Search Results (1,315)

Mitigating climate change through the reduction of atmospheric CO₂ emissions remains a critical global priority. Solid adsorbents, particularly shales, have become promising options for CO₂ storage due to their favorable structural and chemical properties. In this study, a solid sorbent was developed by pyrolyzing shale at 800 °C under a nitrogen (N₂) atmospheric condition, yielding spent shale. The key physicochemical properties influencing CO₂ sorption were characterized using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Brunauer–Emmett–Teller (BET) surface area analysis, and Temperature-Programmed Desorption (TPD). Mineralogical analysis revealed the presence of quartz, feldspars, clays, and carbonate minerals. The spent shale exhibited surface areas of 30–34 m²/g and pore diameters ranging from 3 to 10 nm. TPD results confirmed the presence of active adsorption sites, with a maximum CO₂ sorption capacity of about 1.62 mmol/g—surpassing several commercial sorbents. Adsorption behavior was best described by the Sips and Toth isotherm models (R² > 0.99), indicating multilayer and heterogeneous adsorption processes. Kinetic modeling using both pseudo-first-order and pseudo-second-order equations revealed that CO₂ uptake was governed by both diffusion and chemisorption mechanisms. These findings positioned spent shale as a low-cost, efficient sorbent for CO₂ storage, promoting circular resource utilization and advancing sustainable carbon management strategies. This novel shale-derived material offers a competitive pathway for carbon capture, storage, and sequestration applications. Full article

Carbon Capture and Storage (CCS) is a key technology for achieving carbon neutrality goals. Relevant foreign research began in the 1970s, but overall it remains in the exploration and demonstration stage. Clarifying the geological parameters and characteristics of reservoir–caprock systems in CCS projects is of great significance to the effectiveness and safety of long-term storage. By reviewing 15 typical global CCS projects, this paper identifies that ideal reservoirs are gently structured sandstones with few faults (characterized by high porosity, high permeability, and large scale, which are conducive to CO₂ diffusion) or basalts (which can react with CO₂ for mineralization, enabling permanent storage). Caprocks are mainly composed of thick mudstone and shale; composite caprocks consisting of multi-layer low-permeability formations and tight interlayers within reservoirs have stronger sealing performance. Additionally, they should be far from faults, and sufficient caprock thickness is required to reduce leakage risks. Meanwhile, this paper points out the challenges faced by CCS technology, such as complex site selection, limitations in long-term monitoring, difficulties in designing injection parameters, and challenges in large-scale deployment. It proposes suggestions including establishing a quantitative site selection system, building a comprehensive monitoring network, and strengthening collaborative optimization of parameters, so as to provide a basis for safe site selection and assessment. Full article

Tight gas reservoirs are characterized by low porosity, low permeability, and strong heterogeneity. CO₂ flooding, as an important approach for enhancing gas recovery while achieving carbon sequestration, is often restricted by gas channeling. Based on the sandstone reservoir parameters of the Shihezi Formation in the Ordos Basin, a two-dimensional fracture–matrix coupled numerical model was developed to systematically investigate the effects of fracture number, fracture inclination, fracture width, injection pressure, and permeability contrast on gas breakthrough time and sweep efficiency. A second-order regression model was further established using response surface methodology (RSM). The results show that a moderate fracture density can extend breakthrough time and improve sweep efficiency, while permeability contrast is the fundamental factor controlling gas channeling risk. When the contrast increases from 0.7 to 9.9, the breakthrough efficiency decreases from 88.5% to 68.9%. The response surface analysis reveals significant nonlinear interactions, including the coupled effects of fracture number with fracture width, injection pressure, and inclination angle. Under the optimized conditions, the breakthrough time can be extended to 46,984 h, with a corresponding sweep efficiency of 87.7%. These findings provide a quantitative evaluation method and engineering optimization guidance for controlling CO₂ channeling in tight gas reservoirs. Full article

To enhance the support capacity of cemented paste backfill (CPB) in goaf areas and its ability to sequester CO₂, steel slag and ethylenediaminetetraacetic acid (EDTA) were incorporated into gangue-based cemented backfill materials. A stress–carbonation-coupled reaction system was employed to carbonate the CPB, and the effects of steel slag and EDTA on compressive strength, CO₂ uptake, and microstructure were studied. The findings indicate that steel slag remarkably enhanced the performance of the CPB, with both strength and CO₂ uptake initially increasing before declining as steel slag content increased. The optimum performance was achieved at a steel slag content of 10%. The incorporation of EDTA further enhanced the compressive strength and CO₂ uptake, with the best results at 0.5 g/L. Microstructural analyses demonstrated that steel slag increased the availability of Ca²⁺ and Mg²⁺ in the cement paste system, while EDTA accelerated their leaching, promoted hydration products, and catalyzed carbonation via chelation. However, excessive steel slag or EDTA reduced hydration products and deteriorated material performance. This work may provide a reference for enhancing the properties of CPB and promoting the efficient utilization of coal-based solid wastes. Full article

