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Direct air capture (DAC) technology plays a crucial role in mitigating the effects of global warming by capturing carbon dioxide (CO 2) directly from the atmosphere. A significant technical challenge for DAC is its high thermal energy consumption, which results in an unacceptable overall cost (600 $ t CO 2 – 1). The combination of a high-temperature heat pump (HTHP) and DAC system offers a substantial reduction in thermal energy consumption, decreased reliance on renewable energy sources, and enhanced DAC system flexibility. This study presents three distinct thermal integration strategies that combine an HTHP with solid adsorbent-based DAC and verifies their effectiveness in reducing energy consumption and CO 2 emissions compared to a traditional DAC system. Among them, the deeply integrated DAC-HTHP system (I-DAC) exploits low-grade adsorption heat and waste heat, providing direct heating and cooling energy to the DAC system via refrigerant condensation and evaporation processes. Simulation results indicate that the I-DAC system achieves an extremely low operating energy consumption of 2.77 GJ t CO 2 – 1 , representing a 69.5% reduction than traditional DAC under the same conditions. Consequently, the I-DAC offers a cost-effective (32.0–46.2 $ t CO 2 – 1) negative emission solution. We also demonstrate that the I-DAC is promising for wide application in cities to recycle waste heat and remove CO 2 from the air. The comprehensive implementation of the I-DAC in 105 cities could yield a net annual productivity of 980 MtCO 2. • Proposed a deeply thermal integrated DAC system (I-DAC) with waste heat recovery heat pump. • I-DAC achieved a 69.5% reduction in specific energy consumption compared to base-DAC. • I-DAC offers a cost-effective and scalable negative emission solution for climate change mitigation. • Successful implementation of I-DAC in 105 cities could yield a net annual capture capacity of 980 MtCO 2 by 2050. • Highlights the potential of I-DAC to recycle waste heat and remove CO 2 from the air, with policy implications [ABSTRACT FROM AUTHOR]

• An overview of remote sensing systems and applications in vegetation monitoring. • A review on detecting CO 2 leakage effect on vegetation using hyperspectral imaging. • Identification of major issues on distinguishing CO 2 leakage-derived plant stress. • Recommendation on an integrated remote-sensing monitoring system at CCS sites. Carbon Capture and Storage (CCS) is an emerging climate change mitigation technology which prevents carbon dioxide (CO 2) from entering the atmosphere, so as to reduce greenhouse gas emissions. Environmental monitoring in CCS sites is critical for ensuring that any CO 2 leakage and its effect on biota, especially vegetation, is detectable. It also plays an important role in creating a social license to operate and assuring the general public that the mechanisms for leak detection and remediation are in place. This review overviews current remote sensing technologies for vegetation monitoring of CCS sites/regions (with a focus on rangelands and pastures), including medium-to-high resolution satellite, aerial (both manned and unmanned aircrafts) and in situ sensors and methods. Our literature survey has pointed out that remote sensing, particularly hyperspectral sensors, can accurately detect CO 2 leakage derived effects on vegetation. It can compensate the two main drawbacks of operational systems for detecting these effects over large areas. One is the areas affected tend to be relatively small (1–15 m); and the other is symptoms in vegetation tissues tend to be similar to other stresses, such as nutrient or water deficiency. With this in mind, we have recommend that a comprehensive system should be put in place. It integrates continuous monitoring with ad-hoc detection to assess vegetation conditions in a planned CCS site. Site-based pheonocams and area-based medium-resolution satellite remote sensing sources can be used to compare any given point in time (e.g. the injection point) with the condition at the same location in the past. Before an injection commences, a baseline assessment should be conducted using the combination of high-resolution aerial hyperspectral imaging and medium-resolution long-term data from Landsat sensors. Further acquisition of high-resolution aerial imagery (ideally hyperspectral) is particularly useful following specific detected CO 2 leaking events. Aiming at bridging the gaps between research, development and implementation of CCS, this review will contribute to environmental and social impacts of sustainable energy policies, including climate change mitigation and environmental pollution reduction. [ABSTRACT FROM AUTHOR]

