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Accurate estimate of the size of land carbon sink is essential for guiding climate mitigation actions to fulfill China's net-zero ambitions before 2060. The atmospheric inversion is an effective approach to provide spatially explicit estimate of surface CO 2 fluxes that are optimally consistent with atmospheric CO 2 measurements. But atmospheric inversion of China's land carbon sink has enormous uncertainties, with one major source arising from the poor coverage of CO 2 observation stations. Here we use a regional atmospheric inversion framework to design an observation network that could minimize uncertainties in inverted estimate of China's land carbon sink. Compared with the large spread of inverted sink (∼1 Pg C a−1) from state-of-the-art inversions using existing CO 2 observations, the uncertainty is constrained within 0.3 Pg C a−1 when a total of 30 stations were deployed, and is further reduced to approximately 0.2 Pg C a−1 when 60 stations were deployed. The proposed stations are mostly distributed over areas with high biosphere productivity during the growing season, such as Southeast China, Northeast China, North China, and the Tibetan Plateau. Moreover, the proposed stations can cover areas where existing satellites have limited coverage due to cloud shadowing in the monsoon season or over complex topography. Such ground-based observation network will be a critical component in the future integrated observing system for monitoring China's land carbon fluxes. [ABSTRACT FROM AUTHOR]

In recent times, various types of water purification plants have been employed to produce clean water from seawater, as a means to overcome water deficit problems. However, this process results in the production of highly concentrated reject brine solutions, which can cause significant environmental and ecological problems due to their high ionic concentration when released into the near-shore area without treatment. Conversely, these reject brine solutions can be regarded as a promising reactant for providing metal cations during the conversion of CO 2 into inorganic materials, rather than treating them as wastewater. This study proposes a CO 2 -based post-treatment process for desalinated reject brine and investigates the relationship between the ionic concentration of the reject brine solution and the polymorphic properties of inorganic compounds produced by the reaction between metal cations and CO 2. The polymorphic properties of metal carbonates were investigated with respect to the gradual changes in the concentration of the reject brine solution through dilution and concentration. As a result of this study, the degree of reaction inhibition was found to be based on the concentration of the reject brine solutions, and these results can be applied in multidisciplinary areas, including climate change mitigation, post-treatment of desalinated brine, and advanced materials and resource production. [Display omitted] [ABSTRACT FROM AUTHOR]

Direct air capture (DAC) of CO 2 is considered one of the most promising carbon capture methods to reduce ambient CO 2 concentration for climate change mitigation. Biochar represents an attractive adsorbent for DAC because it is environmentally friendly and cost-effective. In this work, KOH-activated bamboo biochar shows the CO 2 capture capacity of 3.49 mmol g−1 (25 °C, 1 bar), and it is used as an adsorbent to perform direct air capture using a fixed-bed reactor with an ambient CO 2 capture capacity of up to 51.74 μmol g−1. Furthermore, the effect of relative humidity on CO 2 adsorption by biochar was investigated and exhibited promising stability under 2.7% relative humidity. However, the biochar activity for CO 2 capture is reduced to 63.88% under 67.1% humidity after 50 cycles. [Display omitted] • KOH was used to activate bamboo-derived biochar. • Bamboo biochar was investigated in direct air capture of CO 2. • Gas selectivity of biochar during direct air capture. • Effect of relative humidity on direct air capture efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comprehensive overview of the advantages for MOFs-derived catalysts is summarized, focusing on enhancive promoters of CO 2 hydrogenation. • The different reaction pathways of CO 2 hydrogenation are concluded, aiming to provide thoroughly understanding for catalysts synthesis. • Synergy effect of different metal-based MOFs catalysts is summarized, supplying outlooks of MOFs-based catalysts for catalytic applications. Conversion of carbon dioxide (CO 2) into high-value chemical products is one promising way to generate clean energy and climate change mitigation. However, reducing CO 2 is generally challenging due to its stable chemical properties and strong C=O bonds. The application of metal-based catalysts could significantly decrease the energy barrier for CO 2 hydrogenation. Recently, the catalysts derived from metal-organic frameworks (MOFs) have shown great potential in catalytic applications for CO 2 hydrogenation. This review provides a comprehensive overview of the advantages of MOFs-derived catalysts in catalytic applications, focusing on commonly used bimetallic catalysts and their mechanistic understanding in enhancing catalytic performances. Additionally, we provide an overview of some bimetallic-based MOFs catalysts, offering convenience and insights for researchers to directly understand the potential applications of MOFs-derived catalysts. [ABSTRACT FROM AUTHOR]

To effectively mitigate climate change, policymakers worldwide established various GHG tracking and trading systems. In the light of ambitious climate goals, stricter regulations, and increasing demand for climate action, various groups such as researchers and governmental institutions suggested additional approaches. This paper addresses the complexity that arises from the breadth of suggested approaches and implemented systems for GHG tracking and trading. By doing so, it synthesizes relevant dimensions in a way that is understandable to enterprises and policymakers, enabling them to design meaningful systems incorporating the reduction of GHG emissions and advance cleaner production. Therefore, this paper presents a first-of-its-kind taxonomy of GHG tracking and trading approaches through a systematic literature review. It illustrates ten main design and implementation dimensions with 30 corresponding characteristics. To accelerate decarbonization, this paper sets impulses for future GHG tracking in the electricity sector based on semi-structured expert interviews. Consecutively, it provides policy directions for CO 2 -adaptive decision-making for enterprises, formulated as a Call for Action with seven prospective questions. These include, for example, questions concerning technical aspects like data management, legal issues like the sufficiency of existing data security and privacy regulations, as well as economic topics like the calculation of an appropriate local and temporal granularity. • Presenting a first-of-its-kind taxonomy of GHG tracking and trading approaches through a systematic literature review. • Creating targeted knowledge for enterprises and policymakers for designing meaningful systems to reduce GHG emissions. • Setting impulses for future GHG tracking in the electricity sector based on semi-structured expert interviews. • Providing policy directions for CO 2 -adaptive decision-making for enterprises, formulated as a Call for Action. [ABSTRACT FROM AUTHOR]

The aim of this paper is to assess carbon dioxide (CO 2) reduction research and strategies, in view of the 2030 Sustainable Development Goals (SDG), and in particular SDG 13 'Climate Action', achievement. According to current understanding, limiting global warming to a determined temperature level requires stabilization of atmospheric greenhouse gases by achieving net-zero emissions. This implies that all residual emissions should be counterbalanced by natural or technical long-term storage sinks. Therefore, CO 2 reduction and storage appear to be essential for curtailing global warming and for the stabilization of global climate, as a precondition for the achievement of SDGs. Catalyst preparation has a high impact on carbon removal technology, especially as far as the most promising methods, such as electrochemical and photochemical reduction, are concerned. Even if the two technologies might preliminarily appear different, the inner mechanisms, that is, electron transfer and surface absorption, are common to both. This study analyses recent literature on CO 2 catalytic reduction through the analysis of network maps created by VOSviewer to spotlight the most promising areas for the sector's improvement. [ABSTRACT FROM AUTHOR]

Monitoring CO 2 concentrations in urban areas is crucial for determining the efficacy of climate change mitigation policies. However, highly heterogeneous land use, local geography, and local convection patterns, which vary throughout the urban landscape, complicate this task. To establish continuous monitoring programs, it is important to first determine the heterogeneity of urban landscapes on the ground. To understand the role these factors play in the distribution of CO 2 over an urban area, we conducted a CO 2 measurement campaign over the Metropolitan Area of Barcelona (AMB) over four urban land uses: impervious, green, forest, and agricultural. There is a clear tendency for CO 2 mixing ratios to decrease as the degree of urban vegetation increases, even in the midst of a developed boundary layer. For example, CO 2 concentrations were 429 and 427 ppm at forest and agricultural sites, respectively, while 485 ppm was reported at urban sites. A decrease in atmospheric CO 2 was observed from 458 to 428 ppm in the gradient from urban to suburban areas, in which the biosphere component increased. The biosphere component of the CO 2 signal was significant and was observed in the gradient from urban to suburban areas, which averaged a reduction from 458 to 428 ppm. Our findings show that the large spatial variability in CO 2 concentrations (ranging from 410 to 495 ppm) is best explained by anthropogenic activity. We propose increasing the spatiotemporal resolution of CO 2 monitoring in the AMB to determine these trends more precisely over longer periods of time. • First data showing CO 2 concentration distribution over the Metropolitan Area of Barcelona. • CO 2 concentrations decrease from urban to suburban areas as biosphere increases. • Local mixing ratios of CO 2 strongly linked to temporal changes in air masses. [ABSTRACT FROM AUTHOR]

