Resume/ Abstract

Mining and mineral processing residues (or by-products, depending on the viewpoint and origin) have been a focal point of site management and environmental protection for decades. Recently, the opportunity to use them to reduce the carbon footprint of such operations has gained increasing scientific and commercial interest. Our research group, across institutions (KU Leuven, Sheridan College, and the University of Guelph), has been working on these topics since 2010. Post-pandemic, we have seen a noticeable upshift in the urgency and financial backing to turn some of the conceptual goals into practical reality. These approaches can be classified into at least four main streams, which our recent research has focused on: (i) the use of silicate minerals for carbon sequestration via direct or indirect mineral carbonation; (ii) the use of silicate minerals for enhanced weathering either on-site in tailings storage sites or ex-situ in land applications; (iii) the need or desire to recover remaining critical metals from mine wastes; and (iv) the use of residues (innate or modified) as valuable materials in other industries or the use of by-products of residue processing for such ends. This presentation explores the approaches and findings of our recent projects.

In Project A, our research has attempted to predict the carbon drawdown of storage mine tailings under ambient conditions. The research question was whether the mine tailings produced could, even if slowly and to a relatively small extent, offset the expected emissions of the mine site. We devised accelerated laboratory tests that informed an empirical long-term weathering model, giving special attention to the mineralogy and intra-particle mineral assemblages to infer conservative mechanisms for reliable estimates.

In Project B, we have been developing a low-carbon approach to adapt conventional hydrometallurgical methods for processing mine tailings and low-graded ores for critical metals recovery. Key concepts include producing lixiviating agents through scalable and efficient electrolytic processes, selecting sufficiently reactive feedstock, and ensuring a zero-waste process. We target the production of mixed metal oxides, silica, and magnesium oxide, focusing on approaches to meet expected commercial grades.

Project C is an ongoing effort to support scientific development, knowledge transfer, and commercial developments in enhanced rock weathering (ERW) and its monitoring, reporting, and verification (MRV). While much attention has focused on freshly mineable minerals (basaltic, wollastonitic, and dunite rocks), there is significant potential for mined residues to play an important role, especially in locations far from sources of the former. We discuss important factors in selecting and using silicate minerals for ERW and their impact on ERW MRV'ing.