Global climate change is a pressing problem caused by the accumulation of anthropogenic greenhouse gas emissions in the atmosphere. Carbon dioxide (CO 2 ) capture and storage is a promising component of a portfolio of options to stabilize atmospheric CO 2 concentrations. Meaningful capture and storage requires the permanent isolation of enormous amounts of CO 2 away from the atmosphere. We investigate the effectiveness of heterogeneity-induced trapping mechanism, in potential synergy with a self-sealing gravitational trapping mechanism, for secure CO 2 storage in marine sediments. We conduct the first comprehensive study on heterogeneous marine sediments with various thicknesses at various ocean depths. Prior studies of gravitational trapping have assumed homogeneous (deep-sea) sediments, but numerous studies suggest reservoir heterogeneity may enhance CO 2 trapping. Heterogeneity can deter the upward migration of CO 2 and prevent leakage through the seafloor into the seawater. Using geostatistically-based Monte Carlo simulations of CO 2 transport in heterogeneous sediment, we show that strong spatial variability in permeability is a dominant physical mechanism for secure CO 2 storage in marine sediments below 1.2 km water depth (less than half of the depth needed for the gravitational trapping). We identify thresholds for sediment thickness, mean permeability and porosity, and their relationships to meaningful injection rates. Our results for the U.S. Gulf of Mexico suggest that heterogeneity-assisted trapping has a greater areal extent with more than three times the CO 2 storage capacity for secure offshore CO 2 storage than with gravitational trapping. These characteristics offer CO 2 storage opportunities that are closer to coasts, more accessible, and likely to be less costly. [ABSTRACT FROM AUTHOR]

This paper provides pathways of the carbon content of electricity extracted from the Intergovernmental Panel on Climate Change’s fifth Assessment Report scenarios database. It demonstrates three policy-relevant aspects of the carbon content of electricity that are implicit in most integrated assessment model results but under-discussed in academia and the policy debate. First, climate stabilization at any level from 1.5 °C to 3 °C requires the carbon content of electricity to decrease quickly and become almost carbon-free before the end of the century. As such, the question for policy makers is not whether to decarbonize electricity but when and how to do so. Second, decarbonization of electricity is still possible and required if some of the key zero-carbon technologies—such as nuclear power or carbon capture and storage—turn out to be unavailable. Third, progressive decarbonization of electricity is part of every country’s cost-effective means of contributing to climate stabilization. The pathways of the carbon content of electricity reported here can be used to benchmark existing decarbonization targets, such as those set by the European Energy Roadmap or inform new policies in other countries. They can also be used to assess the desirable uptake rates of electric and plug-in hybrid vehicles, electric stoves and heat pumps, industrial electric furnaces, or other electrification technologies. [ABSTRACT FROM AUTHOR]

Switzerland and Europe are currently at a crossroads with respect to its electricity policy. Several existing nuclear and fossil fuel power plants are to be retired in the coming years. Meanwhile, ambitious carbon dioxide (CO 2 ) emission reductions are envisaged, which could penalise fossil power plants and encourage investments in renewable-based electricity generation. Switzerland and a few other countries in Europe have decided to phase-out their nuclear capacity, thereby removing a low-carbon source of electricity in the medium- to long-term future. In order to understand possible electricity transition pathways for Switzerland, electricity supply options for Switzerland and its four neighbouring countries namely Austria, France, Germany and Italy are analysed to assess non-nuclear alternatives under a stringent climate mitigation policy. The cross border Swiss TIMES electricity model (CROSSTEM), a cost optimisation framework with a long time horizon and an hourly temporal resolution, is used for this analysis. In the absence of any CO 2 emission reduction targets, gas-based generation supplemented by electricity imports is the cost-effective alternative to nuclear for Switzerland. For a low carbon electricity system, natural gas based generation with Carbon Capture and Storage (CCS), complemented by an accelerated investment in renewable generation is required. Traditional electricity trade patterns have to be revised, with significant increases in cross-border interconnector capacities necessary to transfer electricity to Switzerland from countries with abundant renewable resources such as Germany and Italy. The average cost of electricity in a decarbonised electricity sector would increase in the range of 30–120% by 2050 compared to today, depending on the scenario assumptions. The availability of CCS technology and the requirement for electricity storage are particularly important to achieve a complete decarbonisation of the electricity sector with a nuclear phase-out. [ABSTRACT FROM AUTHOR]

