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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]

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]

[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]

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]

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]

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]

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]

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 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]

• Four scenarios investigated for CO 2 removal services and e-fuels/chemicals exports. • First study to explore the impact of such services on an exporting sunbelt country. • Offering such services and exports lowers several domestic cost metrics. • Concentrated solar thermal and solar PV equally optimal for CO 2 removal. • Regional distribution of installed capacities relies on renewables' full load hours. Transitioning to 100% renewable energy to mitigate climate change requires solutions for hard-to-abate energy sectors. It must also be complemented with negative emissions technologies to ensure climate security. Previous studies have investigated the feasibility of e-fuels and e-chemicals production for export and some carbon dioxide removal technologies in several regions. This study investigates, for the first time, the techno-economic impacts of offering such services on an exporting country's energy system as it transitions to 100% renewable energy by 2050. Egypt is used as a representative case study for sunbelt countries with adequate land area. Four scenarios with different system configurations have been investigated using the LUT Energy System Transition Model and compared to a reference 100% domestic renewable energy system. The results show that Egypt can technically provide 5% of the required global carbon dioxide removal capacity starting from 2035, and 10% of Europe's demand for e-fuels and e-chemicals starting from 2025 within land use constraints. The provision of both services enhances the domestic energy system performance by reducing the levelised costs of important feedstocks, carbon dioxide and hydrogen, as well as other domestic cost metrics and system losses. These findings are extendable and relevant to similar sunbelt countries. They are also relevant to European countries looking to fulfil their climate targets while diversify their energy imports sources. Overall, this study is an important step in 100% renewable energy transition research and international climate change mitigation efforts. [ABSTRACT FROM AUTHOR]

We investigate the feasibility of industrial-scale geological carbon sequestration as an effective climate change mitigation technology. We do so by performing numerical simulations of coupled multiphase flow and geomechanics on a representative field-scale geological model in the Gulf of Mexico that could become a typical CO 2 storage site. We use our representative model to investigate two potential hazards associated with large-scale CO 2 storage: (1) The potential that CO 2 might migrate to shallower formations and (2) The potential that CO 2 injection might induce seismicity due to destabilization of pre-existing faults. At our study location, we find that extensive distribution of clay minerals in fault zones in combination with large fault throws result in widespread occurrence of low-permeability faults that prevent migration of CO 2 outside of the injection interval. Low-permeability faults act as flow barriers and can result in reservoir compartmentalization and pore pressure build-up. For our field-scale geological model, we find that the risk of induced seismicity is controlled by the choice of the injection location with respect to pre-existing low-permeability faults. Our model results indicate that industrial-scale CO 2 storage in the Gulf of Mexico is feasible, but that a priori reservoir characterization and the choice of injection location are crucial to mitigate the potential occurrence of induced seismicity and CO 2 migration to shallower formations. • Coupled flow and geomechanics modeling of CO 2 storage for a typical field of the GoM. • Choice of well locations is critically important for limiting reservoir pressure build-up. • CO 2 storage in the GoM shows promise for climate-change mitigation efforts in the US. [ABSTRACT FROM AUTHOR]

In this study, we investigate the impact on shipping emissions from improving operational efficiency in a maritime chokepoint such as a canal. We consider several scheduling proposals that allow for different levels of speed reduction for incoming vessels and estimate the resulting emission reduction compared to a benchmark established from ship position data. For our case study of the Panama Canal, we estimate that the canal could have removed up to 1.8 million tonnes of CO 2 e per year for the period of 2019 to 2021. Our findings suggest that emission reduction can be easier to obtain at intermediate points as many of the contractual barriers to improving operational efficiency do not apply. [ABSTRACT FROM AUTHOR]

