The Paris Agreement goal to limit the global average temperature increase to below 2°C cannot be achieved without atmospheric CO₂ removal (CDR) on the order of tens of gigatonnes per year by 2100. Such a formidable challenge requires an urgent assessment of all possible routes to CDR, as further delayed mitigation will have an increasingly damaging effect on the environment. The challenge is pertinent to industrial sectors which produce several Gt of CO₂ per year and are susceptible to financial impacts due to nascent carbon taxes worldwide, and other negative environmental impacts brought on by the generation of vast amounts of solid and liquid waste materials (e.g., rock cuttings and overburden, fine mine tailings, glassy slags, fly ashes and desalination reject brines). Geochemical CDR strategies in such industrial wastes, where the natural process of rock weathering and carbonate precipitation is utilised to uptake CO₂, is a potentially significant CDR approach for bicarbonate (alkalinity) and carbonate generation, requiring material assessment and enhancement schemes to fully realise the high removal potential.

The DETAILS project (Developing enhanced weathering methods in mine tailings for CO₂ sequestration; Marie Skłodowska-Curie grant agreement ID: 101018312) is exploring the CO₂-water-solid waste material reactivity of a range of mine tailings, slags and fly ashes, sourced from industrial centres globally. The range of materials includes those considered to be chemically and mineralogically promising for CDR (e.g., mine tailings derived from olivine dunite, Ni sulphide and diamond kimberlite operations, carbonate marble fines), materials with limited or unknown CDR potential (e.g., Al-bauxite-related red muds, borate tailings, ilmenite tailings, products from SO₂ processing, copper smelting produced slags and combustion fly ashes), and materials generally considered unfavourable (e.g., Cu and fluorite tailings). For all materials, the key to CDR strategy utilisation is the ability of favourable minerals to undergo significant dissolution for alkalinity generation and possible subsequent carbonation, on appropriate human timescales (e.g., seconds up to decadal), either naturally or through achieving enhanced rates of dissolution and precipitation.

Changes to water chemistry through reactions with CO₂ and powdered material samples were monitored throughout the experiment. These include changes to pH, alkalinity, silica, Ca²⁺ and Mg²⁺ cations, (Mg-Ca cations required for reactions with CO₂ to produce stabilised bicarbonate and carbonate ions). Preliminary results reveal that Mg- and Ca-bearing minerals within some wastes react with CO₂ to form alkalinity, suggesting potential for CDR strategies. Methods to increase reaction rates will be explored, such as a microbially-induced pH switch to increase the kinetics of mineral dissolution and mineral carbonation (e.g., oxidation and reduction reactions associated with microbial metabolisms active in sulphur and nitrogen cycling). A better understanding of reaction kinetics for a wider range of industrial wastes will help future projects to confirm or re-consider the viability of materials for CDR strategies, and to better identify opportunities for upscaled pilot schemes with further implemented geochemical CDR methods to speed up reaction kinetics.

How to cite: Bullock, L., Fernandez-Turiel, J.-L., and Benavente, D.: Experimental investigation of multiple industrial wastes for geochemical carbon dioxide removal strategies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-384, https://doi.org/10.5194/egusphere-egu23-384, 2023.

The use of hyperspectral imaging (HSI) at different scales has become a big ally for a large range of applications in remote sensing, especially within the mining life cycle. In this contribution, we explore the use of HSI sensing, particularly to monitor mine waste at different constellations that might face environmental damaging phenomena: Acid Mine Drainage (AMD). Failure to accurately monitor and remediate such a complex process, leads to long-term impacts on ecosystems and human health, in addition to significant financial consequences and reputational damage to operators. We propose a workflow to integrate hyperspectral visible to near-infrared (VNIR) data, together with mineralogical and geochemical data to precisely map the extent of acid mine drainage using machine learning algorithms. Collected data from the field and further laboratory analyses on a few specimens provide the ground-truth and training data to support the proposed mapping algorithms. Results consist of semi-quantified concentration of dissolved metals, physicochemical properties in water bodies, and associated AMD minerals sub-products (e.g., goethite, jarosite, schwertmannite) within mine waste materials, as well as mineralogical characterization for predictive modeling at laboratory scale.  Regardless of the scale of acquisition, spectral imaging represents a cost-effective tool to enhance the quality of classical environmental analyses both in active and post-mining scenarios, which can increase the overall accuracy of the monitoring, allowing frequent and multi-temporal observations to reveal risk scenarios, take fast corrective actions and keep a continuous control.

