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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]

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]

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

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

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]

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

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]

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]

• 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]

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

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

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

In this study, the price of carbon is used to incentivize a reduction in the release of CO 2 emissions and an increase in sequestration of CO 2 through forestry activities. Forest managers essentially have two options for increasing carbon sequestration (i.e., creating carbon offset credits): (1) avoid or delay harvest of mature timber; or (2) harvest timber and allow natural or artificial regeneration (with ‘regular’ or ‘seed-selected’ growing stock). A forest management model representative of the southern interior of British Columbia is described and used to examine forest conservation that prevents emissions of CO 2 , and even-flow and commercial harvesting where timber is processed into long-lived wood products that store carbon and residuals for energy. The objective of the model is to maximize net discounted returns to commercial timber operations plus the benefits of managing carbon fluxes. The model tracks carbon in living trees, organic matter, and post-harvest carbon pools. It also includes various parameters related to the weighting of future carbon flows, anticipated price of carbon, whether and to what extent use of biomass reduces fossil fuel emissions from generating electricity or production of non-wood construction materials, et cetera. The results demonstrate that the decision about which forestry activities generate carbon offset credits and how many is essentially a political and not a scientific one. [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]

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]

• 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] • 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]

This study investigates the evolutionary trends of the international collaborations among the research community of carbon capture and storage (CCS) by looking at the collaboration network of countries publishing on CCS. The study also examines the evolution of major research topics in this field by exploring the co-occurrence network of keywords associated with CCS publications. The analysis is carried out based on the CCS related publications extracted from Scopus.com from 1980 to 2013. From the number of annual CCS publications, it seems that CCS research has closely followed the trend of international negotiations on climate change mitigation. The study elaborates how both international collaboration network and knowledge structure of the field have notably developed and interlinked over the years especially after 2005 during which almost 94% of the publications appeared. [ABSTRACT FROM AUTHOR]

[Display omitted] Mitigation of climate change by reducing the anthropogenic CO 2 emissions has recently gained huge momentum. A prime pathway to achieve it in the short-medium term lies within capturing CO 2 from industries' flue gases. Post-combustion CO 2 capture (PCC) is the most mature methodology for large-scale CO 2 capture and closest to market. However, the conventional chemical absorption-based PCC process implies high regeneration energy requirements, constituting the majority of the energy load when adding PCC to the plant from which the CO 2 is going to be captured. As such, reducing the overall parasitic load of the conventional process is of interest. Changing the solvent or improving the process flowsheet are two main methodologies to achieve higher energetic efficiency and lower exergy losses. As there are several reviews dealing with novel solvents, this review critically evaluates the progress in improving the conventional PCC process through modifications of process configurations and shadowed by solvent replacements as drop-in solutions. The process configurations were grouped into absorption and stripping enhancement categories. A comparative analysis was conducted between the different available schemes in the literature and interactions between solvents and process configurations were showcased, highlighting the advantages and shortcomings of some of them. The review reveals the need for standardized framework and optimization algorithms using exergo-economic performance indicators for integrated solvent and process synthesis. [ABSTRACT FROM AUTHOR]

• The main thermodynamic challenges associated with CO 2 transport via pipeline has been analysed. • A critical review of main flow-assurance issues related to CO 2 pipelines has been presented. • The impact of impurities, typology and their concentrations has been included. • Corrosion control strategies and water content limits have been collected through a literature review. • A collection of design parameters useful to technicians and operators has been reported. Environmental issues related to climate change have constantly been increasing in the last years, and global emissions must be managed wisely, adopting the most powerful and effective strategies available. Carbon Capture Utilization and Storage (CCUS) is claimed as a solid climate mitigation strategy for the most challenging emissions and the production of blue hydrogen. The development of an international CO 2 transportation network is considered a necessary cross-cutting topic in the whole Carbon Capture and Storage sector. CO 2 pipeline development is an essential aspect for the realization of most decarbonization CCS projects. Large-scale CCS projects will require the management and transport of CO 2 in the presence of impurities at lower costs than traditional CO 2 pipelines utilized for Enhanced Oil Recovery (EOR). Thus, the accuracy of modelling carbon dioxide in the presence of other components needs to be assessed. Corrosion prediction and control are strongly related to water content and introduces uncertainties in terms of costs and corrosion risks, especially in the presence of other components and possible cross-chemical reactions. In this work, the process and flow assurance challenges related to the design of a CO 2 pipeline have been reviewed in terms of impurities, water content, and corrosion, as well as low-temperature scenarios. The main scope of this paper is to analyse the aspects that can be improved and the ones that need for further research from a thermodynamic point of view. This will help the design of a next generation of CO 2 pipelines with low CAPEX (capital expenditure) and OPEX (operating expense), suitable for large-scale CCS projects and meeting the Paris Agreements. [ABSTRACT FROM AUTHOR]

