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Evaluating carbon footprint pressure (CFP) scientifically and quantifying the environmental impact of economic activities precisely are crucial for informing policies on carbon emission reduction and achieving carbon neutrality in China. This study revealed China's CFP from 2005 to 2021 using data sets of fossil fuel carbon emissions and vegetation carbon sequestration from remote sensing. We investigated the drivers of CFP using LMDI decomposition. Additionally, we used the Tapio model to examine the decoupling of CFP and economic growth. The findings indicate that China's CFP has increased over time and shows a positive spatial correlation. Rapid economic growth and significant population expansion are the primary drivers of the surge in CFP. Conversely, optimizing energy structure, reducing energy intensity, and enhancing ecological quality are key to alleviating the rising pressure on China's carbon footprint. Moreover, we observe a weak decoupling of China's CFP and economic growth. Notably, it is more challenging to achieve an ideal decoupling state in the western region than in the central and eastern regions. • We constructed the CFP index based on remote sensing data. • China's CFP has shown an upward trend over time. • Provincial CFP has positively correlated spatial agglomeration characteristics. • GDP and population size are the main reasons for China's CFP increase. • China's CFP and GDP generally show a weak decoupling state. [ABSTRACT FROM AUTHOR]

Direct air capture, an emerging technology, captures carbon dioxide from the atmosphere and has initiated global demonstrations, highlighting the need for comprehensive operational understanding and effective planning methods. To this end, the paper delves into an in-depth analysis of the operational traits of direct air capture and formulates strategic optimization methods. Firstly, this paper analyzes the operational characteristics of direct air capture, examines the operational mechanisms and energy flow interactions of absorption-based and adsorption-based direct air capture, and reviews the current status of engineering demonstrations of direct air capture technology, highlighting the current technological bottlenecks in project applications. Subsequently, the paper proposes a planning and optimization model for direct air capture loads, incorporating subsidy mechanisms, and develops a dual-layer optimization model aimed at minimizing investment and operational costs. Finally, the effectiveness of the modeling and planning methods proposed in this paper is validated through numerical analysis. Furthermore, the reduction potential of direct air capture is analyzed in conjunction with the theory of carbon emissions flow in the power system. This research aims to provide valuable insights and practical recommendations for the design and demonstration of direct air capture projects. • Direct air capture requires green electricity. • Fixed cost subsidies best support direct air capture due to high initial costs. • Absorption-based direct air capture cuts carbon emissions better than adsorption. [ABSTRACT FROM AUTHOR]

This study proposes a novel system designed to turn waste masks (WM) into hydrogen while aiming at carbon neutrality. The system utilizes plasma gasification to primarily convert WM into syngas, which is subsequently upgraded through water gas shift to enhance hydrogen fraction. To mitigate carbon emissions, carbon capture techniques including monoethanolamine-based carbon absorption and oxy-fuel combustion are incorporated into the system. A high-fidelity model of the designed process is developed in Aspen Plus. Machine learning-driven optimization is applied to identify the optimal operating conditions. Utilizing Gaussian process regression-based surrogate optimization, the system achieves around 0.5 kg CO 2 eq/kg H 2 of levelized emissions per unit hydrogen (LEH) in the reaction stage and the execution time required for optimization is only 4 s, outperforming detailed process models-based optimization. Energy assessment highlights plasma gasification and CO 2 absorption as the primary sources of energy loss. Furthermore, life cycle analysis indicates that CO 2 absorption is the primary contributor to carbon emissions, accounting for approximately 60% of the total emissions. With levelized emissions of 1.27 kg CO 2 eq/kg WM and 5.18 CO 2 eq/kg H 2 , the designed system demonstrates superiority over conventional medical waste treatment and hydrogen production methods. • A waste mask-to-H 2 system with carbon capture is designed and modeled. • Zero direct carbon emission is achieved. • GPR-based surrogate optimization demonstrates high efficiency. • The optimal system shows an emission of 1.27 kg CO 2 eq per kg waste mask. • The system is potential in carbon reduction by comparative analysis. [ABSTRACT FROM AUTHOR]

In this work, an optimal algorithm-based integration of solar thermal energy with carbon capture and desalination processes were proposed. The stripper columns, identified as the most energy-consuming equipment, were designed with constant capacities to ensure practicality and applicability. Results show that, without affecting the power plant's efficiency, using a solvent tank as an energy storage system (scenario-2) increases total CO 2 capture from 45 % to 98 % compared to a part-time solar power system (scenario-1). Utilizing two solvent tanks reduces waste energy from 87 % to 67 % (scenario-3), while achieving 100 % CO 2 capture. Using three different stripper columns (scenario-4) lowers the levelized cost of energy by 20 %. Incorporating an additional multiple effect distillation system (scenario-5) reduces levelized cost of energy and energy loss by 26 % and 74 %, respectively. Approximately 28 % of the total solar energy collected (4.64 × 106 MWh) was used to capture 1.57 × 106 ton.year−1 of CO 2. The remaining energy was used in desalination to produce 9.4 × 106 m³.year−1 of fresh water, increasing overall energy efficiency from 28 % to 81 %, and reducing waste energy to 0.88 × 106 MWh, just 26 % of previous scenarios' waste. • Introducing reasonable integrations of solar energy, CO 2 capture, and desalination units. • Developing an optimal algorithm to maximize the CO 2 capture while minimize the energy loss. • The stripper columns were considered with practical and applicable design. • An effective energy storage system was designed based on a three stage solvent regeneration process. [ABSTRACT FROM AUTHOR]

The energy crisis and rising waste production results in the need for more waste-to-energy solutions. However, capturing fossil-based carbon from waste incineration is crucial. The power consumption and overall impact of the carbon capture process are essential for the identification of the most suitable solution. The aim of this paper is to promote a time-efficient optimization, optimize a membrane-based post-combustion carbon capture process, and quantify its impacts on a waste-to-energy plant for various system configurations with different levels of CO 2 recovery and purity. The proposed robust evaluation of the system with non-linearities resulted in the utilization of genetic algorithms with subsequent verification. Quantifying power consumption allows the comparison of different carbon capture technologies. The results confirm the importance of process optimization, show the influence of individual parameters, and quantify the disproportionate drop in power consumption with decreasing target CO 2 recovery. The power consumption can be as low as 1.14 GJ/tonne of CO 2 for CO 2 purity of 95 % and recovery of 50 % and 1.66 GJ/tonne of CO 2 for CO 2 purity of 95 % and recovery of 90 %. The results also suggest that carbon neutrality can be achieved without compromising the R1 efficiency classification of energy recovery. [Display omitted] • Modeling a multi-stage membrane post-combustion carbon capture system. • Optimization of process parameters using heuristic algorithms. • Analysis of the trade-off between power consumption and total membrane area. • Evaluation of different multi-staged systems configurations. • Assessment of the system's impact on a waste-to-energy plant. [ABSTRACT FROM AUTHOR]

Negative emission technologies (NETs) that perform carbon dioxide removal (CDR) are now part of the decarbonization strategies to reach net-zero emissions. However, NETs will consume resources that will compete with other societal priorities. Thus, NET portfolios that provide a technology mix are better for sustainability and risk management. This study proposes a two-step approach to optimize and check the robustness of NET portfolios, particularly for industrial-scale applications where resource availability fluctuates due to variations in energy, water, and fertilizer supply. The first step involves the process graph (P-graph) framework to generate optimal and near-optimal solution structures at minimum cost. The second step measures the probability of failure of these solutions against resource availability variations through Monte Carlo simulation. By comparing the cost and probability of failure, decision-makers can select a recommended solution that strikes a balance between robustness and cost. The proposed approach is demonstrated in two case studies involving NET portfolios. The first case study investigates the performance of optimal and near-optimal solutions of NET portfolios, while the second case study focuses on bioenergy with carbon capture and storage portfolios using different feedstocks. In both cases, the results show that near-optimal solutions with higher costs but lower probabilities of failure exist, enabling decision-makers to weigh robustness against cost. This study contributes to developing and analyzing robust decarbonization decision support models, addressing the critical need for sustainable and risk-managed NET portfolios. [Display omitted] • A two-step method for generating robust CDR portfolios is proposed. • The first step uses P-graph to generate solution structures. • The second step subjects the solution structures to Monte Carlo simulation. • The method shows the tradeoff between the robustness and cost. [ABSTRACT FROM AUTHOR]

Although carbon capture, utilization, and storage (CCUS) has enormous emission reduction potential and application prospects, it still faces many obstacles and challenges in the actual deployment and promotion process. This study aims to evaluate the spatial suitability of the CCUS layout comprehensively and deeply analyze key development obstacles to provide a scientific basis for the promotion and layout of CCUS. Therefore, this article constructs a combination of Geographic Information Systems (GIS), Decision-making trial and evaluation laboratory (DEMATEL) method, and Interpretive structure model (ISM). Firstly, a comprehensive evaluation is conducted on the suitability of the CCUS layout in China based on GIS technology, identifying high-potential areas. The results indicate that when the threshold is 80 % of the highest score for suitability, a total area of 1.46 million square kilometers is suitable for the CCUS project layout. When it dropped to 60 %, this data increased to 2.04 million square kilometers. These areas are mainly distributed in large basin areas with abundant resources. Secondly, the DEMATEL-ISM analysis framework is improved to systematically identify and analyze the key obstacles that constrain the promotion of CCUS in China. The results indicate that there is a very complex relationship between the obstacles that constrain the development of CCUS, with the fundamental reasons being the lagging technological level and imperfect policies and regulations. Finally, goal-oriented suggestions and response measures were proposed, and targeted analysis was conducted on high-suitability areas. This study constructed an interdisciplinary methodology interpretive model to provide decision support for the CCUS layout and targeted strategies to break through current development barriers and promote the rapid development of CCUS. • An interdisciplinary explanatory model is constructed to analyze the potential of CCUS layout and development obstacles. • Conduct the model validation using China as the empirical research region. • Identify the spatial areas suitable for CCUS layout in China. • Identify the key obstacles that hinder the development of CCUS and conduct in-depth causal and hierarchical analysis. • Policy suggestions and solutions for target-oriented CCUS layout in China are given. [ABSTRACT FROM AUTHOR]

