Recent developments on carbon capture and storage: An overview

Interzeolite conversion of a micronsized FAU to a nanosized CHA zeolite free of organic structure directing agent with a high CO2 capacity

The interzeolite transformation of a micronsized FAU zeolite to a nanosized CHA zeolite via alkali treatment is presented. The impact of the selection of the FAU zeolite starting material on the properties of the produced CHA zeolite was analyzed by XRD, ICP, SEM, TEM, N₂ and CO₂ adsorption, and in situ FT-IR. The analysis showed that the choice of starting FAU zeolite had a large impact on the chemical composition, size, morphology, and porosity of the produced CHA zeolite. The as prepared CHA samples show high capacity toward CO₂ (4.26 mmol g⁻¹) and it was demonstrated that the chemisorbed vs. physisorbed CO₂ was controlled by varying the amount of alkali cations in the CHA zeolite.

The interzeolite transformation of a micronsized FAU zeolite to a nanosized CHA zeolite via alkali treatment is presented.

The Separative Performance of Modules with Polymeric Membranes for a Hybrid Adsorptive/Membrane Process of CO2 Capture from Flue Gas

Commercially available polymeric membrane materials may also show their potential for CO₂ capture by the association of the membrane process with other separation techniques in a hybrid system. In the current study, PRISM PA1020/Air Products and UBE UMS-A5 modules with membrane formed of modified polysulfone and polyimide, respectively, were assessed as a second stage in the hybrid vacuum swing adsorption (VSA)–membrane process developed in our laboratory. For this purpose, the module permeances of CO₂, N₂, and O₂ at different temperatures were determined, and the separation of CO₂/N₂ and CO₂/N₂/O₂ mixtures was investigated in an experimental setup. An appropriate mathematical model was also developed and validated based on experimental data. It was found that both modules can provide CO₂-rich gas of the purity of > 95% with virtually the same recovery (40.7−63.6% for maximum carbon dioxide content in permeate) when fed with pre-enriched effluent from the VSA unit. It was also found that this level of purity and recovery was reached at a low feed to permeate the pressure ratio (2−2.5) in both modules. In addition, both modules reveal stable separation performance, and thus, their applicability in a hybrid system depends on investment outlays and will be the subject of optimization investigations, which will be supported by the model presented and validated in this study.

Modification of Poly(4-methyl-2-pentyne) in the Supercritical Fluid Medium for Selective Membrane Separation of CO2 from Various Gas Mixtures

The modification of highly permeable films of brominated 1,2-disubstituted polyacetylene, poly(4-methyl-2-penthyne), via incorporation of in situ formed butylimidazolium bromide is reported for the first time. Principal possibility and efficiency of supercritical CO₂ and CHF₃ use as reaction media for the corresponding process, namely for quaternization of butylimidazole by brominated polymer are revealed. As a result, we prepared new membrane materials possessing promising properties such as stability toward organic solvents, good mechanical properties and significantly improved CO₂-selectivity while maintaining gas permeability at high values. Comparative analysis of the results allowed us to determine content and conditions for the incorporation of butylimidazolium groups optimal for most efficient separation of CO₂ from industrial gas mixtures. These results are of interest for the designing of new CO₂ selective membranes.

Recent Advances in Photocatalytic CO2 Utilisation Over Multifunctional Metal–Organic Frameworks

The efficient conversion of carbon dioxide (CO2) to high-value chemicals using renewable solar energy is a highly attractive but very challenging process that is used to address ever-growing energy demands and environmental issues. In recent years, metal–organic frameworks (MOFs) have received significant research attention owing to their tuneability in terms of their composition, structure, and multifunctional characteristics. The functionalisation of MOFs by metal nanoparticles (NPs) is a promising approach used to enhance their light absorption and photocatalytic activity. The efficient charge separation and strong CO2 binding affinity of hybrid MOF-based photocatalysts facilitate the CO2 conversion process. This review summarises the latest advancements involving noble metal, non-noble-metal, and miscellaneous species functionalised MOF-based hybrid photocatalysts for the reduction of CO2 to carbon monoxide (CO) and other value-added chemicals. The novel synthetic strategies and their corresponding structure–property relationships have also been discussed for solar-to-chemical energy conversion. Furthermore, the current challenges and prospects in practical applications are also highlighted for sustainable energy production.