Abstract: Mitigation of the global climate change via sequestration of anthropogenic carbon dioxide (CO2) in geologic formations requires assessment of the reservoir storage capacity and cap rock seal integrity. The typical cap rock is shale or mudstone rich in clay minerals that may significantly affect the effectiveness of the CO2 trapping. Specific objectives of this study were to conduct experimental investigation into the processes associated with CO2 and H2O trapped in swelling clay, namely, Wyoming and Texas montmorillonite powder. Combined (same-sample) multi-technique data – manometric sorption isotherm hysteresis, diffuse reflectance infrared spectroscopy ‘trapped CO2’ fingerprints, irreversible X-ray diffraction patterns for the clay interlayer in intermediate hydration state, and HF acid digestion resulting in formation of non-extractable F:CO2 adducts – corroborate a hypothesis that carbon dioxide molecules can be irreversibly trapped via anomalous extreme confinement in the galleries associated with montmorillonite interlayer, which may result in formation of carbonates in the longer term. Validation on Arizona montmorillonite lumps substantiated the evidence that such processes may occur in natural clay deposits but possibly on a different scale and at a different rate. [Copyright &y& Elsevier]

Abstract: Gases like CH4, CO2 and H2 may play a key role in establishing a sustainable energy system: CH4 is the least carbon-intensive fossil energy resource; CO2 capture and storage can significantly reduce the climate footprint of especially fossil-based electricity generation; and the use of H2 as energy carrier could enable carbon-free automotive transportation. Yet the construction of large pipeline infrastructures usually constitutes a major and time-consuming undertaking, because of safety and environmental issues, legal and (geo)political siting arguments, technically un-trivial installation processes, and/or high investment cost requirements. In this article we focus on the latter and present an overview of both the total costs and cost components of the distribution of these three gases via pipelines. Possible intricacies and external factors that strongly influence these costs, like the choice of location and terrain, are also included in our analysis. Our distribution cost breakdown estimates are based on transportation data for CH4, which we adjust for CO2 and H2 in order to account for the specific additional characteristics of these two gases. The overall trend is that pipeline construction is no longer subject to significant cost reductions. For the purpose of designing energy and climate policy we therefore know in principle with reasonable certainty what the minimum distribution cost components of future energy systems are that rely on pipelining these gases. We describe the reasons why we observe limited learning-by-doing and explain why negligible construction cost reductions for future CH4, CO2 and H2 pipeline projects can be expected. Cost data of individual pipeline projects may strongly deviate from the global average because of national or regional effects related to the type of terrain, but also to varying costs of labor and fluctuating market prices of components like steel. [Copyright &y& Elsevier]