How to cite: Flores, H., Rudoplh, T., and Möllerherm, S.: Hyperspectral sensing as a tool for smart environmental monitoring in mine waste management, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7324, https://doi.org/10.5194/egusphere-egu23-7324, 2023.

In the current energy transition, many governments have made plans to reduce energy production by coal. Therefore, Germany has set the ambition to close coal mines in 2030 (Wehrmann et al., 2021). The many years of mining produced a large amount of mine waste, used as a landfill. In the TRIM4mining project, a consortium of industry and academia investigate the environmental impact of coal mine waste. The samples used for this study are from the Schleenhein and Profen lignite mines in East Germany. Throughout the project, various samples were collected of specific lithologies in the mine, lithology mixtures and two drill cores of 50 meters drilled on the mine waste dump.

This study focuses on testing the applicability of Fourier Transform Infrared Spectroscopy (FTIR) for analysing lignite waste material samples. Here, the data is discussed regarding the liquefaction potential, acidification potential, secondary recovery, and heavy metal concentration. An additional abstract is submitted to present the result on how FTIR data can be used for regression modelling with the aim to integrate geochemistry and spectral infrared data for mine waste characterization.  

Preliminary results have shown clear spectral features that can be used to distinguish coal, silt, sand and clay material. Every meter of the waste material is measured to allow a core logging analysis. Besides the interpretation of the coal, clay, sand and silt fraction, various data analysis techniques are applied to interpret smaller variations in the FTIR data, that could be of interest to the environmental impact of coal mine waste.

How to cite: Kamps, O., Maghsoudi, F., Desta, F., and Buxton, M.: Fourier Transform Infrared data analysis to analyse the environmental impact of coal mine waste, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16221, https://doi.org/10.5194/egusphere-egu23-16221, 2023.

Due to technological advances demand for rare earth elements (REEs) have been increased. However, exploration or secondary recovery of these elements has not been done properly except for a few countries in the world that supply REEs, such as China. Many studies using inductively coupled plasma mass spectrometry (ICP-MS) have been conducted on analyzing, and finding relationships of the REEs with other elements. Although these laboratory measurements are accurate, they are expensive and time-consuming. Also, a methodology or a model that helps geologists estimate the REE contents in situ is missing. Therefore, we combine the results of ICP with Fourier-Transformed Infrared (FTIR) spectroscopy to model and predict the REE contents within soil samples of mine waste dumps. The FTIR is a portable instrument that has shown many potentials in measuring mineral and organic material absorption features within the Mid-IR range.

Several studies have indicated the potential of lignite mines in the enrichment of REE minerals. Therefore, we have chosen two lignite mines: Profen and Schlenheein within Germany.  During the Miocene, different sub-tropical plants were developed within catchment basins. The decreased plants were covered by soil and glacial during the ice age. Then, the decreased plants sunk into swamps and decomposed into peats. Two parameters of ground heat and pressure led to the H, O, and nitrogen removal and formation of coal seams at the end of the Tertiary.

From the Profen area as our model training area, some of the thirteen samples (70% of the data used for training and 30% for testing), and from the Schlenheein area as our testing area, some of the hundred samples (all data were used for testing and validation) were collected from different waste dumps. The samples were used to collect the FTIR spectra and ICP-MS, and X-ray Diffractograms (XRD). The FTIR spectra were interpreted and validated with the XRD outputs. A matrix consisting of FTIR wavenumbers and their corresponding reflectance value, and ICP elemental content were created. The REEs were considered as the target parameters for modeling and FTIR wavenumbers were used as input parameters for modeling using stepwise multiple linear regression (SMLR). The SMLR models were investigated by checking the corresponding molecular bands assigned to the wavenumbers within the models and ensuring mineralogical sensibility. For the evaluation of the models, coefficient determination (R²) and root-mean-square error (RMSE) were computed. Finally, the models were applied on the testing data of the Profen area to assess their performances. Finally, the models were applied on the Schlenheein area and assessed.