This article provides a comprehensive review of the chemistry, production technology, and utilization of nanolime. Particular attention is given to the synthesis of Ca(OH)₂ nanoparticles through both bottom-up and top-down approaches, highlighting how modern techniques enable precise control of particle size, morphology, and stability. The physicochemical properties of nanolime are discussed in relation to its role as a highly reactive, multifunctional additive, i.a., for cementitious systems, asphalt, and autoclaved products. Its applications are explored with emphasis on performance improvement in construction engineering, including enhanced strength, durability, self-healing potential, and compatibility with low-carbon binders. Beyond construction, nanolime is also examined as a material with relevance to environmental protection, CO₂ sequestration, and heritage conservation. The review demonstrates that nanolime is a versatile and strategic material whose properties can be tailored to specific engineering needs, though challenges such as agglomeration, carbonation control, scalability, and long-term durability remain. Future research directions are outlined, focusing on sustainable production methods, functional integration into next-generation binders, and cross-disciplinary applications. Full article

This study evaluated the ability of microalgae to produce carbonate minerals through CO₂ uptake, in comparison with abiotic, direct chemical synthesis through CO₂ absorption. A freshwater microalga (Synechococcus elongatus) isolated from garden soil in East Anglia, UK, was cultivated under laboratory conditions with CO₂ injection to generate a bicarbonate-rich aqueous solution, in which Fe²⁺, Mg²⁺, and Ca²⁺ ions were added to facilitate carbonate formation. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses revealed distinct morphologies and mineral types. The algae-based process precipitated calcite, siderite, magnesite, and dolomite, whereas the abiotic process yielded, respectively, calcite, siderite, high-Mg calcite and nesquehonite. Biogenic minerals were finer and more morphologically diverse than their abiotically formed counterparts. The results indicated that microalgae produced 0.21 mol/L of calcium carbonate, compared to 0.51 mol/L obtained through abiotic CO₂ sequestration, and a comparable yield of about 0.25 mol/L reported for Sporosarcina pasteurii-induced precipitation. Acid resistance tests showed that algae-induced minerals had similar or improved resistance to acidic conditions compared to minerals formed through abiotic CO₂ consumption. Overall, despite slower kinetics, algae-induced carbonate precipitation offers advantages for soil stabilization by biocementation in the context of environmental sustainability, climate change mitigation and circular economy. Full article

The Global Cement and Concrete Association (GCCA) estimated that by 2050, 36% industry-wide sustainable value will be created, which includes sequestering CO₂ into the cement and concrete industry to produce commercially feasible high-value products. Direct utilization of CO₂ in the cement and concrete industry, which utilizes natural and sustainable materials, is gaining momentum. Naturally occurring mixtures of hydro magnesite and huntite are important industrial minerals which, upon endothermic decomposition over a specific temperature range, will release water and CO₂. This unique chemistry has led to such mixtures being successfully utilized as fire retardants, replacing aluminum hydroxide or Alumina Tri-Hydrate (ATH). Despite the developed marketplace for magnesium-based fire-retardant products, there is little mention of CO₂ mineral carbonation methods, which attempt to recover and convert magnesium from natural seawater or industrial waste into oxides or carbonates as part of the carbon sequestration initiative. The hypothesis to be proven in this work states that if the process of seawater mineral carbonation is prematurely quenched, Mg²⁺ ionic species in seawater adsorbed on the calcite lattice formation will be trapped and therefore recovered in various oxidized forms, such as magnesium oxides, magnesium hydro magnesite, and magnesium carbonate precipitates. A novel method to recover magnesium Mg²⁺ ions from seawater was successfully explored and documented; as such, from an initial concentration of 1250 ppm Mg²⁺ in raw seawater, the average concentration of spent Mg²⁺ ions after the reaction was as low as 20 ppm. A very efficient near-total recovery of Mg²⁺ from the seawater into the solid precipitates was recorded. Subsequently, the process for continuous seawater mineral carbonation for the production of magnesium/brucite/huntite products was successfully proven and optimized to operate with a 30 s reaction time, a dynamic feedstock concentration, [CaO] at 1 gpl in seawater and a room temperature reaction temperature (30 °C), where the average yield of the fire-retardant magnesium-based compounds was 26% of the synthesized precipitates. Approximately 5000 g of the hydro magnesite materials was molded into a fire-retardant brick or concrete wall, which was subjected to an accredited fire performance and durability testing procedure BS476-22:1987. There were encouraging results from the fire resistance testing, where the fire-retardant material passed BS476-22:1987, with performance criteria such as physical integrity failure, the maximum allowable face temperature, and a minimum duration before failure, which was up to 104 min, evaluated. Full article