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

In the context of modern science, there is a growing interest in the creation of novel porous materials capable of acting as sorbefacients for small gas molecules. This is critical in terms of innovative energy alternatives as well as a healthier environment. In an effort to overcome the consequences of global industrialization, one of humanity's most severe problems, intensive attempts have been made to prevent CO 2 from entering the carbon cycle, as the ever-increasing CO 2 pollution in the earth's atmosphere. Owing to their high porosity, presence of ultra-small pores, structural diversity, high stability, and excellent recyclability, researchers claim that zeolite–an inexpensively accessible sorbent–could be an excellent prototype for CO 2 sorption. Here, we provide an exhaustive review of re-engineered zeolites as a sustainable material for selective CO 2 capture and storage; the progress so far indicates fast removal of CO 2 , and more work conforming to simple scalability, energy and time efficiency application can be done to improve the challenges. [Display omitted] • Discussed the importance of size change from micro to nano level and their proficiency in Carbon capture and storage. • Role of reshaping changes and site selectivity enhancement in CO 2 monetization. • Role of biomass-based material on CO 2 sequestration has also been illustrated. • Strategies to promote circular economics by using wastes as precursors in synthesis of zeolites. • Discussed novel green technologies in constructing reshaped zeolite. [ABSTRACT FROM AUTHOR]

Research and observable climate impacts point almost unequivocally to the need for a larger and faster climate mitigation effort that includes capturing and permanently storing CO 2 both from large sources and from the atmosphere directly. Carbon capture and storage technologies are mature and available, with considerable real-world experience, but their deployment is still limited. We examine why this is so and suggest viable path forward. [ABSTRACT FROM AUTHOR]

• Reactive Mg-hydroxides and silicates in mine tailings offer vast sink for ambient CO 2. • Lower mineralization deep in tailings piles underuses storage capacity. • Climate, CO 2 availability, waste composition, and biotic agents are controlling factors. • Isotope analysis and geochemical modeling have become necessary tools to track CO 2. • Learnings from CO 2 sequestration in tailings are valuable for pedospheric-C sinks. Induced by fossil fuels combustion, GHGs emissions play a key role in the atmospheric CO 2 level elevation. Accordingly, many mitigation strategies have been proposed to uptake atmospheric CO 2. However, most of these methods demand industrial facilities, usually coming along with obstructive expenses. Residues produced from mining operations are among cheap and naturally occurring materials propounded for stable carbon sequestration through mineralization. Brucite and chrysotile are the major candidates for passive carbon mineralization in mining residues, belonging to magnesium hydroxide and magnesium silicates groups, respectively. This review paper critically explores available literature on mechanisms governing atmospheric CO 2 capture in the mining residues, with an emphasis on the mine tailings. Firstly, the overall image of carbon mineralization in mineral residues is discussed in this paper. This entails the occurrence and the mechanisms governing the carbonation in the surface and deep layers of the mining residue piles. Secondly, factors that likely affect the mineralization are illustrated. Then, two tools, carbon isotopes and geochemical modeling, utilized for discriminating atmospheric CO 2 and characterizing mineralization in the tailings are described, respectively. Finally, various conditions leading to different Mg-carbonates formation, carbonation rate estimations, and technologies proposed for enhancing carbonation in the mining residues are explored. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) is one of the most promising mitigation strategies for reducing the emissions of carbon dioxide (CO 2) to the atmosphere and may substantially help to decelerate global warming. There is an increasing demand for CCS sites. Nevertheless, there is a lack of knowledge of the environmental risk associated with potential leakage of CO 2 from the storage sites; and even more, what happens when the seepage stops. Can the environment return to the initial equilibrium? Potential effects on native macrofauna were studied under a scenario of a 50-day CO 2 leakage, and the subsequent leak closure. To accomplish the objective, Trondheim Fjord sediments and clams were exposed to an acidified environment (pH 6.9) at 29 atm for 7 weeks followed by a 14-day recovery at normal seawater conditions (pH 8.0, 29 atm). Growth and survival of clams exposed to pressure (29 atm) and reduced pH (6.9) did not significantly differ from control clams kept at 1 atm in natural seawater. Furthermore, bioaccumulation of elements in the soft tissue of clams did not register significant variations for most of the analysed elements (Cd, Cr, Pb, and Ti), while other elements (As, Cu, Fe, Ni) had decreasing concentrations in tissues under acidified conditions in contrast to Na and Mg, which registered an uptake (Ku) of 111 and 9.92 μg g−1dw d−1, respectively. This Ku may be altered due to the stress induced by acidification; and the element concentration being released from sediments was not highly affected at that pH. Therefore, a 1 unit drop in pH at the seafloor for several weeks does not appear to pose a risk for the clams. Image 1 • Acidification and recovery were assessed with high-pressure bioassays. • No mortality was reported for Astarte sp. for a pH 7.0 scenario. • Normal growth of shell length was recorded after CO 2 exposure and a recovery period. [ABSTRACT FROM AUTHOR]