Seagrass meadows deliver a range of ecosystem services, where one of the more important is the capacity to store carbon and serve as sinks for atmospheric carbon dioxide. The capacity of seagrass meadows for carbon storage might, however, be modified and complicated by several factors; one important factor is the possible effects of calcification within the meadows. In tropical areas, seagrass meadows can contain high proportions of calcareous organisms, which through their calcification may cause release of CO 2. To study this aspect of the CO 2 balance within tropical seagrass systems, we investigated the air-water CO 2 flux in seagrass mesocosms with different plant community compositions, i.e. mixtures of seagrass and calcifying macroalgae, having similar overall photosynthetic oxygen evolution rates. The measured CO 2 fluxes changed both in rate and direction over the day and were significantly related to plant community composition. Downward fluxes of CO 2 were found only over vegetation with high proportion of seagrass and in the afternoon, whereas occurrence of calcifying algae appeared to reverse the flow. A partial least squares (PLS) regression model indicated that pH, pCO 2 and dissolved inorganic carbon (DIC) were the primary environmental variables predicting the CO 2 fluxes. Our findings show that algal calcification might partly counteract the carbon sequestration in seagrass meadows. • CO 2 fluxes over the surface were significantly related to plant community composition. • Downward fluxes of CO 2 were found only over vegetation with high proportion of seagrass. • pH, pCO 2 and dissolved inorganic carbon (DIC) were the primary environmental variables predicting the CO 2 fluxes. [ABSTRACT FROM AUTHOR]

Clean vehicle fleet will greatly benefit air quality and climate change mitigation. Here, we employ an integrated model to systematically investigated the contribution of combined clean vehicle policies to "emissions, exposure, and health benefits" from a regional perspective 2019–2035 in China. We find that driven by clean vehicle polices, the national vehicle CO 2 will likely to peak around 2028 with about 1327 million tons, and then reduce by 7.8% from 2028 to 2035. The developed region will peak CO 2 before 2030, while the developing region probably peak after 2030. In general, most air pollutants emissions from vehicles will decrease, subsequently leading to obvious PM 2.5 and O 3 exposure decrease. About 68 thousand PM 2.5 related and 33 thousand O 3 related deaths will be avoided 2019–2035 nationwide. Note that the health benefits are unequal, with higher PM 2.5 -O 3 related excess deaths be avoided per 100000 in developed region than developing region. Besides, results show that emission standard upgrade contributes largest to emission reduction and related health benefits, followed by electric vehicles, road-to-railways and waterways, and fuel consumption regulation in general. This work is able to provide valuable information for policy makers to collaboratively reduce CO 2 , air pollutants and premature deaths in China and other developing countries. [Display omitted] • Emissions in CO 2 and air pollutants were both investigated based on a dataset with 27 vehicle categories from 338 cities. • The contribution of vehicle clean policies to abated PM 2.5 -O 3 exposure and related deaths was quantified and decomposed. • This work proposed region-specific clean vehicle pathways from a national and regional perspective 2019-2035. [ABSTRACT FROM AUTHOR]

Bioeconomy addresses the triple balancing challenge posed by the Paris Agreement: inducing additional GHG mitigation alongside biophysical carbon dioxide removals, while keeping fossil carbon in the ground. The use of woody plants as construction materials could simultaneously address this challenge: CO 2 is absorbed through photosynthesis, while wood-based products provide mitigation by replacing either petrochemical materials such as plastic boards or energy-intensive materials like bricks. This study combines, at the scale of France, static and dynamic life cycle assessment with soil carbon simulations to investigate the long-term environmental performance of using, as input for the building sector, black locust (Robinia pseudoacacia L.) planted on "carbon vulnerable lands". These are areas specifically selected for their low soil organic carbon (SOC) levels and low potential to interfere with food security. After the consecutive cultivation of three rotations, black locust was shown to stock an additional 92000 kg ha−1 of carbon in soils as SOC. The mitigation effect from the plastic board replacement is the major contributor to the assessed environmental impacts, including climate change, leading the black locust system to generally perform better than the reference system where the carbon vulnerable areas are left as they are with their initial vegetation. Considering that cultivation starts in 2022, the dynamic evaluation of the global mean temperature change (GMTC) shows that the black locust system results in net negative emissions in the near- and mid-term, but with a GMTC overshot in the second half of the century. Even if a considerable carbon stock is created through time (e.g., 81% and 39% of the carbon captured by photosynthesis, in 2050 and 2100 respectively), the GHG emissions stemming from manufacturing and end-of-life processes were shown to offset the benefit of carbon capture. [Display omitted] • Black locust plantation and utilization in buildings induce negative emissions. • Black locust system yields greater climate benefits than the initial vegetation. • Plastic board replacement explains the superior performance for 13/16 impacts. • By 2136, the largest temperature reduction of 3.9E-09 K per ha is simulated. • 15% of the carbon captured by 3 rotations is still stocked after 260 years. [ABSTRACT FROM AUTHOR]

