of the most recent initiatives along the mining value chain that are part of the industry’s proactive pursuit to implement low-cost, scalable solutions for CCS and CCUS. Collectively, these have the potential to make mining a cornerstone in global efforts to combat climate change.

BHP: Mount Keith nickel mine

The Mt Keith project at BHP’s Nickel West mine in Western Australia presents a pioneering example of the potential of CCS from tailings. 

While carrying out field tests, researchers from UBC’s Carbmin Research Group led by Prof. Greg Dipple, discovered that the mine’s tailings pile was passively removing CO₂ from the air and capturing approximately 40,000t/y, already offsetting around 11% of the mine’s total GHG emissions without the company being aware of it. 

Building upon this discovery, BHP then partnered with Arca Climate Technologies, a spin-off of UBC co-founded by Prof. Greg Dipple, and embarked on a groundbreaking 18-month pilot project for air-to-rock carbon mineralisation at the Mt Keith mine. 

Supported by a C$1.25 million grant from the BC Centre for Innovation and Clean Energy (CICE), Arca’s approach utilises autonomous rovers, surface manipulation technology, and machine learning algorithms to accelerate carbon mineralisation in the mine’s tailings area in a single step.

Launched in early 2023, the project aims to validate Arca’s methodology for capturing and permanently storing atmospheric carbon dioxide, while also showcasing the safe and successful integration of the technology within an operational mine site. 

Newmont and the REMineD project

US-based gold miner Newmont has embarked on a similar quest to explore a novel technology for direct air carbon sequestration in mine tailings as part of a three-year project called REMineD which also launched in 2023. 

Funded by the US Department of Energy, the US$4.3 million project is conducted in partnership with the US National Renewable Energy Laboratory (NREL), the University of California Los Angeles, Lawrence Berkeley National Laboratory, and the Missouri University of Science and Technology.

Going beyond just capturing and permanently storing the carbon, this initiative focuses on the utilisation part of CCUS by aiming to covert carbonate minerals in tailings into durable products for the construction sector, thereby reducing CO₂ footprints in construction materials, like concrete, and facilitating the production of sustainable building materials. 

In addition, REMineD aims to provide resources for further recovery of valuable rare earth elements (REEs) from tailings and thus enable new revenue streams from sustainable building materials and recovered REEs.  

De Beers: Gahcho Kué diamond mine

De Beers also began conducting initial field trials for carbon mineralisation at the Gahcho Kué open-pit operation situated in the Mackenzie district of the Northwest Territories, approximately 280 km northeast of Yellowknife, in 2023. 

These trials are part of UBC’s BRIMM carbon sequestration project, again, under the leadership of Prof. Dipple, and partially funded by a C$2 million grant from the Natural Resources Canada Clean Growth Program to run trials and field tests for carbon sequestration generated at the participating mine sites, one of which is Gahcho Kué.

In an article published by Mining.com, Sarah McLean, Environmental and Permitting Manager for De Beers Group, highlighted the project’s focus on assessing the potential of processed kimberlite, a byproduct of diamond mining, to sequester CO₂ emitted by the mine’s diesel generators during operations.

Aside from De Beers, the consortium consists of UBC’s BRIMM Bradshaw Research Institute for Minerals and Mining as well as the University of Alberta, Trent University in Ontario, the Institut national de la recherche scientifique in Quebec, Giga Metals and FPX Nickel.  

FPX-Nickel: Baptiste mine development

Another partner in the BRIMM carbon sequestration project, FPX Nickel, is assessing the potential for carbon mineralisation at its proposed Baptiste mine in British Columbia. 

Tailings at the mine are expected to amount to about 40Mt/y. If complete carbon mineralisation turns out to be economically feasible at the mine, estimates by researchers from Trent University estimate that approximately 18Mt/y of CO₂ could be sequestered. 

This would cover not only the 400-500,000t of CO₂ that the mine is expected to emit annually, but also a quarter of BC’s annual GHG emissions.