Limiting global warming to "well below 2°C" as stated in the Paris Agreement requires ambitious emissions reductions from all sectors. Rapid technology cost declines in the energy sector are changing energy investment and emissions, even with the weak climate policies currently in place. We assess how energy supply costs and carbon dioxide removal (CDR) availability affect mitigation by performing a sensitivity analysis with the energy-economy-climate model REMIND. We use new scenarios with carbon price paths that aim to reduce the frequently seen temperature overshoot. Further, we measure the sensitivities of mitigation indicators to the costs of technologies across economic sectors. We assess the sensitivity to nine techno-economic parameters: the costs of wind, solar, biomass, gas, coal, oil, nuclear, and electric/hydrogen vehicles, as well as the injection rate of Carbon Capture and Storage (CCS). While technology costs play a role in shaping optimal pathways, we find that transport sector costs affect the economics of deep decarbonization, whereas costs of renewables are more important for scenarios under weak climate policies. This further highlights the value of renewable energy deployment as a no-regrets option in climate policy. In terms of the sensitivity of model outputs, economic indicators become more sensitive to costs than emissions, with increasing policy stringency. • The transport sector costs affect the economics of deep decarbonization. • The costs of renewables are more important for scenarios under weak climate policies. • Renewable energy deployment is a no-regrets option in climate policy. • Even in "favorable" price scenarios, optimal emissions need to reach zero by 2065. • Robust and broad policy support is needed for achieving the goals of the Paris Agreement. [ABSTRACT FROM AUTHOR]

• Origins of 90% capture assumption explained. • Cost of near 100% capture calculated. • CO 2 concentration drives costs of capture. Carbon capture and storage (CCS) will have an essential role in meeting our climate change mitigation targets. CCS technologies are technically mature and will likely be deployed to decarbonise power, industry, heat, and removal of CO 2 from the atmosphere. The assumption of a 90% CO 2 capture rate has become ubiquitous in the literature, which has led to doubt around whether CO 2 capture rates above 90% are even feasible. However, in the context of a 1.5 °C target, going beyond 90% capture will be vital, with residual emissions needing to be indirectly captured via carbon dioxide removal (CDR) technologies. Whilst there will be trade-offs between the cost of increased rates of CO 2 capture, and the cost of offsets, understanding where this lies is key to minimising the dependence on CDR. This study quantifies the maximum limit of feasible CO 2 capture rate for a range of power and industrial sources of CO 2 , beyond which abatement becomes uneconomical. In no case, was a capture rate of 90% found to be optimal, with capture rates of up to 98% possible at a relatively low marginal cost. Flue gas composition was found to be a key determinant of the cost of capture, with more dilute streams exhibiting a more pronounced minimum. Indirect capture by deploying complementary CDR is also assessed. The results show that current policy initiatives are unlikely to be sufficient to enable the economically viable deployment of CCS in all but a very few niche sectors of the economy. [ABSTRACT FROM AUTHOR]

