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Planned decommissioning of coal-fired plants in Europe requires innovative technical and economic strategies to support coal regions on their path towards a climate-resilient future. The repurposing of open pit mines into hybrid pumped hydro power storage (HPHS) of excess energy from the electric grid, and renewable sources will contribute to the EU Green Deal, increase the economic value, stabilize the regional job market and contribute to the EU energy supply security. This study aims to present a preliminary phase of a geospatial workflow used to evaluate land suitability by implementing a multi-criteria decision making (MCDM) technique with an advanced geographic information system (GIS) in the context of an interdisciplinary feasibility study on HPHS in the Kardia lignite open pit mine (Western Macedonia, Greece). The introduced geospatial analysis is based on the utilization of the constraints and ranking criteria within the boundaries of the abandoned mine regarding specific topographic and proximity criteria. The applied criteria were selected from the literature, while for their weights, the experts' judgement was introduced by implementing the analytic hierarchy process (AHP), in the framework of the ATLANTIS research program. According to the results, seven regions were recognized as suitable, with a potential energy storage capacity from 1.09 to 5.16 GWh. Particularly, the present study's results reveal that 9.27% (212,884 m2) of the area had a very low suitability, 15.83% (363,599 m2) had a low suitability, 23.99% (550,998 m2) had a moderate suitability, 24.99% (573,813 m2) had a high suitability, and 25.92% (595,125 m2) had a very high suitability for the construction of the upper reservoir. The proposed semi-automatic geospatial workflow introduces an innovative tool that can be applied to open pit mines globally to identify the optimum design for an HPHS system depending on the existing lower reservoir. [ABSTRACT FROM AUTHOR]

Rainfall leads to the deterioration of slope stability conditions, while intense rainfall has been commonly associated with landslides on natural or engineered slopes. Deep excavations, typically related to geo-resources exploitation, e.g., in the case of surface mining, are often affected by rainfall events that jeopardize their stability. In this work, rainfall infiltration is directly incorporated in the slope stability analysis; this investigation is currently missing from the literature as mainly empirical methods are used regarding deep excavations. The very deep slopes from lignite mines are employed as typical examples, often reaching 200 m and presenting smooth inclinations and fine-grained soils. A general numerical framework was used; the safety factor's deterministic analysis was supplemented by a Monte Carlo investigation to determine the probability of failure. The importance of the involved parameters—slope geometry, rainfall intensity, and soil properties—was studied through a parametric analysis. Initially, a typical slip surface is presented, relatively deep and reaching from toe to crest. The critical mechanism was the development—after the rainfall—of a smaller and more local than the initial (before rainfall) slip surface. Although the final surface is smaller than the initial one, it can be more than 50 m high denoting a significant hazard. The most influential parameters are rainfall intensity, soil permeability, and slope height. This study can serve as a basis for similar preliminary analysis in practice. Stability and reliability analysis reveals the need to supplement conventional safety factors with the probability of failure for a broader and improved overview. [ABSTRACT FROM AUTHOR]

The development of three-dimensional geological models has proven to be critical for conceptualizing complex subsurface environments. This is crucial for mining areas due to their various hazards and unstable conditions. Furthermore, three-dimensional (3D) models can be the initial step for the development of numerical models in order to support critical decisions and sustainable mining planning. This paper illustrates the results and the development phases of a 3D geological model within the boundaries of the Kardia lignite deposit in western Macedonia, Greece. It also highlights the usefulness of a Geographic Information System (GIS) methodology in the subsurface geological and hydrogeological analysis regarding the Underground Coal Gasification (UCG) methodology. In addition, the work focuses on the integrated geospatial framework that was developed to support the Coal-to-Liquids Supply Chain (CLSC) integration in unfavorable geological settings. A 3D subsurface geological model of the study area was developed to identify a suitable area for in situ coal conversion and UCG considering criteria related to specific coal thickness and depth. In this context, the suggested integrated geomodelling workflow can positively contribute to the implementation of conventional and innovative mining, saving time and reducing the cost to improve the quality of information needed to support decisions related to UCG implementation. [ABSTRACT FROM AUTHOR]