[Display omitted] • The capture and utilization of CO 2 is crucial for climate change mitigation. • A plasmon-enhanced photoelectrochemical process for CO 2 and N 2 into urea was proposed. • The plasmonic Au nanostructures are tuned to maximize CO 2 and N 2 PEC reduction activity. • A PEC system based on Au nanosheets yielded higher urea (of 98.5 µg urea mg cat -1 h−1) and FE of 22.7% The photoelectrochemical reduction of CO 2 and N 2 (N 2 CO 2 RR) is a promising method of producing urea under ambient conditions since highly active and stable electrocatalysts are desired. Plasmonic metals have attracted considerable attention due to their enhanced electrochemical activity at visible and near-infrared wavelengths (NIR). Herein, the morphology of Au was tuned to spherical nanoparticles, nanorods, and nanosheets by utilizing a variety of structure-directing agents. Among them, Au nanosheets (Au NSs) can absorb a broad spectrum of NIR wavelengths, enabling electrochemical reduction of N 2 into NH 3 , with high yield rates and higher Faradic efficiency (FE) than most of the N 2 RR results reported. In addition, a distal associative pathway for N 2 RR into NH 3 has been established over Au NSs. Additionally, the Au NSs photocathode demonstrates high stability over a period of 10 consecutive runs. In addition, this work provides a guide to fabricating highly stable photocathodes that convert N 2 and CO 2 into urea. Au NSs photocathode achieves a maximum urea yield rate of 98.5 µg urea mg cat -1h−1 and FE of 22.7% at −0.7 V vs. RHE. Results show that the N 2 and CO 2 is the primary factor for urea production, whereas reducing NO 3 – and HCO 3 – contributes significantly to the total urea yield rate. Density functional theory calculations (DFT) reveal that Au NSs play a crucial role in promoting N 2 and CO 2 adsorption, activation, and stimulating the coupling reaction between C-N to form urea by the distal mechanism. As a result, this work opens up the possibility of developing hybrid catalytic systems for simultaneously reducing nitrate-containing wastewater and CO 2 , thus producing urea-rich treated water for agricultural use and achieving carbon neutrality. [ABSTRACT FROM AUTHOR]

Renewable energy can play an important role in India's climate change mitigation, as India has great potential for renewables, especially solar and wind. This paper analyses the role of renewables to meet India's possible 2050 climate change mitigation targets using a multi-region global energy system model called TIAM-UCL, where India is explicitly represented as a separate region. TIAM-UCL is a cost optimisation model. The climate policy is applied to all regions in the model based on equal per capita emissions of 1.3 tCO 2 by 2050. Analysis shows that renewable energy can play an important role to decarbonise the economy, especially the power sector. Two low-carbon scenarios are explored, the first allowing for carbon capture and storage (CCS) technology deployment and the second excluding this technology. In the first low-carbon scenario (LC1), the most critical renewable energy technologies in the power sector are biomass with CCS, solar and wind. In the second low-carbon scenario (LC2), without CCS, there is an even greater role for solar and wind. Over the whole Indian economy, by 2050 renewables contribute 57% of the total CO 2 reductions in LC1 (relative to a reference scenario with no CO 2 target) and 63% of the CO 2 reductions in LC2. [ABSTRACT FROM AUTHOR]

