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Serpentinite Carbonation for CO2 Sequestration
Abstract
Serpentinites offer a highly reactive feedstock for carbonation reactions and the capacity to sequester carbon dioxide (CO2) on a global scale. CO2 can be sequestered in mined serpentinite using high-temperature carbonation reactors, by carbonating alkaline mine wastes,
or by subsurface reaction through CO2 injection into serpentinite-hosted aquifers and serpentinized peridotites. Natural analogues to serpentinite carbonation,
such as exhumed hydrothermal systems, alkaline travertines, and hydromagnesite–magnesite playas, provide insights into geochemical
controls on carbonation rates that can guide industrial CO2 sequestration. The upscaling of existing technologies that accelerate serpentinite carbonation may prove sufficient for offsetting
local industrial emissions, but global-scale implementation will require considerable incentives and further research and
development.
... Although various highly reactive hydroxide salts such as brucite also generate alkalinity and capture carbon effectively, they are not widely available in large enough quantities to contribute to gigatonne-scale CDR (Power et al. 2013). The most useful silicates are those that can both effectively capture the most protons per mole of silicate dissolution and dissolve the fastest. ...
... They are globally abundant and occur in areas easily accessible to humans. Combined, the CDR potential of their known reserves is estimated to be in the tens of thousands of GtCO 2 (Lackner 2002;Power et al. 2013), orders of magnitude greater than what is needed to permanently sequesteranthropogenic CO 2 emissions. The questions surrounding methods of carbon capture via ultramafic minerals therefore relate to the scientific, engineering, political, and economic logistics of implementation at large scales, which we explore below. ...
... The total CDR potential of known, global reserves of ultramafic minerals lies in the range of several tens of thousands of GtCO 2 , orders of magnitude greater than what is required to sequester anthropogenic CO 2 emissions (Lackner 2002;Power et al. 2013). Although geochemical CDR thus offers tremendous potential, implementing it at scale carries economic constraints that must be taken into account. ...
One of the greatest threats facing the planet is the continued increase in excess greenhouse gasses, with CO2 being the primary driver due to its rapid increase in only a century. Excess CO2 is exacerbating known climate tipping points that will have cascading local and global effects including loss of biodiversity, global warming, and climate migration. However, global reduction of CO2 emissions is not enough. Carbon dioxide removal (CDR) will also be needed to avoid the catastrophic effects of global warming. Although the drawdown and storage of CO2 occur naturally via the coupling of the silicate and carbonate cycles, they operate over geological timescales (thousands of years). Here, we suggest that microbes can be used to accelerate this process, perhaps by orders of magnitude, while simultaneously producing potentially valuable by-products. This could provide both a sustainable pathway for global drawdown of CO2 and an environmentally benign biosynthesis of materials. We discuss several different approaches, all of which involve enhancing the rate of silicate weathering. We use the silicate mineral olivine as a case study because of its favorable weathering properties, global abundance, and growing interest in CDR applications. Extensive research is needed to determine both the upper limit of the rate of silicate dissolution and its potential to economically scale to draw down significant amounts (Mt/Gt) of CO2 Other industrial processes have successfully cultivated microbial consortia to provide valuable services at scale (e.g., wastewater treatment, anaerobic digestion, fermentation), and we argue that similar economies of scale could be achieved from this research.
... The necessity for carbon dioxide removal (CDR) from the atmosphere on the order of tens of gigatonnes (Gt) per year by 2100 (Intergovernmental Panel on Climate Change (IPCC ), 2018, 2019; National Academies of Sciences, Engineering, and Medicine (NASEM) 2019; United Nations Environment Programme (UNEP) 2022) is a formidable challenge, requiring an urgent evaluation of different available CDR strategies. One emerging approach is through ex-situ geochemical CDR, such as targeted enhanced weathering, ocean alkalinity enhancement (OAE), and mineral carbonation approaches using industrial by-products (Bullock et al., 2021;Campbell et al., 2022;Declercq et al., 2023;Lu et al., 2023;Mervine et al., 2018;Paulo et al., 2021;Power et al., 2020;2013a;2013b;Pullin et al., 2019;Stubbs et al., 2022;Wilson et al., 2009a;. The principle is to promote or accelerate natural chemical weathering through the utilisation of loose, excavated, or processed natural materials (e.g., basalt) or artificial materials (e.g., industrial wastes). ...
