Search Results (834)

Open-pit coal mining in arid and desert regions causes extensive and persistent surface disturbance, yet long-term monitoring of disturbance and backfilling processes remains challenging. Existing time-series change detection approaches can identify spectral changes but provide limited information on mining disturbance types and their evolution pathways. To address this issue, an automated surface disturbance detection method (Auto-SD) was developed for open-pit coal mines in arid and desert environments. This method integrates disturbance-type identification and temporal information extraction using the tasseled cap brightness (TCB) component to characterize changes associated with surface material exposure and accumulation. Using Landsat imagery from 1990 to 2023, Auto-SD was applied to 89 open-pit coal mines in China’s arid and desert regions, achieving an overall classification accuracy of 0.84. The cumulative disturbed area reached 423.10 km², while the internal dumping area reached 94.25 km², indicating limited backfilling recovery. Disturbance intensified after 2006, whereas backfilling lagged behind, forming a trajectory of rapid expansion, delayed recovery, and gradual stabilization. Spatially, mining areas exhibited a progressive transition from external dumping to internal dumping and backfilling. Furthermore, cumulative pit area generally followed an S-shaped growth pattern with mining duration. These findings provide new insights into long-term mining landscape evolution and support ecological restoration assessment and sustainable resource management in arid mining regions. Full article

To clarify the stage-dependent stress superposition in gob-side roadways beneath irregular overlying goafs, the #52109 material roadway was investigated using a MATLAB-based analytical stress-transfer model, key-strata mechanics, FLAC3D simulation, and field monitoring. The analytical results revealed an approximately elliptical “stress-bubble” distribution with a maximum increment of 4.82 MPa beneath the overlying remnant coal bodies and a second roof-induced stress peak of 1.22 MPa at 14.88 m from the adjacent goaf boundary, governed mainly by Sub-key Strata 2 and 3. At the actual vertical separation of 71.5 m between the roof of the #52109 material roadway and the base of the overlying goaf, the two stress-component curves calculated in MATLAB intersected at 59.1 m from the projected boundary of the overlying remnant coal body, defining a site-specific transition between the dominant stress sources. Beyond 59.1 m, the lateral abutment stress induced by the #52107 goaf was dominant; within this distance, the downward-transmitted stress from the remnant coal body increased rapidly and was superimposed on the lateral abutment stress. The analytical and FLAC3D models predicted maximum total vertical stresses of 32.19 and 32.51 MPa, respectively, with a difference of 0.32 MPa (0.99%); the numerical model also qualitatively reproduced the corresponding spatial transition in the stress pattern. The combined results identified the sections 250–485 m and 680–1305 m from the roadway entrance as high-hazard zones. After targeted large-diameter borehole destressing and roof pre-splitting blasting were implemented, field monitoring recorded a maximum side deformation of 77.9 mm, while low-energy seismic events accounted for 94.33% of all monitored events. These findings provide a quantitative basis for hazard zoning and regional pressure relief in gob-side roadways beneath irregular overlying goafs. Full article

Geopolitical disruptions of natural gas supply have repeatedly forced importing countries to reorganize their electricity systems, yet it remains unclear whether such disruptions are followed by movement of structurally different economies toward comparable energy-security and sustainability outcomes. This study compares Germany, a high-income economy exposed to the 2022 curtailment of Russian pipeline gas, with Jordan, a developing import-dependent economy exposed to the repeated sabotage of the Arab Gas Pipeline after 2011, using harmonized generation-mix and carbon intensity data for Germany over 1985–2024 and Jordan over 2000–2022, supplemented by weekly German market data. The generation fuel mix concentration is measured with a Herfindahl-based Supply Concentration Index (SCI), structural change is estimated with segmented interrupted time series (ITS) regressions inferred through Newey–West heteroskedasticity- and autocorrelation-consistent standard errors, and the joint security–sustainability position of each country is summarized with a newly proposed Energy Vulnerability–Transition Index (EVTI) that combines diversification, renewable penetration, and carbon intensity performance. The results show that Jordan’s 2011 disruption was associated with a baseline estimated change in its carbon intensity trajectory from +3.32 to −12.63 gCO₂/kWh per year and with renewable growth of +2.39 percentage points per year from a near-zero base, while Germany’s 2022 disruption was associated with a temporary carbon intensity shock, visible in a coal reactivation index that peaked at 1.26 and a sixfold wholesale price increase, followed by a policy-supported return to the pre-existing decarbonization pathway. The Germany–Jordan EVTI ratio narrowed from 6.5× in 2014 to 1.8× in 2022, and this convergence is robust to alternative component weightings. The findings indicate that geopolitical gas disruptions, despite their high short-run costs, were followed in both contexts by measurable movement toward more diversified and lower-carbon electricity systems, with direct implications for Sustainable Development Goal (SDG) 7. Full article