CO 2 concentration in the atmosphere has crossed an unprecedented level of 420 ppm, causing catastrophic events like climate change. Climate change mitigation via carbon capture is crucial for reducing CO 2 emissions. Among various CO 2 capture technologies, adsorption is considered one of the most efficient and promising techniques. In recent times, substantial research has been conducted on producing cost-effective and efficient adsorbents for CO 2 capture via the thermal and chemical treatments of biomass. In this review, we discuss key scientific results to give broad insight into the recent progress in biomass conversion to activated porous carbon (APC). The effects of various chemical and thermal treatments on the textural properties and CO 2 adsorption capacity of APC are comprehensively discussed. CO 2 adsorption mechanism based on interaction with the surface functionality is thoroughly explained. The economic aspects of APC synthesis and post-combustion CO 2 capture using APC are systematically reviewed. [Display omitted] • Use of biomass based activate porous carbon (APC) for CO 2 capture is reviewed. • CO 2 adsorption mechanism on APC surface is thoroughly explained. • APC surface functionalization via metal doping and heteroatom doping is discussed. • Economics of APC synthesis & large-scale CO 2 capture on APC is critically reviewed. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) in basalt is being actively investigated as a scalable climate change mitigation option. Accurate geochemical modeling prediction of the extent and rate of CO 2 mineralization is a critical component in assessing the local and global feasibility and efficacy of this strategy. In this study, we review basalt-CO 2 -water interaction experimental studies conducted during the last two decades to determine whether they provide useable information for geochemical modeling. Most of the cited experiments generate data on the temporal evolution of water composition, and a few provide identification of secondary precipitates and their compositions, offering information about the reactivity of basalts and the likelihood of secondary carbonate mineralization at various temperatures, pHs, and p CO 2 conditions. However, most experiments provide insufficient information on the properties and quantity of secondary minerals formed, prohibiting accurate mass balance calculations and hence more quantitative geochemical modeling studies. Primary Ca, Mg, and Fe-bearing minerals in basalt control the availability of major ions released into aqueous solution for carbonate precipitation, and many secondary minerals, i.e., smectites, Ca-Mg-Fe carbonates, and zeolites, provide sinks for the same major ions, some of which are difficult to quantify experimentally. Thus, we have a "multi-source and multi-sink" inverse mass balance modeling problem with insufficient constraints on the bulk system in which the temporal evolution of major ions does not provide sufficient information on which mineral(s) dissolve or the sequence of dissolution and precipitation reactions. Going forward, this review highlights the need for providing better-constrained experimental data to calibrate basalt-CO 2 -water geochemical models. Hence, we propose that future experimental work should focus on trace elements and multiple isotopic tracers as well as emphasize the need for better characterization of the solid reaction products with modern analytical instruments. [ABSTRACT FROM AUTHOR]

Climate change poses a significant threat to humanity and human activity is largely responsible for it. Clinical microbiology laboratories have their unintended shares in carbon dioxide (CO 2) emissions. The aim of this study is to estimate CO 2 emission of a clinical microbiology laboratory and to propose initiatives to reduce the emissions. CO 2 emission of instruments was estimated based on their electricity consumption. CO 2 emitted in producing consumables was estimated by weighing the consumables needed to perform major tests in a large academic hospital. A systematic literature review was performed to identify studies on the impact of clinical microbiology laboratories on the environment. A short survey was sent to four major manufacturers of agar plates on initiatives to reduce the environmental impact of their products. Opinion was given on activities that can reduce CO 2 emission in laboratories. The study shows that the largest amount of CO 2 emission in the microbiological laboratories comes from consumables and personnel commuting. For example, the production and transportation of agar plates needed to culture samples for a year in a hospital with 1320 beds result in 16 590 kg CO 2 is emitted. All survey participants mentioned that they were committed to reduce environmental impact of their products. The initiatives to reduce CO 2 emission can be performed at the laboratory and at policy level, such as reducing the number of tests to only the necessary amount to reduce consumables. The calculations contribute to map CO 2 -related emissions in clinical microbiology laboratory activities, and the proposed initiatives to reduce the CO 2 may serve as starting point for further discussions. [ABSTRACT FROM AUTHOR]

Rising greenhouse gas emissions, especially CO 2 , intensify global warming. Carbon Capture and Storage (CCS) is vital for reducing emissions from industrial sources, crucial for addressing climate change urgently. This study explores reservoir characterization challenges for CCS in the Penobscot field, offshore Nova Scotia. We used to cross-plots of geophysical logs to establish relationships between petrophysical properties and subsurface litho-facies, differentiating sand and shale facies within the Mississauga Formation (Early to Middle Cretaceous). Seismic impedance inversion distinguished between reservoir and non-reservoir facies. Multi-attribute assisted transformed seismic data and a support vector machine algorithm predicted litho-facies probabilities and effective porosity volumes in 3D space. The permutation predictor importance analysis was performed to assess the relative importance of input features in facies probabilities and effective porosity prediction. The structural component delineated the CO 2 injection trap boundary. Integrated analysis of structural configuration, litho-facies probability, effective porosity, and cap-rock sealing integrity validated zones for CO 2 storage. The dry, abandoned well L-30 in the structural high zone is recommended as a pilot CO 2 injector well. This study provides critical insights into reservoir characterization for CO 2 sequestration, aiding climate change mitigation through effective CCS, and recommends geomechanical studies and time-lapse seismic monitoring. • Identified promising sites for CO 2 storage in Penobscot field, Canada Offshore. • Predicted impedance, facies probabilities, and effective porosity with high accuracy. • Enhanced discrimination between the reservoir and non-reservoir facies. • Assessed lithological and petrophysical characteristics of the reservoir and cap rocks. • Emphasised storage site identification as a strategy to mitigate climate change. [ABSTRACT FROM AUTHOR]

Bauxite residue or Red Mud (RM) is a by-product from alumina refineries. It has a high pH of 11–13 and accumulates globally at 200 million tons yearly, totalling about 4.6 billion tons. Being an alkaline anthropogenic geomaterial, its adsorption properties and reactivity with acidic gases make it a potential sink for CO 2 and SO X emissions from the aluminium industry. It offers both research challenges and opportunities for its utilisation at an industrial scale. In particular, carbon capture and mineralisation (CCM) within RM has been demonstrated in situ and waste disposal areas through direct air trapping of atmospheric CO 2. The RM-CO 2 system is also operated in ex-situ conditions in various physical states, such as powder, wet cakes, and slurry, with yields of carbonates as CaCO 3 , Na 2 CO 3 , and FeCO 3. Our contribution as a review illuminates significant advancements made and challenges for enhancing the mineral carbonation potential of RM, thereby delineating areas necessitating further exploration. Although, researchers have primarily focused on accelerating the CCM process in RM through slurry carbonation techniques. Recent advancements in filter press technologies have favoured soda recycling and wet cake disposal of RM, creating artificial mountains of RM stacks. With changing disposal trends for RM, it is vital to understand the mechanisms that govern long-term atmospheric CO 2 trapping in RM disposal areas. Recent investigations of techniques, hydrothermal treatment and dual-stage calcification-carbonation methods have expanded the domain of CCM in RM. Given the global need to reduce CO 2 emissions, CCM using RM does offer promising insights on account of its unique physicochemical and mineralogical properties. We, although presume that RM alone will not fully offset the CO 2 emissions of the aluminium industry. Enhanced weathering and mineral carbonation could reduce over 50% of refinery emissions. Uncertainties persist regarding methods of CO 2 sequestration potential and techno-economic feasibility when tested at a field scale. Moreover, contrasting results are revealed, primarily regarding changing disposal trends, variabilities in mineralogy, and limited knowledge of micro-mechanisms of the CCM process in RM. This work elucidates existing knowledge on synthesising CO 2 mineralisation, pathways, and mechanisms under various states associated with leveraging RM as a significant carbon sink in current and future climate change mitigation efforts. [Display omitted] • Illustrates RM mineral carbonation process and mechanistic models for CCM methods (slurry, semi-dry, atmospheric). • CCM potential is studied along with mechanisms using hydrothermal treatment, siderite formation and calcification-carbonation method. • Guidelines for RM sample extraction methods based on its physico-geochemical changes in BRDA with atmospheric CO 2. • Current and future research directions are discussed. [ABSTRACT FROM AUTHOR]

Efforts to enhance greenhouse gas (GHG) emission reduction in East Asia play a pivotal role on both global and regional scales in advancing climate mitigation strategies. This study aimed to better constrain anthropogenic CO 2 emission estimates by expanding the network of near-surface in-situ stations for CO 2 observations across South Korea. To achieve an optimal CO 2 network design, we conducted an Observing System Simulation Experiment (OSSE) coupled with the Stochastic Lagrangian Transport model (STILT), utilizing meteorological data from the Korean Integrated Model (KIM). Our inversion setup incorporated two CO 2 emission datasets with a 0.1o resolution: EDGAR v6 for prior emissions and GRACED for truth emissions. A uniform model-mismatch error of 3 ppm was introduced across sites. The effectiveness of the existing five in-situ stations, termed the base network, in South Korea was evaluated to gauge their ability to constrain CO 2 surface flux estimates. However, the findings revealed a reduction in flux uncertainty of only 29.2%, which fell short of the desired uncertainty reduction goal. In this base network, the Lotte World Tower (LWT: 37.5126°E, 127.1025°E) in Seoul and the Anmyeondo (AMY: 36.538576° N, 126.330071° E) site in Taean county stood as major contributors, with estimated reductions of 17.48% and 6.35%, respectively. Consequently, we proposed and developed an extended network, identifying seven candidate sites based on consideration of logistical factors, existing infrastructures, and proximity to the emission source regions. An incremental optimization scheme ranked their contributions, resulting in an additional 25% reduction, bringing the total to 54.13%. However, it is noteworthy that diminishing returns (ranging from 13% to less than 0.1%) were observed with an increase in station count mainly due to the possibility that adding a station earlier in the sequence might render subsequent stations redundant. Despite this, the proposed CO 2 network successfully reduced uncertainty in emissions, narrowing the gap with the objectives of the Global Greenhouse Gas Watch (G3W). • Designing CO 2 near-surface observation network over South Korea. • New stations selected considering logistic factors, existing infrastructures, and proximity to emission sources. • The base network was able to reduce 29.18% of the uncertainty in CO 2 emissions. • Extending network, by adding new seven candidate sites, led to a total uncertainty reduction of 54.13%. [ABSTRACT FROM AUTHOR]