The rapidly increasing global demand for energy poses a significant challenge for the oil and gas industries, necessitating a delicate balance between meeting this demand and reducing greenhouse gas (GHG) emissions. In this context, identifying a method that can effectively convert or utilize GHGs while simultaneously enhancing energy efficiency is crucial. Converting GHG into liquid solvent for enhanced oil recovery (EOR) appears to be an efficacious strategy. Herein, dimethyl ether (DME) as a renewable solvent from GHG capture and utilization with its cyclic pathways is proposed, where a) DME production begins with the capture and conversion of GHGs, potentially resulting in a zero-carbon production process through the integration of renewable energy sources and carbon capture technologies; b) DME acts as a versatile fuel that can be blended with conventional fuels or used in its pure form in engines, substantially reducing transportation emissions due to DME's low carbon content and clean burning characteristics; c) DME's distinctive oil-water phase behavior significantly enhances its efficacy in both heavy oil thermal recovery and light oil water flooding processes; d) the solubility of DME in water mitigates solvent losses, thereby promoting more efficient subsurface and surface solvent recovery operations; and e) DME can be hydrolyzed to produce hydrogen, making it a viable transitional fuel. This perspective concludes by discussing the challenges and opportunities in the energy field to guide future research. These prospects include a) elucidating the renewable and functional properties of DME in innovative EOR mechanisms; b) providing strategic insights for the oil industry on emission reductions in upstream transportation, EOR, and post-EOR solvent recovery through a comprehensive DME pathway; and c) exploring the potential of DME as a transitional solvent for GHG reduction and hydrogen production within the broader context of the energy transition. • DME as a renewable solvent from GHGs with its cyclic pathway is proposed. • DME begins with the GHGs conversion, which may lead to a zero-carbon DME production. • DME's unique oil-water phase behavior enhances its effectiveness in various EOR processes. • The solubility of DME in water enhances its subsurface and surface solvent recovery. • DME can be converted into hydrogen, making it a potential transitional fuel. [ABSTRACT FROM AUTHOR]

The adsorption technology plays a significant role in the carbon capture domain for mitigating the CO 2 emissions, whereas the heterogeneous character is presented in practical adsorption process. In this study, a multi-node thermodynamic model is established for temperature-vacuum swing adsorption (TVSA) considering the end non-uniform adsorption. It shows superior performance for the assessment of practical TVSA cycle compared with lumped model. Through the influence analysis of different operation parameters based on multi-node model, specific exergy consumption increases from 41.6 to 62.4 kJ/mol caused by simultaneous drop of heat consumption and lift of work consumption as feed pressure raises from 1.0 to 3.0 bar. Exergy efficiency ranges between 13.8 % and 15.0 % as CO 2 concentration increases from 10 % to 20 %. However, those under ppm-level are below 0.86 %, presenting the higher exergy consumption but lower desorption capacity represented for direct air capture. The heat consumption of front half part of adsorption bed is 39.7 % higher than the latter one, proving the potential cascaded desorption of subzone heating is superior for reducing the energy consumption. Furthermore, exergy consumption is lifted due to enhancement of work consumption of vacuum pump as vacuum pressure reduces from 1.0 to 0.02 bar, resulting exergy efficiency drops from 19.6 % to 13.4 %. • A multi-node thermodynamic model considering non-uniform absorption was established. • The multi-node model showed better evaluation performance contrasted lumped model. • 39.7 % more heat was needed while desorbing the front half part of absorption bed. • Recovery raised but exergy efficiency dropped due to the reduce of vacuum pressure. [ABSTRACT FROM AUTHOR]

Biomethane power generation, particularly chemical looping combustion technology, has garnered significant attention recently due to its ability to capture CO 2 in situ. In this study, dual bed layers oxygen carriers (DBL) for chemical looping combustion of methane were designed. The LaFe 0.93 Ni 0.07 O 3 oxygen carrier with excellent CH 4 partial oxidation was applied in upper bed layer and low-cost red mud was located into lower bed layer. This tandem reaction showed much higher methane conversion (87.1 %) than that over the single oxygen carrier of red mud (33.9 %) and the mechanically mixed oxygen carrier of LaFe 0.93 Ni 0.07 O 3 and red mud (77.7 %). In addition, the mechanically mixed sample showed a quick deactivation, with the methane conversion dropping 54.2 % after 40 redox cycles due to the encapsulation of the active LaFe 0.93 Ni 0.07 O 3 by red mud, while the double bed system showed high stability in the long-term redox cycle. The limitedly increased crystallite size of LaFeO 3 , as well as completely replenished lattice oxygen, were responsible for superior activity and stability of DBL. This study provides a new strategy to improve the efficiency of chemical looping combustion of methane in fixed bed reactor by tandem reactions over different oxygen carriers with complementary functions in terms of activity and cost. • A tandem reactions strategy for improving the efficiency of chemical looping combustion of methane in fixed bed reactor was provided. • The obvious increased crystal size and coarsening particles can be alleviated by the double bed layer design. • The double bed layer design provides supports for direct utilization of red mud. [ABSTRACT FROM AUTHOR]

This study assesses the impact of conservation agriculture (CA) and weed management practices on the productivity, profitability, energy use, and carbon sustainability of a maize-wheat cropping system. Fifteen treatment combinations, incorporating five tillage methods (conventional-till maize and wheat [CT-CT], conventional-till maize and zero-till wheat [CT-ZT], zero-till maize and zero-till wheat [ZT-ZT], zero-till maize and zero-till plus residue in wheat [ZT-ZTR], and zero-till plus residue maize and wheat [ZTR-ZTR]) and three weed management practices (recommended herbicide [H-H], integrated weed management [IWM-IWM], and hand weeding [HW-HW]), were tested in a strip plot design. The results showed that ZTR-ZTR significantly increased system productivity (6.90 Mg ha−1), net returns, and benefit-cost ratio (BCR; 2.69), compared to CT. However, CT systems had 173 % higher energy use efficiency (EUE) and 170 % higher energy intensity (EI) than CA systems. CA-based treatments used about 15 % direct renewable energy and 85 % indirect renewable energy, while CT systems used 15–20 % direct non-renewable energy and 85–86 % indirect non-renewable energy. Among weed management practices, recommended herbicides (H-H) led to the highest productivity (6.71 Mg ha−1), EUE (9.80), net returns (3003 US$ ha−1), and BCR (3.08), but also higher carbon footprints. This underscores the balance between productivity, energy efficiency, and carbon in agriculture. • CA (ZTR-ZTR) showed 103% higher productivity, 107% profitability, and 108% carbon sequestration vs. conventional practices (CT-CT). • CA system increased productivity by 118%, profitability by 114%, and carbon sequestration by 113% compared to zero tillage (ZT-ZT). • Recommended herbicides (H-H) improved system productivity by 111%, energy efficiency by 106%, and benefit-cost ratio by 118% vs. IWM practices. • Residue incorporation improved soil organic carbon and sequestration vs. no residue and conventional practices. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the influence of CO 2 injection rate and memory water on guest exchange and hydrate reformation behavior in CH 4 hydrate-bearing sediment, using a one-dimensional (1-D) reactor to optimize depressurization-assisted replacement. Increasing the CO 2 injection rate facilitated the rapid sweeping of CH 4 into the pore space of the hydrate-bearing sediment, inducing immediate hydrate reformation and preventing CH 4 re-enclathration in the middle region of the 1-D reactor. Despite dissociating 50 % of the initial CH 4 hydrate for depressurization-assisted replacement, the replacement efficiency converged at around 70 % due to drastically reformed gas hydrates hindering mass transfer. Introducing time intervals between depressurization and replacement to reduce the residual memory effect of water led to delayed hydrate reformation, altering the longitudinal distribution of replacement efficiency in the 1-D reactor. An increase in replacement efficiency toward the outlet was seen, suggesting that improved CO 2 propagation in the hydrate-bearing sediment resulted in a higher CO 2 concentration in the vapor phase at the point of hydrate reformation, in turn enhancing CO 2 storage efficiency in the newly formed hydrates. These experimental results highlight the importance of CO 2 injection rates and time intervals in determining the hydrate reformation behaviors of hydrate-bearing sediments and optimizing the efficiency of depressurization-assisted replacement. [Display omitted] • The influence of CO 2 injection rate and memory water on depressurization-assisted replacement was investigated. • Increasing the CO 2 injection rate reduced CH 4 re-enclathration and thereby improved replacement efficiency. • High CO 2 injection rates led to the rapid recovery of hydrate saturation, which hindered mass transfer. • Introducing time intervals between depressurization and replacement reduced the residual memory effect of water. • Longer time intervals delayed hydrate reformation, thereby enhancing replacement efficiency. [ABSTRACT FROM AUTHOR]

Global climate change has escalated in recent years. Carbon dioxide capture, enhanced oil recovery (EOR)-utilization and storage (CCUS-EOR) has the potential to significantly mitigate greenhouse gas emissions by storing CO 2 underground, all while providing economic advantages. Hence, it is essential to comprehensively understand the CCUS-EOR mechanism and properly forecast its efficiency to mitigate the greenhouse effect. Nonetheless, current intelligent approaches are typically data-driven only and are unable to reveal the CCUS-EOR's physical mechanism. Therefore, we propose an interpretable causal-based temporal graph convolutional neural network (TGCN) framework, called Causal TGCN (CTGCN). The proposed framework integrates the causal graph into TGCN, based on Peter and Clark Momentary Conditional Independence plus (PCMCI+) for causal discovery. We comprehensively evaluated the effectiveness for causal discovery and prediction performance of the CTGCN model for CO 2 -EOR and storage. The findings indicate that the proposed model can appropriately forecast subsurface hydrocarbon production and CO 2 storage capacity. In addition, it can effectively identify the CO 2 -WAG dynamic mechanism and the hydrocarbon causal flow pathways. Consequently, it effectively investigates the potential causal physical mechanisms of CCUS-EOR. It is noteworthy that we discovered that the predictive performance of deep learning methods can be significantly enhanced even if the model is embedded with a static causal discovery graph. To the best of our knowledge, our study is the first to use causal deep learning methods in the field of CCUS to reveal the causal mechanism of CO 2 -EOR and storage. This has immense importance in enhancing our comprehension of the operations of the complex spatio-temporal systems in CCUS and energy engineering in the future. • Causal knowledge is integrated into the DL prediction methods in CCUS-EOR firstly. • CTGCN successfully identify the CCUS-EOR dynamic mechanism and causal pathways. • CTGCN shows excellent performance due to its causal and spatiotemporal dependence. • A template is provided for causal discovery and prediction in energy engineering. [ABSTRACT FROM AUTHOR]

