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The extensive deposits of calcium carbonate (CaCO 3 ) generated by marine organisms constitute the largest and oldest carbon dioxide (CO 2 ) reservoir. These organisms utilize macromolecules like peptides and proteins to facilitate the nucleation and growth of carbonate minerals, serving as an effective method for CO 2 sequestration. However, the precise mechanisms behind this process remain elusive. In this study, we report the use of sequence-defined peptoids, a class of peptidomimetics, to achieve the accelerated calcite step growth kinetics with the molecular level mechanistic understanding. By designing peptoids with hydrophilic and hydrophobic blocks, we systematically investigated the acceleration in step growth rate of calcite crystals using in situ atomic force microscopy (AFM), varying peptoid sequences and concentrations, CaCO 3 supersaturations, and the ratio of Ca 2+ / HCO 3 - . Mechanistic studies using NMR, three-dimensional fast force mapping (3D FFM), and isothermal titration calorimetry (ITC) were conducted to reveal the interactions of peptoids with Ca 2+ and HCO 3 - ions in solution, as well as the effect of peptoids on solvation and energetics of calcite crystal surface. Our results indicate the multiple roles of peptoid in facilitating HCO 3 - deprotonation, Ca 2+ desolvation, and the disruption of interfacial hydration layers of the calcite surface, which collectively contribute to a peptoid-induced acceleration of calcite growth. These findings provide guidelines for future design of sequence-specific biomimetic polymers as crystallization promoters, offering potential applications in environmental remediation (such as CO 2 sequestration), biomedical engineering, and energy storage where fast crystallization is preferred., Competing Interests: Competing interests statement:The authors declare no competing interest.

The CO 2 displacement of coal seam gas can simultaneously promote gas extraction and CO 2 sequestration, with gas injection pressure being a key factor influencing both efficiency and safety. This study examined the impact of varying CO 2 injection pressure on gas extraction and sequestration. The findings indicated that higher CO 2 injection pressures reduced the gas injection and extraction time costs, increased the equilibrium pressure and coal seam temperature, and decreased carbon sequestration efficiency. As the CO 2 injection pressure increased, the CH 4 cumulative desorption capacity and desorption rate rose by 4.98%, the time to reach the residual gas content critical value (TLV of 2 m 3 /t) shortened by 62.04 min, and the maximum CO 2 storage per unit mass of coal increases by 3.6 m 3 /t. Increasing the injection pressure enhanced gas desorption and CO 2 sequestration. A higher CO 2 injection pressure resulted in a higher CH 4 yield rate and a reduced CO 2 injection rate in the later stages. Therefore, it is advisable to reduce the CO 2 injection pressure during the low efficiency desorption stage., (© 2024. The Author(s).)

Aims: This study continues our previous investigation of the intrinsic degradation of phosphogypsum (PG) by indigenous microorganisms on amending adequate nutrients. We aim to unravel the intricate mechanisms involved in PG biotransformation by a bacterial consortium., Methods and Results: We isolated and characterised seven multi-metal-resistant bacterial strains from a nutrient-amended PG-contaminated microcosm and identified them through 16S rRNA gene sequencing. Primarily aerobic, gram-positive chemolithotrophs, these strains demonstrated significant heavy metal (HM) uptake and PG degradation potential.Further analysis revealed that all strains produced carbonic anhydrase (CA), while six also produced urease, which may facilitate microbial-induced carbonate precipitation (MICP). Microstructural and elemental analysis using SEM-EDX and XRD confirmed the PG bio-transformation, indicating substantial increases in carbonate concentrations and reductions in sulfate levels., Conclusions: The consortium, composed of seven urease and CA-producing bacterial strains, effectively degraded PG, transforming it from an acidic to an alkaline state and significantly enhancing CO2 sequestration., (© The Author(s) 2024. Published by Oxford University Press on behalf of Applied Microbiology International.)

Superhydrophobic surfaces applying on concrete can greatly improve the durability of concrete by preventing the damage from water. However, traditional design of superhydrophobic concrete surfaces by external coating encounters to problems of flaking and poor surface robustness, while that by adding hydrophobic agents or particles faces the challenges of strength damage of concrete. Drawing inspiration from the carbonation phenomenon of concrete, here a new design of in situ growing superhydrophobic structures on concrete is proposed: The concrete sample is impregnated into Mg 2+ -containing silane-water system with continuous CO 2 injection. The contact angle of the concrete surface achieves 171.9° without obvious strength decrease after 120 min, which are mainly attributed to the formation of Ca x Mg 1-x CO 3 crystals with micro-nano-structures and the reduction of carbonates surface energy by silane. This superhydrophobic concrete structure can be divided into a superhydrophobic-hydrophobic-hydrophilic three layers structure, providing the stable water-proof protection under mechanical fatigue, capillary water absorption, UV aging, sulfate attack, and impurity water impact tests due to the in situ growing robust superhydrophobic structures. Furthermore, it captures 29.80 g m -2 CO 2 during the reaction process, providing new insights for the design and preparation of eco-friendly superhydrophobic concrete., (© 2024 Wiley‐VCH GmbH.)

Learning operators with deep neural networks is an emerging paradigm for scientific computing. Deep Operator Network (DeepONet) is a modular operator learning framework that allows for flexibility in choosing the kind of neural network to be used in the trunk and/or branch of the DeepONet. This is beneficial as it has been shown many times that different types of problems require different kinds of network architectures for effective learning. In this work, we design an efficient neural operator based on the DeepONet architecture. We introduce U-Net enhanced DeepONet (U-DeepONet) for learning the solution operator of highly complex CO 2 -water two-phase flow in heterogeneous porous media. The U-DeepONet is more accurate in predicting gas saturation and pressure buildup than the state-of-the-art U-Net based Fourier Neural Operator (U-FNO) and the Fourier-enhanced Multiple-Input Operator (Fourier-MIONet) trained on the same dataset. Moreover, our U-DeepONet is significantly more efficient in training times than both the U-FNO (more than 18 times faster) and the Fourier-MIONet (more than 5 times faster), while consuming less computational resources. We also show that the U-DeepONet is more data efficient and better at generalization than both the U-FNO and the Fourier-MIONet., (© 2024. The Author(s).)

The current review presents a discussion on the utility of neutron scattering, with emphasis on neutron total scattering and small-angle neutron scattering (SANS), to explore the structural properties and the phase behaviour of fluids confined in nanopores. The effectiveness of contrast matching SANS on the evaluation of accessibility of porous materials to invading fluids is highlighted too. This review provides also an overview regarding the neutron scattering studies on the structure and the accessibility of greenhouse gases in the complex pore network of geomaterials, with applications to CO 2 geological sequestration and enhanced oil and gas recovery., (© 2024 The Author(s). ChemPlusChem published by Wiley-VCH GmbH.)