... Of the global annually generated silicate-hosted tailings, potentially up to 2 Gt may be identified as materials of high reactivity with CO 2 and of high CDR potential . These materials include reactive minerals derived from asbestos and talc-hosting serpentinite-hosted deposits (Dichicco et al., 2015;McCutcheon et al., 2016;Power et al., 2013b;Paulo et al., 2021;Wang and Maroto-Valer, 2011), Ni-rich sulphide deposits (Assima et al., 2014;Kandji et al., 2017;Power et al., 2020;Wilson et al., 2014), kimberlite diamond mines (Bullock et al., 2023b;Mervine et al., 2018;Paulo et al., 2021;Wilson et al., 2009b;Zeyen et al., 2022), and olivine and serpentine-rich dunites mined as refractory minerals (Bullock et al., 2023a;Hangx and Spiers, 2009;Kremer et al., 2019;Kremer and Wotruba, 2020;Renforth et al., 2015;Schuiling and de Boer, 2011;ten Berge et al., 2012). ...
Industrial solid waste by-products are being increasingly employed for geochemical carbon dioxide removal (CDR) strategies due to their fine grain size, accessibility, and large annual production tonnages. Here, a range of such by-products has been tested experimentally for their reactivities with CO 2 and water. Sample solutions were monitored for 100 h for changes in chemistry, and solid samples were characterised pre-and post-experiment. Samples rich in Ca-and Mg-bearing minerals, such as dunite, kimberlite, and ilmenite mine tailings, as well as marble quarry cuttings, were key cation sources. Ni sulphide, fluorite and borax tailings, coal-fired power plant fly ashes, and red mud samples showed high dissolution rates. The highest reaction rates were often observed during the initial few hours, and compared well to rates determined for rocks typically targeted for CDR purposes, such as basalt and gabbro. Several samples also showed secondary carbonate precipitation, suggesting opportunities for the development of single-step CDR technologies. Overall, the results of this study indicate that several industrial by-products can provide sufficient cations at favourable dissolution rates for geochemical CDR purposes. Any on-site or near-site conditions for reaction acceleration such as heat, concentrated CO 2 or microbes , could further increase favourability for geochemical CDR opportunities.
... Like Peridotite, it is commonly found in areas of oceanic crust that have been uplifted and exposed to the surface, such as ophiolites and tectonic mélanges. Serpentinite has also been of interest to geologists due to its unique properties and significance in geologic processes, including its potential for mineral carbonation (Power et al., 2013). It is rich in magnesium and other elements and is often associated with the formation of various mineral deposits, including chromite, and nickel (Power et al., 2013;Schulte et al., 2006). ...
... Serpentinite has also been of interest to geologists due to its unique properties and significance in geologic processes, including its potential for mineral carbonation (Power et al., 2013). It is rich in magnesium and other elements and is often associated with the formation of various mineral deposits, including chromite, and nickel (Power et al., 2013;Schulte et al., 2006). Occurrences in Australia are numerous within WA (Barry, 1974;Butt et al., 1981;Fisher, 2012; and NSW (Brown et al., 1992;Stevens, 1972) topping the list of documented occurrences across mines and prospects. ...
... Therefore, the knowledge of geochemical features of serpentinite rocks is another important tool for environmental monitoring, since the weathering of ophiolite outcrops can represent a potential source of toxic elements [26], in particular the first-row transition elements. On the other hand, serpentinites have the ability to sequester carbon dioxide (CO 2 ) and provide a highly reactive feedstock for carbonation reactions; indeed, with the use of high-temperature carbonation reactors, alkaline mine wastes, or subsurface reactions involving the injection of CO 2 into serpentinite-hosted aquifers and serpentinized peridotites, CO 2 can be sequestered in serpentinite that has been mined [78,79]. ...
Serpentinite rocks testify to the ocean-floor metamorphism that took place and transformed the original mineralogy and fabric of previous ultramafic rocks. Due to their tectonic and petrological importance, in recent decades, there has been increasing interest in serpentinites. From the economic point of view, it is worth noting that, due to their beauty and attractiveness, serpentinite rocks have been exploited and traded as building and ornamental stones since prehistorical times worldwide. In this work, we provide a comprehensive report of the petrographic, mineralogical, petrophysical, and geochemical features of the serpentinites cropping out in the northern sector of the Calabria–Peloritani Orogen (Italy), where the historical quarries are located. Since these serpentinite rocks have been traded for a long time and employed as an excellent building material, their detailed knowledge may provide a useful tool to understand their behavior when they are employed as building materials, to predict their performances upon emplacement in monuments, and to plan correct restoration by considering the provenance of the lithotypes employed. Moreover, comprehensive characterization is also particularly important because it has been reported that serpentinites from Calabria may contain asbestiform and other fibrous minerals, as testified by the occurrence of chrysotile, tremolite, and actinolite asbestos located within the veins, which could lead to health problems due to asbestos fiber exposure. Finally, serpentinite may be considered as an important potential CO2 sequestration sink.