Platform chemicals (VFAs) production through CO 2 utilization technologies plays a crucial role in international efforts for climate change mitigation. In this study, a new approach for sustainable and eco-friendly CO 2 bioconversion to acetic acid proposed using 4 g L−1 magnesium ribbon (Mg0) in-situ and homoacetogen-enriched anaerobic granular sludge. To suppress methanogenesis three inhibition strategies were investigated. The use of NaCl (50, 70, 90 g L−1), 2-bromoethanesulfonate (4 mM BES), and a short heat-shock pre-treatment were applied to anaerobic granular sludge. The most effective strategy for methanogenesis inhibition and acetic acid production was the thermal treatment producing 2023,07 mg L−1 of acetic acid after 32 days (Cycle 7) with a maximum production rate of 234,58 mg L−1 day−1 at cycle 3 (after 14 days). Following the system with BES producing 1369,45 mg L−1 of acetic acid with a maximum production rate of 111,76 mg L−1 day−1 at cycle 3. The systems exposed to NaCl generated fewer VFAs compared to the other two systems (BES, Heat-shock). After the third cycle and until the end of the experiment (cycle 7), at the two systems (BES, Heat-shock), the acetic acid production rate slightly increased, whereas the methane significantly increased. At the end of cycle 7, the hydrogenotrophic methanogens Methanolinea was found in a high relative abundance and hydrogenotrophic methanogens acted antagonistically towards homoacetogens. [Display omitted] • CO 2 conversion to acetic by Mg0 and homoacetogens enriched culture was shown. • Heat pre-treatment of AnGrSL resulted in a production rate of 235 mg Ac L−1 day−1. • Addition of BES in AnGrSL resulted in 111 mg Ac L−1 day−1 at the 3rd cycle. • Exposure of AnGrSL to high salinity inhibited both methanogens and homoacetogens. • CH 4 was identified at the last cycles and was mainly due to hydrogenotrophic Methanolinea. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phase equilibria of CO 2 + DIOX hydrate for C DIOX between 0.05 mol% and 5.56 mol% • The kinetics of CO 2 + DIOX hydrate is quantified with morphology observation. • Phase separation of DIOX/H 2 O above 3.1 MPa weakens the promotion effect of DIOX. • A comprehensive evaluation of DIOX in the application of hydrate-based CO 2 storage. To reduce anthropogenic CO 2 emissions for the mitigation of climate change require novel CCUS solutions. Hydrate-based CO 2 sequestration (HCS) is a novel carbon-neutrality technology that aims to store CO 2 in solid hydrate form with long-term stability. However, imminent issues exist for the application of HCS in terms of demanding thermodynamic conditions, slow formation kinetics, and low CO 2 gas uptake. These challenges necessitate the quest for an efficient and eco-friendly CO 2 hydrate promoter. In this study, 1,3-dioxolane (DIOX) as a low-toxicity CO 2 hydrate promoter was systematically examined. The phase equilibria, cage occupancy, and the kinetics of binary CO 2 + DIOX hydrate were measured for DIOX concentrations (C DIOX) varying from 0.05 mol% to 5.56 mol%. It was confirmed that DIOX is a dual-function promoter for CO 2 hydrate, but its promotion effect is weakened for C DIOX between 0.60 mol% and 1.00 mol% and for all C DIOX at relatively high pressure. The CO 2 uptake in the hydrate phase increases with C DIOX above 2.00 mol% and is the highest for C DIOX = 5.56 mol% (57.08 ± 6.39 mmol/mol). Based on the morphology observation, hydrate transits from ice-like to slurry to mushy-like and finally to snow-like with increasing C DIOX. Interestingly, we observed that the aqueous phase separates into two phases (i.e., DIOX-rich and H 2 O-rich) at pressure above 3.09 MPa, which explains the gradual loss of the promotion effect. The results of our study provide a comprehensive evaluation on DIOX as a possible promoter for CO 2 hydrate in HCS application. [ABSTRACT FROM AUTHOR]