Succinic acid (SA), one of the 12 top platform chemicals produced from biomass, is a precursor of various high value-added derivatives. Specially, 1 mol CO 2 is assimilated in 1 mol SA biosynthetic route under anaerobic conditions, which helps to achieve carbon reduction goals. In this review, methods for enhanced CO 2 fixation in SA production and utilization of waste biomass for SA production are reviewed. Bioelectrochemical and bioreactor coupling systems constructed with off-gas reutilization to capture CO 2 more efficiently were highlighted. In addition, the techno-economic analysis and carbon sequestration benefits for the synthesis of bio-based SA from CO 2 and waste biomass are analyzed. Finally, a droplet microfluidics-based high-throughput screening technique applied to the future bioproduction of SA is proposed as a promising approach., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Lin, Li, Wang, Hu, Qin, Xia, Hu, Liu and Luo.)

Occurrences of natural magnesium alumina silicate hydrate (M-(A)-S-H) cement are present in Feragen and Leka, in eastern and western Trøndelag Norway, respectively. Both occurrences are in the subarctic climate zone and form in glacial till and moraine material deposited on ultramafic rock during the Weichselian glaciation. Weathering of serpentinized peridotite dissolves brucite and results in an alkaline fluid with a relatively high pH which subsequently reacts with the felsic minerals of the till (quartz, plagioclase, K-feldspar) to form a cement consisting of an amorphous material or a mixture of nanocrystalline Mg-rich phyllosilicates, including illite. The presence of plagioclase in the till results in the enrichment of alumina in the cement, i.e., forms M-A-S-H instead of the M-S-H cement. Dissolution of quartz results in numerous etch pits and negative quartz crystals filled with M-A-S-H cement. Where the quartz dissolution is faster than the cement precipitation, a honeycomb-like texture is formed. Compositionally, the cemented till (tillite) contains more MgO and has a higher loss of ignition than the till, suggesting that the cement is formed by a MgO fluid that previously reacted with the peridotite. The M-(A)-S-H cemented till represents a new type of duricrust, coined magsilcrete. The study of natural Mg cement provides information on peridotites as a Mg source for Mg cement and as a feedstock for CO 2 sequestration.

The hydration of CO 2 suffers from kinetic inefficiencies that make its natural trapping impractically sluggish. However, CO 2 -fixing carbonic anhydrases (CAs) remarkably accelerate its equilibration by 6 orders of magnitude and are, therefore, "ideal" catalysts. Notably, CA has been detected in ureolytic bacteria, suggesting its potential involvement in microbially induced carbonate precipitation (MICP), yet the dynamics of the urease (Ur) and CA genes remain poorly understood. Here, through the use of the ureolytic bacterium Sporosarcina pasteurii , we investigate the differing role of Ur and CA in ureolysis, CO 2 hydration, and CaCO 3 precipitation with increasing CO 2(g) concentrations. We show that Ur gene up-regulation coincides with an increase in [HCO 3 - ] following the hydration of CO 2 to HCO 3 - by CA. Hence, CA physiologically promotes buffering, which enhances solubility trapping and affects the phase of the CaCO 3 mineral formed. Understanding the role of CO 2 hydration on the performance of ureolysis and CaCO 3 precipitation provides essential new insights, required for the development of next-generation biocatalyzed CO 2 trapping technologies.

In recent years, a new class of highly crystalline advanced permeable materials covalent-organic frameworks (COFs) have garnered a great deal of attention thanks to their remarkable properties, such as their large surface area, highly ordered pores and channels, and controllable crystalline structures. The lower physical stability and electrical conductivity, however, prevent them from being widely used in applications like photocatalytic activities and innovative energy storage and conversion devices. For this reason, many studies have focused on finding ways to improve upon these interesting materials while also minimizing their drawbacks. This review article begins with a brief introduction to the history and major milestones of COFs development before moving on to a comprehensive exploration of the various synthesis methods and recent successes and signposts of their potential applications in carbon dioxide (CO 2 ) sequestration, supercapacitors (SCs), lithium-ion batteries (LIBs), and hydrogen production (H 2 -energy). In conclusion, the difficulties and potential of future developing with highly efficient COFs ideas for photocatalytic as well as electrochemical energy storage applications are highlighted., (© 2023 The Chemical Society of Japan & Wiley-VCH GmbH.)

The utilization of steel slag for CO 2 sequestration is an effective way to reduce carbon emissions. The reactivity of steel slag in CO 2 sequestration depends mainly on material and process parameters. However, there are many puzzles in regard to practical applications due to the different evaluations of process parameters and the lack of investigation of material parameters. In this study, 318 samples were collected to investigate the interactive influence of 12 factors on the carbonation reactivity of steel slag by machine learning with SHapley Additive exPlanations (SHAP). Multilayer perceptron (MLP), random forest, and support vector regression models were built to predict the slurry-phase CO 2 sequestration of steel slag. The MLP model performed well in terms of prediction ability and generalization with comprehensive interpretability. The SHAP results showed that the impact of the process parameters was greater than that of the material parameters. Interestingly, the iron ore phase of steel slag was revealed to have a positive effect on steel slag carbonation by SHAP analysis. Combined with previous literature, the carbonation mechanism of steel slag was proposed. Quantitative analysis based on SHAP indicated that steel slag had good carbonation reactivity when the mass fractions of "CaO + MgO", "SiO 2 + Al 2 O 3 ", "Fe 2 O 3 ", and "MnO" varied from 50-55%, 10-15%, 30-35%, and <5%, respectively.

Human survival is threatened by the rapid climate change due to global warming caused by the increase in CO 2 emissions since the Second Industrial Revolution. This study developed a secondary cement product production technology by replacing cement, a conventional binder, with calcium silicate cement (CSC), i.e., CO 2 reactive hardening cement, to reduce CO 2 emissions and utilize CO 2 from the cement industry, which emits CO 2 in large quantities. Results showed that the carbonation depth, compressive strength increase rate, and CO 2 sequestration rate increased as the CSC content increased, suggesting that CSC can be applied as a secondary cement product.