Underground coal mining can induce deformation and failure of overlying strata and ground surface, which seriously endangers the safety of human life and property. During mining, the immediate roof rock successively experiences initial caving (fixed support on four sides) and periodic caving (fixed support on three sides and free on one side). Different boundary conditions alter the unloading and deformation processes such as cracking and fracturing of immediate roof rock, thereby affecting its subsequent mechanical behavior of compaction and deformation, and resulting in differences in the movement law of overlying strata. In this paper, the numerical simulation method is adopted to investigate the variation laws of unloading and fracturing characteristics of immediate roof rock under initial caving and periodic caving with thickness-width ratio (t/w), length-width ratio (l/w), unloading stress (σ_u) and specimen strength (σ_c), and the corresponding action mechanism is revealed. The fractal evolution law of fractured immediate roof rock obtained from this study can quantitatively evaluate the compaction characteristics of caved rock, provide refined parameter support for surface subsidence prediction and possess guiding significance for stope surrounding rock control engineering. The results show that the fragments formed after the failure of immediate roof rock are mainly block-strip shaped under both first caving and periodic caving conditions. With the increase in the thickness-width ratio, the flexural rigidity of immediate roof rock increases and crack propagation is restrained, so that the particle-size–mass fractal dimension of fragments increases first and then decreases for the two caving modes. The increase in length-width ratio weakens the propagation of secondary fractures and raises the particle size of fragments, while the overall variation in particle-size–mass fractal dimension is small under the two working conditions. As the unloading stress continuously rises, the coupled tension-shear effect inside the rock gradually intensifies, and the failure mode changes from tension-shear failure to global shear failure. Accordingly, both the particle-size–mass fractal dimension and fractal dimension of crack distribution increase first and then decrease under first caving and periodic caving conditions. The increase in the strength of immediate roof rock raises the energy consumption during rock failure, and large-size fragments are more likely to be generated, which reduces the particle-size–mass fractal dimension and increases the particle size of fragments under both caving modes. Meanwhile, internal micro-fractures continuously initiate and propagate with the growth of rock strength. For specimens with relatively high strength, crack propagation is inhibited and the development of secondary fractures is weakened, leading to an evolution trend that the fractal dimension of crack distribution increases first and then decreases. Under identical parameter conditions, the particle-size distribution and crack complexity for first caving are mainly affected by geometric parameters; the particle size of fragments is primarily controlled by specimen strength; and the unloading stress threshold governs the transition of failure mode. For periodic caving, the crack-initiation location is first determined by asymmetric boundary constraints. The thickness-width ratio dominates the particle-size distribution of fragments, and unloading stress as well as specimen strength further regulate the complexity of cracks. Full article