Materials and logistics for carbon dioxide capture, storage and utilization

The efforts to curtail carbon dioxide presence in the atmosphere are a strong function of the available technologies to capture, store and usefully utilize it. Materials with adequate CO₂ sorption kinetics that are both effective and economical are of prime importance for the whole capture system to be built around. This work identifies such materials that are currently used in CO₂ adsorption beds/columns at different global locations, along with their vital operational parameters, logistics and costs. Three main classes of materials currently in use to that end are discussed in detail here, namely solid sorbents, advanced solvents membrane systems. These materials are then compared in terms of their potential CO₂ uptake, operating parameters and ease of use and implementation of the respective technology. Tabular data are appended to each technology covered with the most relevant advantages and disadvantages. With such comprehensive survey of the recent state-of-the-art materials, recommendations are also made to facilitate the selection of systems based on their CO₂ yield, price and suitability to the geographical location.

Incorporation of trivalent cations in NaX zeolite nanocrystals for the adsorption of O2 in the presence of CO2

The O₂ and CO₂ sorption properties of nanosized zeolite X with faujasite type structure through a partial ionic exchange of sodium (Na⁺) by trivalent cations (Gd³⁺ and Ce³⁺) were evaluated. Three faujasite samples were studied, the as-synthesized Na-X possessing Na⁺ solely, and the modified samples Na-Gd-X and Na-Ce-X containing Gd³⁺ (1.8 wt%) and Ce³⁺ (0.82 wt%), respectively. Incorporating scarce amounts of trivalent cations modified the adsorption affinity of zeolites towards O₂ and CO₂ as demonstrated by in situ Fourier-transform infrared spectroscopy (FTIR). While Na-Ce-X encounters the highest O₂ physisorption capacity, the Na-Gd-X is adsorbing the highest quantities of molecular CO₂. All three samples exhibit the chemisorbed CO₂ in the form of carbonates, while the Na-X stores carbonates in monodentate and polydentate forms, the Na-Gd-X and Na-Ce-X allow the formation of polydentate carbonates only. Density functional theory (DFT) calculations revealed that trivalent cations tend to adsorb gases through two cations simultaneously which explains the presence of polydentate carbonates exclusively in the corresponding modified zeolites. The DFT results confirmed the higher affinity of Na-Gd-X and Na-Ce-X nanocrystals towards O₂ in the presence of CO₂. The affinity of Na-Gd-X and Na-Ce-X nanocrystals towards O₂ opens the door of their use as oxygen transporters for medical applications where CO₂ is constantly present. The toxicity of the nanosized zeolites and their performance in O₂ release are reported too.

Reduced Graphene Oxide/Polymer Monolithic Materials for Selective CO2 Capture

Polymer composite materials with hierarchical porous structure have been advancing in many different application fields due to excellent physico-chemical properties. However, their synthesis continues to be a highly energy-demanding and environmentally unfriendly process. This work reports a unique water based synthesis of monolithic 3D reduced graphene oxide (rGO) composite structures reinforced with poly(methyl methacrylate) polymer nanoparticles functionalized with epoxy functional groups. The method is based on reduction-induced self-assembly process performed at mild conditions. The textural properties and the surface chemistry of the monoliths were varied by changing the reaction conditions and quantity of added polymer to the structure. Moreover, the incorporation of the polymer into the structures improves the solvent resistance of the composites due to the formation of crosslinks between the polymer and the rGO. The monolithic composites were evaluated for selective capture of CO₂. A balance between the specific surface area and the level of functionalization was found to be critical for obtaining high CO₂ capacity and CO₂/N₂ selectivity. The polymer quantity affects the textural properties, thus lowering its amount the specific surface area and the amount of functional groups are higher. This affects positively the capacity for CO₂ capture, thus, the maximum achieved was in the range 3.56–3.85 mmol/g at 1 atm and 25 °C.

Potential of tea plants in carbon sequestration in North-East India

The potential of carbon (C) sequestration through photosynthesis depends on the nature of different plant species. Tea (Camellia sinensis L.) is an evergreen perennial plant and cultivated over a wide region in the world, and its potential to sequestrate atmospheric carbon dioxide (CO₂) in plant biomass is already evaluated. However, proportions of assimilated CO₂ which tea plant can sequestrate in their biomass and in soil are not evaluated before. In this experiment, ten (10) 6-month old tea plants of four different cultivars (TV1, TV20, S3A/3, and TV23) were transplanted in the field and CO₂ assimilation flux of tea plants was periodically measured under in situ condition using close-chamber method at 15 days interval throughout the year. The cumulative CO₂ assimilation flux of young tea plants varied within 31.82-249.22 g CO₂ plant^-1 year^-1; however, it was estimated that tea bushes also emitted 5.2-70.8 g CO₂ plant^-1 year^-1 due to aerobic respiration. After 1 year, tea plants were uprooted and the changes in their biomass were compared as the measure of their C-sequestration within the study duration. The weight gain in the whole plant biomass was proportional to the CO₂ assimilation potential of tea cultivars. Overall, tea plants sequestrated 50.8% of the assimilated atmospheric CO₂ in their biomass. The study revealed that tea bushes release organic C through the root exudates, the amount of which was equivalent to 5.9-8.6% of the assimilated CO₂. Those secreted root exudates have potential to increase organic C up to 44-48 kg ha^-1 year^-1 in tea-growing soil.