This paper reports for the first time the use and application of a novel technique in the characterization of mineral carbonation reaction and CO 2 sequestration in soil stabilization using flow meters. Soils based on SiO 2 with two different sizes were tested. Lime (Ca(OH) 2 ) was used as the reactant. Instant CO 2 flow rate (L/min), total CO 2 volume (L), temperature (°C), and absolute pressure (kPa) were monitored and recorded for 1 h by flow meters connected to the mold inlet and outlet. It was determined that the mineral carbonation reaction started in the first seconds and ended before the 5th minute. The mineral carbonation is a short-term and potential reaction, and it is not a time-dependent reaction. It is separated from other carbonation reactions with these characteristics. The highest CO 2 captured value was obtained in the soil mixed with 5% lime, where fines were not used. The second highest CO 2 captured value was obtained in soil mixed with 1% lime, where fines were not used. CO 2 captured with 1% lime is more than CO 2 captured with 5% lime in the soil containing fines. Accordingly, 1-5% lime can be used in soil carbonation studies. According to the soil properties, the highest CO 2 captured and the CO 2 efficiency was achieved with the use of 6-7% water by weight., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Hydrogen is a promising source of alternative energy. Fermentative production is more feasible because of its high hydrogen generation rate, simple operating conditions, and utilization of various organic wastes as substrates. The most significant constraint for biohydrogen production is supplying it at a low cost with fewer impurities., Results: Leaf biomass of Calotropis procera was used as a feedstock for a dark fermentative production of hydrogen by Bacillus coagulans AH1 (MN923076). The optimum operation conditions for biohydrogen production were 5.0% substrate concentrationand pH 9.0, at 35 °C. In which the biohydrogen yield was 3.231 mmol H 2 /g dry biomass without any pretreatments of the biomass. A freshwater microalga Oscillatroia sp was used for upgrading of the produced biohydrogen. It sequestrated 97 and 99% % of CO 2 from the gas mixture when it was cultivated in BG11 and BG11-N media, respectively After upgrading process, the residual microalgal cells exhibited 0.21mg/mL of biomass yield,high content of chlorophyll-a (4.8 µg/mL) and carotenoid (11.1 µg/mL). In addition to Oscillatroia sp residual biomass showed a lipid yield (7.5-8.7%) on the tested media., Conclusion: Bacillus coagulans AH1 is a promising tool for biohydrogen production avoiding the drawbacks of biomass pretreatment. Oscillatroia sp is encouraged as a potent tool for upgrading and purification of biohydrogen. These findings led to the development of a multiproduct biorefinery with zero waste that is more economically sustainable., (© 2023. BioMed Central Ltd., part of Springer Nature.)

The concentration of CO 2 in the atmosphere is constantly increasing, leading to an increase in the average global temperature and, thus, affecting climate change. Hence, various initiatives have been proposed to mitigate this process, among which CO 2 sequestration is a technically simple and efficient approach. The spontaneous carbonation of ashes with atmospheric CO 2 is very slow, and this is why accelerated carbonation is encouraged. However, not all ashes are equally suitable for this process, so a methodology to evaluate their potential should be developed. Such a methodology involves a combination of techniques, from theoretical calculations to XRF, XRD, DTA-TG, and the calcimetric determination of the CaCO 3 content. The present study followed the approach of exposing ashes to accelerated carbonation conditions (4% v / v CO 2 , 50-55% and 80-85% RH, 20 °C) in a closed carbonation chamber for different periods of time until the maximum CO 2 uptake is reached. The amount of sequestered CO 2 was quantified by thermogravimetry. The results show that the highest CO 2 sequestration capacity (33.8%) and carbonation efficiency (67.9%) were obtained for wood biomass bottom ash. This method was applied to eight combustion ashes and could serve to evaluate other ashes or comparable carbon storage materials.

Microbial electrosynthesis (MES) is an emerging electrochemical technology currently being researched as a CO 2 sequestration method to address climate change. MES can convert CO 2 from pollution or waste materials into various carbon compounds with low energy requirements using electrogenic microbes as biocatalysts. However, the critical component in this technology, the cathode, still needs to perform more effectively than other conventional CO 2 reduction methods because of poor selectivity, complex metabolism pathways of microbes, and high material cost. These characteristics lead to the weak interactions of microbes and cathode electrocatalytic activities. These approaches range from cathode modification using conventional engineering approaches to new fabrication methods. Aside from cathode development, the operating procedure also plays a critical function and strategy to optimize electrosynthesis production in reducing operating costs, such as hybridization and integration of MES. If this technology could be realized, it would offer a new way to utilize excess CO 2 from industries and generate profitable commodities in the future to replace fossil fuel-derived products. In recent years, several potential approaches have been tested and studied to boost the capabilities of CO 2 -reducing bio-cathodes regarding surface morphology, current density, and biocompatibility, which would be further elaborated. This compilation aims to showcase that the achievements of MES have significantly improved and the future direction this is going with some recommendations. Highlights - MES approach in carbon sequestration using the biotic component.- The role of microbes as biocatalysts in MES and their metabolic pathways are discussed.- Methods and materials used to modify biocathode for enhancing CO 2 reduction are presented., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Ibrahim, Salehmin, Balachandran, Hil Me, Loh, Abu Bakar, Jong and Lim.)

By-products from the non-ferrous industry are an environmental problem; however, their economic value is high if utilized elsewhere. For example, by-products that contain alkaline compounds can potentially sequestrate CO 2 through the mineral carbonation process. This review discusses the potential of these by-products for CO 2 reduction through mineral carbonation. The main by-products that are discussed are red mud from the alumina/aluminum industry and metallurgical slag from the copper, zinc, lead, and ferronickel industries. This review summarizes the CO 2 equivalent emissions generated by non-ferrous industries and various data about by-products from non-ferrous industries, such as their production quantities, mineralogy, and chemical composition. In terms of production quantities, by-products of non-ferrous industries are often more abundant than the main products (metals). In terms of mineralogy, by-products from the non-ferrous industry are silicate minerals. Nevertheless, non-ferrous industrial by-products have a relatively high content of alkaline compounds, which makes them potential feedstock for mineral carbonation. Theoretically, considering their maximum sequestration capacities (based on their oxide compositions and estimated masses), these by-products could be used in mineral carbonation to reduce CO 2 emissions. In addition, this review attempts to identify the difficulties encountered during the use of by-products from non-ferrous industries for mineral carbonation. This review estimated that the total CO 2 emissions from the non-ferrous industries could be reduced by up to 9-25%. This study will serve as an important reference, guiding future studies related to the mineral carbonation of by-products from non-ferrous industries., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Microalgae CO 2 sequestration has gained considerable attention in the last three decades as a promising technology to slow global warming caused by CO 2 emissions. To provide a comprehensive and objective analysis of the research status, hot spots, and frontiers of CO 2 fixation by microalgae, a bibliometric approach was recently chosen for review. In this study, 1561 articles (1991-2022) from the Web of Science (WOS) on microalgae CO 2 sequestration were screened. A knowledge map of the domain was presented using VOSviewer and CiteSpace. It visually demonstrates the most productive journals (Bioresource Technology), countries (China and USA), funding sources, and top contributors (Cheng J, Chang JS, and their team) in the field of CO 2 sequestration by microalgae. The analysis also revealed that research hotspots changed over time and that recent research has focused heavily on improving carbon sequestration efficiency. Finally, commercialization of carbon fixation by microalgae is a key hurdle, and supports from other disciplines could improve carbon sequestration efficiency., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Microbial consortia consisting of phototrophs and heterotrophs have raised extensive attention due to their potential in sustainable biotechnology. The challenge remains in the selection of appropriate partners since most heterotrophic microorganisms cannot naturally use the intermediate carbohydrates secreted by autotrophic partners. In a recent study, the Ni Lab has developed a highly compatible autotrophic-heterotrophic symbiotic system comprising Synechococcus elongatus and Vibrio natriegens. V. natriegens (the sucrose utilization module) shows a high degree of nutritional complementarity and culturing compatibility with the engineered S. elongatus (the CO 2 sequestration module). The combination of both species channels CO 2 into various valuable chemicals, enabling carbon-negative biosynthesis., (© 2023 Wiley-VCH GmbH.)