The world has seen an increase in the popularity of renewable-based energy systems. However, because of their erratic nature, fossil fuels cannot be entirely phased out. Utilizing carbon dioxide in greenhouses close to power plants and generating extra power electricity from dissipated thermal energy are appealing strategies that cause us to have a cleaner environment and affordable power electricity. To exploit the high enthalpy of expelled gases from a gas turbine, the gas turbine was coupled with an absorption refrigerant cycle and an organic Rankine cycle and analyzed. Additionally, a deep artificial neural network method was used to calculate all functions in a rapid optimization and accurate 4E analysis. The carbon dioxide emissions subsided from 0.9183 to 0.41 kg CO2/s, and the optimization time improved 257 times after using the trained machine learning model. An adsorption technique for CO2 separation is used for the proposed system because of its lower energy consumption. The maximum exergy and energy efficiencies were attained at 36.71 % and 49.2 %, respectively, and parametric studies are being assessed. Due to increases in harvests and efficiencies, the net annual interest has increased by 21.8 %, up to 22.5 million dollars. • Capturing CO2 from conventional systems integrated into a greenhouse causes a cleaner environment and more crops. • Preventing release of 0.5083 kg CO2/s into the environmental by absorbing it in a greenhouse. • Using a deep learning model of the system decreases optimization time by up to 257 times. • Using excessive energies in the system for greenhouse and optimization increases efficiencies by almost 10 percent and total interest. [ABSTRACT FROM AUTHOR]

To mitigate the significant carbon footprint of traditional ironmaking, this study evaluates four advanced direct reduced iron (DRI) systems powered primarily by biomass. These innovative systems employ chemical looping technology and CO 2 capture techniques to produce carbon-negative iron. Detailed system modeling, optimization, and thermodynamic evaluations have been performed to analyze exergy flows, energy consumption composition and carbon emissions. Results show that chemical looping gasification requires substantial power input for CO 2 removal, whereas systems based on chemical looping hydrogen production (CLHP) naturally capture CO 2 , significantly reducing energy consumption. Without CH 4 -assisted carburization, CLHP-DRI systems demand more energy due to the reverse water-gas shift reaction. Thus, CH 4 -assisted carburization is crucial for maximizing the benefits of CLHP. Compared to the traditional MIDREX process, the CH 4 -assisted CLHP-DRI system achieves a 7.6 % reduction in energy consumption. Environmentally, these systems offer a carbon-negative potential between 0.836 and 1.079 t-CO 2 /t-DRI, demonstrating substantial promise for sustainable iron production. • Four systems for achieving carbon-negative direct reduced iron ore were proposed. • Biomass was used as the main energy source for producing reducing gas and carburizing gas. • Exergy analysis, energy consumption and carbon-negative potential analysis were conducted on each system. • Compared to MIDREX process, the energy consumption can be reduced by up to 7.6 %. [ABSTRACT FROM AUTHOR]

Promoting the widespread adoption of multi-complementary low carbon power generation technologies is a fundamental strategy for attaining carbon neutrality within the electricity sector. In the context of electricity market reform, this study develops an agent-based modeling framework integrated simulation with optimization. The model uses agent-based simulation to analyze annual market dynamics and low-carbon technology diffusion, with a two-stage optimization for energy storage and spot market simulation. The research findings indicate: (1) For different power generation technologies, the spot market can establish differentiated average prices, making the market price of carbon-captured coal power higher than that of conventional coal power, which are advantageous in reducing the subsidies required to promote the diffusion of carbon capture technology. (2) Expanding the spot market scale and implementing differentiated capacity compensation mechanisms both promote carbon capture technology diffusion. Nevertheless, with the marginal clearing mechanism, thermal power holds a average price advantage than renewable energy. Failing to control the growth of thermal power capacity will result in increased carbon emissions. (3) After 2030, energy storage's role in balancing supply and demand grows. Storage capacity should align with renewable energy scale and the regional characteristics of wind and solar resources to prevent overbuilding and stranded assets. [Display omitted] • An agent-based modeling framework integrated simulation with optimization was built. • Explored the impact of electricity spot market on the diffusion of low-carbon technologies. • Spot market establishes diverse electricity prices for various power generation technologies. • Inhibiting coal capacity expansion is more crucial than promoting low-carbon technology. • Energy storage capacity should align with regional characteristics and the transition stage. [ABSTRACT FROM AUTHOR]

CO 2 absorption-microalgae conversion (CAMC) system can be a sustainable technology to achieve low-energy carbon capture and resource utilization in response to zero carbon. However, light stress could restrict the carbon utilization efficiency of CAMC system. In this study, melatonin (MT) and indole-propionic acid (IPA) as phytohormones, were used to promote the carbon fixation capacity and biomass yield of CAMC system under light stress, and the potential mechanism was also discussed. Both MT and IPA promoted the growth of Spirulina , and 10 mg-MT group obtained the highest biomass and carbon fixation capacity, which were 27.61 % and 30.62 % higher than control. MT and IPA promoted the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), enhancing antioxidant activity to avoid oxidative damage. The results of transmission electron microscopy (TEM) and cell apoptosis showed MT and IPA reduced cell membrane damage and apoptosis. Phytohormones induced the carbon flux flow to the synthesis of carbohydrate and protein, and increased carbohydrate and protein productivity. Moreover, the maximum phycocyanin content and yield were 13.74 % and 43.25 % higher than the control. Therefore, adding phytohormones was an effective strategy to achieve high-value bioresources of microalgae in CAMC system under light stress. [Display omitted] • MT and IPA improved the performance of CAMC under light stress. • The maximum carbon fixation capacity improved 30.62 %. • MT and IPA reduced cell membrane damage and apoptosis. • Phytohormones induced the carbon flux toward carbohydrate and protein synthesis. [ABSTRACT FROM AUTHOR]

This research provides a comprehensive analysis of the transition pathways towards net-zero emissions in Indonesia's energy sector by 2050, focussing on overcoming the country's fossil fuel dependency. Utilising EnergyPLAN and MultiNode simulations across three scenarios: Nationally Determined Contribution, High Electrification and Moderate Electrification, the paper presents thorough scenario development and cross-sectoral analysis to capture future energy systems from both supply and demand sides. It contributes notably by detailing scenario-specific energy demands, such as industry sector energy efficiency and electric vehicle penetration and introducing a novel modelling approach that segments the Indonesian energy system into five regional systems. Modelling results indicate the necessity of transitioning towards 100 % renewable energy, emphasising the central role of electricity in future energy systems and the importance of regional connectivity in achieving net-zero emissions. Results also reveal that the Moderate Electrification scenario offers a cost-effective route to net-zero emissions by reducing energy demand and fully exploiting renewable energy sources. The paper concludes with policy recommendations to boost energy efficiency, accelerate electrification, initiate interconnected regional energy systems, and leverage carbon capture and storage as a supplementary measure. • Pathways to achieve net-zero emissions by 2050 are explored. • EnergyPLAN and MultiNode simulations are employed to analyse three scenarios. • Indonesia's energy system is segmented into five regional systems. • A detailed future energy demand analysis is presented. • Results identify electricity as the primary backbone of future energy systems. [ABSTRACT FROM AUTHOR]

The efficient use of energy is an important challenge in engineering tasks. Even with the end-of-pipe treatment method, the carbon capture process has possibilities to improve its efficiency with heat integration. Since exergy analysis helps detect the most efficient way of energy intensification, exergy investigation based on thermodynamic analysis is carried out to improve energy efficiency. Two cases for exergy destruction calculation can be considered and compared depending on the operation of the capture process: (i) the stand-alone situation, where utilities are applied, and (ii) the total site integration, where sources and sinks are available at every temperature level of the carbon capture process. Besides heat integration, the application of oxyfuel technology can further improve thermodynamic efficiencies reducing the detrimental exergy destruction. Air-combustion exhibits higher exergy destruction compared to oxyfuel-combustion, particularly at high carbon dioxide removal efficiency levels. Heat-integrated configurations nearly double thermodynamic efficiency, especially in the cases of oxyfuel technologies. Therefore, it is recommended that, for the sake of cleaner energy production, both oxyfuel technologies and heat integration should be applied to enhance carbon capture process' energy efficiency. [Display omitted] • Thermodynamic efficiencies of air and oxyfuel combustion processes are assessed. • Heat integration significantly improves thermodynamic efficiency. • The exergy destruction of oxyfuel combustion is lower than that of air combustion. • The efficiency further improves if the capture process is integrated into total site condition. [ABSTRACT FROM AUTHOR]

The existence of organic matters in naturally hydrate-bearing sediments would notably impact the CH 4 extraction from reservoirs via CO 2 swapping. In this work, the depressurization-assisted flue gas replacement was explored with artificial hydrate-bearing clay-silt sediments containing organic matter. The effect of organic matter type and content, depressurization moment and amplitude was systematically investigated. The results showed that the replacement was promoted at 5.0 wt% sulfonated lignin (SL) before depressurization, while it was inhibited at a lower SL content and this inhibition was weakened after depressurization. The CH 4 replacement ratio and CO 2 sequestration ratio increased as the fulvic acid (FA) content increased. For the organic matter-contained systems, the earlier depressurization moment was conducted, the higher CH 4 recovery was obtained. The CH 4 replacement ratio increased with the increase of depressurization amplitude, which reached 71.48 % in the 3.0 wt% FA system at the depressurization amplitude of 3.0 MPa. Aspen simulation revealed that the energy consumption was mainly caused by compression, there exist an optimum injection pressure of flue gas for the energy return on investment. The findings provide useful information for the depressurization-assisted flue gas replacement and would contribute to the actual NGH exploitation in the future. [Display omitted] • Depressurization-assisted flue gas replacement was explored with artificial hydrate-bearing clay-silt sediments. • Effects of organic matter type and content, depressurization moment and amplitude were investigated. • Early depressurization moment in organic matter-contained systems contributed to CH 4 recovery. • Aspen simulation revealed that energy consumption was mainly caused by compression. [ABSTRACT FROM AUTHOR]