In the context of the new power system, coal-fired units are transitioning into peaking units. This study investigates the combustion characteristics and NO_X emissions of a 600 MW opposed wall-fired boiler within a load range of 50% to 20%, and further analyzes the impact of burner operation modes on boiler performance at the 20% ultra-low load. The results indicate that as the boiler load decreases from 50% to 20%, the average temperature in the primary combustion zone drops from 1634.3 K to 1457.0 K, and the ignition distance extends from 0.228 m to 0.260 m, leading to a significant decline in combustion stability. Notably, at the 20% ultra-low load, although the drop in temperature suppresses the formation of thermal NO_X, the flow short-circuiting caused by the shrinking of the recirculation zone results in pulverized coal particles missing the optimal reduction window; the formation pathway dominated by fuel NO_X causes the NO_X concentration at the furnace outlet to surge to 670.6 mg/m³. Furthermore, the burner operation modes significantly influence boiler performance at the 20% ultra-low load. While ensuring combustion stability, operating the lower-tier burners effectively reduces NO_X emissions by up to 21.6%. Considering both combustion stability and NO_X emissions, prioritizing the operation of lower-tier burners is recommended. This study reveals the underlying mechanisms behind the surge in NO_X concentrations at ultra-low loads of 20% and proposes optimal burner operation strategies, providing a theoretical foundation for the clean and stable operation of boilers during deep peak shaving. Full article

South Africa’s updated Nationally Determined Contribution sets a 2030 emissions ceiling of 420 MtCO₂. Using historical data from 2000 to 2023 and projections to 2050, this study identifies optimal decarbonization pathways by integrating logistic decay model, linear programming, genetic algorithm optimization (Decay–LP–GA), and Pareto analysis. A prior study notes that 2023 emissions lie substantially below the NDC ceiling, leaving 239.1 MtCO₂ of unused carbon space. However, the present study finds that optimized pathways transcend rather than utilize this space, achieving 67–85% emissions below 2023 levels. Notably, aggressive near-term coal phase-out increases 2050 emissions by disrupting efficiency investment, indicating that timing governs long-term outcomes. The optimal strategy therefore prioritizes slow near-term coal reduction (0.69% annually) to allow front-loaded efficiency gains (4.46% annually) through 2035, followed by accelerated phase-out to achieve 96% reduction by 2050. This sequencing reduces cumulative emissions by 8.0% (300 MtCO₂) relative to the LP minimum. The Pareto frontier spans 51.5–92.6 MtCO₂ in 2030 and 52.8–64.2 MtCO₂ in 2050, with all Pareto-optimal solutions requiring coal shares below 40% by 2030, conflicting with Integrated Resource Plan constraints. Consequently, maintaining a ≥40% coal floor raises minimum feasible emissions to 101.5 MtCO₂, generating a 22.8–49.4 MtCO₂ feasibility gap. The findings show that optimal strategy is not to use its remaining carbon space, but to render the 420 MtCO₂ target redundant through front-loaded efficiency gains and strategically timed coal phase-out, providing clear direction for sustainable climate finance. Full article

The global shift toward clean and low-carbon household energy is central to achieving the Sustainable Development Goals and improving welfare in developing countries, yet it also raises distributional concerns about who benefits and who is left behind. Using five rounds of data from the China Family Panel Studies (CFPS) spanning 2014–2022, this study employs a two-way fixed-effects model with province and year dummies and the Bootstrap method to examine the association between cooking energy transition and rural household development resilience. The results show that the share of traditional solid fuels (fuelwood and coal) declined from 56.29% in 2014 to 36.56% in 2022, while the share of fossil gas rose from 22.26% to 39.91%, indicating a transitional stage in rural cooking energy use. Cooking energy transition is positively associated with rural household development resilience. Household education and farmers’ digital literacy are positively associated with both cooking energy transition and household development resilience, suggesting they may be relevant channels. The association is more pronounced among households with a low elderly dependency ratio, poor infrastructure accessibility, and adequate energy affordability, underscoring that the benefits of energy transition are not evenly distributed. These findings highlight the importance of inclusive and differentiated energy policies for ensuring that the gains from clean cooking reach the most vulnerable rural households. Full article