The increasing rate of carbon dioxide (CO 2 ) emissions and its impact on global warming are a tremendous problem globally. To control these problems, the present research attempted to employ the Azolla pinnata for growth-dependent enhanced CO 2 sequestration using cattle waste (cow dung, CD and cow urine, CU). Two experiments of A. pinnata growth using six different percentages of CD and CU (0.5, 1.0, 5.0, 10, 20 and 40%) were conducted to determine the optimum doses of CD and CU for the maximum growth of A. pinnata and to assess the growth dependent enhanced CO 2 sequestration of A. pinnata using CD and CU. The maximum growth of A. pinnata was achieved at the doses of 10% CD (weight 2.15 g and number 77.5) and 0.5% CU (weight 2.21 g and number 79.5). The highest rate of CO 2 sequestration was found in the treatments of 10% CD (346.83 mg CO 2 ) and 0.5% CU (356.5 mg CO 2 ) in both experiments. Due to possessing the huge biomass production and high CO 2 sequestration properties of A. pinnata within a short span of time using the cattle waste (cow dung and cow urine), therefore, it can be concluded that the explored mechanism would be a simple and potentially novel approach in order to sequester the CO 2 and transform into useful plant biomass for the minimization of CO 2 emitting problems in the current global warming scenario., Competing Interests: The authors declare that they have no competing interests in the present paper., (© 2023 The Authors.)

The objective of the present study was to explore three types of vibro-compacted precast concrete mixtures replacing fine and coarse gravel with a recycled/mixed concrete aggregate (RCA or MCA). The portlandite phase found in RCA and MCA by XRD is a "potential" CO 2 sink. CO 2 curing improved the compressive strength in all the mixtures studied. One tonne of the mixtures studied could be decarbonised after only 7 days of curing 13,604, 36,077 and 24,635 m 3 of air using natural aggregates, RCA or MCA, respectively. The compressive strength obtained, XRD, TGA/DTA and carbon emission evaluation showed that curing longer than 7 days in CO 2 was pointless. The total CO 2 emissions by a mixture using CO 2 curing at 7 days were 221.26, 204.38 and 210.05 kg CO 2 eq/m 3 air using natural aggregates, RCA or MCA, respectively. The findings of this study provide a valuable contribution to carbon emission evaluation of CO 2 curing in vibro-compacted precast concrete with recycled/mixed concrete aggregates (RCA or MCA). The technology proposed in this research facilitates carbon capture and use and guarantees enhanced compressive strength of the concrete samples.

Mining wastes or combustion ash are materials of high carbon sequestration potential but are also known for their toxicity in terms of heavy metal content. To utilize such waste materials for engineered carbon mineralization purposes, there is a need to investigate the fate and mobility of toxic metals. This is a study of the coprecipitation of metals with calcium carbonate for environmental heavy metal mitigation. The study also examines the stability of precipitated phases under environmentally relevant acid conditions. For a wide range of cadmium (Cd) and zinc (Zn) concentrations (10 to 5000 mg/L), induced coprecipitation led to greater than 99% uptake from water. The calcium carbonate phases were found to contain amounts as high as 9.9 wt % (Cd) and 17 wt % (Zn), as determined by novel synchrotron techniques, including X-ray fluorescence element mapping and three-dimensional (3D) nanotransmission X-ray microscopy (TXM). TXM imaging revealed first-of-a-kind observations of chemical gradients and internal nanoporosity within particles. These observations provided new insights into the mechanisms leading to the retention of coprecipitated heavy metals during the dissolution of calcite in acidic (pH 4) solutions. These observations highlight the feasibility of utilizing carbonate coprecipitation as an engineered approach to the durable sequestration of toxic metals.

To prevent drastic climate changes due to global warming, it is necessary to transition to a carbon-neutral society by reducing greenhouse gas emissions in all industrial sectors. This study aimed to develop carbon utilization sequestration technology that uses the concrete slurry water generated during the production of concrete as a new CO 2 sink to reduce CO 2 emissions from the cement industry. This was achieved by performing supercritical CO 2 carbonation by varying the concrete slurry waste (CSW) ratio. The study's results confirmed that, according to the CSW ratio (5 to 25%), complete carbonation occurred within only 10 min of the reaction at 40 °C and 100 bar.

CO 2 sequestration engineering is promising for carbon-negative biosynthesis, and artificial communities can solve more complex problems than monocultures. However, obtaining an ideal photosynthetic community is still a great challenge. Herein, we describe the development of a highly compatible photosynthetic community (HCPC) by integrating a sucrose-producing CO 2 sequestration module and a super-coupled module. The cyanobacteria CO 2 sequestration module was obtained using stepwise metabolic engineering and then coupled with the efficient sucrose utilization module Vibrio natriegens. Integrated omics analysis indicated that enhanced photosynthetic electron transport and extracellular vesicles promote intercellular communication. Additionally, the HCPC was used to channel CO 2 into valuable chemicals, enabling the overall release of -22.27 to -606.59 kgCO 2 e kg -1 in the end products. This novel light-driven community could facilitate circular economic implementation in the future., (© 2022 Wiley-VCH GmbH.)

Despite the consensus that keeping global temperature rise within 1.5 °C above pre-industrial level by 2100 reduces the chance for climate change to reach the point of no return, the newest Intergovernmental Panel on Climate Change (IPCC) report warns that the existing commitment of greenhouse gas emission reduction is only enough to contain the warming to 3-4 °C by 2100. The harsh reality not only calls for speedier deployment of existing CO 2 reduction technologies but demands development of more cost-efficient carbon removal strategies. Here we report an ocean alkalinity-based CO 2 sequestration scheme, taking advantage of proton consumption during nitrate assimilation by marine photosynthetic microbes, and the ensuing enhancement of seawater CO 2 absorption. Benchtop experiments using a native marine phytoplankton community confirmed pH elevation from ~8.2 to ~10.2 in seawater, within 3-5 days of microbial culture in nitrate-containing media. The alkaline condition was able to sustain at continued nutrient supply but reverted to normalcy (pH ~8.2-8.4) once the biomass was removed. Measurements of δ 13 C in the dissolved inorganic carbon revealed a significant atmospheric CO 2 contribution to the carbonate alkalinity in the experimental seawater, confirming the occurrence of direct carbon dioxide capture from the air. Thermodynamic calculation shows a theoretical carbon removal rate of ~0.13 mol CO 2 /L seawater, if the seawater pH is allowed to decrease from 10.2 to 8.2. A cost analysis (using a standard bioreactor wastewater treatment plant as a template for CO 2 trapping, and a modified moving-bed biofilm reactor for nitrate recycling) indicated that a 1 Mt CO 2 /year operation is able to perform at a cost of ~$40/tCO 2 , 2.5-5.5 times cheaper than that offered by any of the currently available direct air capture technologies, and more in line with the price of $25-30/tCO 2 suggested for rapid deployment of large-scale CCS systems.