Natural climate solutions (NCS) offer immediate and cost-effective ways to tackle the climate crisis by transforming atmospheric carbon to soil carbon or avoiding greenhouse gas emissions. However, the climate mitigation potential and economic costs of NCS for cropping systems in China remain inconclusive. The major objectives of this study are (i) to estimate the NGHG reduction potential across Chinese main cropping systems caused by NCS, (ii) to quantify the economic costs of adopting optimal management with different abatement potentials. The Denitrification-Decomposition (DNDC) model was used to estimate the NGHG, including SOC sequestration, N 2 O emissions, and CH 4 emissions. After calibration, we ran the DNDC model with derived data at municipality-level. We estimated the NGHG under current management, adopting optimal management individually, and integrated optimal management to project the maximum NGHG reduction potential caused by NCS. We used the marginal abatement cost method to estimate the economic cost. The four natural climate solutions, N fertilization management (NFM), straw returning management (SRM), tillage management (TM), and rice irrigation management (RIM) can reduce national NGHG in main cropping systems by approximately 118.8 Tg CO 2 -eq, 116.3 Tg CO 2 -eq, 35.2 Tg CO 2 -eq, and 74.4 Tg CO 2 -eq, respectively. The integrated optimal management may potentially reduce NGHG by 256.9 Tg CO 2 -eq, equivalent to 90.2% of current NGHG, and 80% of which can be realized at the price of CN¥ 285 (Mg CO 2 -eq)−1. We further identify the priority NCS for different crops and regions and conclude that nitrogen fertilization management should be the priority NCS at the national level. Our findings highlight the great potential of NGHG reduction by adopting NCS precisely and the importance of optimizing agricultural management as a whole, and they will help policy makers to develop smart-agriculture in China. [Display omitted] • Estimating net greenhouse gas emissions (NGHG) reduction potentials of agriculture. • IPCC recommended tier 3 method was applied for seven cropping systems in China. • The integrated optimal management may potentially reduce NGHG by 256.9 Tg CO 2 -eq. • 80% of NGHG mitigation can be realized at the price of CN¥ 285 (Mg CO 2 -eq)−1. • The priority NCS was identified for different crops and regions. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are one of the most promising functional materials for CO 2 adsorption and transformation owing to their abundant active sites, easily functionalized surface, and highly adjustable pore structure, among others. This review discussed the recent research outputs in the synthesis and catalytic applications of MOFs – based nanocatalysts for CO 2 capture and conversion. The focus was on papers published in the last five years. The different synthetic methods of MOFs and MOF-based nanocomposites were elaborated. More so, the performance of MOFs as adsorbents in CO 2 capture and the proven performance enhancement strategies which include functionalization and compounding with other materials as nanocomposites were discussed in detail. Special emphasis was given to the different transformation routes of CO 2 viz. hydrogenation, photocatalysis, electrocatalysis, photoelectrocatalysis, and chemical fixation. As against what is obtainable in most similar reviews, the review provides insight into the application of MOF-based materials in integrated CO 2 capture and transformation. The work further provides an elaborate discussion of the current challenges and future perspectives. The reported works indicated that these MOF-based materials possessed the required competence for the adsorption and transformation of CO 2 into valuable products, making them excellent choices for practical applications. [Display omitted] • The uncontrolled release of CO2 into the atmosphere is a threat to human survival. • CO2 capture and transformation are one of the significant climate change mitigation options. • MOFs are one of the most promising functional materials for CO2 adsorption and transformation. • MOF synthesis methods are solvothermal, microwave-assisted, mechanochemical, electrochemical, and sonochemical. • CO2 transformation techniques are hydrogenation, photocatalysis, electrocatalysis, photoelectrocatalysis, and chemical fixation. [ABSTRACT FROM AUTHOR]

Planning power system (PS) towards renewable energy is crucial for reducing carbon dioxide (CO 2) emission as well as mitigating climate change. However, the inherent uncertainty and hierarchical structure of PS pose intractable challenges to the planning process. This study develops a multi-GCM-based interval bi-level programming (MIBP) method that can balance two-level decision-making conflict between CO 2 -emisison reduction and system cost minimization. MIBP can also deal with uncertainties expressed as interval values in objective functions and constraints. Then, a MIBP-PS model is formulated to plan PS for China (2021–2050), where the upper-level objective is to minimize CO 2 emission and the lower-level objective is to minimize the system cost. The major findings are: (i) the CO 2 emission for PS would reach peak value before 2030 and then reduce by [10.2, 20.4]% in 2050, which is mainly owing to the curtailment of fossil fuel; (ii) compared with the conventional model, CO 2 emission from MIBP-PS model could decrease by [3.1, 4.8]%, which shows the superiority of the developed model; (iii) the fossil-fuel power would be gradually replaced by renewable energy, and the proportion of coal-fired power would decrease by 38.8% by 2050, especially small coal-fired facilities (i.e., below 0.3 GW) should be gradually phased down. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sand tank experiments and modified invasion percolation simulations were conducted. • Simulation results match experimental results reasonably well despite discrepancies. • Curved barriers can greatly enhance CO 2 trapping while gradations do not. • Longer barriers retain more CO 2 regardless of barrier topography. • A tradeoff exists between the vertical and lateral plume migration extent. Assuring secure containment of stored CO 2 is of paramount importance—for climate change mitigation, for permitting, and for reassuring the public. Regional seals, such as those sealing petroleum accumulations, have proven to be effective for securing CO 2. However, the goal of permanent sequestration can also be satisfied with "composite confining systems" consisting of multiple, possibly discontinuous flow barriers that, in aggregate, create a system with very high permeability anisotropy and effectively retard the vertical migration of CO 2. This study focuses on investigating the barrier characteristics necessary for effective containment of CO 2 , using both physical flow experiments and modified invasion percolation simulations. The simulations are calibrated to the physical experiments and are used to further extend the analysis. Results show that for a composite confining system, a) even barriers with low capillary entry pressure contrast to the underlying flow unit can divert rising CO 2 ; b) curved or anticlinal barrier topography can enhance CO 2 trapping; c) fining-upward gradations make little difference to barrier effectiveness or CO 2 retention; d) longer barriers retain more CO 2 regardless of barrier topography. Finally, field-scale simulations have demonstrated the importance of barrier length for increasing CO 2 storage capacity. The results presented can be used to inform the development of new screening criteria for characterization and effectiveness of composite confining systems. [ABSTRACT FROM AUTHOR]

Over millions of years, the interaction of marine basalt with percolating seawater in low-temperature ocean floor hydrothermal systems leads to the formation of calcite and aragonite. The presence of these minerals in marine basalts provides evidence for substantial CO 2 fixation in these rocks. Here, we report on laboratory experiments to study this process under enhanced CO 2 partial pressures (p CO 2) at 130 °C. Mid-ocean-ridge-basalt (MORB) glass was reacted with North Atlantic Seawater charged with CO 2 in batch experiments lasting up to 7 months. For experiments initiated with seawater charged with ~2.5 bar p CO 2 , calcite and aragonite are the first carbonate minerals to form, later followed by only aragonite (±siderite and ankerite). For experiments initiated with seawater charged with ~16 bar p CO 2 , magnesite was the only carbonate mineral observed to form. In total, approximately 20% of the initial CO 2 in the reactors was mineralized within five months. This carbonation rate is similar to corresponding rates observed in freshwater-basalt-CO 2 interaction experiments and during field experiments of the carbonation of basalts in response to CO 2 -charged freshwater injections in SW-Iceland. Our experiments thus suggest that CO 2 -charged seawater injected into submarine basalts will lead to rapid CO 2 mineralization. Notably, at p CO 2 of tens of bars, magnesite will form, limiting the formation of Mg-rich clays, which might otherwise compete for the Mg cation and pore-space in the submarine basaltic crust. This suggests that the injection of CO 2 -charged seawater into subsurface basalts can be an efficient and effective approach to the long-term safe mineral storage of anthropogenic carbon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coastal landfills in Seychelles are a large source of GHGs and marine debris. • Profitability of MOL measures is dependent on SB material existing in the SIDS. • Small-scale MOL measures under CDM can be profitable for CER prices of 26 €/tCO 2 eq. • MOL can be cost-effective for GHG emission abatement from domestic climate efforts. • MOL measure contributes to certain SDG achievement – mainly SDG8, SDG13, and SDG14. Unclosed coastal landfills in small island developing states are major sources of greenhouse gases and other environmental impacts. This is a major problem for sustainable waste management systems mainly due to the lack of economic resources. The clean development mechanism (CDM) appears as a possibility to facilitate sustainable financing. Implementing a methane oxidation layer (MOL) emerges as a feasible technical option for this kind of small landfills since landfill gas extraction is usually not viable. This paper presents a techno-economic and environmental assessment of MOL implementation in the Providence landfill (Seychelles) as a small-scale CDM measure. Results show that the MOL measure could avoid by 2030 between 94 and 20 kt CO 2 eq. Concerning profitability, results clearly show that it depends on the existence of stabilized biomass material within the island. Thus, the MOL measure starts to be profitable in some scenarios for certified emission reductions (CER) prices higher than 26 €/t CO 2 eq. that seem possible depending on the emissions' market development. When not profitable under CDM, the MOL measure might be used to reduce CO 2 emissions from the domestic climate effort under the Paris Agreement since the unitary abatement costs is between 10 and 423 €/t CO 2 eq. Moreover, the MOL measure contributes to the sustainable development goals (SDG) achievement – mainly SDG8, SDG13, and SDG14. Finally, results call for a prompt action in Seychelles since the sooner the MOL is implemented after the landfill is closed, the more profitable. [ABSTRACT FROM AUTHOR]

Reducing CO 2 emissions is crucial to climate change mitigation, but there has been little progress made in the transport sector. Public transport could make a significant contribution, which would require substantial changes in travel demand. In various national transport models proportionally increasing capacities have been assumed; this must be scrutinized in the light of urgency, long-term planning and construction processes and limited financial resources. This paper presents an approach that addresses previous obstacles to the integration of unchanged capacities, namely the lack of a detailed public transport service model and rapidly increasing computation times even in small networks. Based on widely available data on public transport supply and the consideration of previous studies on the relationship between variable vehicle load and the resulting costs for passengers, an extension for a nationwide transport model is developed. In two scenarios – a substantial reduction in local public transport fares and the introduction of a charge for motorized private transport – it is shown that significantly different demand effects occur when passenger load is considered. [ABSTRACT FROM AUTHOR]