Coal phase-out regions concentrate the distributional risks of the energy transition, yet the tools used to identify energy-poor households in these territories still rely mainly on income and welfare criteria. This study asks whether such criteria can identify the households that suffer. Drawing on a survey of 706 households across six municipalities of Western Macedonia, Greece, the core territory of the national lignite phase-out, we validate a four-item Thermal Stress Index (polychoric ω = 0.885; loadings = 0.71–0.88; no differential item functioning by gender, income, or survey wave) and test nine hypotheses and one descriptive benchmark on prevalence, mechanisms, typologies, and targeting. Winter thermal inadequacy reaches 22.9%, which sits above the 19.0% national EU-SILC figure, reported as descriptive context. Dwelling energy features dominate all socioeconomic predictors of severe thermal stress (pseudo-R-squared 0.482 against 0.024), and no direct tenure association remains once envelope quality is included, while the protective association of income operates primarily through dwelling quality and is not observed across the range of inefficient dwellings. Latent class analysis identifies a hidden energy poverty class, 19.5% of households with severe experiential deprivation, above-average income, and no payment problems. A machine learning targeting audit shows that administrative criteria alone identify severely stressed households and show no discriminative capacity for identifying severely stressed households (AUC = 0.517), whereas adding dwelling and financial-strain information raises discrimination to an area under the curve of 0.938. Finally, in this sample, income-based screening is weakly associated with the households reporting severe thermal deprivation. Full article

The marine and continental transitional facies coal of the Longtan Formation in western Guizhou Province is a key area for coalbed methane (CBM) exploration and development in Southwest China and has numerous resources; however, the exploration and development effects have been average. The development status of the Longtan Formation is such that it presents prominent compatibility issues, challenging production layer combinations, and limited production capacity. On the basis of the “three-step method” of the multicoal seam coproduction combination method and considering the influence of effective gas content and coal seam modification on productivity, a new CBM production seam combination optimization method is developed in which acoustic logging is used to elucidate the coal structure of a coal seam. The combination optimization of production layers in 9 typical wells in the study area was carried out, and the influencing factors and geological insights were discussed. The following conclusions were drawn: Under the multiple influences of the in situ stress mechanism, temperature, and formation pressure, the effective gas content of the coal seam first increases and then decreases, with the highest value occurring at approximately 600 m, and the gas saturation continues to increase. The in situ permeability and transformation permeability first decreased, then increased, and then decreased, and the turning depths were 400 m and 600 m. The productivity potential of the combined mining combination tended to increase with increasing depth. At depths up to 1000 m, a 100 m interval is the optimal combined span, 550–750 m is the enrichment high-permeability window, and it is also the best depth for coal seam joint mining. At a depth of 1000 m, the permeability and effective gas content of the coal seam decreased, whereas the gas saturation and desorption pressure increased, which increased the development potential and research value of the CBM reservoir. Full article

To elucidate the structural evolution of fracture networks around gas drainage boreholes and their controlling mechanisms on grouting sealing performance, a coal seam in the Zhongmacun Mine (No. 2-1 coal seam) was selected as the engineering background. An integrated approach combining borehole camera observation, gray-level co-occurrence matrix (GLCM) texture analysis, and fractal theory was adopted to systematically characterize the development behavior, spatial heterogeneity, and fractal evolution of fracture networks under different stress zones surrounding the borehole. Furthermore, the quantitative relationship between fracture structure characteristics and grouting parameters was explored. Results indicate that three axial stress-related zones are formed, including a stress-relief zone (0–4 m), a post-peak stress concentration zone (4–20 m), and a pre-peak stress concentration zone (>20 m), with fracture development strongly dependent on stress state. Quantitative analysis based on GLCM parameters and their coefficients of variation reveals a progressive transition from highly complex and strongly heterogeneous fracture structures in the stress-relief zone to simpler and weakly heterogeneous characteristics in the pre-peak stress concentration zone. The fractal dimension (D) decreases from 1.847–1.907 to 1.676–1.713 across these zones, consistent with the evolution trends of GLCM metrics. Based on the relationship between fractal dimension and fracture connectivity, a prediction model for the equivalent permeability of fracture networks based on fractal dimension was established, and the quantitative relationship between grouting pressure and fractal dimension, slurry viscosity, and diffusion radius was derived, providing a theoretical method for analyzing the correlation between fracture structure characteristics and grouting parameters. On this basis, a zonal differentiated grouting sealing optimization scheme was proposed, and a theoretical calculation method for grouting pressure and sealing section length based on fractal parameters was established, providing theoretical references and technical support for precise sealing of gas drainage boreholes. Full article