With long-term prospects indicating worldwide increasing urbanization over the next decades, cities are responsible for a growing share of global greenhouse gas emissions. This makes local policies more important in mitigating climate change, and calls for efficient tools allowing local decision makers to measure the impact of urban areas under their control. This study introduces a parsimonious screening tool to cater to this need and allow local governments to gauge and monitor consumption-based climate change footprint of cities. The tool consists of multiple-regression models that operate on easily accessible city data. To demonstrate its applicability, the per capita climate change footprint is estimated for 949 cities. Australian cities are found to have the highest per-capita footprint, averaging 20.4 t CO 2 -eq, while South American cities have the lowest per-capita footprint, averaging 8.1 t CO 2 -eq. The results are evaluated against IPCC climate change mitigation pathways to judge which cities are on track to an absolute sustainable level of greenhouse gas emissions. Few cities are found to be on track to comply with the necessary levels for 2030, and the findings thus substantiate that cities all over the planet need major actions to comply with the required climate change mitigation. • New screening method for estimating climate change footprint of cities. • Cities' footprint can be estimated using few simple explanatory variables. • Considered 707 cities, Latin American cities have the lowest per capita footprint. • To follow global mitigation pathways most cities need to reduce their footprint. • Decision-makers should consider absolute targets and plan strategies accordingly. [ABSTRACT FROM AUTHOR]

In the course of developing innovative approaches for climate change mitigation, CO 2 sequestration in saline aquifers has drawn attention to itself as an appealing and effective procedure. Simultaneous brine production facilitates storage capacity enhancement in aquifers through formation depressurization. This study is devoted to developing an analytical optimization model for CO 2 sequestration projects with simultaneous brine production from a technical and economical perspective. While previous studies have provided analytical optimization models for simple CO 2 injection scenarios, this research aims to improve the former models by utilizing more precise transient pressure calculation formulations, up-to-date economic analysis and extending the models to also account for simultaneous brine production in CO 2 storage projects. Through this model, the effect of different design parameters including well spacing, the number of injection and production wells, production-to-injection ratio, and carbon revenue can be assessed on the project's storage capacity and net revenue. Subsequently, the design parameters for the most environmentally and financially beneficial scenarios can be identified. The developed optimization model can serve as a fast and accurate pre-implementation tool for the case by case assessment and comparison of different CO 2 sequestration project designs. In order to put the model to test, the developed multi-well pressure evolution formulation is used to predict pressure changes in a synthetic aquifer formation throughout several sequestration projects. This profile is then compared with numerical simulation results. The maximum CO 2 injection rate and thus storage capacity for numerous project designs is then calculated based on a correlation between a reference injection rate, the time-dependant pressure profile for this rate and the aquifer's formation fracture pressure. Finally the effect of different design parameters is assessed on the storage capacity and net revenue and the fundamentals of selecting the best project design is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Midpoint and endpoint environmental profiles for bio-based isobutene are performed. • Pre-treatment represents the largest environmental burden due to steam demand. • From a system approach, co-produce lignin increases the impacts of the biorefinery. • In a product point view, the isobutene profile benefits sharing impacts with lignin. • Allocation method is a relevant decision to declare an environmental profile product. Moving toward a bioeconomy system is fundamental to climate change mitigation, nevertheless, the biotechnological routes should guarantee an environmental sustainability. Isobutene, a precursor in several industrial applications, is one of those chemicals that the environmental effects of its bio-based production have been scarcely explored. This study aims to assess the environmental performance of two biorefinery systems: the first one focuses only on the production of isobutene (I) and the second one on the co-production with lignin (I + L), both from the valorisation of wheat straw. The Life Cycle Assessment methodology is used to determine the environmental impacts considering mid-point and end-point categories. Biorefineries report 0.65 and 1.32 kg CO 2 -eq per kg of biomass processed for I and I + L system, respectively. The most affected endpoint damage category corresponds to Human Health, regardless of the scenarios. Moreover, the pre-treatment stage constitutes the main hotspot of both systems considering midpoint and endpoint perspectives. [ABSTRACT FROM AUTHOR]

