PASTE & TAILINGS
WSP argues that carbon dioxide removal via mineral carbonation of tailings is a promising new approach
Tailings tasks
From the latest in filter press technology to recent paste projects, Paul Moore looks at some developments in this vital area of waste management in mining
We start this year’ s paste and tailings focus by looking at tailings in a slightly different way – that is as a feedstock for mineral carbonation. Sean Capstick, Global Mining Net Zero Lead, and Bart De Baere Senior Geochemist, both at WSP, in a recent article looked at the specific problem of carbon dioxide removal using mineral carbonation of tailings. They state:“ Too often, mining is seen as part of the decarbonisation problem. Mineral carbonation offers the chance to change that narrative, allowing mining companies to take the lead in carbon dioxide removal and avoid not just their own emissions but those of other hard-to-abate sectors. In a world already struggling to meet its net-zero commitments, it is an opportunity that all those working in the mining industry should consider seriously.”
CO 2 emissions and mine tailings are two of the more complex challenges facing miners. Carbon dioxide removal via mineral carbonation of tailings the authors argue is a promising new approach that could have a positive impact on both.
But its viability will depend on multiple lifecycle factors, evolving within a developing Carbon Dioxide Removal( CDR) ecosystem.“ With many miners establishing net-zero commitments, the industry’ s decarbonisation efforts are becoming more urgent. Miners are also the chief suppliers of minerals critical to global decarbonisation efforts. Demand for these minerals is thus expected to grow significantly. At the same time, mining operations are becoming more complex as deeper and lower-grade deposits are opened up. This combination of factors will likely place upward pressure on mining-related emissions.”
It is also a fact that some greenhouse gas emissions in the broader economy are challenging, if not impossible, to avoid or abate. These include agricultural and waste NOx emissions, aviation and shipping CO2 emissions, and CO 2 emissions from building heating and cooling. Strategies that generate net negative emissions are therefore needed to achieve economy-wide carbon neutrality.
Capstick and Baere state:“ In this intricate net-zero landscape, there is mounting interest in carbon dioxide removal( CDR). CDR is a catch-all term covering processes that extract and securely store CO 2 from the atmosphere, helping to tackle hard-to-abate and historical CO 2 emissions. These systems can be biological, such as afforestation and reforestation, or technological, such as direct air carbon capture and storage. CDR offsets are commercially tradable with prices predominantly defined by their degree of permanence and additionality, as tracked via a measurement, reporting, and verification protocol.”
Mineral carbonation is one method of lowering emissions from on-site or off-site sources and permanently storing captured CO 2 within a CDR ecosystem. It describes processes that react CO 2 with an alkaline feedstock to form solid carbonate minerals. One example is the injection of CO 2( dissolved in water) into mafic and ultramafic geologic formations. However, mineral carbonation can also be accelerated and better controlled at the surface wherever there is a source of solid alkaline material. And this is where CDR meets the mining industry.
Certain mine tailings offer a potential feedstock for mineral carbonation and the opportunity for mines to become integral parts of the carbon dioxide removal ecosystem, either as feedstock suppliers to off-site mineralisation plants or as carbon storage facilities in their own right. This would allow mining companies to participate in carbon markets to lower their own carbon pricing obligations or generate revenue. Mineral carbonation could also help stabilise and neutralise tailings, mitigating safety risks, while providing ongoing local employment after commercial mining has ceased.
They continue:“ The idea of carbonating mine tailing is still relatively novel. Although the benefits are persuasive, challenges lie ahead, not least as it brings together two particularly thorny issues: tailings disposal, which is one of the most regulated industrial processes in the world, and the safety and permanence of CO 2 transport and storage systems- topics that have proven to excite public opinion. Mines will, therefore, require robust processes and procedures to assess the viability of mineral carbonation in mine tailings from initial planning through the complete project lifecycle, including how it interacts with ongoing mining operations and closure.”
This is a multi-stage process involving multiple considerations, including the potential to install direct air carbon capture onsite may be limited, or the quantity of removals may be lower than the mineralisation capacity. Integrating onsite sources of CO 2( eg a smelter) with mineral carbonation could address these issues but will require a mine process assessment.“ If no onsite source exists, will CO 2 be transported to the site, or could an alkaline material be produced and transported instead? Matching the mineral carbonation technology to these sources will help to define the scope of the project.”
Mines with suitable feedstock will need to quantify the potential amount of CO 2 that could be removed at their site, identify the most suitable mineral carbonation process applicable to their site, and develop a sitespecific protocol to ensure future recognition of any carbon capture.
Designing, constructing, and implementing mineral carbonation processes will require confirming the physical and geochemical stability of the carbonised tailings or mineral carbonation byproducts( or process byproducts if the mineralisation occurs offsite) and integrating, as applicable, an additional process step before tailings deposition.
Monitoring, reporting, and verifying CO 2 sequestration will be needed, including annual reporting and independent thirdparty verification.
Finally, mines will need to demonstrate the carbonised tailings’ long-term physical and geochemical stability for sustainable closure while, where applicable, allowing for continued post-closure carbonation activities.
McLanahan’ s QUICKCHANGE to transform filter press maintenance
McLanahan, in collaboration with its sister company Diefenbach, has introduced the QUICKCHANGE™ system- a patent-pending innovation it says set to transform filter press maintenance, including in tailings management. Engineered for speed,
18 International Mining | JUNE 2025