Reducing carbon footprints and enhancing operational flexibility are crucial for the future development of coal-fired power plants (CFPPs). This necessitates the deployment of post-combustion carbon capture (PCC) and molten-salt heat storage (MSHS) systems. Given the various integration schemes and complex interactions, understanding the comprehensive performance of the integrated CFPP-PCC-MSHS system is important. This paper proposes an integration scheme for 1000MWe ultra-supercritical CFPP, solvent-based PCC and MSHS, achieving cascade energy utilization. A dynamic simulation model for the CFPP-PCC-MSHS system is developed to understand the dynamic couplings between subsystems. Comprehensive performance analyses are conducted to evaluate the thermodynamics, flexibility and safety of the integrated system under various operating conditions. Simulation results indicate that deploying MSHS reduces the thermal and exergy efficiencies of the CFPP-PCC system by 0.18 % and 0.19 %, respectively, but effectively expands the adjustable power load range by 6.08 % under the fixed 90 % CO 2 capture rate mode. Meanwhile, the integration of MSHS offers alternative pathways to improve the power ramping rate to 13.33 MW/min. The heat charging/discharging process of MSHS induces fluctuations in temperature and pressure within the turbine, potentially affecting plant operating safety. This paper provides useful insights for the design, retrofit and operation of new generation of CFPPs. • A dynamic model of the integrated CFPP-PCC-MSHS system is developed. • The integration of MSHS reduces thermal and exergy efficiencies by 0.18 % and 0.19 %. • MSHS enlarges power range of CFPP-PCC by 6.08 % under 90 % CO 2 capture condition. • Deploying MSHS offers effective pathway to improve the power ramping rate of CFPP. • Deploying MSHS induces pressure and temperature variations at each turbine stage. [ABSTRACT FROM AUTHOR]

For cold energy utilization in the liquefied natural gas (LNG) regasification process, integrated cryogenic CO 2 capture using high-grade cold energy is a mainstream method. However, high-grade cold energy for carbon capture may lead to a decrease in cold energy utilization efficiency. This paper aims to propose a hybrid system in which high-grade cold energy is used for liquid air energy storage (LAES) and post-combustion amine scrubbing technology is considered to replace cryogenic carbon capture for improved working efficiency. The medium and low-grade cold energy is utilized for similar working processes, e.g., organic Rankine cycle (ORC), carbon dioxide liquefaction, and data center cooling for comparison. Results show that the proposed hybrid system can produce 437.7 MW of power, 28.8 t·h−1 of CO 2 capture capacity, and 23.0 MW of cooling capacity, respectively. The levelized cost of electricity and the annual revenue are 112.3 $·MWh−1 and 2.17 million $, respectively. LNG cold energy utilization efficiency, system energy efficiency, and cold exergy efficiency are 53.4 %, 24.0 %, and 51.5 %, higher than similar processes using cryogenic CO 2 capture. It is demonstrated that the proposed system could be a promising method for cold energy utilization and post-combustion capture. • A hybrid system is proposed for LNG cold energy utilization and post-combustion capture. • Cold energy efficiency of the system is much improved when compared with cryogenic capture. • Cold energy utilization efficiency of the hybrid system could achieve 53.4 %. • The LCOE and the annual revenue are 112.3 $·MWh−1 and 2.17 M$, respectively. [ABSTRACT FROM AUTHOR]

Pipelines serve as a critical means of transporting CO 2 within Carbon Capture, Utilization, and Storage (CCUS) technology. Elevated transport pressures may lead to unforeseen pipeline ruptures. To provide practical recommendations for the design of CO 2 pipelines and mitigate the risk of ruptures, this study establishes a one-dimensional Homogeneous Equilibrium Mixture (HEM) model. The model is currently used to predict the decompression behavior in existing pure CO 2 rupture tests. Future work will address rupture tests and predictions involving impure CO 2. The results indicate that due to differences in pressure reduction caused by decompression waves, the likelihood of long-range ruptures occurring in density CO 2 pipelines is lower compared to supercritical CO 2 pipelines. The crack propagation velocity and crack arrest pressure of pipelines designed according to ASME B31.3 are calculated using the High Strength Line Pipe Committee (HLP) model. Although the crack propagation velocity is lower than the decompression wave speed, the crack arrest pressure may fall below the rupture pressure, with the pressure at 1.6 m from the rupture point remaining above the crack arrest level for 1 ms post-rupture, a duration that is especially prolonged in larger-diameter pipelines. It is recommended to consider additional thickness beyond the calculated minimum thickness. • A one-dimensional model for predicting CO 2 pipeline rupture processes is developed. • High-pressure liquid CO 2 can reduce the likelihood of long-range fractures. • Pipelines designed by ASME B31.3 effectively reduce crack propagation velocity. • The designed crack arrest pressure may be lower than the rupture pressure. • It is recommended to increase the thickness margin beyond the calculated thickness. [ABSTRACT FROM AUTHOR]

Hydrogen-rich syngas, produced by underground coal gasification (UCG) process, is a valuable feedstock for chemical industry. However, it can contain large quantities of carbon dioxide (CO 2), which requires separation and sequestration to reduce the carbon footprint of the process. This study explores mechanisms influencing coal permeability when CO 2 is injected back into the coal through existing gasification chambers. Two main mechanisms affecting permeability are thermal effects associated with underground coal gasification and CO 2 -related coal matrix swelling. The effects of thermal processes and CO 2 flooding on the fracture network of the coal are investigated through a series of comprehensive experiments. Thermal treatment of the studied sample at a temperature of 210 °C shows a notable effect on fracture morphology, increasing width and permeability by up to a factor of 2 and 5, respectively. CO 2 flooding, on the other hand, impairs fracture network due to chemisorption driven processes, leading to irreversible changes. Following CO 2 flooding experiment, fracture porosity decreases by a factor of three and subsequently permeability declines by 70–80 % within the studied effective stresses range. Our characterization study indicates that thermal treatment significantly increases permeability, compensating for impairments to the fracture network associated with CO 2 injection. • Fracture network is characterized by micro-CT, air flooding, and helium porosimetry. • Thermal treatment enlarges fracture width and subsequently permeability increases. • Interaction of CO 2 with coal matrix results in irreversible changes in fracture network. • Matrix swelling driven by chemisorption processes declines permeability. • Cumulative impact of thermal treatment and CO 2 on fracture network is positive. [ABSTRACT FROM AUTHOR]

Supercritical carbon dioxide (SC– CO 2) serves as a promising anhydrous fracturing fluid that has the potential to simultaneously enhance shale gas recovery and accomplish CO 2 sequestration within shale reservoirs. However, the hydromechanical properties of shale are considerably affected by CO 2 -brine-shale interaction. This study conducted shale imbibition experiments involving subcritical/supercritical CO 2 saturated brine (Sub/SC-CO 2 +brine). Triaxial compressive strength tests were performed to evaluate the impact of Sub/SC-CO 2 +brine imbibition on the mechanical properties of shale, as well as the influence of SC-CO 2 +brine imbibition on shale permeability. The results indicate that, after SC-CO 2 brine imbibition, noticeable macroscopic cracks are formed parallel to the bedding plane. The imbibition of Sub/SC-CO 2 +brine results in the reduction in axial stress and Young's modulus, while simultaneously increasing the axial strain of shales. Compared to Sub-CO 2 +brine, SC-CO 2 +brine exhibits a higher imbibition pressure and a more intense geochemical reaction with shale. Due to increased compressibility sensitivity, the averaged permeability after SC-CO 2 +brine imbibition shows a reduction of nearly 70 % compared to that before imbibition. The insights from this research are expected to provide theoretical support for shale gas recovery and CO 2 geological sequestration. • The effects of Sub/SC-CO2+brine imbibition on the mechanical properties of shale were investigated. • Compared to SC-CO2 +brine imbibition, Sub-CO2+brine imbibition induced higher axial stress and lower axial strain. • The permeability reduced by more than an order of magnitude due to SC-CO2+brine imbibition. [ABSTRACT FROM AUTHOR]

Hydrate-based CO 2 sequestration (HBCS) under seafloor with huge storage capacity and long-term mechanical stability is attractive for large-scale carbon reduction. However, as representative geochemical constituents of marine sediments, swelling clay minerals still play ambiguous roles in hydrate phase transition and sedimentary structure stability. In this study, pore-scale behaviors of hydrate deposition and reservoir structure evolution in the presence of montmorillonite (MMT), a representative swelling clay, was investigated using low-field nuclear magnetic resonance (LNMR) technique. Total inter-particle interaction energy of 195.4 K b T ensured the dispersion of clay in 0.5 wt% MMT system, which facilitated homogeneous hydrate formation by providing nucleation sites and surface electric fields, improving hydrate conversion from 78.2 % to 89.6 %. Weak water activity caused by strong water absorption of swelling clay resulted in a 14.4 % reduction in CO 2 storage capacity of high-concentration (10.0 wt%) MMT reservoir. Hydrate phase transition accompanied by the migration of MMT particles and liquid water synergistically contributed to sedimentary structure evolution. Migration of MMT-rich fluid with high viscosity could cause irreversible geologic damages by exacerbating sedimentary skeleton deformation. This work reveals the interaction between swelling clay and CO 2 hydrate at microscopic scale, providing new perspectives for effective implementation of CO 2 geologic sequestration in marine sediments. [Display omitted] • Revealing the interaction of swelling clay with CO 2 hydrate from the pore scale. • The presence of montmorillonite improves the homogeneity of hydrate distribution. • Concentrated clay fluids provide mass transfer resistance for hydrate formation. • Clay agglomeration and migration can cause irreversible damage to the reservoir. • A small amount of clay allows for homogeneous and dense hydrate-based CO 2 storage. [ABSTRACT FROM AUTHOR]