The bioeconomic potential of monopodial and sympodial bamboos is not well understood. Therefore, Net primary productivity (NPP), total biomass, carbon (C) stock, soil organic carbon (SOC), CO 2 sequestration, and bioenergy potential were studied in a sympodial Chimonocalamus griffithianus and a monopodial Phyllostachys mannii bamboo in Meghalaya, north-eastern India. P. mannii stand with mean culm density 16,877 ha−1, height 14.8 m and diameter 4.4 cm, accumulated 107.56 Mg ha−1 biomass with a total NPP of 18.83 t ha−1yr−1. It stored 50.67 Mg C ha−1 in biomass, 77.28 Mg C ha−1 in soil, and had sequestration potential of 469.58 t CO 2 ha−1. C. griffithianus stand with mean clump density 1065 ha−1, mean culm density 52,185 ha−1, height 7.19 m and diameter 3.04 cm, accumulated 67.08 Mg ha−1 biomass with a total NPP of 15.30 t ha−1 yr−1. It stored 31.30 Mg C ha−1 in biomass, 83.25 Mg C ha−1 in soil, and had sequestration potential of 420.40 t CO 2 ha−1. Matured culms (>2–3 years old) of P. manni and C. griffithianus produced 143.08–166.65 MW h and 87.13–101.48 MW h of energy per ha, respectively. Although landuse history and site characteristics of the two stands were not 100 % identical, significantly greater (p < 0.05) standing biomass, NPP, growth rate, carbon sequestration potential, and energy values of P. mannii than C. griffithianus makes the monopodial bamboo a better choice for energy plantation and climate change mitigation tool than the sympodial. • Monopodial bamboo, Phyllostachys mannii , surpasses sympodial Chimonocalamus griffithianus in bioeconomic potential. • P. mannii exhibits higher biomass, NPP, carbon sequestration, and energy values. • Comparative analysis reveals the superior suitability of monopodial bamboo for energy plantations. • Results provide valuable insights for sustainable development in India's biobased economy. • Study contributes to understanding the role of bamboos in mitigating climate change. [ABSTRACT FROM AUTHOR]

Carbon dioxide removal (CDR) is recognized as an important tool for addressing residual emissions and achieving net-zero emission targets. While some have cautioned that a focus on CDR in policy processes may lead to delayed efforts to mitigate emissions, others have argued that such concerns are unwarranted. Nevertheless, the circumstances under which CDR could help or delay emissions mitigation in given contexts remain unclear. This paper explores the emerging discourse on CDR in Switzerland. We examined how the CDR community legitimizes CDR and limits its scope, and what the implications are for emissions mitigation. Switzerland is home to growing businesses in CDR and has pioneered the implementation of international offsetting projects under Article 6.2 of the Paris Agreement. We found that numerous promises help legitimize and attract interest in CDR. Actors use discursive strategies and rules to limit CDR and avoid disappointment in its contribution to climate mitigation. The idea that emission reduction should prevail over removal is promoted accordingly, which ironically helps legitimize the CDR idea yet dodges the question of how much removal is possible and for balancing which emissions. Superficial engagement with the issue is reinforced by the normalization of inflated promises and the sentiment that the mitigation deterrence rhetoric erodes trust in CDR. We argue that this can contribute to mitigation delays by evading the debate on what it is possible to remove and taking resources from alternative measures. We recommend a thorough discussion to examine the risks and the implementation of rules that minimize them. • Mitigation deterrence discourse leads to efforts to avoid substitution dynamics. • "Reductions first" legitimizes CDR without coordinating emission residuals. • Inflated promises of CDR may reduce resources for more realistic measures. • Attention to CDR dynamics is required to help achieve comprehensive decarbonization. [ABSTRACT FROM AUTHOR]

Policies that incentivize the capture and geological storage of CO 2 from large point sources ('CCS'; and more recently, atmospheric removals), have so far tended to reward the resultant avoided CO 2 emissions (or CO 2 removals) achieved by operators at the point of capture. The expectation has been that geological CO 2 storage sites, as well as the connecting infrastructure, will be developed and operated based upon the funding delivered from the single point of incentive (e.g. under an emissions trading system or a carbon tax, only CO 2 capture installation operators are absolved of the obligation to acquire and surrender CO 2 emission rights or to pay the tax). Project-based crediting mechanisms (e.g. in the voluntary carbon market) tend to treat the entire chain of operations as a single entity to be supplied with emission reduction or removal credits. Consequently, there has been minimal explicit financial incentive to store CO 2. Yet a multiple gigaton-per-year scale capture and storage industry requires complex CO 2 networks to evolve, with multiple sources connecting to multiple sinks, with installations owned by different operators with different technical expertise, climate mitigation goals and obligations. This multiplicity of goals and incentives can create agency problems and cross-chain risks, which impact negatively upon investment decisions. In this paper, we review the history, evolution and potential of geological net zero (GNZ) and carbon storage (or takeback) obligation concepts applied to fossil carbon producers and suppliers as a means to address these risks alongside policies aimed at atmospheric net zero (ANZ) and fossil carbon emitters. [ABSTRACT FROM AUTHOR]

• We conducted interviews with 35 experts involved in mCDR research and development. • Interviews revealed tensions regarding four themes. • Expert consensus on these tensions is unlikely, but they raise important questions. • Governance of mCDR would benefit from exploring these in expert and public fora. While research on marine carbon dioxide removal (mCDR) expands apace, significant unknowns persist regarding the risks and benefits of individual mCDR options. This paper analyses the assumptions and expectations that animate expert understandings of mCDR, with a focus on issues that are central to the responsible governance of this emerging field of climate action. Drawing upon interviews with experts involved in mCDR research projects both academic and entrepreneurial, we highlight four thematic tensions that orient their thinking but are often unstated or left implicit in scientific and technical assessments: (1) the relevance of 'naturalness' as a criterion of evaluation for mCDR approaches; (2) the perceived need to accelerate research and development activities via alternative paradigms of evidence-building; (3) a framing of mCDR as a form of waste management that will, in turn, generate new (and currently poorly understood) forms of environmental pollutants; and (4) a commitment to inclusive governance mixed with difficulty in identifying specific stakeholders or constituencies in mCDR interventions. Although expert consensus on these four issues is unlikely, we suggest ways of ensuring that consideration of these themes enriches debate on the responsible development of novel mCDR capabilities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biochemical content increased at the expense of biomass production. • CO 2 at 5% produced 4% more carbohydrates but at a 50% reduction of Chlorella biomass. • Carotenoids contents increased at the cost of 32% reduced Nostoc biomass production. • CO 2 at 10% significantly promoted protein, carbohydrate and lipids in Chlamydomonas. Microalgae's exceptional photosynthetic prowess, CO 2 adaptation, and high-value bioproduct accumulation make them prime candidates for microorganism-based biorefineries. However, most microalgae research emphasizes downstream processes and applications rather than fundamental biomass and biochemical balances and kinetic under the influence of greenhouse gases such as CO 2. Therefore, three distinctly different microalgae species were cultivated under 0% to 20% CO 2 treatments to examine their biochemical responses, biomass production and metabolite accumulations. Using a machine learning approach, it was found that Chlorella sorokiniana showed a positive relationship between biomass and chl a, chl b, carotenoids, and carbohydrates under increasing CO 2 treatments, while Chlamydomonas angulosa too displayed positive relationships between biomass and all studied biochemical contents, with minimal trade-offs. Meanwhile, Nostoc sp. exhibited a negative correlation between biomass and lipid contents under increasing CO 2 treatment. The study showed the potential of Chlorella , Chlamydomonas and Nostoc for commercialization in biorefineries and carbon capture systems where their trade-offs were identified for different CO 2 treatments and could be prioritized based on commercial objectives. This study highlighted the importance of understanding trade-offs between biomass production and biochemical yields for informed decision-making in microalgae cultivation, in the direction of mass carbon capture for climate change mitigation. [ABSTRACT FROM AUTHOR]

• CCUS development among EU countries with the latest progress in the field. • Realization of EGD targets with CCUS technology in EU. • Applicability of benchmarking method to compare environmental profiles. • UK and the Netherlands are among top countries with rapid CCUS development. • Poland and Germany with a high level of difficulty in achieving the EGD targets. Carbon Capture Utilization and Storage (CCUS) is a technology highlighted as one of the tools in climate change mitigation and one of the ways to reach the goal of 1.5℃ set by the Paris Agreement. The European Commission (EC) developed this goal by creating and implementing the European Green Deal (EGD) – the European Union's (EU) environmental policy. This paper provides an analysis of environmental policies and an overview of crucial CCUS projects of selected member states based on a benchmarking analysis of 27+ UK member states. An overall review of a total of 28 countries was undertaken based on economic and environmental factors. Afterward, a benchmarking analysis was performed ranking the countries according to the TOP10 for the selected five categories: total net emissions with international transport, percentage share of the energy sector, percentage share of fossil fuels, percentage share of fossil fuels in the Gross Electricity Production (GEP), and numbers of CCUS projects. Subsequently, a detailed and comprehensive overview of four selected member states was done, with a special focus on the national energy policy towards net-zero emission goals, the role of CCUS in domestic environmental policy, with current projects and facilities development. Finally, this paper outlines how the EGD has reformed the national energy policies of selected member states, and what is the part of CCUS technology in the national efforts towards climate neutrality. [ABSTRACT FROM AUTHOR]