“The project represents a significant step towards the development of more sustainable mining practices by offering the prospect of a carbon-neutral mine as well as other benefits, such as dust management and the stabilisation and cementation of tailings piles,” Martin Turenne, FPX Nickel’s president and CEO, told the Northern Miner. 

Canada Nickel Company: In Process Tailings Carbonation 

Canada Nickel Company Inc. is pioneering yet another, slightly different, approach to carbon sequestration. With the discovery of a potentially revolutionary carbon capture method called ‘In Process Tailings Carbonation’ (IPT Carbonation), the company aims to enrich waste minerals with CO₂ before they are discharged to tailings facilities.

This process works by leveraging tailings from the mineral processing circuit and conditioning them with CO₂ for a brief period and has yielded groundbreaking results from its laboratory tests. 

These tests demonstrate that the IPT Carbonation process could render the company’s tailings at its Crawford operations carbon neutral within a mere 36 hours, producing up to 21t of CO₂ credits per tonne of nickel in just six days, according to an article published by Global Mining Review. 

With its vision of establishing a zero-carbon industrial cluster in the Timmins region, Canada Nickel aims to produce NetZero Nickel™, NetZero Cobalt™, and NetZero Iron™ in the foreseeable future. 

It will do this by integrating IPT and real-time quantification of carbon capture into standard metallurgical accounting systems and streamlining the process of obtaining CO₂ offsets even before tailings discharge. 

Rio Tinto: partnering with Carbfix for green aluminum 

Further down the value chain, Rio Tinto’s ISAL aluminium smelter in Hafnarfjörður in Iceland is situated on basaltic rock formations that have proven highly suitable for carbon sequestration. 

Although the smelter is already 100% powered by renewable hydropower, in 2021 Rio Tinto partnered with Carbfix, a subsidiary of Iceland’s Reykjavik Energy, to advance CCUS technology. 

Since 2014, Carbfix has already successfully captured over 73,000t of CO₂ from the Hellisheidi geothermal power plant, utilising Iceland’s basalt formations to convert the gas into stable carbonate minerals, according to a Reuters news release.

The collaboration with Carbfix will enable Rio Tinto to establish the Coda Terminal, the world’s first mineral carbon storage hub, with plans to drill initial injection wells soon and commence operation by 2025. 

Through this partnership, Rio Tinto anticipates not only mitigating carbon emissions from its smelting operations, but also generating carbon credits from its basalt-rich land, which could make it the first carbon net-negative aluminum smelter in the world. 

Outlook: from junior miners to abandoned mine sites

Whether enhancing the natural process of capturing carbon from the atmosphere in existing tailings facilities at active or abandoned mine sites, conditioning mineral processing waste with CO₂, or injecting carbon into feasible rock formations, including CO₂ bought from nearby industries, the mining industry may play a much more central role in implementing CO₂ storage technologies than anticipated. 

Given the speed of innovation and discovery over the past couple of years, mining companies with deposits or tailings containing ultramafic rocks favorable for carbon mineralisation may also be well positioned to become carbon negative much faster than expected.

While the idea of a nickel mine or aluminum smelter being net negative in terms of carbon emissions may have seemed far-fetched a couple of years ago, it might be a reality much sooner than originally thought possible. 

Tailings of abandoned mine sites may soon be repurposed as carbon sinks or even repurposed into resources for creating sustainable construction materials and other products.

Furthermore, junior miners may be able to reach more favorable financing and investment conditions and go through permitting processes more swiftly if they can build in a net-zero carbon strategy from the onset of project development. 

To conclude, the impacts of successful CCS and CCUS technology development and implementation will go beyond climate mitigation by providing an exciting and promising pathway to rewrite the role mining companies play in creating sustainable and carbon-free industries. 

*These projects are just a handful of those underway across the globe. If you know of any others, feel free to add them in the article comments so that we can continue the conversation.