Post combustion Carbon capture based on chemical absorption is the best-known technology to reduce CO 2. Recently, attention has been paid to biphasic solvents due to their excellent potential in reducing energy consumption. This study investigated carbon dioxide absorption by biphasic non-aqueous triethylenetetramine (TETA)-ethanol solvent in a T-shaped microchannel. Effect of four parameters including: concentration of TETA (4–8 wt%), liquid flow (2–5 ml/min), inlet CO 2 concentration (5–20 vol%) and gas flow (100–175 ml/min) have been examined. Mass transfer characteristics has been assessed by investigation of absorption percentage, molar flux and overall mass transfer coefficient. The results show that increasing the concentration of amine diminishes all three responses by increasing the solution viscosity. As a result, it decreases the penetration of CO 2 in the solution and the rate of absorption. Furthermore, the TETA-ethanol phase change solvent has been compared with aqueous monoethanolamine (MEA). The results of this comparison indicated that the efficiency of CO 2 absorption and mass transfer coefficient, for TETA-ethanol biphasic solvent are higher than MEA solvent, respectively. Finally, the dimensionless Damköhler number (Da) was utilized in the new correlation to predict K L a for CO 2 absorption into TETA-Ethanol solution with acceptable accuracy. • CO 2 absorption by biphasic TETA-ethanol solvent was investigated in a microchannel. • The mass transfer coefficient for biphasic solvent was 14.38 % higher than MEA solvent. • Damköhler number was utilized in the new correlation to predict K L a. [ABSTRACT FROM AUTHOR]

CO 2 hydrate caps can effectively reduce the leakage risk from subsea CO 2 sequestration. TBAB (tetrabutylammonium bromide) affects temperature and pressure required for the CO 2 hydrate formation, which improves hydrate cap application. This study analyzes hydrate formation and decomposition characteristics in TBAB + CO 2 system under different initial pressures and TBAB concentrations. The results show that the addition of TBAB effectively expand CO 2 hydrate stable area and prevent CO 2 leakage. 5 wt% TBAB not only provides crystal nucleus for hydrate formation and shortens the induction period, but also increases CO 2 hydrate cap temperature to 290.3 K. The hydrate decomposition process in TBAB system is divided into CO 2 ·nCO 2 and TBAB·26H 2 O·nCO 2 decomposition stage. Comparing with hydrate decomposition process in pure water system, it is found that TBAB mainly affects the second stage of hydrate decomposition process. In 5 wt% TBAB system, the hydrate decomposition process was affected by TBAB after more than 68 % hydrate decomposition. It is found that the hydrate decomposition rate with TBAB is almost 1/7 of that without TBAB. This study provides experimental support for expanding the application of CO 2 hydrate caps, and provides a basis for determining the geological storage area of CO 2 in sediments. • TBAB is employed to enlarge hydrate stable area to ensure CO 2 storage safety. • TBAB concentration is contributive to the expansion of thermodynamic stability. • CO 2 +TBAB hydrate forms without induction period due to the semi-structure. • The decomposition rate of CO 2 +TBAB hydrate is almost 1/7 of that in pure water. [ABSTRACT FROM AUTHOR]

A multi-stage compression train with intermediate cooling used to inject carbon dioxide (CO 2) in a well is modeled using two distinct configurations, direct and assisted cooling. The main difference between these configurations is that, in the latter, the process water responsible for the intermediate cooling is cooled down by a refrigeration cycle. These configurations are thermodynamically modeled while aiming to investigate the effect of key parameters on two main variables: (i) the overall global conductance and (ii) the overall power consumed by the compressors and auxiliary cooling systems. The results for direct cooling indicate that the power consumed by the compression train is inversely related to the global conductance, while an increase in the number of intermediate compression stages also reduces the global conductance. The assisted cooling, which considered 20 different working fluids for the refrigeration cycle, presented a minimal value for the global conductance for a given value of the overall power consumed by the compressors (train and refrigeration cycle). Finally, a comparison between both configurations reveals that while direct cooling offers a better compromise solution between global conductance and power consumption, assisted cooling can produce a significant reduction of global conductance. • Analysis and optimization of intermediate cooling systems for CO 2 compression trains in a FPSO. • Use of direct and assisted intermediate cooling arrangements. • Compromise solution analysis in terms of power consumption and space allocation. [ABSTRACT FROM AUTHOR]

Nowadays, power sector is faced with the challenge of low-carbon transition by reducing carbon emissions while ensuring sufficient electricity supply. However, the prolonged transition process may present long-term uncertainties related to the concurrent tasks of regulating total carbon emissions and providing abundant electricity. The variation of these tasks poses a potential threat to the success of low-carbon transition. To confront this challenge, this study proposes a power system expansion planning model which integrates transmission expansion, renewable generation expansion, energy storage systems deployment coordinated with the retirement of coal-fired power plants and retrofit of coal-fired power plants to carbon capture power plants in compliance with transition targets. Then, a risk-averse planning strategy countering the long-term uncertainties of transition tasks is adopted to constitute a two-level multi-objective planning framework based on information gap decision theory. And the second-level risk-averse model is reformulated with an augmented normalized normal constraint method to obtain the Pareto frontier. Numerical results indicate that integrating the retirement and retrofit of coal-fired power plants yields a significant reduction in total cost (4.71 %), compared to a case without such integration. And the transition tasks can be accomplished in a robust way by preferred risk-averse approach. • Propose a holistic low-carbon oriented power system expansion planning model. • Address the uncertainties of transition tasks by multi-objective IGDT-based model. • Address the conflicting objectives by augmented normalized normal constraints. • Adjust the risk-hedging level according to the planner's preference. • Implement the cost-effective analysis and sensitivity analysis on case studies. [ABSTRACT FROM AUTHOR]

A novel zero-carbon emission combined cooling, heating and power (CCHP) system is currently proposed. The thermal energy of the solid oxide fuel cell (SOFC) exhaust is recovered in a transcritical CO 2 (T- CO 2) power cycle. Relying on the efficient utilization of liquefied natural gas (LNG) cold energy, CO 2 capture has been achieved at low energy consumption. The thermodynamic performance is evaluated by using energy and exergy analysis methods for this hybrid process. The electrical, exergy, and CCHP efficiencies are obtained as 60.37 %, 62.83 %, and 79.09 %, respectively. The CO 2 condenser, with the largest exergy destruction ratio (18.60 %) and a low exergy efficiency (37.16 %), is regarded as the weakest point in terms of thermodynamic perfectibility. In addition, the influences of the current density, stack temperature and pressure, and fuel utilization rate have also been studied from different aspects of system performance. The current density, stack temperature, stack pressure, and fuel utilization rate are recommended as 0.3 A/cm2∼0.4 A/cm2, 900 °C, 5 bar, and 85 %, respectively. This research provides practical reference and pragmatic guidance for the integration, analysis, and optimization of SOFC-based CCHP systems. • A novel SOFC-based CCHP system is proposed, utilizing the cold energy of LNG. • The zero-carbon emission in this novel system is realized with low energy consumption. • Energy, exergy, and parametric analyses are conducted for the system evaluation. • The electrical, exergy, and CCHP efficiencies are 60.37 %, 62.83 %, and 79.09 %. • The effects of key parameters are studied from different aspects of system performance. [ABSTRACT FROM AUTHOR]

A dry sorbent post-combustion CO 2 capture process using a circulating fluidized bed (CFB) was developed to a 10 MWe scale. Particle attrition is a major challenge for many CFBs owing to the loss of particles and increased operating costs. Furthermore, predicting and alleviating the rate of particle attrition in an entire CFB is difficult owing to limited information on attrition in the riser and cyclone. This study experimentally investigated particle attrition in risers and cyclones and the effect of system scale-up using CO 2 adsorbent particles used in a 10 MWe scale CFB. Experiments were conducted in two types of CFBs to measure the attrition rate in the riser and cyclone for 22 and 12 h for each experimental condition. To verify the scaled-up effect, internals were added to the riser to measure the effect of the surface-area-to-volume ratio. Correlations for the attrition rate of CO 2 adsorbent particles in riser and cyclone were proposed, and a model for the scale-up effect was suggested. In the 10 MWe scale system, particle attrition mainly occurred in the cyclone (58.0 %) and riser (37.3 %) according to the calculation, and the calculated overall attrition rate reasonably matched the operational data. Figure: (a) Calculated attrition rate of CO 2 adsorbent particles in the circulating fluidized bed of 10 MWe scale CO 2 capturing process, and (b) effect of cyclone inlet gas velocity on the particle attrition rate in cyclone. [Display omitted] • Particle attrition mainly occur in the cyclone and riser of a CFB. • Attrition rate in cyclone was proportional to the square of the gas velocity. • The top size of fines formed by attrition in riser increased with gas velocity. • Attrition rate in the riser increases by increasing surface area. • Correlation for particle attrition rate in the riser and cyclone are proposed. [ABSTRACT FROM AUTHOR]

The integration of a carbon capture system is an effective way to reduce CO 2 emissions from coal-fired power plants, but the carbon capture system consumes much steam and power, which causes a high efficiency penalty. In this study, thermodynamic analyses were conducted on the coal-fired power plant integrated with carbon capture system under load cycling operation conditions. Results show that the exergy efficiency penalty increases with the decrease of power load ration, and the exergy efficiency of coal-fired power plant decreases by 8.29 and 10.02 % under 100 and 30 % load ratios with the integration of carbon capture system, respectively. The irreversibility of carbon capture system increases with the decrease of load ratio of coal-fired power plant. To enhance the performance of coal-fired power plant integrated with carbon capture system under load-cycling operation conditions, the pressure sliding operation strategy is proposed. The performance of the integrated system can be improved by increasing the absorber pressure when the load ratio is below 75 %. Moreover, decreasing the stripper pressure is beneficial to reduce the energy consumption. As a result, by pressure sliding strategy, the exergy efficiency is improved by 0.23, 0.31, 0.3, 0.37 % under 100 %, 75 %, 50 % and 30 % load ratios, respectively. • A new operation strategy of pressure sliding for carbon capture system is proposed. • The performance of CFCC under load cycling operation conditions was evaluated. • Influences of the operation pressure of key devices were quantitatively analyzed. • The exergy performance was increased by 0.3–0.37 % under low power load ratio. [ABSTRACT FROM AUTHOR]