• CO 2 sequestration and EGR are experimentally evaluated in two shale gas reservoirs. • Pore heterogeneity and connectivity are evaluated via multifractal analysis. • Shale composition controls on gas storage is evaluated from gas adsorption measurements. • Links between MICP and gas adsorption measurements were used to evaluate EGR suitability. In the global effort toward climate change mitigation, geologic storage of CO 2 in shale plays is becoming critical while it can improve production from these reservoirs. In this study, the gas storage capacity and CO 2 sequestration suitability of the Longmaxi and Niutitang shale gas reservoirs is investigated and compared via XRD analysis, programmed pyrolysis, low pressure N 2 and CO 2 adsorption, high pressure CH 4 adsorption, and MICP analysis. Results showed that clay and TOC controls on micropore heterogeneity and connectivity happens only within the Longmaxi Formation. Furthermore, both components play a role in the adsorbed quantities of gas in the formation which revealing a higher storage capacity in mesopore-macropores. This was verified by a positive correlation between adsorbed volume within the mesopore-macropore space. The Longmaxi Formation was also found to own better pore connectivity and PSD homogeneity of mesopore-macropores, indicating easier pathways for CO 2 movement channels within the pore network. Furthermore, the samples from the Longmaxi exhibited a positive relationship between adsorbed volume with the CO 2 breakthrough pressure and median pore diameter, alike between the mesopore-macropore volume and CO 2 breakthrough pressure. This means, the injected CO 2 will displace adsorbed methane within the mesopore-macropore and will be adsorbed and stored in such pores. Overall, superiority of the Longmaxi shale over the Niutitang for CO 2 storage and EGR would be significant for future operations in similar shale gas reservoirs in China and around the globe. [ABSTRACT FROM AUTHOR]

• A thorough analysis on variations of CO 2 fluxes and carbon budget was conducted. • Nitrogen and water conditions were primary factors controlling maize seasonal NEE. • NBP for the winter wheat-maize rotation system ranged from -239.1 to 237.0 gCm−2. • Net ecosystem GHG emissions ranged from -39.23 to 325.23 gCm−2 for the wheat system. • Nitrogen and water application should be optimized for climate smart agriculture. Investigating CO 2 fluxes and carbon budget in agro-ecosystems is essential to develop climate smart agriculture. Here, we conducted a thorough analysis on the daily, seasonal and inter-annual variations in CO 2 fluxes and carbon budget in a winter-wheat and summer-maize rotation system in the North China Plain (NCP) to better understand the CO 2 flux exchange and the underlying mechanisms of carbon budget dynamics. During 2003-2010, the inter-annual variability of monthly gross primary productivity was significantly correlated with leaf area index (LAI), temperature and net radiation. The inter-annual variability of monthly ecosystem respiration was significantly correlated with LAI, soil temperature and moisture. Daily and monthly variability in net ecosystem exchange (NEE) was significantly correlated with LAI. At a seasonal scale, soil moisture was one of the primary factors controlling carbon sequestration of wheat system. Nitrogen application rate and water conditions were the primary factors controlling carbon sequestration of maize system. The NEE for winter wheat system, maize system, and winter wheat-maize rotation system in the NCP ranged from -418 to -29, -448 to -119, and -857 to -274 gCm−2, respectively. The net biome productivity (NBP) for winter wheat system, maize system, and winter wheat-maize rotation system in the NCP ranged from -223 to 151, -236 to 94, and -239 to 237 gCm−2, respectively. Taking greenhouse gas (GHG) emissions from irrigation, fertilization, herbicides, fungicide, insecticide, and field operations, the associated net GHG emissions ranged from -39 to 325 gCm−2 for wheat system and -22 to 287 gCm−2 for maize system. Wheat and maize systems in the region were a medium source of GHG emissions in most of years, mainly due to the large application rates of fertilization and irrigation. Our findings gain new insights into the mechanisms underlying the inter-annual variations in CO 2 fluxes and carbon budget, highlighting the optimization of genotype, environment and management interactions to realize climate smart agriculture. [ABSTRACT FROM AUTHOR]