A Review of CO2 Storage in View of Safety and Cost-Effectiveness

The emissions of greenhouse gases, especially CO2, have been identified as the main contributor for global warming and climate change. Carbon capture and storage (CCS) is considered to be the most promising strategy to mitigate the anthropogenic CO2 emissions. This review aims to provide the latest developments of CO2 storage from the perspective of improving safety and economics. The mechanisms and strategies of CO2 storage, focusing on their characteristics and current status, are discussed firstly. In the second section, the strategies for assessing and ensuring the security of CO2 storage operations, including the risks assessment approach and monitoring technology associated with CO2 storage, are outlined. In addition, the engineering methods to accelerate CO2 dissolution and mineral carbonation for fixing the mobile CO2 are also compared within the second section. The third part focuses on the strategies for improving economics of CO2 storage operations, namely enhanced industrial production with CO2 storage to generate additional profit, and co-injection of CO2 with impurities to reduce the cost. Moreover, the role of multiple CCS technologies and their distribution on the mitigation of CO2 emissions in the future are summarized. This review demonstrates that CO2 storage in depleted oil and gas reservoirs could play an important role in reducing CO2 emission in the near future and CO2 storage in saline aquifers may make the biggest contribution due to its huge storage capacity. Comparing the various available strategies, CO2-enhanced oil recovery (CO2-EOR) operations are supposed to play the most important role for CO2 mitigation in the next few years, followed by CO2-enhanced gas recovery (CO2-EGR). The direct mineralization of flue gas by coal fly ash and the pH swing mineralization would be the most promising technology for the mineral sequestration of CO2. Furthermore, by accelerating the deployment of CCS projects on large scale, the government can also play its role in reducing the CO2 emissions.

Enhanced microbial respiration due to carbon sequestration in pruning litter incorporated soil reduced the net carbon dioxide flux from atmosphere to tea ecosystem

BACKGROUND

Tea (Camellia sinensis L.) bushes are periodically (at 3-4 year intervals) pruned (cut from top) to maintain vegetative growth stage and constant height. Plant residues (prunings litter) generated after pruning are generally left in the field as a potential source of organic matter in soil. Organic carbon (C) sequestration due to pruning litter incorporation is expected to increase microbial activity in soil. Being an evergreen plant, tea bushes assimilate atmospheric carbon dioxide (CO₂ ) throughout the year; however, the relation between decomposition of pruning litters and net CO₂ flux for tea plantation have not been studied before. The objective of this experiment was to evaluate the relation between organic C accumulation and microbial respiration in pruning litters incorporated soil and its subsequent effect on the net CO₂ flux from the atmosphere to tea plantation.

RESULTS

Tea bushes assimilated 1878.2-2371.2 kg CO₂ ha^-1 from the atmosphere within December to November; however, pruned bushes assimilated 1451.7-1840.8 kg CO₂ ha^-1 within the same period. Decomposition of pruning litters added organic matter in soil, which was mostly accumulated in larger soil aggregates having 2.0-0.25 mm size. Such organic matter accumulation significantly increased microbial respiration in those aggregates, which in turn increased the overall rate of CO₂ emission from soil to the atmosphere.

CONCLUSION

Decomposition of pruning litters leads to emission of 426.5-530.4 kg CO₂ ha^-1 from soil. Hence, pruned areas recorded relatively lower (16.0-27.4%) net CO₂ flux from the atmosphere to tea ecosystem as compared to unpruned tea bushes. © 2019 Society of Chemical Industry.