The results showed that Ti has a high correlation with Y and other REEs (approximately 0.7). Also, the presence of titanite was confirmed by the XRD as titanite. Therefore, titanite is the main source of REEs within the waste dumps which was identifiable via the FTIR wavenumbers. The Profen Y model showed an R² of 0.6 for training and testing and 0.55 for the Schlenheein area. The models showed that the FTIR is a powerful tool to quantitatively predict REE contents with an acceptable R² and RMSE.

How to cite: Maghsoudi Moud, F., Kamps, O., Desta, F., and Buxton, M.: Multi-sensor approach for modeling rare earth elements within the lignite waste dumps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16360, https://doi.org/10.5194/egusphere-egu23-16360, 2023.

Carbon dioxide, which is a direct product of the combustion of fossil fuels is the main component that enhances the greenhouse effect on Earth. For years, solutions have been developed to reduce the carbon dioxide present in the atmosphere. One of the methods of CO₂ reduction is the mineral carbonation of rocks and anthropogenic materials. As a result of the reaction of silicates with CO₂, new carbonate minerals that are stable under surface conditions are formed. Ultramafic rocks are considered one of the best substrates for mineral carbonation with the experiments showing relatively high carbonation efficiency. This is because they contain abundant Mg-rich minerals (olivine, serpentine) that readily react with CO₂-rich fluids to form Mg-carbonates and silica. However these rocks contain also high abundances of metallic elements, in particular Ni, Cr, and Co, that may be mobilized during the carbonation experiments. This presentation aims at the characterization of selected ultramafic mine waste, in terms of the metallic element content. The goal of our research is to answer the question of whether it is possible to simultaneously bind both CO₂ and metallic elements using mineral carbonation experiments.
We have chosen three types of ultramafic rocks for our study, two are from abandoned quarries and the third is a mine waste accompanying magnesite exploitation. Their chemical composition is characteristic of ultramafic rocks with high contents of silica and magnesia (both up to 40 wt %), with minor Fe₂O₃ and alumina (up to 10 and 3 wt % respectively). Metallic element content reaches values of up to 3,400 mg kg^-1 for Cr, 2,500 mg kg^-1 for Ni, and 125 mg kg^-1 for Co. Two rocks represent partially serpentinized peridotites, whose main minerals are olivine and serpentine. The third rock is serpentinite, composed almost exclusively of serpentine group minerals. The minor phases in all the rocks are chlorite and spinel group minerals, with variable chemical compositions ranging from magnesiochromite through Cr-magnetite to magnetite. Peridotites contain amphiboles as minor components whereas carbonates (dolomite and magnesite) and sulfides (mainly Ni-Fe sulfides) were identified as accessory minerals in all the samples. The main Cr-bearing phases are the spinel group minerals, in the case of Ni these are serpentines and olivines, while Co is mainly concentrated in sulfides. Bulk chemical analyses of magnesite veins, naturally occurring in one of the quarries, revealed up to 250 mg kg^-1 of Ni, and up to 3 and 5 mg kg^-1 of Cr and Co, respectively. Although this indicates that magnesite has the potential to structurally incorporate Ni, further investigations are required to constrain the incorporation mechanism and the potential for the immobilization of Cr and Co in carbonate minerals.
Acknowledgment
The work is funded by the National Science Centre, research project No. 2021/43/B/ST10/01594.

How to cite: Kierczak, J., Cieślik, B., Pietranik, A., Łacińska, A., and Bateman, K.: Ultramafic mine waste - potential material for CO2 storage and metallic elements immobilization, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5427, https://doi.org/10.5194/egusphere-egu23-5427, 2023.

Extractive waste (EW), including tailings, are produced in large quantities during mining activities.

In recent years, the linear economic model (based on “take-use-and-throw” approach) has been replaced by a circular approach, in which even waste and extractive residues acquire importance through sustainable use and recovery.

The use and recovery of EW shows also positive technological (in term of technological innovations), economic and social (in terms of new expertise and skills linked to sustainability), and environmental impacts (to be evaluated and faced to reduce the ecological footprint).

The use and recovery of EW takes place through the application and development of innovative protocols linked to waste exploitation (sustainable and environmentally friendly), i.e. BAT, which aim at the technological and process improvement of the activities and at the production of renewed, highly performing green materials. Mining waste and tailings, if suitably characterized, can be used to improve and make sustainable the works connected to the management of mining activities.