Over the past two decades, the world has experienced a significant and relentless increase in environmental degradation, measured through carbon emissions (CO₂). These emissions have been one of the persistent global concerns. South Africa boosts abundance of natural resources and some of the world’s most substantial mineral deposits, endowments in the form of precious metals, diamonds and gold. The paper aims to examine the impact of socio-economic and energy-related factors on environmental degradation from a South African perspective. Using multivariate annual data spanning from 1991 to 2022, the Autoregressive Distributed Lag Model (ARDL) was employed to determine both short-run and long-run impact of financial development (FD), renewable energy (RE), non-renewable energy (NRE), unemployment rate (UNE), economic growth (GDPPC), and population growth (PoPG) on CO₂ emission. The results show that NRE remains a dominant driver for environmental degradation, while RE is positively associated with emissions under current system conditions. FD exhibits short-run emission-intensity but long-run mitigation effects. The results suggest a need for relevant policymakers to prioritize coal displacement, stimulate economic growth and promote access to green financing, and related technologies and consumption, to enhance and promote environmental quality in South Africa. The conclusion is that South Africa’s energy-economy nexus is still at a transitional stage, where targeted policy intervention and structural reform are essential to accelerate the shift towards a low-emission economy. Future research can extend the analytical depth by exploring asymmetries, disaggregating fossil fuels, and incorporating broader environmental indicators. Full article

The Shendong Mining Area, located in the transition zone between the northern Loess Plateau and the Mu Us Sandy Land, is a representative ecologically fragile region and desert coal base in China. Using Google Earth Engine (GEE) and Landsat imagery from 1999 to 2024, this study constructed a long-term remote sensing ecological index (RSEI) dataset and integrated the Theil–Sen median slope estimator, Mann–Kendall test, and Hurst exponent to examine the spatiotemporal evolution, future trajectories, and multi-stage driving mechanisms of eco-environmental quality (EEQ) at the mining-area and individual-mine scales. At the mining-area scale, RSEI showed pronounced interannual fluctuations and a weak downward trend, characterized by a two-stage, wave-like trajectory with a narrowing amplitude. The mean RSEI and standard deviation decreased from 0.5669 and 0.0855 during 1999–2010 to 0.5182 and 0.0501 during 2011–2024. Moderate and good grades predominated, with lower EEQ in the mining core and higher EEQ in peripheral buffer zones. Across 13 representative mines, ecological quality generally remained moderate but exhibited spatial and stage-dependent heterogeneity, with Liuta Mine showing the greatest variability. Slight degradation was the dominant trend, although local recovery occurred, and Hurst analysis revealed marked spatial differences in future trajectories. RSEI variations in the Shendong Mining Area exhibited pronounced spatial and stage-dependent associations with high-intensity mining, climatic water–heat conditions, topographic background, and ecological governance and restoration processes. No continuous and irreversible overall decline was observed; however, without an independent non-mining control, the findings represent integrated ecological responses within the mining area rather than causal estimates of mining’s net ecological effect. Full article