Homogeneous nucleation of carbon dioxide in supersonic nozzles I: experiments and classical theories

We studied the homogeneous nucleation of carbon dioxide in the carrier gas argon for concentrations of CO2 ranging from 2 to 39 mole percent using three experimental methods. Position-resolved pressure trace measurements (PTM) determined that the onset of nucleation occurred at temperatures between 75 and 92 K with corresponding CO2 partial pressures of 39 to 793 Pa. Small angle X-ray scattering (SAXS) measurements provided particle size distributions and aerosol number densities. Number densities of approximately 1012 cm-3, and characteristic times ranging from 6 to 13 μs, resulted in measured nucleation rates on the order of 5 × 1017 cm-3 s-1, values that are consistent with other nucleation rate measurements in supersonic nozzles. Finally, we used Fourier transform infrared (FTIR) spectroscopy to identify that the condensed CO2 particles were crystalline cubic solids with either sharp or rounded corners. Molecular dynamics simulations, however, suggest that CO2 forms liquid-like critical clusters before transitioning to the solid phase. Furthermore, the critical clusters are not in thermal equilibrium with the carrier gas. Comparisons with nucleation theories were therefore made assuming liquid-like critical clusters and incorporating non-isothermal correction factors.

Climate engineering management: an emerging interdisciplinary subject

Purpose

Climate engineering management (CEM) as an emerging and cross-disciplinary subject gradually draws the attention to researchers. This paper aims to focus on economic and social impacts on the technologies of climate engineering themselves. However, very few research concentrates on the management of climate engineering. Furthermore, scientific knowledge and a unified system of CEM are limited.

Design/methodology/approach

In this paper, the concept of CEM and its characteristics are proposed and elaborated. In addition, the framework of CEM is established based on management objectives, management processes and supporting theory and technology of management. Moreover, a multi-agent synergistic theory of CEM is put forward to guide efficient management of climate engineering, which is composed of time synergy, space synergy, and factor synergy. This theory is suitable for solving all problems encountered in the management of various climate engineering rather than a specific climate engineering. Specifically, the proposed CEM system aims to mitigate the impact of climate change via refining and summarizing the interrelationship of each component.

Findings

Overall, the six research frontiers and hotspots in the field of CEM are explored based on the current status of research.

Originality/value

In terms of the objectives listed above, this paper seeks to provide a reference for formulating the standards and norms in the management of various climate engineering, as well as contribute to policy implementation and efficient management.

Harmful effects of cocaine byproduct in the reproduction of sea urchin in different ocean acidification scenarios

This study has as main objective assessing the toxicity of crack-cocaine combined with different scenarios of ocean acidification on fertilization rate and embryo-larval development of Echinometra lucunter sea urchin. Effects on early life stages were assessed at five different concentrations (6,25 mg.L^-1; 12,5 mg.L^-1; 25 mg.L^-1; 50 mg.L^-1 and 100 mg.L^-1) of crack-cocaine at four different pH values (8.5; 8.0; 7.5; 7.0). The pH values were achieved using two different methodologies: adding hydrochloric acid (HCl) and injecting carbon dioxide (CO₂). The fertilization test did not show significant differences (p ≤ 0.05) compared with control sample at pH values 8.5; 8.0 and 7.5. Results of embryo-larval assays showed a half maximal effective concentration (EC50) of crack-cocaine at pH values tested (8.5, 8.0, 7.5) as 58.83, 10.67 and 11.58 mg/L^-1 for HCl acidification and 58.83, 23.28 and 12.57 mg/L^-1 for CO₂ enrichment. At pH 7.0 the effects observed in fertilization rate and embryo development were associated with the acidification. This study is the first ecotoxicological assessment of illicit drug toxicity in aquatic ecosystems at different ocean acidification scenarios.

Investment Decisions of Fired Power Plants on Carbon Utilization under the Imperfect Carbon Emission Trading Schemes in China

Carbon capture, utilization, and storage (CCUS) is one of the most effective technologies to reduce CO2 emissions and has attracted wide attention all over the world. This paper proposes a real option model to analyze the investment decisions of a coal-fired power plant on CCUS technologies under imperfect carbon emission trading schemes in China. Considering multiple uncertainties, which include carbon trading price volatility, carbon utilization revenue fluctuation, and changes in carbon transport and storage cost, the least squares Monte Carlo simulation method is used to solve the problems of path dependence. The research results show that the independent effects of carbon trading mechanisms on investment stimulation and emission reduction are limited. The utilization ratio of captured CO2 has significant impacts on the net present value and investment value of the CCUS project. Moreover, the investment threshold is highly sensitive to the utilization proportion of food grade CO2 with high purity. It is suggested that the Chinese government should take diverse measures simultaneously, including increasing grants for research and development of carbon utilization technologies, introducing policies to motivate investments in CCUS projects, and also improving the carbon emission trading scheme, to ensure the achievement of the carbon emission reduction target in China.