Mining operations can drastically affect the stability of nearby areas. A representative case for this has been the Mavropigi mine, a part of an open-pit lignite mining complex in northwestern Greece. Mavropigi is a vast excavation that has reached 150 m depth and has posed severe challenges and stability issues that caused problems in the area. In 2010, noteworthy surface tension cracks appeared near the excavation, leading to extensive monitoring and countermeasures, while various studies were conducted. The present work aims to revisit the case study of Mavropigi from a different than the previous perspectives. Previous studies were based only on continuum approaches, thus understating or ignoring the effect of discontinuities. Nevertheless, the area has an intense tectonic past and faults that interact with soil movements. In this work, advanced, discontinuous numerical modelling through the distinct element method was used to understand better the role of slope-fault interaction in the case study of Mavropigi and assess the faults' effect on the area's response. The results emphasised the influence of faults on ground movements. The fault's existence increases the impact of the mine operations on the surrounding area significantly and intensifies the possibility of structural damage in nearby constructions. The analysis confirms that the open-pit mine's effect on the surrounding area can be amplified under complex geological conditions, in this case, the presence of faults nearly parallel to the slope inclination. [ABSTRACT FROM AUTHOR]

Featured Application: This work has application in coal and lignite mining excavations and areas, especially during decarbonization and towards a post-coal and post-lignite era. Areas that hosted coal and lignite mines are now being reclaimed—often by installing renewable energy systems—and targets are being set to fulfill new energy principles in relation to energy production, harvesting, and storage. The appropriate and sustainable exploitation of these areas is directly related to their safety and stability. A new perspective is presented for evaluating the slope stability of coal and lignite mines due to rainfall. The case of Greek lignite mining areas is employed to illustrate the methodology. Initially, past climatic records of rainfall are documented and analyzed; rainfall intensity varies from light (0.8 mm/h) to heavy (up to 9 mm/h). Few extreme phenomena are documented, with the maximum intensity being 17 mm/h. Furthermore, climatic projections of future trends are performed with open-access tools to anticipate possible deviations from the baseline conditions. Although the mean temperature is expected to increase, projections show that the past rainfall range is not expected to change. Finally, the effect of rainfall infiltration on the stability of a typical open-pit lignite mining slope is investigated by finite element analysis. The precipitation range defined by the environmental analysis is used. The SF is practically constant for the lower rainfall intensities (0.8–2.2 mm/h). For the higher intensities of 6.4 mm/h, 9 mm/h, and 17 mm/h, the SF decrease is almost the same (from 2.08 to 1.9), with reduction rates of 8.3%, 8.9%, and 9.3%, respectively. The effect of the critical geotechnical properties—groundwater table depth, unsaturated zone properties, and soil permeability—is also examined for a complete evaluation. [ABSTRACT FROM AUTHOR]

In many circles, brown coal continues to be viewed as a cheap source of energy, resulting in numerous investments in new opencast brown coal mines. Such a perception of brown coal energy is only possible if the external costs associated with mining and burning coal are not considered. In past studies, external cost analysis has focused on the external costs of coal burning and associated emissions. This paper focuses on the extraction phase and assesses the external costs to agriculture associated with the resulting depression cone. This paper discusses the difficulties researchers face in estimating agricultural losses resulting from the development of a depression cone due to opencast mineral extraction. In the case of brown coal, the impacts are of a geological, natural-climatic, agricultural-productive, temporal, and spatial nature and result from a multiplicity of interacting factors. Then, a methodology for counting external costs in crop production was proposed. The next section estimates the external costs of crop production arising from the operation of opencast mines in the Konin-Turek brown coal field, which is located in central Poland. The analyses conducted showed a large decrease in grain and potato yields and no effect of the depression cone on sugar beet levels. Including the estimated external costs in the cost of producing electricity from mined brown coal would significantly worsen the profitability of that production. [ABSTRACT FROM AUTHOR]