Crop residue burning is a common practice in many parts of the world that causes air pollution and greenhouse gas (GHG) emissions. Regenerative practices that return residues to the soil offer a 'no burn' pathway for addressing air pollution while building soil organic carbon (SOC). Nevertheless, GHG emissions in rice-based agricultural systems are complex and difficult to anticipate, particularly in production contexts with highly variable hydrologic conditions. Here we predict long-term net GHG fluxes for four rice residue management strategies in the context of rice-wheat cropping systems in Eastern India: burning, soil incorporation, livestock fodder, and biochar. Estimations were based on a combination of Tier 1, 2, and 3 modelling approaches, including 100-year DNDC simulations across three representative soil hydrologic categories (i.e., dry, median, and wet). Overall, residue burning resulted in total direct GHG fluxes of 2.5, 6.1, and 8.7 Mg CO 2 -e in the dry, median, and wet hydrologic categories, respectively. Relative to emissions from burning (positive values indicate an increase) for the same dry to wet hydrologic categories, soil incorporation resulted in a −0.2, 1.8, or 3.1 Mg CO 2 -e change in emissions whereas use of residues for livestock fodder increased emissions by 2.0, 2.1, or 2.3 Mg CO 2 -e. Biochar reduced emissions relative to burning by 2.9 Mg CO 2 -e in all hydrologic categories. This study showed that the production environment has a controlling effect on methane and, therefore, net GHG balance. For example, wetter sites had 2.8–4.0 times greater CH 4 emissions, on average, than dry sites when rice residues were returned to the soil. To effectively mitigate burning without undermining climate change mitigation goals, our results suggest that geographically-target approaches should be used in the rice-based systems of Eastern India to incentivize the adoption of regenerative 'no burn' residue management practices. • Efforts to build SOC for climate change mitigation, while simultaneously avoiding burning, may have unintended consequences. • Tier 1, 2, and 3 modelling approaches were used to compare no-burn rice residue pathways. • Field hydrology had a dominant effect on methane emissions. • Soil incorporation of residues increased emissions relative to open burning, except in comparatively dry fields. • Biochar is estimated to have the lowest GHG emissions of the evaluated 'no burn' alternatives. [ABSTRACT FROM AUTHOR]

Animal production faces challenges related to thermal comfort, air quality, and carbon dioxide (CO 2) emissions, thereby the need for more efficient and sustainable systems due to climate change. This study examines green roofs and their potential to absorb atmospheric CO 2 and reduce heat load through photosynthesis and evapotranspiration, resulting in decreased energy consumption and increased CO 2 emissions. The maximum CO 2 concentration limit in animal production facilities is 3000 ppm. Depending on the ventilation system used in broiler production facilities, the CO 2 concentration can exceed 2000 ppm. Dark House poultry facilities tend to have higher concentrations reaching up to 777 ppm. In pig farming, the nursery sector has higher concentrations of CO 2 , exceeding 1200 ppm. In dairy farming, the number of milkings, the type of ventilation system and local climatic conditions can affect the CO 2 concentration, reaching values of up to 1401 ppm. C3 plants have a CO 2 saturation point at 800 ppm and C4 plants at 200 ppm. The CO 2 balance in animal production facilities that use a green roof can be done considering the CO 2 produced and the CO 2 absorbed. Green roofs are therefore considered a sustainable solution for animal production. Its implementation enhances air quality in the facilities, supporting the reduction of environmental impacts and mitigation of climate change effects caused by the agroindustry. This investigation underscores the significance of green roofs, emphasizing their environmental, social, and economic benefits, as well as their applicability in animal production. • It is possible to estimate the CO 2 balance in animal production facilities with a green roof. • Green roof can improve air quality in animal production. • Green roof can reduce the thermal stress of the animals in the premises. • Green roof can contribute to the sustainability of animal production. [ABSTRACT FROM AUTHOR]

CO 2 , a byproduct from various industrial reactions, must not be released into the atmosphere and should be managed through capture, conversion, and utilization. The first step in converting CO 2 into valuable products is to break the C–O bond. This work focuses on designing Single Atom Catalysts (SACs) by doping Cu(211) surface with 13 different s, p, and d block elements with an aim to minimize the activation barrier for C–O bond cleavage. Our work demonstrates that SACs of Mg/Al/Pt@Cu(211) favor CO 2 chemisorption compared to Cu(211) where CO 2 physisorbs. The barrier for CO 2 dissociation is lowest for Mg@Cu(211) and it increases in the order Mg@Cu(211) < Al@Cu(211) < Pt@Cu(211) < Zn@Cu(211) < Ga@Cu(211) < Cu@Cu(211) < Pd@Cu(211). These findings suggest that doping Cu(211) with earth-abundant metal like Mg can potentially be a viable catalyst for CO 2 conversion, providing a promising solution to reduce carbon footprint and mitigate climate change. [Display omitted] • Investigating interaction of CO2 with SACs@Cu(211) by employing periodic DFT. • Doping Cu(211) with single metal atom enhances its catalytic activity. • Significant lowering of the barrier for reducing CO2 to CO on Mg/Al/Pt@Cu(211). • Mg@Cu(211) demonstrates superior performance by exhibiting the lowest barrier. [ABSTRACT FROM AUTHOR]

• An isolated strain of Parachlorella kessleri was evaluated as an extracellular carotenoid producer. • Photobioreactor kinetic assays were performed under different CO 2 concentrations. • Physiological parameters and pH profiles varied in response to CO 2. • CO 2 levels in the gas inlet affected the fatty acid composition and carotenoid yields. Large-scale cultivations of photoautotrophic microorganisms represent a very promising and potentially cost-effective alternative for climate change mitigation, when associated to the co-production of high value bioproducts, such as fatty acids and carotenoids, considering the growing demand for natural products. During microalgae cultivation, CO 2 enrichment is a requirement to reach high productivities, although high CO 2 levels are normally stressful to microalgae. On the other hand, cellular stress is a well reported strategy to induce carotenoid and fatty acids production. This work evaluated extracellular carotenoid production from the mangrove-isolated microalga Parachlorella kessleri cultivated under 5, 15 and 30% CO 2 in stirred tank photobioreactors. In the 10th day of cultivation, CO 2 supply was interrupted until the end of the cultivation (14th day), causing a stressful and imperative condition for microalgae cells to release the red pigment. Growth kinetics, physiological parameters and bioproducts production were evaluated. Growth kinetics were similar under all tested conditions and differences were not statistically significant, with the highest values of μ max , biomass concentration, lipid content and CO 2 fixation rate of 0.77 d−1, 1.24 g L−1, 241 mg g−1 (dw) and 165 mg L−1 d−1, respectively. In contrast, total carotenoid concentrations varied significantly (p < 0.01), with the highest concentration of 0.030 μg mL-1 under 5% CO 2. The produced red pigment presented antioxidant activity and characteristics of carotenoids confirmed by UV–vis and tandem mass spectrometry (MS/MS). The fatty acid profiles in the biomass varied in response to CO 2 levels in the cultivations. In general, higher CO 2 concentrations (15 and 30%) favored the production of saturated and mono-unsaturated fatty acids, suitable as biodiesel feedstock, while drastically decreased the production of the polyunsaturated. [ABSTRACT FROM AUTHOR]

• Constructing waste to energy platform was achieved by macadamia nutshell pyrolysis. • For a sustainable energy production, CO 2 was utilized as a reactive gas medium. • Two stage CO 2 -cofeeding pyrolysis expedited syngas (H 2 and CO) formation. • Thermal cracking of VOCs via catalytic pyrolysis enhanced syngas formation. Here in this study, we laid great stress on a development of sustainable waste-to-energy (WtE) platform via CO 2 -cofeeding catalytic pyrolysis of macadamia nutshell (MNS) at mild temperature region. To this end, one-stage and two-stage (non-catalytic/catalytic) pyrolysis of MNS was performed to establish the fundamental relationship of temperature effect on syngas formation. The formation of gaseous pyrolysates was substantially enhanced when two-stage pyrolysis of MNS was applied, and second heating zone isothermally ran at 700 °C. Such the enhanced generation of gaseous pyrolysates from two-stage MNS pyrolysis of MNS was likely due to temperature-driven cracking of volatile organic compounds (VOCs). Also, catalytic two-stage pyrolysis of MNS was performed at lower isothermal running temperature (500 °C) over Ni/SiO 2 and Co/SiO 2. The enhanced formation of syngas (H 2 and CO) was observed from catalytic pyrolysis of MNS. Therefore, pyrolysis of MNS over Ni/SiO 2 or Co/SiO 2 could be a reliable platform for enhancing syngas formation at mild temperature (≤ 500 °C) under CO 2 environment. In addition, all experimental findings suggested that the use of CO 2 is beneficial in the WtE platform, and the use of CO 2 could be a practical climate change mitigation measure. [ABSTRACT FROM AUTHOR]

• The role of alkali cations on the CO 2 to carbon nanotube transformation is probed. • CO 2 is converted to CNTs either directly from the air, or with smokestack or pure CO 2. • Superalloy nickel anodes are effective for molten carbonate electrolysis. • Thermal balance and a secondary pure O 2 product are achieved in the CO 2 electrolysis. The electrochemical splitting of CO 2 in molten carbonate salt electrolytes can form a valuable product, carbon nanotubes, and with this product a value-incentivized pathway of climate change mitigation by transforming CO 2 from a greenhouse gas pollutant into a useful resource. Instability of the anode can provide a challenge for a commercialization of this electrochemical technology. A nickel superalloy (Inconel 718) anode is shown to be highly stable for the scalable controllable, electrosynthesis of nano-carbons from CO 2 in molten carbonates salts. Unlike pure nickel anodes that degrade (corrode) in the presence of potassium carbonate containing molten electrolytes, Inconel is stable as an anode even in these electrolytes. This opens up more cost-effective electrolytes (less expensive than lithium carbonate), and the systematic variation of alkali cation carbonates is explored. Coupled with a brass cathode, uniform carbon nanotubes (CNT) are efficiently synthesized by electrolysis of CO 2 in either pure Li 2 CO 3 or in ternary electrolytes, Li 2 CO 3 -Na 2 CO 3 -LiBO 2 or Li 2 CO 3 -K 2 CO 3 -LiBO 2. These results increase the foundation of understanding of the electrolytic splitting of carbon dioxide and provide the data for developing a high-efficiency CO 2 electroreduction for the production of carbon nanotubes. [ABSTRACT FROM AUTHOR]