International oil price volatility poses severe risks to macroeconomic stability and energy security, presenting complex policy challenges for China as it simultaneously pursues economic growth and a low-carbon transition. To bridge the gap between general equilibrium reallocation and transition quality, this study couples an 18-sector recursive dynamic computable general equilibrium (CGE) model with a super-efficiency slacks-based measure (SBM) model to evaluate China’s macroeconomic path and green total factor productivity (GTFP) from 2023 to 2045. We simulate a permanent 200% international oil price shock starting from 2026—conceived as a tail-risk stress test—together with alternative shock scenarios of varying magnitude and persistence (P50, P100, and a five-year temporary variant of P200_5Y), and evaluate four counterfactual policies under the P200 stress-test condition: household transfers (Tran_HG), price regulation (P_REG), structural tax reduction (T_RED), and energy-transition acceleration (Delta_ENE). The shock triggers imported cost-push inflation and a regressive shift toward coal, with the long-run damage governed jointly by shock magnitude and persistence; since GTFP deteriorates monotonically with shock size, the apparent emission reductions under extreme shocks suggest a contraction-driven “efficiency illusion” rather than genuine green improvements. Individually, P_REG and T_RED are effective only as temporary shields, Tran_HG provides the strongest welfare protection but amplifies the high-carbon rebound, and Delta_ENE uniquely improves resilience and green efficiency simultaneously. Building on these results, a combined policy package (COM) is further designed and simulated, which exhibits positive complementarities; it cuts the 2026 GDP loss by about 70%, turns GDP and welfare losses into net gains by 2043 and 2040, respectively, and delivers favorable green-transition outcomes. These findings call for coordinated, phased policy packages in which fiscal space rotates from emergency shields to demand-side repair and, ultimately, to electrification-led structural transformation. Full article

This study presents an integrated multidisciplinary framework for evaluating the reuse of abandoned underground mining infrastructure in Bosnia and Herzegovina as sustainable underground energy storage systems that support the energy transition and decarbonization. The research focuses on the Central Bosnia and Tuzla coal basins, using case studies from the Zenica and Tuzla mining regions to assess Underground Pumped Hydroelectric Energy Storage (UPHES), Compressed Air Energy Storage (CAES), and gravity-based energy storage technologies. The methodology integrates geological and geotechnical characterization, thermo-hydro-mechanical (THM) analysis, thermodynamic calculations, and Multi-Criteria Decision Analysis (MCDA) to evaluate technical, operational, and safety performance. Methane mitigation, smart ventilation, thermal stability, and geomechanical behavior under cyclic loading were also considered. The results indicate that sedimentary coal basins are well suited for UPHES and gravity-based storage systems, with UPHES capacities reaching 1.75 GWh per cycle under optimized conditions, while the separately evaluated solid-mass gravity storage system provides a capacity of 6.15 MWh. Evaporite formations in the Tuzla Basin offer favorable conditions for CAES because of the low permeability and plasticity of halite, enabling storage capacities exceeding several GWh. THM analysis confirmed acceptable geomechanical stability during cyclic operation, while the economic assessment based on the Levelized Cost of Storage (LCOS) demonstrated the long-term competitiveness of Abandoned Mine Energy Storage (AMES) compared with battery technologies. Overall, the findings highlight abandoned mines as strategic low-carbon assets for renewable energy integration and regional post-mining transition. Full article

This study examines the determinants of conditional volatility in energy-sector equity returns and their implications for sustainable energy resilience, energy security, and investment stability. Using a multi-stage econometric framework, the analysis investigates how global financial, commodity, and macroeconomic shocks are transmitted to volatility dynamics across heterogeneous energy companies. The dataset includes domestic and international firms, enabling a comparative assessment of volatility behavior and risk-transmission mechanisms under different market and institutional conditions. The empirical framework combines ARMA models for return dynamics, EGARCH/GARCH specifications for conditional volatility estimation, and OLS regressions with HAC standard errors to identify key determinants of volatility, including market indices, commodity prices, exchange rates, and major geopolitical and economic events. The findings reveal strong volatility persistence across all assets and asymmetric responses to market shocks in most cases. Global market conditions, particularly lagged MSCI World returns, significantly affect volatility, whereas commodity effects related to oil, gas, and coal remain heterogeneous across firms. Event-based regressors show that systemic shocks, including the COVID-19 pandemic and the European energy crisis, increase volatility, although geopolitical effects depend on firm-specific exposure. The results contribute to the sustainability literature by linking energy-sector financial volatility with market resilience, energy security, and stable investment conditions for the energy transition. Full article