Residual oil zones (ROZ) arise under the oil–water contact of main pay zones due to diverse geological conditions. Historically, these zones were considered economically unviable for development with conventional recovery methods because of the immobile nature of the oil. However, they represent a substantial subsurface volume with strong potential for CO₂ sequestration and storage. Despite this potential, effective techniques for assessing CO₂-EOR performance coupled with CCUS in ROZs remain limited. To address this gap, this study introduces a machine learning framework that employs artificial neural network (ANN) models trained on data generated from a large number of reservoir simulations (300 cases produced using Latin Hypercube Sampling across nine geological and operational parameters). The dataset was divided into training and testing subsets to ensure generalization, with key input variables including reservoir properties (thickness, permeability, porosity, Sorg, salinity) and operational parameters (producer BHP and CO₂ injection rate). The objective was to forecast CO₂ storage capacity and oil recovery potential, thereby reducing reliance on time-consuming and costly reservoir simulations. The developed ANN models achieved high predictive accuracy, with R² values ranging from 0.90 to 0.98 and mean absolute percentage error (MAPRE) consistently below 10%. Validation against real ROZ field data demonstrated strong agreement, confirming model reliability. Beyond prediction, the workflow also provided insights for reservoir management: optimization results indicated that maintaining a producer BHP of approximately 1250 psi and a CO₂ injection rate of 14–16 MMSCF/D offered the best balance between enhanced oil recovery and stable storage efficiency. In summary, the integrated combination of reservoir simulation and machine learning provides a fast, technically robust, and cost-effective tool for evaluating CO₂-EOR and CCUS performance in ROZs. The demonstrated accuracy, scalability, and optimization capability make the proposed ANN workflow well-suited for both rapid screening and field-scale applications. Full article

Enhanced Rock Weathering (ERW) is a promising carbon dioxide removal (CDR) strategy that accelerates mineral dissolution, sequestering atmospheric CO₂ while improving soil health. This study builds on prior applications of soil calcimetry by investigating its ability to resolve short-term carbonate fluxes and rainfall-modulated weathering dynamics in wollastonite-amended croplands. Conducted over a single growing season (May–October 2024) in temperate row-crop fields near Port Colborne, Ontario—characterized by fibric mesisol soils (Histosols, FAO-WRB)—this study tests whether calcimetry can distinguish between dissolution and precipitation phases and serve as a proxy for weathering flux within the upper soil horizon, under the assumption that rapid pedogenic carbonate cycling dominates alkalinity retention in this soil–mineral system. Monthly measurements of soil pH (Milli-Q and CaCl₂) and calcium carbonate equivalent (CCE) were conducted across 10 plots, totaling 180 composite samples. Results show significant alkalinization (p < 0.001), with average pH increases of ~+1.0 unit in both Milli-Q and CaCl₂ extracts over the timeline. In contrast, CCE values showed high spatiotemporal variability (−2.5 to +6.4%) without consistent seasonal trends. The calcimetry-derived weathering proxy, log (Σ ΔCCE/Δt), correlated positively with pH (r = 0.652), capturing net carbonate accumulation, while the kinetic dissolution rate model correlated strongly and negatively with pH (r ≈ −1), reflecting acid-promoted dissolution. This divergence confirms that the two metrics capture complementary stages of the weathering–precipitation continuum. Rainfall strongly modulated short-term carbonate formation, with cumulative precipitation over the previous 7–10 days enhancing formation rates up to a saturation point (~30 mm), beyond which additional rainfall yielded diminishing returns. In contrast, dissolution fluxes remained largely independent of rainfall. These results highlight calcimetry as a direct, scalable, and dynamic tool not only for monitoring solid-phase carbonate formation, but also for inferring carbonate migration and dissolution dynamics. In systems dominated by rapid pedogenic carbonate cycling, this approach captures the majority of alkalinity fluxes, offering a conservative yet comprehensive proxy for CO₂ sequestration. Full article