Increasing CO 2 emission has resulted in pressing climate and environmental issues. While abiotic and biotic processes mediating the fate of CO 2 have been studied separately, their interactions and combined effects have been poorly understood. To explore this knowledge gap, an iron-reducing organism, Orenia metallireducens , was cultured under 18 conditions that systematically varied in headspace CO 2 concentrations, ferric oxide loading, and dolomite (CaMg(CO 3 ) 2 ) availability. The results showed that abiotic and biotic processes interactively mediate CO 2 acidification and sequestration through "chain reactions", with pH being the dominant variable. Specifically, dolomite alleviated CO 2 stress on microbial activity, possibly via pH control that transforms the inhibitory CO 2 to the more benign bicarbonate species. The microbial iron reduction further impacted pH via the competition between proton (H + ) consumption during iron reduction and H + generation from oxidization of the organic substrate. Under Fe(III)-rich conditions, microbial iron reduction increased pH, driving dissolved CO 2 to form bicarbonate. Spectroscopic and microscopic analyses showed enhanced formation of siderite (FeCO 3 ) under elevated CO 2 , supporting its incorporation into solids. The results of these CO 2 -microbe-mineral experiments provide insights into the synergistic abiotic and biotic processes that alleviate CO 2 acidification and favor its sequestration, which can be instructive for practical applications (e.g., acidification remediation, CO 2 sequestration, and modeling of carbon flux).

Wetlands are large sinks of carbon dioxide (CO 2 ) and sources of methane (CH 4 ). Both fluxes can be altered by wetland management (e.g., restoration), leading to changes in the climate system. Here, we use multiple models to assess CH 4 emissions and CO 2 sequestration from the wetlands in China and the impacts on climate under three climate scenarios and four wetland management scenarios with various levels of wetland restoration in the 21st century. We find that wetland restoration leads to increased CH 4 emissions with a national total of 0.32-11.31 Tg yr -1 . These emissions induce an additional radiative forcing of 0.0005-0.0075 W m -2 yr -1 and global annual mean air temperature rise of 0.0003-0.0053 °C yr -1 , across all future climate and management scenarios. However, wetland restoration also resulted in net CO 2 sequestration, leading to a combined net greenhouse gas sink in all climate management scenarios, except in the highest restoration level combined with the hottest climate scenario. The highest climate cooling was achieved under medium restoration, with the climate scenario consistent with the Paris agreement target of below 2 °C, with a cumulative global warming potential of -3.2 Pg CO 2 -eq (2020-2100). Wetland restoration in the Qinghai-Tibet Plateau offers the greatest cooling effect.

The increased concern about climate change is revolutionising the building materials sector, making sustainability and environmental friendliness increasingly important. This study evaluates the feasibility of incorporating recycled masonry aggregate (construction and demolition waste) in porous cement-based materials using carbonated water in mixing followed (or not) by curing in a CO 2 atmosphere. The use of carbonated water can be very revolutionary in cement-based materials, as it allows hydration and carbonation to occur simultaneously. Calcite and portlandite in the recycled masonry aggregate and act as a buffer for the low-pH carbonated water. Carbonated water produced better mechanical properties and increased accessible water porosity and dry bulk density. The same behaviour was observed with natural aggregates. Carbonated water results in an interlaced shape of carbonate ettringite (needles) and fills the microcracks in the recycled masonry aggregate. Curing in CO 2 together with the use of carbonated water (concomitantly) is not beneficial. This study provides innovative solutions for a circular economy in the construction sector using carbonated water in mixing (adsorbing CO 2 ), which is very revolutionary as it allows carbonation to be applied to in-situ products.

The increase in demand of fossil fuel uses for developmental activity and manufacturing of goods have resulted a huge emission of global warming gases (GWGs) in the atmosphere. Among all GWGs, CO 2 is the major contributor that inevitably causes global warming and climate change. Mitigation strategies like biological CO 2 capture through sequestration and their storage into biological organic form are used to minimize the concentration of atmospheric CO 2 with the goal to control climate change. Since increasing atmospheric CO 2 level supports microbial growth and productivity thus microbial-based CO 2 sequestration has remarkable advantages as compared to plant-based sequestration. This review focuses on CO 2 sequestration mechanism in bacteria through different carbon fixation pathways, involved enzymes, their role in calcite, and other environmentally friendly biomaterials such as biofuel, bioplastic, and biosurfactant., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Forests are atmospheric carbon sinks, whose natural growth can contribute to climate change mitigation. However, they are also affected by climate change and various other phenomena, for example, the low growth of coniferous forests currently reported globally, including in the Republic of Korea. In response to the implementation of the Paris Agreement, the Korean government has proposed 2030 greenhouse gas roadmap to achieve a Nationally Determined Contribution (NDC), and the forest sector set a sequestration target of 26 million tons by 2030. In this study, the Korean forest growth model (KO-G-Dynamic model) was used to analyze various climate change and forest management scenarios and their capacity to address the NDC targets. A 2050 climate change adaptation strategy is suggested based on forest growth and CO 2 sequestration., Results: Forest growth was predicted to gradually decline, and CO 2 sequestration was predicted to reach 23 million tons per year in 2050 if current climate and conditions are maintained. According to the model, sequestrations of 33 million tCO 2 year -1 in 2030 and 27 million tCO 2 year -1 in 2050 can be achieved if ideal forest management is implemented. It was also estimated that the current forest management budget of 317 billion KRW (264 million USD) should be twice as large at 722 billion KRW (602 million USD) in the 2030s and 618 billion KRW (516 million USD) in the 2050s to achieve NDC targets., Conclusions: The growth trend in Korea's forests transitions from young-matured stands to over-mature forests. The presented model-based forest management plans are an appropriate response and can increase the capacity of Korea to achieve its NDC targets. Such a modeling can help the forestry sector develop plans and policies for climate change adaptation., (© 2022. The Author(s).)