With the increasing demand for hydrogen (H 2), producing liquefied H 2 with a high energy density (10.1 MJ/L) has become essential. Research on the H 2 liquefaction process, specifically, the effects of various refrigerants and cooling cycles has been conducted. Yet, large-scale use of carbon dioxide (CO 2) in H 2 liquefaction hasn't been achieved. In this study, a cooling cycle that uses captured CO 2 as a refrigerant in large quantities was selected for a 100 tpd H 2 liquefaction process. Optimization minimized the specific energy consumption (SEC), leading to SEC of 7.3 kWh/kgLH 2 , a coefficient of performance of 0.17, a figure of merit of 0.33, a specific exergy efficiency (SEE) of 33 %, and an overall exergy efficiency of 82.2 %. Performance indicators were compared with other processes, showing that the SEC and SEE were improved by 43 % and 50 % compared to commercial processes and by 4 % and 6 % compared to previous studies using CO 2. This study used 5.7 times more CO 2 at the same capacity, utilizing 47.8 Mt of CO 2 , representing 14 % of the CO 2 utilization amount of the total carbon capture and utilization (CCU) project. Thus, the results should facilitate the development of hydrogen liquefaction processes for use in CCU applications in the future. [Display omitted] • Hydrogen liquefaction process using large-scale CO 2 as a refrigerant has been proposed. • SEC and SEE were improved by 43 % and 50 %, respectively, compared to commercial processes. • It is expected to utilize 14 % of the total CO 2 utilization amount in the CCU project. [ABSTRACT FROM AUTHOR]

This research constructs an assessment model for carbon capture and storage (CCS) retrofit of coal-fired power plants (CFPP) by adopting the real option theory. Due to the prohibitive costs associated with retrofitting and insufficient residual lifespan of CFPP, CCS projects may fail to recoup their investment before units are decommissioned. The key contribution of this paper is that it investigates the impact of the residual lifespan of the units on the failure rate of the retrofit investment in addition to the optimal timing of the unit's CCS retrofit. Considering different installed capacities, utilization hours, clean energy subsidy and carbon trading mechanism, this study sets up seven scenarios to assess the impact of different investment environments on the value of project investment. In terms of sensitivity analysis, the residual lifespan of the unit, its interaction with carbon price, carbon price volatility, technological advancement rate, and subsidy level are examined for their impacts on the project investment risk. The findings suggest that the critical period for determining the long-term success of most coal-fired unit retrofits may be present, and more supportive policies need to be examined to facilitate the green transformation and upgrading of coal-fired units. • The impact of coal-fired units' residual lifespan on CCS retrofits is examined. • An assessment model for CCS retrofit is proposed based on real option theory. • Insufficient residual lifespan may lead to failure risk for CCS retrofits. • The current period may be critical for the long-term success of most CCS retrofits. • More policy mixes should be introduced in time to promote the deployment of CCS. [ABSTRACT FROM AUTHOR]

Injecting CO 2 into shale oil reservoirs is one of the most effective methods for enhancing oil recovery (EOR) while simultaneously facilitating CO 2 capture, utilization, and storage (CCUS). However, it is not always that gas dissolution or condensate evaporation reaches equilibrium instantaneously during the CO 2 injection process. In cases where equilibrium is not attained instantaneously, conventional vapor-liquid equilibrium models will have certain limitations in characterizing phase transition hysteresis. These limitations will affect the accuracy of simulating multi-component transport in porous media. In this paper, a robust and generic vapor-liquid non-equilibrium thermodynamic model considering nano-confinement effects (NC) was established by introducing component mass transfer rates proportional to the chemical potential difference. The established model was then used to modify the fully-compositional, projection-based embedded discrete fracture model (pEDFM). Furthermore, C++ hybrid programming and the Graphics Processing Unit (GPU) parallel method were both used to accelerate both the nonlinear and linear solvers. By comparing with results from MATLAB Reservoir Simulation Tools (MRST), Eclipse, and tNavigator, the accuracy and advantages of our solver were demonstrated. The results show that if the underground fluid undergoes a phase transition from a vapor-liquid two-phase state to a single-phase state, non-equilibrium thermodynamic effects need to be considered, and the simulation results show a larger two-phase zone, higher bottom hole pressure, and lower cumulative liquid production. But the nano-confinement effects will weaken the non-equilibrium thermodynamic effects. • A robust and generic vapor-liquid non-equilibrium thermodynamics model. • Non-equilibrium thermodynamics model was introduced into pEDFM for the first time. • The effects of non-equilibrium phase behavior on CO 2 injection were determined. • Impacts of nano-confinement effects on non-equilibrium phase behavior were studied. [ABSTRACT FROM AUTHOR]

Biphasic solvents with primary/secondary amines as the primary absorbent involve a high heat of reaction and low desorption efficiency, limiting their development. A tertiary amine-based biphasic solvent composed of diethylethanolamine (DEEA), 2-Amino-2-methyl-1-propanol (AMP), ethyl acetoacetate (EAA), and H 2 O (referred to as DEEA/AMP/EAA/H 2 O) was proposed, which exhibited superior low-temperature desorption performance and ultra-low regeneration energy. EAA was revealed to facilitate the low-temperature desorption by reducing the activation energy from 6.8 to 2.3 kcal/mol. When regenerated only by heating to 353.15 K, the CO 2 -rich phase showed a significant desorption efficiency of 88.2 %; the desorption capacity and desorption rate were even 2.23 times and 6.84 times higher than 30 wt% MEA at 393.15 K. Moreover, the desorption heat dominated by the deprotonation of tertiary amine was as low as 0.92 GJ/t CO 2 ; and low-temperature regeneration brought extremely low latent heat below 0.062 GJ/t CO 2. Thus, the total regeneration energy was as low as 1.16 GJ/t CO 2. In addition, EAA could trigger the phase separation and increase the absorption rate constant from 3.87 E−4 to 1.36 E−3 s−1, even higher than 30 wt% MEA. The addition of AMP further increased the CO 2 loading (4.34 mol/L) and CO 2 distribution (97.43 %) of the CO 2 -rich phase. [Display omitted] • This study proposed a tertiary amine diethylethanolamine-based biphasic solvent. • It's the first biphasic solvent with desired low temperature desorption performance. • The latent heat was 5 % of MEA, with a total regeneration energy of 1.16 GJ/t CO 2. • Ethyl acetoacetate reduce the energy barrier and enable low temperature desorption. • It showed greater desorption capacity and rate at 353 K than those of MEA at 393 K. Synopsis: A novel DEEA/AMP/EAA/H 2 O biphasic solvent was developed with excellent low-temperature desorption performance and extremely low regeneration energy. [ABSTRACT FROM AUTHOR]

Oxy-fuel combustion, as an important technology to realize CCUS in the field of combustion, needs to control the generation of pollutants such as NO x while realizing CO 2 capture, and the conversion of fuel-N to N 2 is crucial. Previous experiments have provided insights into the influence of different atmospheres on NO during oxy-fuel combustion of alcohols. However, the specific reaction mechanism underlying how the atmosphere and hydroxyl fuels impact NO generation through the free radical pool remains unclear. In this study, the formation and reduction of NO during the oxidation of CH 3 OH/NH 3 and C 2 H 5 OH/NH 3 in O 2 /CO 2 , O 2 /H 2 O and O 2 /CO 2/ H 2 O atmospheres with oxy-fuel condition were investigated by simulation. In the NO generation stage, different H 2 O, CO 2 , O 2 and fuel types have little effect on the peak of NO although they change the NH 3 →NO reaction path. In the process of NO reduction, stage 1 is the main reaction phase of NO→N 2 , and both CO 2 and H 2 O are beneficial for the reduction of NO. But the reduction of NO by H 2 O was more pronounced. In the case of simultaneous addition of H 2 O and CO 2 , the reducing effect of H 2 O and CO 2 alone on NO was attenuated. On the other hand, the reduction effect exerted by H 2 O and CO 2 was stronger in high than in low oxygen-fuel ratio, stronger in C 2 H 5 OH than in CH 3 OH. The reduction of NO by H 2 O and CO 2 is based on the general equation NO→N 2 +O 2. H 2 O is used to promote the reaction in the positive direction by consuming O 2 to convert it to H and OH, so that more of the element O is converted to OH than O 2 to inhibit the production of NO. The CO 2 contributes to the formation of less O 2 during the reduction of N 2 from NO by promoting reaction NO + N→O + N 2 , while the additional OH increases the "capacity" of O 2 in the NO→N 2 +O 2 reaction. • Different H 2 O, CO 2 , O 2 , and fuel types in NO production have little effect on the peak NO production. • N + NO. →N 2 + O and NO + H→N + OH in the NO x reduction stage determine the total fuel-NO production • H 2 O and CO 2 affect NO conversion by influencing the total reaction NO. →N 2 + O 2 [ABSTRACT FROM AUTHOR]