Freshwater bodies are found as significant sources of greenhouse gas to the atmosphere, but their quantitative significance is not yet clear. The rapid increase in hydropower dams and associated emissions has received much attention from hydropower industries, environmentalists, and policymakers from across the globe. The tropical/subtropical eco-regions are, particularly, considered as hotspots from greenhouse gas production point of view as the emitted gases are playing a critical role in climate change. The present paper reviews the uncertainty and limitations of greenhouse gas measurement from Chinese freshwater bodies based on available data. Literature reported that carbon dioxide emission from Chinese lakes falls in the range of 0.01–2.16 μmol m−2s−1 except for Poyang Lake. The CO 2 emission from Chinese hydropower reservoirs is estimated as 0.15–1.11, while for rivers, it is 0.44–4.12 μmol m−2s−1. The methane and nitrous oxide emissions are, however, found less than carbon dioxide emission. The CO 2 emission falls in the range of −0.17–0.54 and 1.08–1.70, respectively higher than global lakes and rivers, while the global reservoirs have emission in the range of −0.17–2.98 μmol m−2s−1. The paper also reports the challenges in the estimation and prediction of greenhouse gas emissions from hydropower reservoirs along with suggested mitigation measures. Image 10945 • GHG emissions have been limited by data availability and inconsistencies in methodological approach. • Investigate uncertainty and limitation of GHG measurement. • Literature reveals CO 2 emission from Chinese rivers is twice than lakes and four times than hydropower reservoirs. • CH 4 and N 2 O emissions are however found less than CO 2 emission. • Suggested mitigation measures to minimize the impact of GHG on climate change. [ABSTRACT FROM AUTHOR]

Air pollution and climate change are currently common global concern issues. Understanding the main pollution sources of fine particulate matter (PM 2.5) and carbon dioxide (CO 2), and the drivers that accelerate their concentrations can provide novel insights into the co-benefits of air-quality improvement and climate change mitigation. Hence, in this study, we conducted source apportionment of PM 2.5 and CO 2 , and obtained impacts of common sources on PM 2.5 -CO 2 using an ensemble source apportionment method. Then, machine learning (ML) methods were utilized to study the effects of different drivers (including main pollution sources and meteorological factors) on PM 2.5 and CO 2. The results demonstrate that coal combustion (40%), vehicle exhaust (37%), and industrial emissions (23%) were the main common sources of PM 2.5 and CO 2. Controlling the combustion of fossil fuels and long-term vehicle electrification still hold significant importance for reducing pollutions and carbon emissions. The results of data-driven ML models show that temperature had the highest effect among meteorological factors, reflecting the seasonal changes of CO 2 and PM 2.5. The study provides a feasible framework for exploring co-benefits of clean air policies on greenhouse gas emissions based on online observation dataset. [Display omitted] • Variation characteristics and sources of PM 2.5 , and CO 2 were analyzed. • Machine learning methods reveal the impact of drivers on PM 2.5 and CO 2. • Secondary sources are still the focus of particle pollution prevention and control. • Controlling the combustion of fossil fuels benefits mitigation of PM 2.5 and CO 2. [ABSTRACT FROM AUTHOR]

• This work offers a comprehensive overview of the latest developments and future prospects in CCTUS technologies. • This work investigates the challenges and opportunities associated with the future adoption and advancement of CCTUS technologies. • This work serves as an invaluable resource for researchers and industry professionals seeking to CCTUS technologies. Carbon capture, transport, utilization, and storage (CCTUS) technologies are widely regarded as crucial solutions for mitigating the impacts of climate change. This review paper offers a comprehensive overview of the latest developments and future prospects in CCTUS technologies. The paper delves into the principles and applications of various CCTUS technologies. The advantages and disadvantages of each technology are explored, along with studies highlighting successful integration of CCTUS technologies. Additionally, the paper investigates the challenges and opportunities associated with the future adoption and advancement of CCTUS technologies. This review serves as an invaluable resource for researchers and industry professionals seeking to comprehend the present state and potential future of CCTUS technologies. [ABSTRACT FROM AUTHOR]

In life-cycle impact assessment, currently available characterisation factors (CF) for climate change impacts on biodiversity are highly simplified and do not consider spatial and taxonomic differentiation of species or local climate variability. We develop the first spatially and taxonomically specific CFs for the impacts of 20 GHGs on biodiversity considering 26,648 species across terrestrial and marine ecosystems. Generally, CFs are higher in the tropics, and marine species are affected more severely than terrestrial ones. When global GHG emissions from 2020 are assessed in a scenario with a global temperature rise of 3 °C by 2100, an average of 0.25%, 0.15% and 0.03% of species are negatively affected in 2100 from CO 2 , CH 4 , and N 2 O emissions, respectively, across the globe. The new CFs can be used at different levels of spatial and taxonomic aggregation to quantify co-benefits for biodiversity of climate change mitigation in tools such as life-cycle assessment, input-output analyses, or integrated assessment models. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Rich portfolios of carbon dioxide removal methods lead to more sustainable modeling outcomes. • Socio-economic pathways significantly affect the direct air capture deployment. • National studies can provide better decision support in a direct air capture context. • Integrated assessment models should include different variants of direct air capture. • Both storage and utilization options should be available in modeling studies. To limit global warming to levels set in the Paris Agreement, integrated assessment modeling highlights the necessity of removing gigatons of carbon dioxide. Direct air capture is one of the potential methods for carbon dioxide removal and has gained significant attention despite being a relatively new technology. While some scenarios can meet Paris targets without relying on direct air capture, other models show the need for up to 38 gigatons/yr of removal by this technology. Such wide variation in projections reflects uncertainty over the feasibility of deploying direct air capture at scale and points the need for greater attention to the model assumptions driving this variation. This study provides a comprehensive review of scenarios from the Intergovernmental Panel on Climate Change Sixth Assessment Report and peer-reviewed studies focusing on direct air capture as a mitigation strategy. The review identifies several key factors contributing to uncertainty in direct air capture projections, including prolonged fossil fuel use, diversity of carbon removal methods, future socio-economic conditions, intergenerational assumptions, deployment limitations, and technology costs. The study recommends conducting multi-model assessments of direct air capture scenarios due to the influence of various assumptions and model structures on projections. The authors also suggest including different variants of direct air capture technology and both carbon utilization and storage pathways in future models, as these factors can impact system demands, economic efficiency, and public acceptability. [ABSTRACT FROM AUTHOR]

• Indoor CO 2 exceeded 1000 ppm 33% of the time and ventilation rates were below 7 L/s. • Increasing ventilation increased CO 2 emissions, energy, and costs between 1 and 4%. • Rooftop gardens always counterbalanced increased CO 2 emissions, energy, and costs. • Enhancing plant growth increases CO 2 emissions benefits by an additional 23%. Building energy use contributes to urban carbon dioxide (CO 2) emissions while inadequate ventilation can yield indoor CO 2 build up from human respiration. However, increasing ventilation rates can add to energy costs and climate burdens. Our objective was to quantify changes in emissions, energy, and financial cost when rooftop garden and ventilation upgrades are done simultaneously, with an opportunity to enhance plant growth from exhausted CO 2. We measured indoor CO 2 concentrations, calculated ventilation rates, and modeled five scenarios to assess these impacts. The indoor CO 2 concentration maximum was 2210 ppm, median was 840 ppm, and 33% of the daytime was spent above 1000 ppm. The estimated ventilation rate was 4 L/s. Our model calculations show that increasing ventilation to recommended levels (7 L/s) would increase total CO 2 emissions, energy use, and cost (1–4%), but this could be counterbalanced by rooftop garden installation benefits, which yielded a net decrease of 23–46% in CO 2 emissions, 12–13% in energy use, and 12–16% in cost. This novel integration of data collection and modeling provides support for the co-benefits of simultaneous improved installation ventilation systems and indoor CO 2 -enhanced rooftop gardens. [ABSTRACT FROM AUTHOR]

The lack of safely managed sanitation services is a major global public health and ecological sustainability challenge. Ecological sanitation (EcoSan) technologies designed to close the "poop loop" through the capture, treatment, and beneficial reuse of human feces can meet this interconnected challenge. EcoSan has the potential to mitigate climate change through the reduction of greenhouse gas (GHG) emissions, yet the climate impacts of EcoSan are poorly understood. We measured GHG emissions (carbon dioxide, CO 2; methane, CH 4 ; and nitrous oxide, N 2 O) from two EcoSan operations in Haiti, as well as two anaerobic waste stabilization ponds and a grass field where sewage is known to be illegally deposited. Carbon dioxide was the major constituent of total GHG emissions from both EcoSan systems. Nitrous oxide emissions were similar across both EcoSan systems, however CH 4 emissions were significantly higher in the system with moister pile conditions. Highest CH 4 fluxes were observed during the first two months of composting in both EcoSan systems. In a paired-comparison, we found that piles with a soil lining had four-fold lower CH 4 emissions and three-fold lower N 2 O emissions compared to piles with a cement lining. Overall climate-forcing effects of emissions from EcoSan were favorable relative to waste stabilization ponds and unmanaged disposal on grass fields. In contrast to EcoSan, CH 4 emissions dominated net emissions from waste stabilization ponds, accounting for 94% of net emissions, and N 2 O emissions were negligible. Methane emissions from waste stabilization ponds were up to 250 times higher than those from EcoSan compost piles. The grass field had a significantly higher CH 4 flux than EcoSan, and the highest N 2 O flux rate observed. Our data suggest that EcoSan systems can contribute to climate change mitigation by reducing GHG emissions relative to alternative sanitation pathways, and EcoSan management conditions can be optimized to minimize emissions. • Greenhouse gas emissions from ecological-based sanitation (EcoSan) systems are poorly quantified. • Composting human waste reduced methane emissions compared to stabilization ponds. • Climate-forcing effects of EcoSan emissions were less than alternative pathways. • Management of compost piles that reduces moisture minimizes methane emissions. [ABSTRACT FROM AUTHOR]