The qualitative-quantitative characterization of EW is essential not only for any subsequent reuse but also for assessing the extent of environmental impacts (AMD, dust, high concentrations of heavy metals, etc.) in the various matrices and risk to human health and the environment.

The application areas of use vary according to the type of waste and mining tailings, the morphological characteristics of the deposits, and the geological, geomorphological and logistic context of the area.

In this study, some examples of sustainable use of tailings and mining waste are presented (i.e. use of calcareous tailings to reduce acid drainage and the production of artificial substrates for environmental rehabilitation, waste for mining backfills, waste/landfill waste recovered for extraction RM/CRM, etc.). Further to this, positive impacts on the economic, environmental and technological/social level are also analysed. The latter actions, together with energy saving and the adoption of appropriate financial instruments, contribute to the transition of mining activities into "sustainable mining".

How to cite: Dino, G., Mancini, S., Casale, M., and Lasagna, M.: Use and recovery of mining waste and tailings for sustainable management of works related to extractive activities, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6013, https://doi.org/10.5194/egusphere-egu23-6013, 2023.

The extraction and processing chain of ornamental stones involves a long trail of waste throughout the process. In fact, about 20-22 % of the original block becomes waste in the cutting operations [1], and it goes up to 75 % of the excavated material when considering the entire chain from extraction to sawing, cutting, and polishing [2]. These percentages are higher in leuco-granite quarries as they are often crossed by dikes and small pegmatite intrusive bodies which are landfilled due to aesthetic defects that make them unusable in the context of ornamental stones.

The waste generated in the context of quarrying activities produces significant landscape and environmental problems due to the high volume and the possible presence of rare metals (Critical Raw Materials - CRMs) that can be mobilized and diffused in the hydrosphere and biosphere. In fact, massive accumulations of waste strongly impact the territories hosting the quarries due to land consumption and as possible sources of pollution [3].

The region of Sardinia (Italy) is the main producer of ornamental granite, with currently more than 350 active and inactive quarries, and huge amounts of waste from granite processing have accumulated in quarry areas throughout the region and these quarries are also near archaeological and landscape interest areas.

This paper focuses on a quarry located in the municipality of Buddusò, in the quarrying district of northern Sardinia. In this quarry, which has been active for over forty years, massive waste deposits have been created and can be seen a few km away from the site.

The aim of this work is to characterize from a geochemical and petrographic point of view the granite waste coming from the quarry and the products obtained through the processes of crushing and gravitational and magnetic separation of the minerals operated on such waste. This is to evaluate the possibilities of recycling granite waste for possible use in the context of the ceramic industry and to explore the possibility of extracting REE since this waste is rich in allanite (rare earth epidote).

The results of the analyses highlighted a rather homogeneous chemical-mineralogical composition of the samples taken from the various landfills present in the quarry under study.

As regards the results of the analyses carried out on the products obtained through the working processes on granite scraps, they have highlighted a high potential of these materials for possible use in the context of the ceramic industry. In fact, the composition of these products showed very low Fe₂O₃ content (< 0.35 %) and falls within the compositional ranges proposed by Fabbri & Fiori [7] of raw materials for mixtures to produce stoneware.

References

• Rana, A. (2016). J. Clean. Prod., 135.
• Silveira L.L.L. et al. (2014) In Tecnologia de Rochas Ornamentais: Pesquisa, Lavra e Beneficiamento; CETEM/MCTI: Rio de Janeiro, Brazil; Chapter 7.
• Lokeshwari M. & Jagadish, K.S. (2016). Procedia Environ. Sci., 35.
• Fabbri, B. & Fiori, C. (1985). Min. Petr. Acta, 29.

How to cite: Vaccaro, C., Aquilano, A., Soro, G., and Marrocchino, E.: Geochemical and mineralogical characterization of granite quarry scraps for their valorization as raw materials for ceramic products., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3582, https://doi.org/10.5194/egusphere-egu23-3582, 2023.