• Hydrogen accounts for 5–10% of total energy in 2050 under 2 °C scenarios. • Hydrogen share increases for a 1.5 °C goal and reaches 15% if CCS is limited. • Transport is the largest consumer of hydrogen, followed by industry and power. • Synthetic hydrocarbons based on hydrogen and direct air capture are an option. • Holistic energy policy design is needed rather than heavy dependence on hydrogen. Hydrogen-based energy carriers, including hydrogen, ammonia and synthetic hydrocarbons, are expected to help reduce residual carbon dioxide emissions in the context of the Paris Agreement goals, although their potential has not yet been fully clarified in light of their competitiveness and complementarity with other mitigation options such as electricity, biofuels and carbon capture and storage (CCS). This study aimed to explore the role of hydrogen in the global energy system under various mitigation scenarios and technology portfolios using a detailed energy system model that considers various energy technologies including the conversion and use of hydrogen-based energy carriers. The results indicate that the share of hydrogen-based energy carriers generally remains less than 5% of global final energy demand by 2050 in the 2 °C scenarios. Nevertheless, such carriers contribute to removal of residual emissions from the industry and transport sectors under specific conditions. Their share increases to 10–15% under stringent mitigation scenarios corresponding to 1.5 °C warming and scenarios without CCS. The transport sector is the largest consumer, accounting for half or more of hydrogen production, followed by the industry and power sectors. In addition to direct usage of hydrogen and ammonia, synthetic hydrocarbons converted from hydrogen and carbon captured from biomass or direct air capture are attractive transport fuels, growing to half of all hydrogen-based energy carriers. Upscaling of electrification and biofuels is another common cost-effective strategy, revealing the importance of holistic policy design rather than heavy reliance on hydrogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bi-level joint-probabilistic programming approach is developed. • It can handle leader–follower issues and joint-probabilistic constraints. • The proposed approach is applied to China's multi-regional energy system model. • The optimal schemes during 2021–2050 under three mitigation scenarios are obtained. • Results are helpful to achieve low-carbon goals in multi-regional energy system. Climate change mitigation and renewable resources utilization are becoming particularly urgent for energy system management. In this study, a bi-level joint-probabilistic programming (BJPP) method is developed for planning multi-regional energy system under different mitigation policies and uncertainties. BJPP can handle leader–follower issues in decision-making process as well as examine the risk of violating joint-probabilistic constraints. Based on the BJPP method, a China's multi-regional energy system (named as BJPP_CMES) model is formulated to provide optimal scheme for energy system planning of China over a long-term horizon (2021–2050) by synergistically minimizing carbon dioxide (CO 2) emission and system cost. A series of scenarios associated with different carbon capture and storage (CCS) levels and violation risks of energy-demand constraints are examined. Results reveal that: (i) the share of non-fossil energy in China's energy supply would keep increasing in 2021–2050, and the highest growth of the renewable supply would occur in Ningxia (rising 47.7%); (ii) Sichuan, Inner Mongolia, and Gansu would be the top three suppliers of renewable electricity; (iii) the CO 2 emission of China would reach a peak of [44.3, 54.8] billion tonnes during the period of 2026–2030; Shandong, Inner Mongolia, and Shanxi would be main contributors of CO 2 emission in the future; (iv) compared with the single-level model, the CO 2 emission from the BJPP_CMES model would reduce by [2.7, 5.7]%; (v) among developed regions, the individual probability level of Jiangsu-Zhejiang-Shanghai is the most significant parameter for both CO 2 emission and system cost. The findings are helpful for decision makers to optimize multi-regional energy system (MES) with a low-carbon and cost-effective manner, as well as to provide useful information for renewable energy utilization and regional sustainable development. [ABSTRACT FROM AUTHOR]