• CO 2 gas bubbles are completely dissolved within 2 m above the seabed. • CO 2 is not emitted into the atmosphere but retained in the North Sea. • Dissolved CO 2 is rapidly dispersed by tidal currents in the North Sea. • Harmful effects on benthic biota occur in the direct vicinity of the leak. • Monitoring has to be performed at the seabed and close to the leak. Existing wells pose a risk for the loss of carbon dioxide (CO 2) from storage sites, which might compromise the suitability of carbon dioxide removal (CDR) and carbon capture and storage (CCS) technologies as climate change mitigation options. Here, we show results of a controlled CO 2 release experiment at the Sleipner CO 2 storage site and numerical simulations that evaluate the detectability and environmental consequences of a well leaking CO 2 into the Central North Sea (CNS). Our field measurements and numerical results demonstrate that the detectability and impact of a leakage of <55 t yr−1 of CO 2 would be limited to bottom waters and a small area around the leak, due to rapid CO 2 bubble dissolution in seawater within the lower 2 m of the water column and quick dispersion of the dissolved CO 2 plume by strong tidal currents. As such, the consequences of a single well leaking CO 2 are found to be insignificant in terms of storage performance. Only prolonged leakage along numerous wells might compromise long-term CO 2 storage and may adversely affect the local marine ecosystem. Since many abandoned wells leak natural gas into the marine environment, hydrocarbon provinces with a high density of wells may not always be the most suitable areas for CO 2 storage. [ABSTRACT FROM AUTHOR]

• Global Change Assessment Model is used to assess CCUS potential in Chinese provinces. • CCUS deployment depends on policy approaches and total mitigation needs. • Near-term CO 2 capture focuses on industrial and synthetic fuel production sectors. • CO 2 capture in the power sector becomes increasingly important toward mid-century. • Storage is not a constraint except for provinces with limited onshore storage. China is the world's largest energy consumer and carbon dioxide (CO 2) emitter. China has committed to limit its greenhouse gas emissions. With its heavy reliance on domestic coal resources, China faces an enormous challenge of transitioning its economy to a low-carbon energy mix to achieve long-term climate and local air quality goals. Carbon capture, utilization, and storage (CCUS) is widely recognized as an important option for emissions mitigation. The near-term readiness and cost of CCUS technologies, the sectors and regions of CO 2 capture, and the location and adequacy of CO 2 storage sites all affect the application of CCUS in China's low-carbon development. This study uses GCAM-China, a global integrated assessment model with details for 31 provinces in China, to examine the role of CCUS as part of China's climate mitigation strategy over the period of its Nationally Determined Contributions as well as in the transition to deeper emissions reductions toward mid-century. The inclusion of new provincial CO 2 storage cost curves gives a more detailed evaluation of where, in terms of geography and sector, and when CCUS deployment in China may take place. The results suggest that the scale of deployment varies depending on socioeconomic development pathways and the level of deployment of other low-carbon technologies. Across provinces and development pathways, early deployment of CCUS occurs within industrial and synthetic fuel production sectors, followed by increased deployment in the power sector by mid-century. Several provinces, such as Shandong, Inner Mongolia, Hebei, and Henan, emerge as particularly important in CCUS deployment, as a result of large CO 2 point sources and storage availability. Results indicate that storage resource availability is unlikely to constrain CCUS deployment in most provinces through the end of the century. [ABSTRACT FROM AUTHOR]

Highlights • Restored, managed wetlands sequestered carbon by inhibiting ecosystem respiration. • Agricultural land uses on degraded peat soils lost soil carbon to the atmosphere. • Large CH 4 emissions result in restored wetlands being short-term greenhouse gas sources. • Restoration often resulted in greenhouse gas switchover times of more than a century. Abstract Restoring degraded peat soils presents an attractive, but largely untested, climate change mitigation approach. Drained peat soils used for agriculture can be large greenhouse gas sources. By restoring subsided peat soils to managed, impounded wetlands, significant agricultural emissions are avoided, and soil carbon can be sequestered and protected. Here, we synthesize 36 site-years of continuous carbon dioxide and methane flux data from a mesonetwork of eddy covariance towers in the Sacramento-San Joaquin Delta in California, USA to compute carbon and greenhouse gas budgets for drained agricultural land uses and compare these to restored deltaic wetlands. We found that restored wetlands effectively sequestered carbon and halted soil carbon loss associated with drained agricultural land uses. Depending on the age and disturbance regime of the restored wetland, many land use conversions from agriculture to restored wetland resulted in emission reductions over a 100-year timescale. With a simple model of radiative forcing and atmospheric lifetimes, we showed that restored wetlands do not begin to accrue greenhouse gas benefits until nearly a half century, and become net sinks from the atmosphere after a century. Due to substantial interannual variability and uncertainty about the multi-decadal successional trajectory of managed, restored wetlands, ongoing ecosystem flux measurements are critical for understanding the long-term impacts of wetland restoration for climate change mitigation. [ABSTRACT FROM AUTHOR]

Highlights • 2050 primary energy use can be the same as in 2010 with a 7-fold increase in GDP. • Coal use can peak around 2020, then oil in 2033, and natural gas in 2045. • Non-fossil energy is 28% in 2030, higher than China's Paris Agreement goal of 20%. • Industry CO 2 emissions can peak ∼2020, buildings ∼2029, and transportation ∼2035. • CO 2 emissions can peak in 2025, earlier than China's Paris Agreement goal of 2030. Abstract As part of its Paris Agreement commitment, China pledged to peak carbon dioxide (CO 2) emissions around 2030, striving to peak earlier, and to increase the non-fossil share of primary energy to 20% by 2030. Yet by the end of 2017, China emitted 28% of the world's energy-related CO 2 emissions, 76% of which were from coal use. How China can reinvent its energy economy cost-effectively while still achieving its commitments was the focus of a three-year joint research project completed in September 2016. Overall, this analysis found that if China follows a pathway in which it aggressively adopts all cost-effective energy efficiency and CO 2 emission reduction technologies while also aggressively moving away from fossil fuels to renewable and other non-fossil resources, it is possible to not only meet its Paris Agreement Nationally Determined Contribution (NDC) commitments, but also to reduce its 2050 CO 2 emissions to a level that is 42% below the country's 2010 CO 2 emissions. While numerous barriers exist that will need to be addressed through effective policies and programs in order to realize these potential energy use and emissions reductions, there are also significant local environmental (e.g., air quality), national and global environmental (e.g., mitigation of climate change), human health, and other unquantified benefits that will be realized if this pathway is pursued in China. [ABSTRACT FROM AUTHOR]

Highlights • Benefits of environmental-economic carbon stock and flow accounts to inform policy. • Similar values of native forest protection for mitigation or timber production. • Protecting forests has many additional co-benefits that provide greater public good. • Recommend adopting comprehensive carbon accounting including all land use activities. Abstract Comprehensive carbon stock and flow accounts integrated with economic information, under an environmental-economic accounting framework, provide a common approach for an information system to improve policymaking for climate change mitigation, sustainable development and forest management. The information system includes environmental and economic data, linkages between land use activities, their co-benefits, inputs to the economy and benefits for human well-being. Forest management was used as an example of application of the accounting framework because it has the greatest climate change mitigation potential of all land use activities. A case study developing carbon accounts for a forest region in south-eastern Australia demonstrated the mitigation benefits of long-term carbon storage and sequestration in native forests. Using environmental-economic accounts helped identify policy and market instruments required to value ecosystem services of carbon storage and sequestration by applying a potential market price for carbon. We identified benefits of native forest protection as a carbon abatement activity, and compared this value to that of current forest management for timber harvesting that reduces carbon stocks. Both land uses provided similar economic contributions (approximately $12 million yr−1, using a minimal carbon price), but native forest protection has additional co-benefits of improving water yield, tourism, recreation and biodiversity conservation. The accounts determine values of land use activities in physical and monetary metrics, and link these to beneficiaries of ecosystem services, so that maximum benefits for public good are identified. Quantifying ecosystem services of carbon storage (protecting stocks) and sequestration (increasing flows) in a native forest region, by applying a potential market price, broadens the policy options for mitigation activities. Adopting a comprehensive accounting system, and changing some of the definitions and rules under the Paris Agreement and national emissions reduction policies and markets, would allow the mitigation benefit of protecting native forests to be realised. [ABSTRACT FROM AUTHOR]

Highlights • We mapped city-level CO 2 emissions simulated by DMSP/OLS nighttime light imagery. • City-level CO 2 emissions were featured as spatial agglomerations. • The GWR revealed significant spatial heterogeneity in the impacts of different factors. • Private car ownership, PCGDP, energy consumption positively affected CO 2 emissions both globally and locally. • The reminder factors studied in the GWR were found to bi-directionally affect CO 2 emissions. Abstract Cities produce over 70% of the global CO 2 emissions that result from energy use, and thus play a key role in climate mitigation and adaptation. While the factors influencing CO 2 emissions have been subject to extensive study, via research that has explored the path of developing a low-carbon economy, little work has been undertaken at the city level as a result of a deficiency in data availability. Addressing this gap, this study firstly estimated CO 2 emissions of cities in China using Defense Meteorological Satellite Program's Operational Linescan System (DMSP-OLS) nighttime light imagery. We then analyzed spatial variations in the estimated CO 2 emissions at the city level, using a spatial analytical model, finding significant spatial autocorrelation in CO 2 emissions. Subsequently, we compared the effects of different socioeconomic factors on CO 2 emissions, using both global and local regression models. The results from the global regression model revealed that private car ownership, economic growth, and energy consumption were the major factors promoting CO 2 emissions in China's cities, while population density had an effect in reducing CO 2 emissions. The use of a Geographically Weighted Regression (GWR) model provided more detailed results, revealing significant spatial heterogeneity in the impacts of different factors. Economic growth, private car ownership, and energy consumption all posed positive effects on CO 2 emissions while the remainder of the factors studied were found to pose a bidirectional impact on CO 2 emissions in different areas of China. Economic growth and private car ownership were to found to exert the strongest positive effects in the cities of western and central China, and energy consumption was shown to significantly and positively influence CO 2 emissions in the southernmost part of China. Urban expansion and road density were identified as key promoting factors in CO 2 emissions in the northeast of China; and the industrial structure demonstrated significantly positive effects in relation to CO 2 levels in cities located in the Beijing-Tianjin-Hebei region. The role of foreign direct investment (FDI) was not found to be significant in most cities expect Guangdong, where a significant positive relationship appeared. [ABSTRACT FROM AUTHOR]