... Brucite and wollastonite skarn were chosen for this study as they have been extensively studied for CO 2 mineralization (Daval et al., 2009(Daval et al., , 2010Harrison et al., 2015;Harrison et al., 2013;Kojima et al., 1997;Power et al., 2021) and have relatively simple mineralogy and fast dissolution rates compared to the kimberlite residues. Serpentine minerals were selected as they are amongst the most abundant minerals in the Venetia kimberlite residues (Stubbs et al., 2022) and other ultramafic mine wastes (Power et al., 2013c;Pronost et al., 2012;Wilson et al., 2009a), making them important minerals to consider for mine waste carbonation. ...
... These reactions can occur passively at the surface of mine tailings storage facilities (TSFs) [10,11]. Carbonation rates in ultramafic tailings are highly variable and are limited by several factors, including the mineralogy and availability of CO 2 and water [12][13][14][15]. Field studies of different ultramafic-hosted mines showed that the CO 2 drawdown rates are largely controlled by the centimeter-scale depth to which CO 2 can diffuse, even when reactive minerals are present [9,16,17]. ...
One method to accelerate carbon sequestration within mine tailings from remote mines involves the injection of diesel generator exhaust into dry stack tailings. The techno-economic feasibility of this approach heavily depends on understanding the flow characteristics inside the perforated injection pipes embedded within the tailings. Two distinctive yet dynamically coupled transport phenomena were identified and evaluated: (i) gas transport inside the pipe and (ii) gas injection into the porous body of the tailings. This paper presents two models to investigate these transport phenomena, a three-dimensional (3D) and a one-plus-one-dimensional (1 + 1)D model. An experimental investigation of the pressure profile through the injection pipe was carried out to validate the models at the experimental scale. To apply the (1 + 1)D model to larger scales, the results were compared with those of the 3D model, as the (1 + 1)D model required significantly less computational resources and time. To include the effect of the perforations in the pipe on the pressure profile of the (1 + 1)D model, an analytical fluid velocity profile was developed in relation to geometric and physical parameters. The performance of the (1 + 1)D model with an impact factor was then evaluated against the 3D model results for the inlet pressure, pressure profile and gas outflow distribution under various conditions than those investigated experimentally. The developed (1 + 1)D model can be used to design an energy-efficient approach for large-scale implementation with a wide range of desired operating parameters.
... well-known low-temperature alteration reactionstransforming unaltered kimberlite (blue ground) into a weathered/friable kimberlite (yellow ground), and the resulting carbon sequestration via the formation of secondary carbonate minerals [2,7,14,25,29]. This natural phenomenon, occurring in kimberlites exposed to Earth's surface weathering conditions, could be accelerated as a by-product of extraction and crushing [19,28]. ...
Microbiological weathering of coarse residue deposit (CRD) kimberlite produced by the Venetia Diamond Mine, Limpopo, South Africa enhanced mineral carbonation relative to untreated material. Cultures of photosynthetically enriched biofilm produced maximal carbonation conditions when mixed with kimberlite and incubated under near surface conditions. Interestingly, mineral carbonation also occurred in the dark, under water-saturated conditions. The examination of mineralized biofilms in ca. 150 µm-thick-sections using light microscopy, X-ray fluorescence microscopy (XFM) and backscatter electron—scanning electron microscopy-energy dispersive x-ray spectrometry demonstrated that microbiological weathering aided in producing secondary calcium/magnesium carbonates on silicate grain boundaries. Calcium/magnesium sulphate(s) precipitated under vadose conditions demonstrating that evaporites formed upon drying. In this system, mineral carbonation was only observed in regions possessing bacteria, preserved within carbonate as cemented microcolonies. 16S rDNA molecular diversity of bacteria in kimberlite and in natural biofilms growing on kimberlite were dominated by Proteobacteria that are active in nitrogen, phosphorus and sulphur cycling. Cyanobacteria based enrichment cultures provided with nitrogen & phosphorus (nutrients) to enhance growth, possessed increased diversity of bacteria, with Proteobacteria re-establishing themselves as the dominant bacterial lineage when incubated under dark, vadose conditions consistent with natural kimberlite. Overall, 16S rDNA analyses revealed that weathered kimberlite hosts a diverse microbiome consistent with soils, metal cycling and hydrocarbon degradation. Enhanced weathering and carbonate-cemented microcolonies demonstrate that microorganisms are key to mineral carbonation of kimberlite.