The mitigation of climate change, abatement of greenhouse gas emissions and thus, fundamentally, the separation of CO 2 from various gas streams are some of the most pressing and multifaceted issues that we face as a society. De-carbonising our entire civilisation will come at a great cost and requires vast amounts of knowledge, initiative and innovation; yet, no matter how much time or money is spent, some sectors simply cannot be de-carbonised without the deployment of carbon capture and storage technologies. The technical challenges associated with the removal of CO 2 are not universal – there exists no single solution. Capturing the CO 2 on solid sorbents has been gaining traction in recent years given its cost-effectiveness as a result of its ease of application, relatively small energy requirements and applicability in a wide range of processes. Even with the myriad materials such as zeolites, carbons, metal organic frameworks, mesoporous silicas and polymers, the challenge to identify a sorbent with optimal capacity, kinetics, selectivity, stability and ultimately, viability, still persists. By tailoring these solid materials through comprehensive campaigns of surface modification, the pitfalls of each can be mollified and the strengths enhanced. This highly specific tailoring must be well informed so as to understand the mechanisms by which the CO 2 is adsorbed, the surface chemistry that has influence on this process, and what methods exist to facilitate the improvement of this. This review endeavours to identify the surface functional groups that interact with the CO 2 molecules during adsorption and the methods by which these functional groups can be introduced. It also provides a comprehensive review of the recent attempts and advancements made within the scientific community in the experimental applications of such methods to enhance CO 2 capture via adsorption processes. The primary search engine employed in this critical review was Scopus. Of the 421 references cited that embody the literature focussed on surface modification for enhancing the selective adsorption of CO 2 , 370 are original research papers, 43 are review articles and 7 are conference proceedings. Image 1 • Critical review of surface modification methods employed to enhance CO 2 adsorption. • Assessment of CO 2 adsorption mechanisms in the context of surface functional groups. • Evaluation of the methods used to introduce functional groups on adsorbent surfaces. • Critical discussion of the reagents used in surface modification of adsorbents. [ABSTRACT FROM AUTHOR]

• i-Tree planting tool was used for a life cycle analysis on current and potential CSS. • The CSS potential of green yards is limited, but the impact increases with upscaling. • Soil with added biochar can significantly contribute to the CSS capacity. • CSS needs more attention in the planning of urban green. Cities have been identified as key actors in climate change mitigation. Nature based carbon sinks have been suggested as a means of mitigating the greenhouse gas emissions of cities. Although there are several studies on the carbon storage and sequestration (CSS) of urban green, the role of residential sites is not fully understood. In addition, the carbon storage of soils is often excluded. Also the implications for planning require more attention. This study estimates the CSS potential of trees and biochar in urban residential yards and identifies effective means to enhance it. Moreover, the study discusses the results at the city scale. The research is based on a case study in Helsinki, Finland, and applies i-Tree planting tool to assess the current and potential life cycle CSS of the case area. The results reveal that trees and the mixing of biochar into growing medium can increase the CSS considerably. The CSS potential of the case area is 520 kg CO 2 per resident during 50 years. The added biochar accounts for 65 % of the capacity and the biomass of trees accounts for 35 %. At the city scale, it would lead to 330 000 t CO 2 being stored during 50 years. The findings suggest that green planning could contribute more strongly to climate change mitigation by encouraging the use of biochar and the planting of trees, in addition to ensuring favourable growing conditions. [ABSTRACT FROM AUTHOR]

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

Carbon dioxide (CO 2) has been proposed to be used as the geothermal working fluid, as it presents enhanced thermodynamic properties for this application when compared with the water-based system. This paper aims to present an overview of the recent research advances on CO 2 -based geothermal systems, particularly CO 2 -enhanced systems and CO 2 -plume geothermal energy technology. The results of the recent operational projects are also described. This emerging technology can improve the efficiency of geothermal systems and their environmental impact, promoting the process sustainability and helping to tackle some of the most important issues that Humanity is facing: (i) global climate change; (ii) energy availability; and (iii) water scarcity. For deployment of this technology at a large scale, some issues and uncertainties were identified. Special attention was focused on the basic findings achieved in operational projects. • CO 2 has enhanced thermodynamic properties for geothermal energy production. • CO 2 -based geothermal systems can offset carbon dioxide capture and storage costs. • The use of CO 2 in these systems improves the energy conversion efficiency. • CO 2 -based systems are a promising technology for climate change mitigation. [ABSTRACT FROM AUTHOR]