To meet the global climate change mitigation targets, more attention has to be paid to the decarbonization of the heating and cooling sector. Aquifer Thermal Energy Storage (ATES) is considered to bridge the gap between periods of highest energy demand and highest energy supply. The objective of this study therefore is to review the global application status of ATES underpinned by operational statistics from existing projects. ATES is particularly suited to provide heating and cooling for large-scale applications such as public and commercial buildings, district heating, or industrial purposes. Compared to conventional technologies, ATES systems achieve energy savings between 40% and 70% and CO 2 savings of up to several thousand tons per year. Capital costs decline with increasing installed capacity, averaging 0.2 Mio. € for small systems and 2 Mio. € for large applications. The typical payback time is 2–10 years. Worldwide, there are currently more than 2800 ATES systems in operation, abstracting more than 2.5 TWh of heating and cooling per year. 99% are low-temperature systems (LT-ATES) with storage temperatures of < 25 °C. 85% of all systems are located in the Netherlands, and a further 10% are found in Sweden, Denmark, and Belgium. However, there is an increasing interest in ATES technology in several countries such as Great Britain, Germany, Japan, Turkey, and China. The great discrepancy in global ATES development is attributed to several market barriers that impede market penetration. Such barriers are of socio-economic and legislative nature. [ABSTRACT FROM AUTHOR]

Biochar production for soil amendment was recently proposed as a tool to mitigate climate change, reducing soil greenhouse gas (GHG) emissions and sequestrating carbon (C) in soil. The aim of this research project was to test the hypothesis that only biochars with specific requirements (low H/C org and O/C org ratios, high C/N ratio) can reduce soil N 2 O emissions without increasing CO 2 emissions in the short term. A 45-days incubation study was carried out, in which six engineered biochars made from the pyrolysis of wood, switchgrass and the solid fraction of pig manure (SFPM), were amended to two agricultural soils (loamy sand and silt loam) at a dose of 2% (w/w) in 1-liter jars. Soil moisture content was adjusted at 80% of water-filled pore space with a solution of ammonium nitrate that corresponds to 170 kg of nitrogen per hectare. N 2 O and CO 2 emissions were analysed on days 2, 3, and then weekly. Soil chemical properties and bacterial richness, composition and taxonomy were analysed after the incubation period. When compared to the control soils without biochar, N 2 O emissions were decreased by 42 to 90%, but only in the silt loam amended with biochars made from wood and switchgrass, these biochars having a high C/N ratio (>30). Lower N-NH 4 + and N-NO 3 − concentrations were observed in these biochar treatments than in control soil. Moreover, two bacterial classes ( Deltaproteobacteria and Thermoleophilia ) were correlated with a decrease in N 2 O emissions. For each type of biochar, those produced at the highest temperature with low O/C org and H/C org ratios resulted in the lowest increase in CO 2 emissions, which could indicate a higher biochar carbon stability. Overall, results of this study demonstrated that biochar can either increase or decrease soil GHG emissions depending on its properties, and that the effect can differ according to soil properties. Future long-term studies in the field in the presence of crop should be carried out in order to validate the conclusions of this study. [ABSTRACT FROM AUTHOR]

The injection and storage of anthropogenic CO 2 in the subsurface is being deployed as a climate change mitigation tool; however, diagenetic-paragenetic heterogeneity in sandstone reservoirs often contributes to interval specific chemomechanical changes that affect injection and can increase leakage risk. Here, we address reservoir heterogeneities' impact on chemomechanical changes in a macroporous-dominated lithofacies of Morrow B sandstone, a formation containing several diagenetically-distinct hydraulic facies while undergoing enhanced oil recovery (EOR) and carbon dioxide (CO 2) sequestration. We performed three flow-through experiments using a CO 2 -charged or uncharged formation water combined with four indirect tensile strength tests per post-test sample. We then used the microstructure and paragenetic sequence to understand chemomechanical weakening with key observations as follows: dissolution of carbonates and feldspars changed porosity; increased permeability led to reclassifying each sample in a different hydraulic flow unit; decreased ultrasonic velocity; and did not lead to a loss of tensile strength. Tensile strength maintenance occurred due to the low abundance and minor dissolution of siderite, the stability of quartz, and the relative position of diagenetic ankerite within feldspar. This macroporous-dominated lithofacies is the primary reservoir for the Morrow B Sandstone, and is analogous to other porous sandstone reservoirs. It represents an end-member of a chemomechanically low-risk siliceous CO 2 sequestration and CO 2 -EOR reservoir. • Despite significant geochemical alteration, CO 2 -fluid rock interaction did not result in loss of tensile strength. • Paragenesis and microstructure are controlling mechanisms of tensile strength maintenance in acidic/neutral fluid conditions. • CO 2 -charged fluids dissolve carbonates and feldspars with concurrent and observable precipitation of iron-rich phases. • Rock interaction with a CO2-charged or uncharged fluid results in large macropores and permeability increases of.51 – 3 mD. • Ultrasonic velocity decreased modestly (2–8%) in all experiments. [ABSTRACT FROM AUTHOR]

• Integrating the source to sink BECCS chain into an energy system optimization model. • CCS cost-storage curves are created to analyze cost-competitiveness of BECCS. • Assess the dynamic relation between negative emissions and land use change emissions. • Total system costs decrease when BECCS is modelled endogenously. • Source-sink matching shows higher CO 2 injection rates (250 Mt CO 2) can be reached than mentioned in scientific literature (up to 135 Mt CO 2). • Unrestricted modeling of BECCS increases demand for biomass. Even though this comes with a higher EF due to LUC emissions, still net GHG benefits are larger. Bioenergy with carbon capture and storage (BECCS) can lead to negative emissions, and is seen as an important option to decarbonize energy systems. Its potential decarbonization contribution depends on low-carbon resource availability, its ability to meet end-use demand and the geological storage potential to safely trap CO 2. Here an energy system model is used to assess the BECCS decarbonization potential in Brazil, considering uncertainty in low-carbon biomass resources, and storage potential, injection rates and costs of CO 2 storage, assessed in eight scenarios. A spatial explicit analysis is done to make improved estimates on the storage potential, injection rates, and costs for CO 2 storage in the Rio Bonito saline aquifer of the Paraná basin. Although there are large differences in storage potential (12–117 Gt CO 2) and costs (on average 5–15 $/t CO 2), the accumulated volume of CO 2 stored between 2010 and 2050 is 2.9 Gt CO 2 for all scenarios, with injection rates around 240 Mt CO 2 in 2050. This shows that BECCS is a cost-competitive option to decarbonize the Brazilian energy system, even under pessimistic estimates of CO 2 storage potential and costs, and low biomass availability. The cheapest sink locations are selected, in the high development scenario. When CCS development is low, injection rates are the limiting factor. Locations are selected with the highest injection rates, even though sometimes more expensive. When CO 2 storage is limited, total system costs increase, mainly because decarbonization of the industry and freight transport sector relies on more expensive decarbonization options such as green hydrogen. [ABSTRACT FROM AUTHOR]

This paper investigates the potential pathways and associated requirements to meet a goal of net-zero greenhouse gas (GHG) emissions from the US commercial aviation sector by 2050 as outlined in the US 2021 Aviation Climate Action Plan. Aviation traffic (RTK) is projected to grow at an average of 2.0% per annum between 2019 and 2050, suggesting that a progressive and ultimately total decoupling of emissions from traffic growth will be required to meet the US aviation sector goal. Aircraft technology advancements, operational efficiency improvements, sustainable aviation fuels, and market-based measures (MBM) are considered as emissions reductions measures towards the goal. A parametric analysis framework is used to develop low, medium, and high emission reduction scenarios for each of these emissions reduction measures. If aircraft technology, operations, and fuels were frozen at 2019 levels, the aviation sector is projected to emit ≈430 million tonnes of CO 2 (MtCO 2) in 2050. Retirements of older aircraft, replaced by current-generation alternatives, may contribute 17% of the total 2050 emissions reduction goal. Further introduction of advanced aircraft technologies may contribute an additional system-level 11% emissions reductions towards the goal. Operational improvements may contribute ≈2% with a range from 1.5 to 4%. The remaining 70% of emissions in 2050 will be addressed through a combination of sustainable fuels and MBM, where appropriate. The level of contribution from fuels will be dependent on continued production ramp-up to meet aviation demand as well as improvements in lifecycle emissions reduction factor (ERF) for current and future fuel feedstock and production pathways, ranging from 0% for current petroleum-based fuels to 100% for sustainable aviation fuels with zero life-cycle emissions. Meeting a net-zero emissions goal by 2050 with SAF would require an increase in SAF production by 57% annually from 2022 to 2030 and 13% per year thereafter, reaching 100% emissions reductions factor by 2050. MBM may fill the gap between residual lifecycle emissions after accounting for all other in-sector improvement opportunities and the goal. [ABSTRACT FROM AUTHOR]