Abstract
There is growing urgency for CO2 removal strategies to slow the increase of, and potentially lower, atmospheric CO2 concentrations. Enhanced weathering, whereby the natural reactions between CO2 and silicate minerals that produce dissolved bicarbonate ions are accelerated, has the potential to remove substantial CO2 on decadal to centennial timescales. The global mining industry produces huge volumes of fine wastes that could be utilised as feedstock for enhanced weathering. We have compiled a global database of the enhanced weathering potential of mined metal and diamond commodity tailings from silicate-hosted deposits. Our data indicate that all deposit types, notably mafic and ultramafic rock-hosted operations and high tonnage Cu-hosting deposits, have the potential to capture ~1.1–4.5 Gt CO2 annually, between 31 and 125% of the industry's primary emissions. However, current knowledge suggests that dissolution rates of many minerals are relatively slow, such that only a fraction (~3–21%) of this potential may be realised on timescales of <50 years. Field trials in mine settings are urgently needed and, if this prediction is confirmed, then methodologies for accelerating weathering reactions will need to be developed.
Highlights
Anthropogenic inputs of carbon dioxide (CO2) to the atmosphere are the primary cause of global warming (Field and Raupach, 2004; Canadell et al, 2007; IPCC, 2014)
The Paris Agreement goal to limit the increase in global average temperature to 1.5◦C is unlikely to be met without deep decarbonisation of the global economy together with large scale CO2 removal (CDR) from the atmosphere of up to ∼10 gigatonnes (Gt) CO2 per year by 2050, rising to ∼20 Gt CO2 year−1 by 2100 (UNEP, 2017; NASEM, 2019; Wilcox et al, 2021)
If the mining industry were to pursue far-reaching decarbonisation through the comprehensive deployment of renewable energy, electrification and improved efficiencies, enhanced weathering of wastes could be a major contributor of negative carbon emissions and potentially accommodate a significant portion of the ∼10 Gt CO2 year−1 (IPCC, 2014) reductions required to meet the 2050 Paris Agreement climate targets
Summary
Anthropogenic inputs of carbon dioxide (CO2) to the atmosphere are the primary cause of global warming (Field and Raupach, 2004; Canadell et al, 2007; IPCC, 2014). The Paris Agreement goal to limit the increase in global average temperature to 1.5◦C is unlikely to be met without deep decarbonisation of the global economy together with large scale CO2 removal (CDR) from the atmosphere of up to ∼10 gigatonnes (Gt) CO2 per year (year−1) by 2050, rising to ∼20 Gt CO2 year−1 by 2100 (UNEP, 2017; NASEM, 2019; Wilcox et al, 2021) This formidable challenge requires the urgent assessment of the full range of potential CDR approaches, as it is unlikely that any single technique will work at the scale required (e.g., Pacala and Socolow, 2004). The essence of the strategy is to mimic and accelerate natural chemical weathering, whereby minerals dissolve and react with atmospheric CO2 and water (H2CO3 carbonic acid; reaction 1) to form bicarbonate solutions stabilised by solubilised cations (e.g., Ca2+, Mg2+; reactions 2 and 3).
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