Microalgae are complex metabolic machineries whose potential has been continuously tapped for wide range of applications. Their suboptimal biomass yield and bioactives production remain the mainstay for their commercialization. To surpass the limitations, genetic engineering and its decisive role in strain improvement have led to the enhancement of quality and yield of products. Meanwhile, the sporadic use of genetic engineering tools specifically toward microalgal strains has limited their applicability. In this context, this article was mainly prepared to highlight the characteristics of microalgae and the introduction of omics approach for the improvement of strain for biorefinery processes. Furthermore, genome editing and gene-interfering tools to augment algal research using reference strains have been described. The progress made by genetic engineering in editing a gene using CRISPR-Cas9 and metabolic engineering of microalgae for biofuel production and CO 2 sequestration have been critically reviewed. As a futuristic alternative, the transgenic microalgae would compete with the existing resources reducing the dependency on fossil fuel in terms of cost, energy production, and efficacy., (© 2022 Wiley-VCH GmbH.)

Azolla is a group of aquatic floating plants that can achieve very high growth rates compared to other aquatic macrophytes, with a doubling time of 2-5 days under optimal growing conditions. The ability of Azolla to grow at such rapid rates allows for the opportunity of utilizing it as a method to sequester a significant amount of atmospheric CO 2 in the form of biomass, which can be locked away to completely remove the carbon from the active carbon cycle, or which can be used in various applications such as animal feeds, biofertilizers, and biofuel production, which in turn will contribute to reduction in the fossil CO 2 emissions. In this desktop study, the potential use of Azolla for mitigating the annual increase in the atmospheric CO 2 levels was addressed, which were estimated at 18.9 billion tons of CO 2 per year. A theoretical setup of 1-ha ponds was assessed to estimate the total Azolla growing area required for counterbalancing the annual atmospheric CO 2 increase. Each 1-ha pond was found capable of capturing 21,266 kg of CO 2 (C) per year. The calculated required total area to mitigate the total annual increase was estimated to be 1,018,023 km 2 (equivalent to around a fifth of the Amazon forest area). Sensitivity analysis, which was based on the variations in the productivity of Azolla due to growing conditions, indicated that the required area would range between 763,518 and 1,527,036 km 2 . This study provides a novel natural method for CO 2 sequestration that has lower environmental impacts compared to conventional sequestration technologies as an alternative green approach for mitigating the effects of fossil fuels., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Spreading olivine powder in seawater to enhance alkalinity through weathering reactions has been proposed as a potential solution to control atmospheric CO 2 concentration. Attention has usually been paid to the chemical properties of seawater after the addition of olivine within lab and modeling studies. However, both microbial acclimation and evolution in such manipulated natural environments are often overlooked, yet they are of great importance for understanding the biological consequences of whether olivine addition is a feasible approach to mitigating climate change. In this study, an olivine addition experiment was conducted to investigate variation in bacterial diversity and community composition in the surface and bottom seawater of a representative marine ranch area in the Muping, Yantai. The results show that the composition of the particle-attached microbial community was particularly affected by the application of olivine. The relative abundance of biofilm-forming microbes in particle-attached fraction increased after the addition of olivine, while no significant variation in the free-living bacterial community was observed. Our study suggests that olivine addition would reshape the bacterial community structure, especially in particle-attached microenvironments. Therefore, the risk evaluation of alkalinity enhancement should be further studied before its large-scale application as a potential ocean geoengineering plan., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ren, Hu, Liu, Zhang, Mou, Pan, Zheng, Li and Jiao.)

The rapid acceleration in emissions of inevitably generated CO 2 due to numerous activities mainly anthropogenic have devastating environmental effects leading to climatic concerns. Hence, significant, sustainable approaches should be developed for reduction of CO 2 emission targets, balancing the existing needs of the current population. Biological carbon acquisition, storage and usage are considered crucial alternative strategies in assimilating inorganic carbon, manifested by diverse variety of microorganisms. Furthermore, central biochemical routes along with associated enzymes serve as considerable factors for understanding molecular microbial CO 2 assimilation. Microorganisms exhibit an impeccable capability to facilitate evolved mechanisms in sequestering inorganic carbon at higher pace to produce biomaterials like biofuels, bioplastics etc. This review endorses the importance of microorganisms in reducing the concomitant release of CO 2 by providing supervision in biotechnological applications (such as genetic engineering, microbial electrosynthesis, gas fermentation and protein engineering) to mitigate CO 2 at an industrial scale., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Strategies for depleting carbon dioxide (CO 2 ) from flue gases are urgently needed and carbonic anhydrases (CAs) can contribute to solving this problem. They catalyze the hydration of CO 2 in aqueous solutions and therefore capture the CO 2 . However, the harsh conditions due to varying process temperatures are limiting factors for the application of enzymes. The current study aims to examine four recombinantly produced CAs from different organisms, namely CAs from Acetobacterium woodii (AwCA or CynT), Persephonella marina (PmCA), Methanobacterium thermoautotrophicum (MtaCA or Cab) and Sulphurihydrogenibium yellowstonense (SspCA). The highest expression yields and activities were found for AwCA (1814 WAU mg -1 AwCA) and PmCA (1748 WAU mg -1 PmCA). AwCA was highly stable in a mesophilic temperature range, whereas PmCA proved to be exceptionally thermostable. Our results indicate the potential to utilize CAs from anaerobic microorganisms to develop CO 2 sequestration applications.

To prevent drastic climate change due to global warming, it is necessary to transition to a carbon-neutral society by reducing greenhouse gas emissions in all industrial sectors. This study aims to prepare measures to reduce the greenhouse gas in the cement industry, which is a large source of greenhouse gas emissions. The research uses supercritical CO 2 carbonation to develop a carbon utilization fixation technology that uses concrete slurry water generated via concrete production as a new CO 2 fixation source. Experiments were conducted using this concrete slurry water and supernatant water under different conditions of temperature (40 and 80 °C), pressure (100 and 150 bar), and reaction time (10 and 30 min). The results showed that reaction for 10 min was sufficient for complete carbonation at a sludge solids content of 5%. However, reaction products of supernatant water could not be identified due to the presence of Ca(HCO 3 ) 2 as an aqueous solution, warranting further research.