An analysis of research hotspots and modeling techniques on carbon capture and storage

With the significant role that carbon capture and storage (CCS) could play in limiting the future temperature increase to below 2 °C higher than pre-industrialization levels, a growing research interest of CCS is attracted to the environmental, economic, and social field. However, a bibliometric analysis-based comprehensive review of CCS which covers mainly all industry sectors and all regions of the globe has not been made yet. To provide deeper insight into the research trends, this study employs a bibliometric analysis to examine the basic features of the literature from 1997 to 2017 and identifies the key research hotspots and modeling techniques by reviewing the current status and new efforts. Based on the analysis of the temporal and spatial trends, disciplines and journals distribution, institutions, authors, and citations, the publications relating to the environmental, economic and social aspects of CCS are assessed. The results indicate that the total number of publications has rapidly increased since 2006 and entered a stable stage. The most productive country, journal, institute, and author are the USA, International Journal of Greenhouse Gas Control, United State Department of Energy, and Rubin E S, respectively. Based on the co-occurrence analysis of keywords, five hot research topics in CCS are recognized, including tackling climate change, CCS technology prospects, cost estimates, sectoral applications, and social attitudes. In addition, three main methodologies including life cycle analysis, optimization methods, and real options methods used in quantifying the social, economic, and environmental impacts of CCS are thoroughly refined based on selection, limitation, and improvement. Finally, the recommendations for CCS future work concerning environmental, economic, and social aspects are proposed.

Direct microbial transformation of carbon dioxide to value-added chemicals: A comprehensive analysis and application potentials

Carbon dioxide storage in petroleum and other geological reservoirs is an economical option for long-term separation of this gas from the atmosphere. Other options include applications through conversion to valuable chemicals. Microalgae and plants perform direct fixation of carbon dioxide to biomass, which is then used as raw material for further microbial transformation (MT). The approach by microbial transformation can achieve reduction of carbon dioxide and production of biofuels. This review addresses the research and technological processes related to direct MT of carbon dioxide, factors affecting their efficiency in operation and the review of economic feasibility. Additionally, some commercial plants making utilization of CO₂ around the globe are also summarized along with different value-added chemicals (methane, acetate, fatty acids and alcohols) as reported in literature. Further information is also provided for a better understanding of direct CO₂ MT and its future prospects leading to a sustainable and clean environment.

Negative emissions technologies: A complementary solution for climate change mitigation

Carbon dioxide (CO₂) is the main greenhouse gas (GHG) and its atmospheric concentration is currently 50% higher than pre-industrial levels. The continuous GHGs emissions may lead to severe and irreversible consequences in the climate system. The reduction of GHG emissions may be not enough to mitigate climate change. Consequently, besides carbon capture from large emission sources, atmospheric CO₂ capture may be also required. To meet the target defined for climate change mitigation, the removal of 10 Gt·yr^-1 of CO₂ globally by mid-century and 20 Gt·yr^-1 of CO₂ globally by the end of century. The technologies applied with this aim are known as negative emission technologies (NETs), as they lead to achieve a negative balance of carbon in atmosphere. This paper aims to present the recent research works regarding NETs, focusing the research findings achieved by academic groups and projects. Besides several advantages, NETs present high operational cost and its scale-up should be tested to know the real effect on climate change mitigation. With current knowledge, no single process should be seen as a solution. Research efforts should be performed to evaluate and reduce NETs costs and environmental impact.

Numerical Study on Gaseous CO2 Leakage and Thermal Characteristics of Containers in a Transport Ship

This study investigates numerically gaseous CO2 leakage characteristics inside the containers of a transport ship and examines thermal effects on the structural damage that might happen in the containers. First, with consideration of the phase change, the ejected mass flow rate was estimated using the commercial code of DNV PHAST. Based on this estimated mass flow rate, we introduced an effective area model for accounting for the fast evaporation of liquefied CO2 occurring in the vicinity of a crack hole. Using this leakage modeling, along with a concept of the effective area, the computational fluid dynamics (CFD) simulations for analyzing transient three-dimensional characteristics of gas propagation in a confined space with nine containers, as well as the thermal effect on the walls on which the leaking gas impinges, were conducted. The commercial code, ANSYS FLUENT V. 17.0, was used for all CFD simulations. It was found that there are substantial changes in the pressure and temperature of the gas mixture for different crack sizes. The CO2 concentration at human nasal height, a measure of clear height for safety, was also estimated to be higher than the safety threshold of 10% within 200 s. Moreover, very cold gas created by the evaporation of liquefied CO2 can cool the cargo walls rapidly, which might cause thermal damage.