Renewable energy-based multigeneration systems for power, hydrogen, and ammonia production suffer from intermittency issues and high production costs. On the other hand, conventional fossil-fuel-based systems yield high levels of CO 2 emissions. Thus, to eliminate the intermittency issue with low production costs and near zero CO 2 emissions, a novel integrated, efficient, compact, and interactive system for power, hydrogen (H 2), and ammonia (NH 3) production is developed and investigated in this study. A direct oxy-combustion supercritical carbon dioxide (DOC-sCO 2) power plant is integrated with a water electrolyzer (WE) and Haber-Bosch process (HBP) system for the cogeneration of power, H 2 , and NH 3 , respectively. The power consumption of the air separation unit (ASU) of the DOC-sCO 2 cycle is significantly reduced by the utilization of the oxygen produced from the WE system. Moreover, the cost of ammonia production is minimized by the internal utilization of the nitrogen gas produced by the ASU. Furthermore, the feedwater of the WE system is supplied internally from the DOC-sCO 2 power block. In addition, the CO 2 emissions of the system are captured to realize near-zero emissions to the ambiance. Based on these features, thorough energy, exergy, economic, and environmental (4E) analyses were performed to evaluate the performance of the proposed system. The obtained results showed an impressive levelized cost of electricity of 3.72¢/kWh, levelized cost of hydrogen of 1.162$/kg H2 , and ammonia of 0.197$/kg NH3 at an overall energy and exergy efficiencies of 44.09 %, and 63.6 %, respectively. The system has no emissions of nitrogen oxides (NOx) and reduces the CO 2 emissions of the H 2 production by 49.6 % and of the NH 3 production by 48.8 % compared to the conventional gasification, SMR, and HBP systems, respectively. This research work also provides insights into wet versus dry cooling, part load operation, and the advantages over renewable-based systems in terms of stability, reliability, and economic feasibility. Novelty aspects of the proposed integrated system for hydrogen, ammonia, and power generation. [Display omitted] • First novel integrated supercritical CO 2 system for power, H 2 and NH 3 generation. • The produced O 2 by the water electrolyzer system is used to minimize the ASU power. • The water produced by the DOC-sCO 2 is used as feedwater for the water electrolyzer. • The produced N 2 by the ASU is used as a feed gas for the Haber-Bosch process. • Notable η o v e r a l l of 44.8 %, LCOE of 3.7¢/kWh, 1.16$/ kgH2 , and LCOA of 0.2$/kg NH3. [ABSTRACT FROM AUTHOR]

Decarbonizing the EU's district heating is crucial for meeting climate goals and securing a sustainable energy future. Currently, district heating suffers from inefficiency, high operating temperatures, significant distribution losses, and reliance on fossil fuels. Literature highlights strategies for reducing emissions, including integrating low-carbon heat sources, lowering supply temperatures, and employing efficient technologies like heat pumps and combined heat and power (CHP). However, the individual effectiveness of these strategies in reducing emissions within existing networks remains unassessed. This study addresses the gap by applying a comprehensive model that evaluates energy and emissions across the district heating supply chain, coupled with a derivative-based sensitivity analysis. We apply this methodology to the national-level district heating systems of Sweden, France, Germany, and Poland. Results indicate that the impact of decarbonization strategies on district heating emissions varies significantly by the system's characteristics, i.e., the energy mix in power and district heating supply and the presence of CHP plants. Primarily, incorporating more low-carbon heat sources emerges as the most effective method for emission reduction across nearly all examined countries. A 1 % increase in the share of low-carbon heat sources can potentially cut emissions by 0.8–1.3 kg CO 2 e per GJ of heat. In countries like Sweden and France, where the power generation already relies heavily on low-carbon resources, technologies which convert electricity to heat—such as heat pumps and electric boilers—rank as the second most effective approach. In contrast, for countries like Germany and Poland, with their moderate to low use of low-carbon power, reducing distribution losses and decreasing heat demand prove more effective, with emission reductions ranging between 0.8-1.3 and 0.7–1.2 kg CO 2 e per GJ in these countries, respectively. Additionally, cutting down power generation in fossil fuel-based CHP plants significantly reduces emissions in these regions. While green hydrogen and carbon capture and storage (CCS) also contribute to emission reductions, a 1 % increase in green hydrogen's share might decrease emissions by just 0.3–0.5 kg CO 2 e per GJ of heat, highlighting their lower effectiveness compared to the aforementioned strategies. These insights hold value for both district heating operators and for technology suppliers seeking decarbonization pathways. This is also true for policymakers focused on climate change mitigation, guiding the distribution of subsidies and R&D investments. • Creation of a framework to evaluate the effectiveness of strategies to reduce emissions in district heating. • Application of the method to the national-level systems of Sweden, France, Germany, and Poland. • Effectiveness of strategies varies significantly by the system's characteristics. • Identification of most effective strategies by country and policy recommendations. [ABSTRACT FROM AUTHOR]

This study investigates methods to reduce heat losses, CO 2 emissions, and improve the overall efficiency of micro gas turbine power plants, considering economic viability as gas turbines are a major component of the global energy supply chain. Heat recovery and carbon capture techniques were employed to achieve these goals. First, a steam Rankine cycle and a greenhouse were designed to integrate with an existing micro gas turbine. Second, the entire system was simulated using thermodynamic, economic, and environmental models. Finally, an optimization process was conducted through a machine learning model using the integrated model. By adding a Rankine cycle, 80 % of the heat losses in a traditional power plant were recovered, converted into electricity and cooling, and resulted in a 3 % efficiency improvement. Additionally, implementing a CO 2 separation and capture unit with utilization in a nearby greenhouse not only enhanced greenhouse profitability but also significantly reduced CO 2 emissions into the atmosphere. While the system's cost rate increased by $40/hour, the investment payback period is only 0.97 years. Furthermore, CO 2 emission rate was reduced by 15 %. [Display omitted] • Propose and analyze an integrated system for CO 2 capturing from a gas turbine. • Employing a techno-economo-environmental analysis for the integrated system. • Optimizing the proposed system and compare it with the existing power plant. • Determining the possibility of implementing such a system as a case study. [ABSTRACT FROM AUTHOR]

Gas flaring and produced water (PW) emissions are common environmental challenges with significant impacts on the oil production industry. This study proposes a novel approach to address these concerns by developing energy self-sufficient networks for simultaneous utilization of flare gas (FG) and PW for sustainable hydrogen production. Three distinct scenarios are analyzed: hydrogen production without CO 2 capture (Hydra), fossil fuel-based (FF) hydrogen production with CO 2 capture and utilization in enhanced oil recovery (HydraCap-FF), and a solar-thermal-assisted HydraCap-FF system (HydraCap-RE). Techno-economic and environmental models are constructed for each scenario's optimal configuration, enabling a comparative analysis of their economic viability and environmental impact. Additionally, the designed systems are examined through a flexibility analysis to evaluate input materials and their influence on the system's viability. Results highlight the promising potential of HydraCap-RE, achieving significant reductions in CO 2 emissions and water footprint compared to traditional methods. The HydraCap-RE generates hydrogen with the cost of 2.86 $/kg H 2, hydrogen yield of 31.25 kg H 2 /100 kg FG, specific emission of 0.86 kg CO 2 /kg H 2 and water footprint of 0.185 kg H 2 O/kg H 2. Moreover, the flexibility analysis indicates that an optimal FG/PW ratio of 0.53 yields the highest economic value. The results demonstrate that deploying HydraCap-FF in the Permian, Bakken, and Eagle Ford shale regions can produce 0.807, 0.454, and 0.121 million tons of hydrogen annually, respectively, and reduce CO 2 emissions by 6.37, 3.58, and 0.956 million tons, respectively. Furthermore, the HydraCap-RE deployment in these shale fields outperformed, with 17 % higher hydrogen production and 28.42 % lower CO 2 emissions. These findings provide valuable insights for decision-makers seeking to reduce CO 2 emissions the oil and gas industries and providing clean and sustainable products for these areas. [Display omitted] • A novel self-sufficient solar assisted driven hydrogen system is designed. • SCWOD system utilizes 10.46 % of FG and treat PW with emission of 2.26 kg CO 2 /kg PW. • HydraCap-FF deployment results in CO 2 reduction of 6.37 Mton/year in Permian basin. • HydraCap-RE generates hydrogen with an emission of 0.87 kgCO 2 /kg H 2. • HydraCap-RE deployment results in 17 % higher hydrogen compared with FF-based systems. [ABSTRACT FROM AUTHOR]

Post-combustion CO 2 capture plants include high costs that are associated with intense energy consumption. Heat pumps can recover heat from the flue gas and other sources in the CO 2 emitting plant and upgrade it to reduce the use of fossil-based steam. The few studies regarding heat pumps in CO 2 capture systems include arbitrary selection among limited working fluids, without optimizing the underlying cycle. This work implements a multi-criteria investigation of the performance of 20 working fluids for vapor compression heat pumps (VCHP) and 21 refrigerant/absorber pairs for absorption heat transformers (AHT), considering the operating optimization of each cycle for each fluid. A cascade cycle combining the two configurations (AHT-VCHP) is proposed, using the optimum fluids cyclopentane and water/potassium nitrate identified for the VCHP and the AHT. The annual operating costs are higher than the annualized capital expenditures. The proposed fluids outperform the conventional options. The VCHP with cyclopentane covers 58 % (2.68 GJ/t CO 2) of the reboiler duty with recovered heat and exhibits the lowest cost of $33.8/tCO 2. This is $18.7/tCO 2 lower than the cost of the conventional direct contact cooling unit that is used in capture plants. The VCHP remains competitive for up to 57 % increase in the electricity price. [Display omitted] • Evaluation of 41 known and novel working fluids through heat pump optimization. • Multi-criteria selection and technoeconomic analysis. • Vapor compression heat pump with cyclopentane covers 58 % of reboiler duty with recovered heat. • Its cost is $18.7/tCO 2 lower than that of a conventional flue gas cooling unit. • Vapor compression heat pump is competitive for up to 57 % higher electricity price. [ABSTRACT FROM AUTHOR]