Mineral carbonation can simultaneously realize the effective treatment of CO 2 and iron and steel slag; thus, it is of great significance for the low carbon and sustainable development of iron and steel industry. In this article, the researches of mineral carbonation process using iron and steel slag as feedstock are reviewed, and the carbonation reaction mechanism and the parameters affecting the reaction rate and carbonation degree are analyzed. Furthermore, the effect of different enforcement approaches, such as ultrasonic enhancement, mixed calcination, microbial enhancement, and cyclic coprocessing on mineral carbonation reaction, is introduced. The additional effects of mineral carbonation, such as solving the problem of poor volume stability of steel slag, weakening the leaching of heavy metal ions, and reducing the pH of the leachate, are also illustrated. Moreover, issues related to mineral carbonation technology that should be emphasized upon soon, such as the production of valuable products, use of industrial wastewater, aqueous phase recycling use, multiparameter coupling analysis, and research on the properties of carbonation residues, are also discussed, which contribute some perspectives to the future development of mineral carbonation of iron and steel slag., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Tailings dam failures can cause devastation to the environment, loss of human life, and require expensive remediation. A promising approach for de-risking brucite-bearing ultramafic tailings is in situ cementation via carbon dioxide (CO 2 ) mineralization, which also sequesters this greenhouse gas within carbonate minerals. In cylindrical test experiments, brucite [Mg(OH) 2 ] carbonation was accelerated by coupling organic and inorganic carbon cycling. Waste organics generated CO 2 concentrations similar to that of flue gas (up to 19%). The abundance of brucite (2-10 wt %) had the greatest influence on tailings cementation as evidenced by the increase in total inorganic carbon (TIC; +0.17-0.84%). Brucite consumption ranged from 64-84% of its initial abundance and was mainly influenced by water availability. Higher moisture contents (e.g., 80% saturation) and finer grain sizes (e.g., clay-silt) that allowed for a better distribution of water resulted in greater brucite carbonation. Furthermore, pore clogging and surface passivation by Mg-carbonates may have slowed brucite carbonation over the 10 weeks. Unconfined compressive strengths ranged from 0.4-6.9 MPa and would be sufficient in most scenarios to adequately stabilize tailings. Our study demonstrates the potential for stabilizing brucite-bearing mine tailings through in situ cementation while sequestering CO 2 .

Ex situ aqueous mineral carbonation of ultramafic mining waste is an evolving technology for the CO 2 sequestration from small- to medium-scale emitters. The mineral ores or mine wastes of associated ultramafic mineralogy are a suitable feedstock for mineral carbonation. The aqueous mineral carbonation at ambient temperature is motivating and attractive from an energy-saving perspective. This study has investigated the CO 2 sequestration potential of a locally available ultramafic material generated from a nickel ore mine with a futuristic scope of integrating the method into an ongoing mineral extraction and/or tailing management operation. The mineral characterization and experimental results indicate that the tested material has CO 2 sequestration potential and underwent carbonation at ambient temperature. The carbonate conversion efficiencies obtained for Ca and Mg from the dissolved ionic forms at optimum conditions are 60% and 25%, respectively. The material was able to sequestrate about 0.12 gCO 2 per g solid at this efficiency. Aragonite and hydromagnesite are the major products that evolved out from the aqueous carbonation. Based on the mineral carbonation results, the novel concept of integrating the evolved method to existing mineral extraction and/or tailings management operation is discussed.

The paper presents the obtention and characterization of Portland cement mortars with limestone filler and nano-calcite additions. The nano-calcite was obtained by the injection of CO 2 in a nano-Ca(OH) 2 suspension. The resulted nano-CaCO 3 presents different morphologies, i.e., polyhedral and needle like crystals, depending on the initial Ca(OH) 2 concentration of the suspension. The formation of calcium carbonate in suspensions was confirmed by X-ray diffraction (XRD), complex thermal analysis (DTA-TG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM and HRTEM). This demonstrates the viability of this method to successfully sequestrate CO 2 in cement-based materials. The use of this type of nano-CaCO 3 in mortar formulations based on PC does not adversely modify the initial and final setting time of cements; for all studied pastes, the setting time decreases with increase of calcium carbonate content (irrespective of the particle size). Specific hydrated phases formed by Portland cement hydration were observed in all mortars, with limestone filler additions or nano-CaCO 3 , irrespective of curing time. The hardened mortars with calcium carbonate additions (in adequate amounts) can reach the same mechanical strengths as reference (Portland cement mortar). The addition of nano-CaCO 3 in the raw mix increases the mechanical strengths, especially at shorter hardening periods (3 days).

A type of highly stable and recyclable clay-based composite was developed for sequestration of CO 2 , which was synthesized by loading melamine (MEL) onto attapulgite (ATT) via a wet impregnation method. The synthesized materials were characterized by N 2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and transmission electron microscopy (TEM). By means of thermal and acidic treatments more active sites of ATT were exposed, and large surface areas were obtained. The MEL molecules were well combined with those exposed sites, which enhanced stability and cyclability for CO 2 sequestration. On the basis of CO 2 adsorption-desorption measurements, the composite of ATT-MEL was found to have a higher CO 2 adsorption capacity (4.91 cm 3 /g) which was much higher than that of CO 2 absorption on bare MEL (1.30 cm 3 /g) at 30 °C. After ten cycles of reusing, the composite exhibited even higher capacity for CO 2 adsorption by an increased percentage of 5.91% (30 °C) and 5.77% (70 °C) compared to the capacity in the first cycle. The reason lies in the strong interaction between melamine and attapulgite matrix which was further confirmed by DFT calculations. The MEL was validated to have advantages over aliphatic amines (TEPA) in modifying ATT to get high stability of CO 2 -adsorbents.

The increased CO 2 quantities in the environment have led to many harmful effects. Therefore, it is very important to decrease the CO 2 levels in the environment. CO 2 capture along with safe and permanent storage using mineral CO 2 sequestration method can play an important role to reduce carbon emissions into the environment. Mineral sequestration is a stable storage method that provides long-term storage and an appropriate substitute for the more popular geological storage method. The process is most suited for places where there is a lack of underground cavities for underground geological storage. Minerals rich in Ca and Mg are used predominantly in carbonation reactions. In addition, those alkaline wastes that are rich in Mg and Ca such as cement waste, steel slag and many process ashes can also be employed in CO 2 sequestration. Mineral carbonation could be used for the sequestration of billions of tonnes of CO 2 every year. However, various drawbacks related to mineral carbonation still need to be addressed, such as resolving the slow rate of reactions, necessity of large amounts of feedstock, decreasing the high overall cost of CO 2 sequestration and reducing the huge energy requirements to accelerate the carbonation reaction. This study explores a number of carbonation methods, parameters that control the process and future potential applications of carbonated products.

Compressed energy storage (CES) of air, CO 2 , or H 2 in porous formations is a promising means of energy storage to abate the intermittency of renewable energy production. During operation, gas is injected during times of excess energy production and extracted during excess demands to drive turbines. Storage in saline aquifers using CO 2 as a cushion or working gas has numerous advantages over typical air storage in caverns. However, interactions between CO 2 and saline aquifers may result in potential operational limitations and have not been considered. This work utilizes reactive transport simulations to evaluate the geochemical reactions that occur during injection and extraction operational cycles for CES in a porous formation using CO 2 as a cushion gas. Simulation results are compared with similar simulations considering an injection-only flow regime of geologic CO 2 storage. Once injected, CO 2 creates conditions favorable for dissolution of carbonate and aluminosilicate minerals. However, the dissolution extent is limited in the cyclic flow regime where significantly smaller dissolution occurs after the first cycle such that CO 2 is a viable choice of cushion gas. In the injection-only flow regime, larger extents of dissolution occur as the fluid continues to be undersaturated with respect to formation minerals throughout the study period and porosity increased uniformly from 24.84% to 33.6% throughout the simulation domain. For the cyclic flow conditions, porosity increases nonuniformly to 31.1% and 25.8% closest and furthest from the injection well, respectively., Competing Interests: No competing financial interests exist., (© Chidera O. Iloejesi and Lauren E. Beckingham 2021; Published by Mary Ann Liebert, Inc.)