• Hubs & cluster systems are recognised to greatly decrease development costs of CCS. • Novel multi-criteria analysis is developed to identify dispersed viable CCS sites. • Spanish case study: 15 priority clusters in 4 regions selected for CCS development. • Up to 68.7 Mt CO 2 per year, 21% of Spanish emissions, can be decarbonised with CCS. • CCS combined with bioenergy and blue hydrogen is key to achieve net-zero targets. Many countries have assigned an indispensable role for carbon capture and storage (CCS) in their national climate change mitigation pathways. However, CCS deployment has stalled in most countries with only limited commercial projects realised mainly in hydrocarbon-rich countries for enhanced oil recovery. If the Paris Agreement is to be met, then this progress must be replicated widely, including hydrocarbon-limited countries. In this study, we present a novel source-to-sink assessment methodology based on a hubs and clusters approach to identify favourable regions for CCS deployment and attract renewed public and political interest in viable deployment pathways. Here, we apply this methodology to Spain, where fifteen emission hubs from both the power and the hard-to-abate industrial sectors are identified as potential CO 2 sources. A priority storage structure and two reserves for each hub are selected based on screening and ranking processes using a multi-criteria decision-making method. The priority source-to-sink clusters are identified indicating four potential development regions, with the North-Western and North-Eastern Spain recognised as priority regions due to resilience provided by different types of CO 2 sources and geological structures. Up to 68.7 Mt CO 2 per year, comprising around 21% of Spanish emissions can be connected to clusters linked to feasible storage. CCS, especially in the hard-to-abate sector, and in combination with other low-carbon energies (e.g., blue hydrogen and bioenergy), remains a significant and unavoidable contributor to the Paris Agreement's mid-century net-zero target. This study shows that the hubs and clusters approach can facilitate CCS deployment in Spain and other hydrocarbon-limited countries. [ABSTRACT FROM AUTHOR]

• An integrated top-down and bottom-up modeling framework was developed. • Analyze low-carbon pathways for Chinese iron & steel industry towards carbon neutrality. • Both the supply-side and demand-side contributions to decarbonization are explored. • Energy-saving retrofitting technologies help short-term CO 2 emissions reduction. • Breakthrough technologies are crucial in achieving carbon neutrality. Iron and steel production in China contributes to 14% of China's total energy-related CO 2 emissions. Decarbonizing the iron and steel sector will therefore play an important role in achieving the goal of carbon neutrality. This study explored possible low-carbon transition pathways for China's iron and steel industry to achieve carbon neutrality by 2050. An integrated approach was developed that combined a computable general equilibrium model and a bottom-up technology-selection module. The results indicated that although energy-saving technologies can reduce CO 2 emissions in the short term, in the long term, adopting breakthrough technologies (e.g., carbon capture and storage (CCS) and hydrogen-based direct reduction (DR)), increasing the share of scrap-based electric arc furnace (EAF) steel production, and decarbonizing upstream energy-supply sectors will be crucial for climate change mitigation. Hydrogen-based DR could be an effective option for CO 2 emission reduction in scenarios where CCS is not available, with its share increasing to 23%–25% by 2050. System-wide cross-sector decarbonization can help achieve climate targets at lower costs through flexible technology combinations and avoid carbon leakage into upstream energy-supply sectors. [ABSTRACT FROM AUTHOR]

• Detailed HTL process design with carbon capture using Selexol™ technology. • HTL process with CCS can reduce GHG emissions by 102–113% compared to fossil base. • The cost of avoided CO 2 is estimated in 75 USD/ton, excluding transport and storage. • Carbon tax and excess heat revenues can compensate the extra cost of carbon capture. • Minimum selling price of upgraded oil decreases by 15% in the best case scenario. The technical and economic feasibility to deliver sustainable liquid biocrude through hydrothermal liquefaction (HTL) while enabling negative carbon dioxide emissions is evaluated in this paper, looking into the potential of the process in the context of negative emission technologies (NETs) for climate change mitigation. In the HTL process, a gas phase consisting mainly of carbon dioxide is obtained as a side product driving a potential for the implementation of carbon capture and storage in the process (BECCS) that has not been explored yet in the existing literature and is undertaken in this study. To this end, the process is divided in a "standard" HTL base and a carbon capture add-on, having forestry residues as feedstock. The Selexol™ technology is adapted in a novel scheme to simultaneously separate the CO 2 from the HTL gas and recover the excess hydrogen for biocrude upgrading. The cost evaluation indicates that the additional cost of the carbon capture can be compensated by revenues from the excess process heat and the European carbon allowance market. The impact in the MFSP of the HTL base case ranges from −7% to 3%, with −15% in the most favorable scenario, with a GHG emissions reduction potential of 102–113% compared to the fossil baseline. These results show that the implementation of CCS in the HTL process is a promising alternative from technical, economic and environmental perspective in future scenarios in which advanced liquid biofuels and NETs are expected to play a role in the decarbonization of the energy system. [ABSTRACT FROM AUTHOR]