Carbon mineralization in mafic-ultramafic rocks is not only a natural process that can form significant carbon sinks in the lithosphere, but also a promising procedure for artificial CO2 storage. In this study, we report unique records of in situ carbon mineralization within fluid inclusions in postcollisional pyroxenite from the Dabie orogen, central China. Olivine, orthopyroxene, clinopyroxene, and amphibole in the pyroxenite trapped CO2-rich magmatic fluids as fluid inclusions, which were subjected to internal carbon mineralization due to interaction between trapped fluids and host minerals during cooling of the pyroxenite. In fluid inclusions, carbonation of olivine produced magnesite, talc, magnetite, and CH4; carbonation of orthopyroxene generated magnesite, talc, cristobalite, and CH4; carbonation of clinopyroxene formed calcite, dolomite, actinolite, talc, cristobalite/quartz, and CH4; carbonation of amphibole created calcite, dolomite, chlorite, cristobalite/quartz, talc, mica, a TiO2 phase, a NaAlSi3O8 phase, and CH4. Carbonation reactions within the fluid inclusions have general implications for reaction pathways of carbon mineralization in mafic-ultramafic rocks. Moreover, it is shown that iron oxidation is thermodynamically favored during high-extents carbonation of diverse mafic minerals in the presence of CO2-rich fluids, facilitating abiotic synthesis of CH4 that is a crucial gas in both natural carbon cycling and engineered carbon storage.
Introduction Fossil fuels produce CO 2 , which is a significant greenhouse gas that contributes to global warming. Environmentally benign use of fossil fuels requires that CO 2 be captured and sequestered. The reactivity of CO 2 with minerals is important to several sequestration strategies. These include aboveground mineralization in which mined rock is reacted with CO 2 to form permanent carbonates and belowground geologic sequestration in which the amount of in situ mineralization is an important factor in repository performance. As part of a general investigation of mineral reactivity in the H 2 O-CO 2 system, we have investigated the reactivity of serpentine [Mg 3 Si 2 O 5 (OH) 4 ] with H 2 O and CO 2 as a function of pH and the addition of potential catalyzing agents (weak acids). Serpentine is a prime candidate for aboveground mineralization but could also occur as a caprock for the injection of CO 2 belowground.
The success of human and industrial development over the past hundred years has lead to a huge increase in fossil fuel consumption and CO2 emission to the atmosphere leading to an unprecedented increase in atmospheric CO2 concentration. This increased CO2 content is believed to be responsible for a significant increase in global temperature over the past several decades. Global-scale climate modeling suggests that this temperature increase will continue at least over the next few hundred years leading to glacial melting, and raising seawater levels. In an attempt to attenuate this possibility, many have proposed the large scale sequestration of CO2 from our atmosphere. This introduction presents a summary of some of the evidence linking increasing atmosphere CO2 concentration to global warming and our efforts to stem this rise though CO2 sequestration.
Near-surface reaction of CO2-bearing fluids with silicate minerals in peridotite and basalt forms solid carbonate minerals. Such processes form abundant veins and travertine deposits, particularly in association with tectonically exposed mantle peridotite. This is important in the global carbon cycle, in weathering, and in understanding physical-chemical interaction during retrograde metamorphism. Enhancing the rate of such reactions is a proposed method for geologic CO2 storage, and perhaps for direct capture of CO2 from near-surface fluids. We review, synthesize, and extend inferences from a variety of sources. We include data from studies on natural peridotite carbonation processes, carbonation kinetics, feedback between permeability and volume change via reaction-driven cracking, and proposed methods for enhancing the rate of natural mineral carbonation via in situ processes ("at the outcrop") rather than ex situ processes ("at the smokestack").