REDD+ has emerged as a global strategy for reducing CO₂ emissions from deforestation and forest degradation and shows great promise for the Extractive Reserves of the Brazilian Amazon (RESEX). It is essential to assess whether REDD+ projects have effectively contributed to the conservation of these areas over time. To address this issue, we analyzed land use and cover dynamics in the RESEX Rio Preto-Jacundá (Rondônia) and its surroundings from 2004 to 2020 to evaluate the impacts of a certified REDD+ project. The following two trend scenarios were simulated: (i) pre-implementation (2004–2012), projected to 2020, and (ii) post-implementation (2012–2020), projected to 2028. Historical maps were derived from the TerraClass dataset, and future projections were generated using Markov Chains combined with Cellular Automata. Forest conservation was evaluated through structural metrics such as the number, size, and shape of forest fragments, and the type, frequency, and length of boundaries with other land uses, using ArcGIS tools and Patch Analyst. Carbon sequestration was estimated from the aboveground biomass values of primary and secondary forests. The results showed that the REDD+ mechanism did not achieve the expected environmental benefits, with a decrease in carbon stocks over time and potential negative effects on the richness and composition of local flora. Full article

To protect the environment, sequestering CO₂ during the extraction of natural gas hydrates is a highly promising carbon-neutral technology. We investigated methane extraction and CO₂ storage by a combined depressurization and CO₂-injection method. In the seabed environment, the hydrate-forming period is ~300 min. When injecting liquid carbon dioxide into the reservoir, a replacement rate of ~11.1% is insufficient to meet the requirements for extracting methane and sealing carbon dioxide. Increasing the depressurization pressure can increase gas production. However, an excessively large depressurization pressure will cause the permeability damage rate (PDR) to reach 76.40%, which is not conducive to the continuous progress of the project. Increasing the depressurization pressure (7 MPa) and extending the depressurization pressure time (3 h) can effectively increase the final hydrate saturation (HS) and protect the reservoir permeability. This means higher reservoir stability and more sealed carbon dioxide. A new method has been proposed, namely, the coupling of depressurization and CO₂ injection. This method actually extends the depressurization time, resulting in an average reservoir permeability of 1.72 millidarcies, thereby achieving a carbon dioxide storage rate of 27.7%. At the same time, it avoids the repeated implementation of pressure reduction and CO₂ injection, reducing the complexity of the project. Full article

Conflicting priorities between policymakers and local communities often compromise conservation outcomes in landscapes reliant on natural resources. Understanding how diverse stakeholders value ecosystem services (ESs) across coexisting land uses is essential; however, empirical evidence from rural Southeast Asia remains limited. This study examined ES perceptions and priorities among community members (n = 500) and experts (n = 30) within a bamboo forest, rice paddy, and teak plantation in Sangthong District, Lao PDR. A two-step survey methodology was employed: initially assessing ES perceptions to filter locally relevant services using a ≥50% recognition threshold, followed by quantifying priorities for this subset through a 100-point allocation task. The results revealed a systematic divergence in priorities rooted in differing knowledge systems. Communities, grounded in traditional ecological knowledge (TEK), prioritized tangible provisioning and cultural services (e.g., food and raw materials). In contrast, experts emphasized regulating services (e.g., carbon sequestration and hazard regulation) and habitat services (e.g., biodiversity and habitat provision). Distinct “ES bundles” also emerged by land use: bamboo (raw materials and freshwater), rice (food and medicine), and teak (timber/bioenergy and regulating services). Our findings suggest a policy transition from single-objective management toward optimizing landscape-level ES portfolios, alongside institutionalizing participatory co-management that formally integrates local knowledge and enhances ES literacy. Full article

Land-use carbon emissions denote the release or sequestration of greenhouse gases (e.g., CO₂, N₂O) resulting from human land-use activities, with land-use changes exerting a major influence on land-use carbon emissions. Revealing the coupling mechanism between land-use changes and carbon emissions is of crucial theoretical significance for achieving “dual carbon” goals and mitigating global climate change. Based on the land-use change data of Jiangxi Province, this study explored the Spatial–temporal relationship between land-use carbon emissions and land-use changes in Jiangxi Province from 2000 to 2020 using a model of land-use dynamic degrees, a model of land-use transfer matrices, and the IPCC carbon emission accounting model. In this study, the factors influencing changes in land-use carbon emissions were comprehensively analyzed using an LMDI model and the Tapio decoupling model. The results indicated that: (1) Jiangxi Province’s land-use changes show a “two-increase, four-decrease” trend, with construction land and unused land experiencing the most significant shifts, while water, grassland, cropland, and forestland changes stayed near 1%. (2) Net land-use carbon emissions exhibit a rapid then gradual increase, with higher emissions in the north/south and lower levels in central regions. While overall land-use carbon emission intensity is declining, per capita emissions continue to rise. (3) Land-use carbon emission changes are primarily driven by emission intensity, land-use structure, efficiency, and economic level. In Jiangxi, economic growth mainly increases land-use carbon emissions, while land-use efficiency enhancement counters this trend. Jiangxi Province shows weak land-use carbon emission–economic growth decoupling, with land-use carbon emissions rising more slowly than economic growth. This study not only provides a typical case analysis and methodological framework for understanding the carbon emission effects of human–land relationships in rapidly urbanizing regions but also offers a specific scientific basis and policy insights for Jiangxi Province and other similar regions to formulate differentiated territorial spatial planning, promote ecological protection and restoration, and achieve green and low-carbon development pathways under the “dual carbon” goals. Full article