Coupling advanced systems with carbon dioxide (CO 2) capture and CO 2 -to-methanol technologies is a possible solution for both greenhouse gas emissions and low-carbon use of fossil energy. In view of this, this study further develops an advanced molten carbonate fuel cell (MCFC)/steam turbine (ST) hybrid system. The existing single pressurized liquefaction for storing CO 2 is expanded to co-exist with liquid methanol synthesis for storing CO 2. In detail, the valid thermodynamic models are presented, and the evaluation criteria for energy conversion are described. The case study shows that the energy efficiency of the referenced MCFC/ST system reaches about 62.60 %, without cutting down this performance, the photovoltaic methanol efficiency is in the range of about 54 %–63 %, which is at a current leading level. This study also investigates the effect of oxygen purity in cryogenic air separation unit (ASU), hydrogen production pressure of proton membrane electrolytic cells (PEMEC), and incident irradiation on CO 2 -to-methanol conversion. The results indicate that O 2 purity of 0.97 in ASU, H 2 production pressure of 13.6 bar in PEMEC and a dual-axis tracking method is recommended. These findings provide theoretical guidance for improving the CO 2 -to-methanol performance and providing a possible solution to the storage of intermittent renewable electricity. • Solar-driven CO 2 -to-methanol process couples carbon capture with carbon sequestration. • Solar methanol efficiency of 54 %–63 % is gained without reducing fuel performance. • Combining PEMEC and MCFC/ST system gives a solution to store intermittent solar power. • A new approach to purifying methanol is proposed by using low-grade steam extraction. • More or all captured CO 2 can be liquid methanol rather than pressurized liquefaction. [ABSTRACT FROM AUTHOR]

Generating clean, efficient, and low-carbon electricity from coal is imperative for limiting the global temperature rise to 1.5 °C. This study presents a near-zero-carbon-emission power generation system that utilizes staged coal gasification. The innovation of this system is the division of coal gasification into two stages: intermediate-temperature pyrolysis, followed by high-temperature gasification. This process begins with utilizing waste heat from the exhaust of a gas turbine to drive the partial gasification of coal during pyrolysis. The nongaseous products from this stage are then completely gasified in the gasifier, and chemical recuperation is performed, in which heat from the syngas at the gasifier's outlet preheats the reactants at the inlet and aids in reforming pyrolysis gas. For CO 2 capture, an oxyfuel combustion strategy is used. Our system produced net electricity and exergy efficiencies of 43.01 and 47.57 %, respectively, surpassing both pre-combustion CO 2 capture systems based on staged coal gasification (improvements of 3.04 and 5.37 %, respectively) and coal-water slurry gasification (improvements of 3.55 and 5.8 %, respectively). Moreover, the carbon emissions from our system are approximately 90 g/kWh lower than those from these systems. Thus, this study offers an environmentally sustainable approach to utilizing coal that may facilitate achieving global environmental goals. • Proposes a near-zero carbon emission coal-based power generation system. • Bifurcates coal gasification into intermediate-temp pyrolysis and high-temp gasification. • Employs oxyfuel combustion strategy for CO 2 capture. • Utilizes high-temperature sensible heat in syngas through chemical recuperation. • Achieves energy and exergy efficiencies of 43.01 and 47.57 %, both superior to the baseline systems. [ABSTRACT FROM AUTHOR]

CO 2 hydrogenation technology is pivotal for achieving low-carbon and sustainable development goals by curbing carbon dioxide emissions and enabling new value chains. Traditional CO 2 hydrogenation systems face challenges like excessive unreacted gas cycling and inefficient component usage. This study employed direct CO 2 hydrogenation for methanol production, and integrated the chemical looping combustion (CLC) concept to enhance energy efficiency and carbon cycle utilization in methanol-electricity production. The proposed method has yielded remarkable results, attaining an exergy efficiency of 57.72 %, with CO 2 equivalent emissions at 0.27 kg CO 2 / kg CH 3 OH . Furthermore, it has demonstrated a reduction of approximately 9.60 % in energy consumption and an impressive 83.63 % decrease in carbon emissions compared to the reference system. Exergoenvironmental analysis was conducted for the entire process and individual units. The results indicated superior environmental performance of the cogeneration system compared to the single-production system when the recycling ratio of unreacted gas (Ru) ranged from 1.64 to 2.72. Furthermore, CLC was identified as a key area requiring optimization within the system and determined by the values of r b , k and B ˙ D , k . This observation remains consistent even as Ru changes. The system showcases significant potential in thermodynamics and environmental sustainability, and lays a theoretical foundation and innovative perspective for CO 2 utilization technologies. • The system for environmentally friendly conversion of CO 2 to CH 3 OH has been proposed. • The exergy efficiency of this process is 57.72 % with a 99.2 % carbon capture rate. • Energy consumption is decreased by 26.08 % compared to a single production system. • When Ru > 1.64, this system offers better environmental benefits than single production system. • A comprehensive evaluation of exergoenvironmental assessment is implemented. [ABSTRACT FROM AUTHOR]

Optimizing the operational parameters of the photosynthetic process is essential for effective microalgae-based CO 2 capture and fixation. This study develops and validates models that can relate the effects of CO 2 concentration and aeration rate on relevant microalgal properties, including biomass productivity and CO 2 biofixation rate. The maximum biomass concentration was predicted as 2.80 g⋅L−1 at the optimal CO 2 concentration of 10.2 % and aeration rate of 0.55 vvm. Based on the proposed models, the CO 2 biofixation rate characterized by carbon content in dry microalgal cells, and the timings of microalgae entering the exponential growth and stationary growth phases were effectively predicted. Furthermore, the lower heating value of harvested microalgal biomass was up to 21.98 kJ⋅g−1 and the dominant fatty acid methyl esters (FAME) species were C16 – C18, highlighting the potential of Chlorella vulgaris as the feedstock for microalgae-based energy production. Consequently, microalgae present a remarkable dual function for CO 2 mitigation and renewable bioenergy production. [Display omitted] • Models simulating microalgal growth and CO 2 fixation rate were developed. • Optimal CO 2 concentration and aeration rate for cell growth were determined. • High biomass of 2.80 g L−1 was achieved at the optimal operational condition. • Chlorella shows high potential on production of combustion fuel and biodiesel. [ABSTRACT FROM AUTHOR]

To establish a sustainable energy system, it is essential to achieve low-carbon and clean utilization of coal. In this study, a novel hydrogen and power cogeneration system with full CO 2 capture that based on coal supercritical water gasification (SCWG) is proposed. Hydrogen is separated from syngas produced by coal SCWG, and the remaining combustible gas is burned to generate power. Moreover, supercritical CO 2 cycle is integrated within the cogeneration system to recover the waste heat with high exergy efficiency. Thermodynamic performances, effects of key operation parameters and off-design performances under part-load conditions of the cogeneration system are analyzed. Under the design condition, the cogeneration system produces 20.26 mol kg−1 hydrogen and generates 8746 kJ kg−1 net power, achieving the high energy efficiency and exergy efficiency of 54.77 % and 52.54 %. The exergy efficiency of cogeneration system can be enhanced by optimizing the operation parameters, which is increased by 0.42 %, 4.03 % and 1.10 % with the optimal coal water slurry concentration (17.5 %), higher gasification temperature (750 °C) and higher gas turbine inlet parameters (1500 °C/3 MPa), respectively. The cogeneration system performance decreases with the power load, and the exergy efficiency decreases by 9.61 % when the system power load reduces from 100 % to 30 %. • A novel hydrogen and power cogeneration system based on coal SCWG is proposed. • Exergy efficiency of the cogeneration system achieves 52.54 % with full CO 2 capture. • Effects of key operation parameters on the system performance are evaluated. • The system off-design performance under part-load conditions is analyzed. [ABSTRACT FROM AUTHOR]

CO 2 sequestration in sediments as hydrate form is considered to be a promising way to achieve CO 2 emission reduction in the atmosphere. The key problem with hydrate-based technology for CO 2 geological storage is the evaluation of the formation process and gas storage capability of hydrate. In this study, the fundamental issue of different particle size and grain grading affected CO 2 hydrate formation and storage characteristics in porous media was deeply analyzed. The effect of various particle sizes and grain grading on the gas consumption rate and gas storage capacity of CO 2 hydrate were quantitatively illustrated. The results indicated that the hydrate formation is more difficult in porous media with tiny particle sizes. The gas storage capacity and gas consumption rate of CO 2 hydrate increased as the particle size increased within a range of 10–63 μm. The maximum gas storage capacity attains 25.65 L/L when the particle size is 63 μm. Besides, compared with single particle size, porous media with grain gradation is adverse to hydrate formation. The results also show that, the obstruction effect on the gas consumption rate and gas storage capacity is more obvious with the increase of the differences in grain gradation. The cooperative impact of particle size and gradation on hydrate formation was studied. The closer the size of the mixed particles is, the more favorable to hydrate formation. The relevant results will aid in comprehending the hydrate formation properties in submarine sediments and will serve as an essential theoretical reference and guide for CO 2 capture and sequestration hydrate-based method. • The formation rate and gas storage capacity of CO 2 hydrate in porous media with different particle sizes and grain gradating have been investigated. • The effect of different particle sizes and grain grading on the formation and gas storage process of CO 2 hydrate were quantitatively illustrated. • The influence mechanism of particle size and grain grading on the formation process and storage characteristics of CO 2 hydrate were revealed. [ABSTRACT FROM AUTHOR]

The persistently high global CO 2 emissions are exacerbating the greenhouse effect issue. Scientists have explored methods such as carbon sequestration via subsea hydrate formation in response to global warming. However, this method faces a series of challenges when injecting CO 2 on a large scale, including the slow formation rate of CO 2 hydrates and potential leakage risks. Specially, the direct injection of promoters could lead to excessively high concentrations of additives close to the injection wells. This would consequently accelerate the local hydrate conversion, potentially causing reservoir blockage problems. The current study proposes a novel strategy involving additives that exhibit varying effects with concentrations. The high-concentration areas close to the wellbore can maintain the permeability by inhibiting hydrate formation; while the reduced concentration further away upon gas migration facilitates the rapid formation of CO 2 hydrates. We successfully demonstrate the spatial and temporal differences in hydrate formation when using such additives. This can also facilitate the rapid formation of a dense hydrate cap layer over the reservoir, potentially preventing the leakage of CO 2 gas. A new type of additive based on egg albumin was developed, which possesses the dual function and exhibits good biocompatibility and specific reservoir stability. • Spatial and temporal differences in the formation of CO 2 hydrates were identified. • A dual-function additive for hydrate-based carbon sequestration was proposed. • The additive was effective in maintaining the reservoir mechanical stability. [ABSTRACT FROM AUTHOR]