Effect of Triblock Copolymer on Carbon-Based Boron Nitride Whiskers for Efficient CO2 Adsorption

Herein, we investigated novel carbon-containing P123 copolymer-activated boron nitride whiskers (P123-CBNW) fabricated via a structure directing approach followed by a single-step heat treatment under N₂. The resulting materials were found to be highly micro- and mesoporous. The influence of the activating agent (P123 copolymer) on the CO₂ adsorption efficiency was determined. The prepared samples possessed high specific surface areas (594–1732 m²/g) and micropore volumes (0.258–0.672 cm³/g). The maximum CO₂ uptakes of the prepared adsorbents were in the range 136–308 mg/g (3.09–7.01 mmol/g) at 273 K and 1 bar and 97–114 mg/g (2.22–4.62 mmol/g) in the following order: CBNW < P123-CBNW3 < P123-CBNW2 < P123-CBNW1 < P123-CBNW0.5. The isosteric heat of adsorption values (∆Q_st) were found to be 33.7–43.7 kJ/mol, demonstrating the physisorption nature of the CO₂ adsorption. Extensive analysis revealed that the presence of carbon, the high specific surface area, the high microporosity, and the chemical structural defects within the adsorbents are responsible for raising the CO₂ adsorption ability and the selectivity over N₂ gas. The fabricated adsorbents show excellent regeneration ability after several repeated adsorption cycles, making the prepared adsorbents promising candidates for gas storage applications.

The Use of Microalgae for Coupling Wastewater Treatment With CO2 Biofixation

Production and emission of CO2 from different sources have caused significant changes in the climate, which is the major concern related to global warming. Among other CO2 removal approaches, microalgae can efficiently remove CO2 through the rapid production of algal biomass. In addition, microalgae have the potential to be used in wastewater treatment. Although, wastewater treatment and CO2 removal by microalgae have been studied separately for a long time, there is no detailed information available on combining both processes. In this review article, microalgae-based CO2 biofixation, various microalgae cultivation systems,¯ and microalgae-derived wastewater treatment are separately discussed, followed by the concept of integration of CO2 biofixation process and wastewater treatment. In each section, details of energy efficiency and differences across microalgae species are also given.

Separation of Carbon Dioxide from Real Power Plant Flue Gases by Gas Permeation Using a Supported Ionic Liquid Membrane: An Investigation of Membrane Stability

The separation of carbon dioxide from coal-fired power plant flue gases using a CO₂/N₂-selective supported ionic liquid membrane (SILM) was investigated and the performance and stability of the membrane during operation are reported. The membrane is composed of a polyacrylonitrile (PAN) ultrafiltration membrane as a support and a selective layer of an ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM Tf2N). The feasibility of large-scale SILM production was demonstrated by the formation of a square-meter-scale membrane and preparation of a membrane module. A flat-sheet envelope-type SILM module containing 0.67 m² of the membrane was assembled. Prior to real flue gas operation, the separation behaviour of the membrane was investigated with single gases. The stability of the SILM during the test stand and pilot plant operation using real power plant flue gases is reported. The volume fraction of carbon dioxide in the flue gas was raised from approx. 14 vol. % (feed) to 40 vol. % (permeate). However, issues concerning the membrane stability were found when SO₃ aerosols in large quantities were present in the flue gas.

Mo-doped boron nitride monolayer as a promising single-atom electrocatalyst for CO2 conversion

The design of new, efficient catalysts for the conversion of CO₂ to useful fuels under mild conditions is urgent in order to reduce greenhouse gas emissions and alleviate the energy crisis. In this work, a series of transition metals (TMs), including Sc to Zn, Mo, Ru, Rh, Pd and Ag, supported on a boron nitride (BN) monolayer with boron vacancies, were investigated as electrocatalysts for the CO₂ reduction reaction (CRR) using comprehensive density functional theory (DFT) calculations. The results demonstrate that a single-Mo-atom-doped boron nitride (Mo-doped BN) monolayer possesses excellent performance for converting CO₂ to CH₄ with a relatively low limiting potential of -0.45 V, which is lower than most catalysts for the selective production of CH₄ as found in both theoretical and experimental studies. In addition, the formation of OCHO on the Mo-doped BN monolayer in the early hydrogenation steps is found to be spontaneous, which is distinct from the conventional catalysts. Mo, as a non-noble element, presents excellent catalytic performance with coordination to the BN monolayer, and is thus a promising transition metal for catalyzing CRR. This work not only provides insight into the mechanism of CRR on the single-atom catalyst (Mo-doped BN monolayer) at the atomic level, but also offers guidance in the search for appropriate earth-abundant TMs as electrochemical catalysts for the efficient conversion of CO₂ to useful fuels under ambient conditions.