At the end of their activity, quarries require environmental recovery in order to ensure a new balance between the quarry site and its physical and ecological context. Moreover, the activities of the ornamental rock extraction produce a large amount of extraction waste which profoundly modify the site's topography in an increasing way as the accumulations are formed progressively during the quarrying process. These wastes can be either recycled as secondary raw materials (e.g., in the context of the ceramic industry) or reused within the quarry site to mould a new topography and a new landscape as a result. Earth sciences and landscape architecture should constitute the disciplinary basis on which to develop the recovery project associated with the supply of secondary raw materials and the environmental improvement of the quarry site. This contribution discusses the case study of the Buddusò granite quarry (northern Sardinia, Italy), where a design methodology based on topology alteration of the site was applied. Through 3D survey and parametric design, it is possible to calculate the waste volumes within the excavation site and estimate how much and in what way the waste material can be recycled and reused. The first phase of the process consists of taking orthophotographic images by drone with subsequent georeferencing through G.P.S. points acquisition. After processing the acquired data, the topography of quarry volumes is recreated in an explorable 3D model. The last phase concerns the design management of the site topology through the application of parametric design tools. The objective is to create an adaptive project based on parameters such as: the balance between excavation and fill volumes; the recycling potential of waste material; the dynamics of water runoff; the ecological and ecosystem site potential; the site accessibility. The presented design methodology can be carried out either in the pre-quarry phase and/or during the quarry's operation, which allows an a priori assessment of what the future landscape will look like as a consequence of quarrying activities and subsequent site recovery. In practical terms, the presented methodology become a preliminary tool for the assessment of landscape evolution scenarios and ensures that the extraction cycle can be completely closed by reintegrating waste volumes into the recovery process. 

How to cite: Tinti, L., Lobosco, G., Medici, M., Aquilano, A., Emanueli, L., and Vaccaro, C.: POST-QUARRY LANDSCAPE. 3D representation and topology alteration as a tool for landscape recovery and secondary raw material procurement in the context of granite quarries., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12445, https://doi.org/10.5194/egusphere-egu23-12445, 2023.

The improvement of safety conditions of unstable rock slopes can be achieved through the use of explosives, for the removal of unstable rock elements. This technique is often applied because, most of time, drill and blast operations, where they can be used, are cheaper and faster than other techniques and require less subsequent maintenance interventions.

When the activity is performed in an area that can be reached by vehicles (quarry area, slope above a road, etc…) it is possible to recover the blasted material.

Depending on the size of the unstable element to be removed, this kind of operations often lead to the production of large quantities of blasted rocks, which most often ends up at landfill or is marginally reused in unqualified manner (construction of temporary tracks, filling voids left by extractive activity, etc…).

Reusing blasted rocks can offer several benefits: more sustainable engineering practices, economic, environmental and social benefits; in particular, this way of operating can preserve natural resources and prevent the production of unwanted waste. As a rule, on-site and nearby-site reuse is preferred to meet sustainable goals. Specific cases where blasted material has been adopted for both slope protection and final rehabilitation works, in a quarry area, can be mentioned.

Unfortunately, due to unclear legislation, lack of technical data and extreme variability of the materials produced (for instance quantity, size and physical properties), the use of blasted material is not common: It can be estimated that only 20-30% of these materials are currently reused properly.

To improve this practice, the type of reuse must be a design goal since the beginning of the planning phase.

According to the quality of the rock mass and the type of blasting, different by-products can be obtained, i.e. armour stones to be applied in hydraulic engineering works, gabion stones, drainage stones and crusher run as a mix of different types of aggregates, that can be employed as paver layer on road construction.

When ornamental stone quarries are involved, hard rock fragments are obtained for high mechanical performances.

The main purpose of blasting demolition of unstable rock elements, as mentioned, is to improve the safety conditions of the site, depending on local features, as well as by the safety of the workers, that can force the blasting scheme geometry and firing and impose important limitations on the operating techniques.

Two case studies will be presented, both in the Verbano-Cusio-Ossola (VCO; Piemonte - NW Italy) extractive area; they show how the blast design can be arranged to obtain different fragmentation and greater quantities of a specific by-product, according to the local needs and specific reuse.

Key words: by products, blasting, muck reuse, solid waste, slope protection.

How to cite: Casale, M., Dino, G. A., and Oggeri, C.: Reuse of by-products coming from blasting of unstable rock elements., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8606, https://doi.org/10.5194/egusphere-egu23-8606, 2023.