It is still an important aspect of global climate research to explore a low-cost method that can effectively reduce the increase of CO 2 concentration in the global atmosphere. Oxalotrophic bacterial communities exist in agricultural or forest soil with ubiquitous oxalate as the only carbon and energy source. When soil oxalate is oxidized and degraded, carbonate is formed along with it. This process is called the oxalate carbonate pathway (OCP), which can increase soil inorganic carbon sink and soil organic matter content. This soil carbon sink is a natural CO 2 trapping system and an important alternative if it is properly managed for artificial sequestration/storage. As the main driver of OCP, the oxalate degrading bacteria are affected by many factors during the oxalate conversion process. Understanding this process and the synergy of oxalogenic plants, saprophytic decomposers, and oxalotrophic bacteria in agricultural or forest soil is critical to exploiting this natural carbon capture process. This article aims to provide a broader perspective of OCP in CO 2 sequestration, biomineralization, and elemental cycling., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Syed, Buddolla and Lian.)

In this study, some important mistakes related to model development process and missing information which should be carefully taken into account by the authors of the previous literature and other researchers are presented. Some important issues are presented to avoid propagation of similar mistakes in the scientific literature., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Microbial-Induced Calcite Precipitation (MICP) stimulates soil microbiota to induce a cementation of the soil matrix. Urea, calcium and simple carbon nutrients are supplied to produce carbonates via urea hydrolysis and induce the precipitation of the mineral calcite. Calcium chloride (CaCl 2 ) is typically used as a source for calcium, but basic silicate rocks and other materials have been investigated as alternatives. Weathering of calcium-rich silicate rocks (e.g., basalt and dolerite) releases calcium, magnesium and iron; this process is associated with sequestration of atmospheric CO 2 and formation of pedogenic carbonates. We investigated atmospheric carbon fluxes of a MICP treated sandy soil using CaCl 2 and dolerite fines applied on the soil surface as sources for calcium. Soil-atmosphere carbon fluxes were monitored over 2 months and determined with an infrared gas analyser connected to a soil chamber. Soil inorganic carbon content and isotopic composition were determined with isotope-ratio mass spectrometry. In addition, soil-atmosphere CO 2 fluxes during chemical weathering of dolerite fines were investigated in incubation experiments with gas chromatography. Larger CO 2 emissions resulted from the application of dolerite fines (116 g CO 2 -C m -2 ) compared to CaCl 2 (79 g CO 2 -C m -2 ) but larger inorganic carbon precipitation also occurred (172.8 and 76.9 g C m -2 , respectively). Normalising to the emitted carbon to precipitated carbon, the environmental carbon cost was reduced with dolerite fines (0.67) compared to the traditional MICP treatment (1.01). The carbon isotopic signature indicated pedogenic carbonates (δ 13 C av = -8.2 ± 5.0‰) formed when dolerite was applied and carbon originating from urea (δ 13 C av = -46.4 ± 1.0‰) precipitated when CaCl 2 was used. Dolerite fines had a large but short-lived (<2 d) carbon sequestration potential, and results indicated peak CO 2 emissions during MICP could be balanced optimising the application of dolerite fines., (Copyright © 2020 Casas, Graf, Brüggemann, Schaschke and Jorat.)

The present research investigates potential of microalgae isolated from sewage treatment plant to utilize sodium bicarbonate as carbon source for CO 2 sequestration and biodiesel production. Eight algal isolates were isolated from waste water of sewage treatment plant, Amity University Haryana, India. The most potent algal isolates were identified and characterized on the basis of growth and lipid content. The efficient isolates ASW1 and ASW2 were identified as Chlorella sp. and Arthronema sp. by 18srRNA and 16srRNA sequencing method. In both isolates, maximum growth was observed under 20-W fluorescent bulb (3500 flux light intensity) with continuous light cycle of 24 h at pH 9.0 and 25 °C on the 20th day of incubation period. CO 2 utilization efficiency of both algal isolates were observed in terms of total CO 2 consumption rate. Under optimized culture conditions, total lipid content and lipid yield was higher in Arthronema sp. (180 mg l -1 ; 32.14%) as compared to Chlorella sp. (98 mg l -1 ; 29.6%) in 50 mM NaHCO 3 . Transesterified lipids were analysed by GC-MS. The fatty acid methyl ester profile of Arthronema sp. was 34.42% saturated and 65.58% unsaturated fatty acid. Chlorella sp. produces 29.80% saturated and 70.20% unsaturated fatty acid. In both isolates, C16 and C18 fatty acids dominated, which is a promising component for biodiesel. Graphical abstract.

The degrees of mineral carbonation in (a) construction and demolition waste (C&DW) and (b) a mixture of cement and fly ash were studied through a dynamic experimental method to determine the variation in the rate and extent of CO 2 sequestration achievable under simulated outdoor conditions. A number of experiments were performed in a self-designed rotating batch reactor by churning the two samples together with CO 2 , which was passed through the mixtures by using water vapor as the medium of transfer. At an injection flow rate of 1 L/min for CO 2 , the theoretical extent of carbonation was observed to be 39.1% for the mixture of cement and fly ash and 25% for C&DW. It was further observed that upon increasing the CO 2 flow rate to 10 L/min, the carbonation in the mixture of cement and fly ash increased by 37.2% after 15 h of rotation at 60 rounds per hour (rph) for a temperature of 40 °C. Weighing, scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS) were performed for the samples before and after the batch reaction to study the quantitative, qualitative and morphological aspects of the process.

Climate change brought about by anthropogenic CO 2 emissions has created a critical need for effective CO 2 management solutions. Microalgae are well suited to contribute to efforts aimed at addressing this challenge, given their ability to rapidly sequester CO 2 coupled with the commercial value of their biomass. Recently, microalgal biofilms have garnered significant attention over the more conventional suspended algal growth systems, since they allow for easier and cheaper biomass harvesting, among other key benefits. However, the path to cost-effectiveness and scaling up is hindered by a need for new tools and methodologies which can help evaluate, and in turn optimize, algal biofilm growth. Presented here is a novel system which facilitates the real-time in situ monitoring of algal biofilm CO 2 sequestration. Utilizing a CO 2 -permeable membrane and a tube-within-a-tube design, the CO 2 sequestration monitoring system (CSMS) was able to reliably detect slight changes in algal biofilm CO 2 uptake brought about by light-dark cycling, light intensity shifts, and varying amounts of phototrophic biomass. This work presents an approach to advance our understanding of carbon flux in algal biofilms, and a base for potentially useful innovations to optimize, and eventually realize, algae biofilm-based CO 2 sequestration.