Comparative effects of seawater acidification on microalgae: Single and multispecies toxicity tests

In order to gain knowledge about the potential effects of acidification in aquatic ecosystems, global change research based on microalgae as sentinel species has been often developed. However, these studies are limited to single species tests and there is still a research gap about the behaviour of microalgal communities under this environmental stressor. Thus, the aim of this study was to assess the negative effects of CO₂ under an ecologically realistic scenario. To achieve this objective, two types of toxicity tests were developed; i) single toxicity tests and ii) multispecies toxicity tests, in order to evaluate the effects on each species as well as the interspecific competition. For this purpose, three microalgae species (Tetraselmis chuii, Phaeodactylum tricornutum and Nannochloropsis gaditana) were exposed to two selected pH levels (7.4, 6.0) and a control (pH 8.0). The pH values were choosen for testing different scenarios of CO₂ enrichment including the exchange atmosphere-ocean (pH 7.4) and natural or anthropogenic sources of CO₂ (pH 6.0). The effects on growth, cell viability, oxidative stress, plus inherent cell properties (size, complexity and autofluorescence) were studied using flow cytometry (FCM). Results showed that T. chuii was the most resistant species to CO₂ enrichment with less abrupt changes in terms of cell density, inherent cell properties, oxidative stress and cell viability. Although P. tricornutum was the dominant species in both single and multispecies tests, this species showed the highest decrease in cell density under pH 6.0. Effects of competence were recorded in the multispecies control (pH 8) but this competence was eclipsed by the effects of low pH. The knowledge of biological interactions made by different microalgae species is a useful tool to extrapolate research data from laboratory to the field.

Tetrel bonds and conformational equilibria in the formamide–CO2 complex: a rotational study

Rotational studies point out that two isomers of the formamide–CO₂ complex are stabilized by the dominated C⋯O tetrel bond.

Advantages of Yolk Shell Catalysts for the DRM: A Comparison of Ni/ZnO@SiO2 vs. Ni/CeO2 and Ni/Al2O3

Encapsulation of metal nanoparticles is a leading technique used to inhibit the main deactivation mechanisms in dry reforming of methane reaction (DRM): Carbon formation and Sintering. Ni catalysts (15%) supported on alumina (Al2O3) and ceria (CeO2) have shown they are no exception to this analysis. The alumina supported catalysts experienced graphitic carbonaceous deposits, whilst the ceria showed considerable sintering over 15 h of DRM reaction. The effect of encapsulation compared to that of the performance of uncoated catalysts for DRM reaction has been examined at different temperatures, before conducting longer stability tests. The encapsulation of Ni/ZnO cores in silica (SiO2) leads to advantageous conversion of both CO2 and CH4 at high temperatures compared to its uncoated alternatives. This work showcases the significance of the encapsulation process and its overall effects on the catalytic performance in chemical CO2 recycling via DRM.

Technology Evolution in Membrane-Based CCS

In recent years, many CO2 capture technologies have been developed due to growing awareness about the importance of reducing greenhouse gas emissions. In this paper, publications from the last decade addressing this topic were analyzed, paying special attention to patent status to provide useful information for policymakers, industry, and businesses and to help determine the direction of future research. To show the most current patent activity related to carbon capture using membrane technology, we collected 2749 patent documents and 572 scientific papers. The results demonstrated that membranes are a developing field, with the number of applications growing at a steady pace, exceeding 100 applications per year in 2013 and 2014. North American assignees were the main contributors, with the greatest number of patents owned by companies such as UOP LLC, Kilimanjaro Energy Inc., and Membrane Technology and Research Inc., making up 26% of the total number of published patents. Asian countries (China, Japan, and Korea) and international offices were also important knowledge sources, providing 29% and 24% of the documents, respectively. Furthermore, this paper highlights 10 more valuable patents regarding their degree of innovation and citations, classified as Y02C 10/10 according to the Cooperative Patent Classification (CPC) criteria.