• We introduce biogas-concrete carbon capture utilization, and storage supply chains. • These innovative supply chains have the potential to permanently remove CO 2 from the atmosphere and store it in concrete. • This climate mitigation solution is available today and can be adopted in a seamless manner. • We quantify the trade-offs between supply chains that store CO 2 in concrete and underground. Bioenergy with carbon capture and storage (BECCS) is a carbon dioxide removal (CDR) solution necessary to achieve net-zero-carbon-emissions goals. While the BECCS potential from large industrial emitters has been quantified, the BECCS potential of small emitters, such as biogas facilities, has not been investigated. Moreover, most BECCS solutions rely on the expected availability of large geological storage capacity for future CDR implementation, although the deployment of CO 2 transport and storage supply chains is still a barrier for geological carbon storage ambitions. An alternative opportunity for permanent sequestration of CO 2 is concrete, in which captured CO 2 can be permanently fixed through carbon dioxide mineralization technologies. We describe and discuss this solution by quantifying the potential of a European bioenergy with carbon capture, utilization, and storage (BECCUS) supply chain, which relies on biogenic CO 2 from biogas facilities as a CO 2 source, and on carbon dioxide mineralization in concrete as a permanent CO 2 sink. This solution is available today, can be adopted seamlessly, and does not need economies of scale for its deployment. We find that European biogas facilities produce 24 Mtons of biogenic CO 2 per year, of which 4 Mtons of CO 2 per year are emitted from facilities already upgrading biogas into bio-methane. We estimate that carbon dioxide mineralization in recycled concrete aggregates in Europe could permanently store up to 8 Mtons of CO 2 per year. Despite the limited storage potential, BECCUS supply chains would reduce CO 2 transportation distance and system complexity compared to BECCS supply chains, and would result in a marketable product, namely concrete. Overall, carbon dioxide mineralization in recycled concrete aggregates combines carbon utilization with permanent sequestration, hence contributing to carbon-neutrality goals. [ABSTRACT FROM AUTHOR]

[Display omitted] • TUEEC in 10 urban agglomerations in China are substantially different. • TUEEC within urban agglomeration have an impact on CO 2 emissions. • Ecological construction partially mitigated emissions growth. • Guarding against unsustainable development is vital to carbon neutral. Urban agglomerations are major generators of CO 2 emissions owing to human socioeconomic activities. Evaluating the trade-offs between urban expansion and ecological construction during rapid urbanization is a crucial step towards climate change mitigation and carbon neutrality. This study investigated the impacts of trade-offs between urban expansion and ecological construction on CO 2 emissions using multi-source data and spatial and statistical analysis. Ten urban agglomerations in China, with various development levels, were selected as study areas. The results indicated that (1) urban development in the 10 urban agglomerations expanded by 90%–288.9%, while ecological land changed by −28.1–2.3%. (2) CO 2 emissions grew by 154.2–291.2% in urban agglomerations, and the south and east of China emitted more CO 2. The high-value clusters of CO 2 inside of all urban agglomerations expanded outward from cities. (3) Urban expansion increased emissions, while ecological construction partially mitigated emissions growth. Moreover, ecological development within cities helps to reduce excessive urban emissions and should be given more attention. (4) It is as important to guard against unsustainable development as it is to reduce existing high emissions. Low-carbon development paths must continue to be supported in western China. On the basis of the results, we identify important implications for meeting China's target of carbon neutrality. These contribute to an understanding of future development modes for urban agglomerations and reveal the impact of trade-offs of land use on CO 2 emissions. [ABSTRACT FROM AUTHOR]

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

• We provide evidence on willingness-to-pay for offsets of flight-related emissions. • We use a revealed-preference approach in a large dataset of a Swiss airline. • WTP for offsetting is low, median WTP is zero. • Our results question results based on hypothetical stated-preferences methods. Voluntary offsetting of flight-related emissions is an important cornerstone of passengers' individual efforts to contribute to climate change mitigation. Hence, many scientific studies have tried to assess people's willingness-to-pay to offset their own flight-related carbon emissions. Up-to-date, these studies are overwhelmingly grounded in hypothetical stated-preference approaches, with very limited knowledge about external validity. Here, we report on an observational field study involving a final sample of 63,520 bookings made with a European airline, allowing us to gauge actual willingness-to-pay for carbon dioxide compensation in a revealed-preference approach. Our pre-registered study shows that the median willingness-to-pay to voluntarily offset a ton of carbon dioxide from flight-related emissions is zero, with the mean willingness-to-pay being around 1 EUR. Aggregated voluntary willingness-to-pay thus dramatically falls short of current prices to offset carbon dioxide, for example through the EU-ETS. Our results thereby question the suitability of self-reported, hypothetical assessments of offsetting and raise caution about the effectiveness of offsetting schemes, which currently do not very successfully internalize flight-related cost of emissions. [ABSTRACT FROM AUTHOR]