Direct light and electron microscopic studies show that cyanobacterial cells serve as nucleation sites for carbonate mineral precipitation in a variety of fresh to saline‐alkaline lakes on the Cariboo Plateau in central British Columbia, Canada, and in mineralized crusts on weathered basalt in Iceland. The carbonate minerals found in association with the cyanobacteria were extremely fine‐grained, and invariably occurred on the external surfaces of the cells. Carbonate mineralogy was variable, ranging from calcite to magnesite, depending on differences in lake and groundwater chemistry (i.e., saturation state of the water with respect to individual carbonate minerals). In microcosm experiments, phototrophic cyanobacterial growth increased alkalinity and the degree of oversaturation with respect to calcite. Calculated values for the saturation state of calcite and magnesite in Cariboo Plateau natural waters exhibited two distinct trends, with (1) high magnesite saturation values in areas where the weathering of magnesium olivine‐rich basalt bedrock determines water chemistry, and (2) high calcite saturation values where bedrock is a mix of basic lava flows, limestone, argillite, and chert. Similar calculations for Iceland show that cold surface waters are generally oversaturated with respect to calcite, as expected for the weathering of calcium plagioclase‐rich lava. These observations of microbial carbonate precipitation in the Caribou Plateau region of British Columbia, Canada, and on the Budarhaun lava plain in Iceland suggest that weathering of silicate minerals in bedrock is biogeochemically coupled to the deposition of carbonate minerals by microorganisms. This process may provide a sink for atmospheric carbon dioxide in terrestrial environments.
We have discovered diffuse warm air vents at the surface of a chrysotile milling waste heap at the Black Lake mine, Thetford Mines, Québec, Canada. The venting areas are inconspicuous, except in winter when the vents form snow-free areas of unfrozen ground, each with a surface area of 1–15 m2. The temperature and chemical composition of the warm air vents have been monitored from March 2009 to July 2010. The temperature of the warm air and ground surface at the venting sites ranged from 6.6 to 20.0 °C, whereas that of the ambient air ranged from –13.2 to 20.0 °C. The difference between atmospheric and vent air temperatures is greater in cold-weather months. The warm air has low CO2 content, but has otherwise normal atmospheric gas composition. Warm air volumetric flow varies from 2.1 to 19.9 L/m2/s in winter, when it contains between <10 and 18 ppm CO2. In summer, the venting areas are more diffuse, with volumetric flow rates ranging from 0.5 to 1.5 L/m2/s, and are less depleted in CO2 (260–370 ppm). Frozen ground is likely focusing airflow in winter compared to summer. We present a conceptual model in which air enters the steep flanks of the chrysotile milling waste heap, into which CO2 reacts with Mg-rich minerals, stripping CO2 from air by exothermic mineral carbonation reactions. Considering the surface area of summer and winter venting areas, flow rates, and concentration of CO2 in warm air vents, we estimate that the Black Lake mine heap passively captures at least 0.6 kt CO2 per year.
A comprehensive low-temperature thermodynamic model for the
geochemically important Na 2CO 3-MgCO
3-CaCO 3-H 2O system is presented. The
model is based on calorimetrically determined Δ fH°
298 values, S° 298 values and C°
p( T) functions taken from the literature as well as on
μ° 298 values of solids derived in this work from
solubility measurements obtained in our laboratories or by others. When
these thermodynamic quantities were combined with temperature-dependent
Pitzer parameters taken from the literature, solubilities calculated for
a wide range of conditions agree well with experimental data. The
results for several subsystems were summarized by depicting the
respective phase diagrams. For the MgO-CO 2-H 2O
subsystem, it was found that the commonly believed stability relations
must be revised, i.e., in the temperature range covered, nesquehonite
never becomes more stable than hydromagnesite at pCO 2
≤ 1 atm. Although the recommended set of thermodynamic data on
sparingly soluble solids was derived from experimental results on mainly
NaClO 4 systems, it can be incorporated in databanks
containing additional Pitzer parameters for modeling more complex fresh-
or seawater systems.
All carbonates associated with the ultramafic rocks and serpentinites of the western United States are shown by their stable isotope ratios to be of near-surface, low-temperature origin. These include vein materials that have been previously classified as hydrothermal. New laboratory and natural data were obtained on the equilibrium isotope relations between hydromagnesite and water. The origins of travertines in the ultramafic area are easily distinguished on the basis of their stable isotope ratios. The extremely heavy isotope ratios of nesquehonites suggest an intricate evaporating-film mechanism of formation.