CO2 bio-fixation and biofuel production in an airlift photobioreactor by an isolated strain of microalgae Coelastrum sp. SM under high CO2 concentrations

Microalgae cultivation is a promising approach to remove ambient CO₂ via photosynthesis process. This paper investigates the impact of high CO₂ concentrations (6, 12, and 16%) on algae growth, CO₂ biofixation, lipid and carbohydrate contents, and nutrient removal of newly isolated microalgae, Coelastrum sp. SM. In addition, the ability of microalgae to produce biodiesel at optimal condition was studied. The microalgae were cultivated in wastewater using an airlift photobioreactor. Under 12% CO₂, the maximum biomass productivity and CO₂ fixation rate were 0.267 g L^-1 day^-1 and 0.302 g L^-1 h^-1, respectively. Total Kjeldahl nitrogen (TKN), total phosphorous (TP), nitrate, and sCOD removal efficiency were 84.01, 100, 86.811, and 73.084%, respectively. Under 12% CO₂ and at the same condition for cell growth, the highest lipid and carbohydrate contents were 3 7.91 and 58.45%, respectively. The composition of fatty acids methyl ester (FAME) of the microalga lipid was defined. Based on the obtained results and FAME profile, Coelastrum sp. SM was a suitable feedstock for biodiesel production and also, the organism had a great potential for CO₂ biofixation, which is also more suitable than any other reported strains in other related studies.

Complex mathematical analysis of photobioreactor system

Modeling as a tool solves extremely difficult tasks in life sciences. Recently, schemes of culturing of microalgae have received special attention because of its unique features and possible uses in many industrial applications for renewable energy production and high value products isolation. The goal of this review is to present the use of system analysis theory applied to microalgae culturing modeling and process development. The review mainly focuses on the modeling of the key steps of autotrophic growth under the integral biorefinery concept of the microalgae biomass. The system approach follows systematically a procedure showing the difficulties by modeling of sub-systems. The development of microalgae kinetics and computational fluid dynamics (CFD) studies were analyzed in details as sub-systems in advanced design of photobioreactor (PBR). This review logically follows the trends of the modeling procedure and clarifies how this approach may save time and money during the research efforts. The result of this work is a successful development of a complex PBR mathematical analysis in the frame of the integral biorefinery concept.

Scrutinising the Gap between the Expected and Actual Deployment of Carbon Capture and Storage—A Bibliometric Analysis

For many years, carbon capture and storage (CCS) has been discussed as a technology that may make a significant contribution to achieving major reductions in greenhouse gas emissions. At present, however, only two large-scale power plants capture a total of 2.4 Mt CO2/a. Several reasons are identified for this mismatch between expectations and realised deployment. Applying bibliographic coupling, the research front of CCS, understood to be published peer-reviewed papers, is explored to scrutinise whether the current research is sufficient to meet these problems. The analysis reveals that research is dominated by technical research (69%). Only 31% of papers address non-technical issues, particularly exploring public perception, policy, and regulation, providing a broader view on CCS implementation on the regional or national level, or using assessment frameworks. This shows that the research is advancing and attempting to meet the outlined problems, which are mainly non-technology related. In addition to strengthening this research, the proportion of papers that adopt a holistic approach may be increased in a bid to meet the challenges involved in transforming a complex energy system. It may also be useful to include a broad variety of stakeholders in research so as to provide a more resilient development of CCS deployment strategies.

Carbon dioxide from geothermal gas converted to biomass by cultivating coccoid cyanobacteria

The Blue Lagoon is a geothermal aquifer with a diverse ecosystem located within the Reykjanes UNESCO Global Geopark on Iceland's Reykjanes Peninsula. Blue Lagoon Ltd., which exploits the aquifer, isolated a strain of coccoid cyanobacteria Cyanobacterium aponinum (C. aponinum) from the geothermal fluid of the Blue Lagoon more than two decades ago. Since then Blue Lagoon Ltd. has cultivated it in a photobioreactor, for use as an active ingredient in its skin care products. Until recently, the cultivation of C. aponinum was achieved by feeding it on 99.99% (4N) bottled carbon dioxide (CO₂). In this investigation, C. aponinum was cultivated using unmodified, non-condensable geothermal gas (geogas) emitted from a nearby geothermal powerplant as the feed-gas instead of the 4N-gas. The geogas contains roughly 90% vol CO₂ and 2% vol hydrogen sulfide (H₂S). A comparison of both CO₂ sources was made. It was observed that the use of geogas did enhance the conversion efficiency. A 13 weeks' average CO₂ conversion efficiency of C. aponinum was 43% and 31% when fed on geogas and 4N-gas, respectively. Despite the high H₂S concentration in the geogas, sulfur accumulation in the cultivated biomass was similar for both gas sources. Our results provide a model of a CO₂ sequestration by photosynthetic conversion of otherwise unused geothermal emission gas into biomass.