The progressive replacement of conventional plastic films with biodegradable alternatives in agricultural systems has led to the accumulation of diverse plastic residues in soils, exerting documented impacts on microbial-mediated ecological processes. However, systematic investigations into how these residues influence organic carbon (C) turnover and inter-aggregate C flows remain critically lacking. This study investigated the effects of diverse plastic film residues on organic C decomposition dynamics and aggregate-associated C sequestration through a 60-day soil incubation experiment. Two representative plastic film types—conventional polyethylene (PE) and biodegradable polylactic acid + polybutylene adipate-co-terephthalate (PAT)—were incorporated into agricultural soil under contrasting organic matter input regimes: with maize straw addition (St) and without any straw addition. The results demonstrated that, in the absence of maize straw, both PE and PAT residues enhanced native soil organic C (SOC) mineralization. Notably, PAT elevated the cumulative CO₂ emission by 7.4% (P < 0.05) relative to the control. PE slightly reduced the final SOC content but increased the proportion of soil gates (Mi) and silt plus clay (S + C) toward Ma. Conversely, PAT exerted a negligible effect on final SOC content but reduced Ma by 40.9% (P < 0.05) and increased Mi by 33.4% (P < 0.05), driving C redistribution from Ma to Mi. In contrast, with the addition of maize straw, both St + PE and St + PAT treatments reduced organic C mineralization and diminished the increases in SOC content. Specifically, St + PAT decreased the cumulative CO₂ emission by 1.9% (P < 0.05) and lowered the SOC content by 7.1% (P < 0.05) compared to straw addition alone (St). Both St + PE and St + PAT also lowered Ma formation; notably, St + PAT significantly reduced Ma by 33.6% and diminished C flow from Mi and S + C into Ma. In conclusion, biodegradable film residues may impede SOC sequestration and macroaggregate-associated C storage by stimulating the mineralization of native SOC and suppressing organic matter decomposition after crop residue input in soil. These findings provide novel insights into the mechanisms governing SOC turnover and C stabilization via soil aggregation in the context of accumulating plastic wastes. Full article

The influence of stress on gas sorption behavior and sorption-induced swelling in coal is critical for the success of CO₂-enhanced coalbed methane recovery (CO₂-ECBM) and geological carbon sequestration—a key strategy for mitigating climate change and promoting clean energy transitions. However, this influence remains insufficiently understood, largely due to experimental limitations (e.g., overreliance on powdered coal samples) and conflicting theoretical frameworks in existing studies. To address this gap, this study systematically investigates the effects of two distinct stress constraints—constant confining pressure and constant volume—on CO₂ adsorption capacity, adsorption kinetics, and associated swelling deformation of intact anthracite coal cores. An integrated experimental apparatus was custom-designed for this study, combining volumetric sorption measurement with high-resolution strain monitoring via the confining fluid displacement (CFD) method and the confining pressure response (CPR) method. This setup enables the quantification of CO₂–coal interactions under precisely controlled stress environments. Key findings reveal that stress conditions exert a regulatory role in shaping CO₂–coal behavior: constant confining pressure conditions enhance CO₂ adsorption capacity and sustain adsorption kinetics by accommodating matrix swelling, thereby preserving pore accessibility for continuous gas uptake. In contrast, constant volume constraints lead to rapid internal stress buildup, which inhibits further gas adsorption and accelerates the attainment of kinetic saturation. Sorption-induced swelling exhibits clear dependence on both pressure and constraint conditions. Elevated CO₂ pressure leads to increased strain, while constant confining pressure facilitates more gradual, sustained expansion. This is particularly evident at higher pressures, where adsorption-induced swelling prevails over mechanical constraints. These results help resolve key discrepancies in the existing literature by clarifying the dual role of stress in modulating both pore accessibility (for gas transport) and mechanical response (for matrix deformation). These insights provide essential guidance for optimizing CO₂ injection strategies and improving the long-term performance and sustainability of CO₂-ECBM and geological carbon storage projects, ultimately supporting global efforts in carbon emission reduction and sustainable energy resource utilization. Full article