Surface lignite mines of the Balkan Peninsula face growing pressure due to the CO2 emissions reduction initiatives, rapidly increasing renewable-power capacity, and cheap natural gas. In this frame, the development of a modern mine land rehabilitation strategy is considered as a prerequisite for mitigating the social and economic impacts for the local communities. In the case of western Macedonia lignite mines, these prospects are investigated based on a PEST (political, economic, social, technological) analysis of seven alternative land uses. Urban (industrial) development, green houses, and industrial heritage parks are considered as the most appropriate land uses for mitigating the socioeconomic impacts due to the loss of employments. For the land uses occupying large areas (i.e., agriculture, forestry, livestock farming, and photovoltaic parks), an optimisation algorithm is proposed for determining the mix of land uses that maximise revenue, equity, and natural conservation and minimise investment. The algorithm was applied using the opinions of 10 experts, who were involved in mine land reclamation projects carried out in the western Macedonia region in the recent past. According to the results obtained, photovoltaic parks are rated as a more attractive investment than extensive agriculture, as regards the anticipation of revenues, while livestock farming and forests are necessary to safeguard the ecosystem's functions. [ABSTRACT FROM AUTHOR]

Weather and climate are parameters vital for the development and flourish of human activities, and they crucially affect mining activities. Coal and lignite (brown coal) mining operations can be aided by appropriate weather or stopped by an extreme weather event that might have catastrophic consequences for a mining area. The same stands for closed and abandoned coal mines, as extreme weather events can have severe consequences. This work aims to obtain a comprehensive overview of the climatic conditions by documenting and reporting them in various European coal and lignite mining regions. Specifically, the chosen regions cover Europe from the north (the United Kingdom) to the south (Greece), from the east (Poland, the Czech Republic) to the west (Spain), and through Europe's center (Germany). A climate baseline is created for the chosen regions to serve as a reference for safety assessment and for evaluating future climate changes. Initially, the general climate of each region was evaluated; additionally, an extensive climate database from 1990 to 2020 was created, including the mean annual temperature and precipitation. Mean values and general trends of increase or decrease during the last 30 years are of interest and were compared for all areas. [ABSTRACT FROM AUTHOR]

The large amount of spoil material produced during the mining process imposes a significant economic and environmental liability on lignite producers. In this context, the present paper provides an overview of the geotechnical characteristics of European lignite mine spoil heaps and discusses their significance to the stability of the heaps. In order to achieve this, samples collected from spoil heaps of Polish, Czech and Greek mines are analysed and the results are compiled with data from the literature. A major conclusion drawn is that both physical and engineering properties of spoil heaps indicate a noteworthy variability, which is larger than typical in situ ground material. This is because of the additional factors affecting spoil heap deposition, such as the transportation and dumping method. Furthermore, failure mechanisms and case histories of large instabilities in lignite spoil heaps are critically discussed in order to better understand triggering failure mechanisms. It is concluded that classical assumptions made for natural soil slopes and relevant limit equilibrium models should be cautiously applied to spoil heaps. The challenges associated with numerical and probabilistic modelling of spoil heap stability, such as the inherent spatial variability of spoils and the time-dependent changes in their geotechnical properties, are also critically discussed. Finally, important research gaps in design and analysis of spoil heap stability, such as the absence of appropriate constitutive models developed specifically for spoil materials, are summarised. [ABSTRACT FROM AUTHOR]

Fly ash from two lignite-fed power stations in Greece (Megalopolis and Meliti) has been utilized to synthesize zeolitic materials with upgraded adsorption capacity. Two different siliceous fly ash samples were subjected to hydrothermal treatment at fixed solid/liquid ratio and constant temperature. The zeolitic products have been characterized for their microstructure, chemical, and mineralogical composition by means of SEM, AAS, and XRD, respectively. The primary zeolitic crystals identified were phillipsite and thomsonite, in Megalopolis and Meliti fly ash, respectively. In light of their prospective utilization as liquid-phase sorbents, the specific surface area and porosity of materials were also determined, by means of N 2 -porosimetry. The zeolitic samples were tested for their actual heavy metal-removal capacity by water sampled from active lignite mines in Northern Greece. Artificial aquatic samples with known concentration of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were also tested, showing that the synthetic zeolitic materials are good to uptake a wide variety of potential pollutants with up to 100% efficiency. The efficiency of the synthetic zeolitic materials was comparatively assessed, showing that the more intense the presence of phillipsite in the synthetic materials, the greater the uptake rates for certain groups of trace elements. [ABSTRACT FROM AUTHOR]