Increase In CO2 Uptake Research Articles

Nanoconfinement-Driven Energy-Efficient CO2 Capture and Release at High Pressures on a Unique Large-Pore Mesoporous Carbon.

Although microporous carbons can perform well for CO2 separations under high pressure conditions, their energy-demanding regeneration may render them a less attractive material option. Here, we developed a large-pore mesoporous carbon with pore sizes centered around 20-30 nm using a templated technical lignin. During the soft-templating process, unique cylindrical supramolecular assemblies form from the copolymer template. This peculiar nanostructuring takes place due to the presence of polyethylene glycol (PEG) segments on both the Pluronic® template and the PEG-grafted lignin derivative (glycol lignin). A large increase in CO2 uptake occurs on the resulting large-pore mesoporous carbon at 270 K close to the saturation pressure (3.2 MPa), owing to capillary condensation. This phenomenon enables a CO2/CH4 selectivity(SCO2/CH4,mol/mol) of 3.7 at 270 K and 3.1 MPa absolute pressure, and a swift pressure swing regeneration process with desorbed CO2 per unit pressure far outperforming a benchmark activated carbon (i.e., notably rapid decrease in the amount of adsorbed CO2 with decreasing pressure). We propose large-pore mesoporous carbons as a novel family of CO2 capture adsorbents, based on the phase-transition behavior shift of CO2 in the nanoconfined environment. This novel material concept may open new horizons for physisorptive CO2 separations with energy-efficient regeneration options.

Understanding the Kinetics of CO2 Hydrate Formation in Dry Water for Carbon Capture and Storage: X-ray Diffraction and In Situ Raman Studies.

Hydrate-based carbon capture and storage (HBCS) is a sustainable and promising approach to combating global warming by utilizing water, which is a ubiquitous resource. Here, we report a comprehensive study of CO2 hydrate formation in dry water (DW), a water-in-air dispersion confined in silica particles, for improving the kinetics of hydrate growth. Utilizing a combination of a home-built high-pressure reactor, in situ Raman spectroscopy, and powder X-ray diffraction (PXRD), we elucidate the crystal structure, growth dynamics, and morphology of CO2 hydrates formed in DW, with and without the kinetic hydrate promoter, l-tryptophan. Our analysis reveals that CO2 forms structure I (sI) hydrate in DW, with hydrate growth occurring both on and beneath the silica shell. This results in a substantial increase in CO2 uptake─approximately 2.8 times higher than that observed in pure water (∼134 v/v compared to ∼48 v/v). Moreover, incorporation of l-tryptophan in DW formation markedly accelerates the DW-CO2 hydrate formation process, reducing both the induction time and the time required to achieve 90% gas uptake at 274.65 K. These findings offer crucial insights into the formation of CO2 hydrate in DW, highlighting its potential to improve the efficiency and scalability of HBCS technologies.

The impact of air pollution control measures and the COVID-19 pandemic on photosynthesis in urban trees

Phytotoxic air pollutants such as atmospheric nitrogen dioxide (NO2) are among the major stresses affecting tree photosynthesis in urban areas. We clarified the relationship between NO2 concentrations and photosynthetic function for three major urban trees, Prunus × yedoensis, Rhododendron pulchrum, and Ginkgo biloba, planted in Kyoto and surrounding cities, combining our published data and new data collected from 2020 to 2023. High NO2 increased long-term water use efficiency for all species. High NO2 decreased photosynthesis in P. yedoensis and R. pulchrum, while for G. biloba, NO2 imposed little effect on photosynthesis. We then focused on the decrease in NO2 due to (1) air pollution control measures from 2005 to 2023 and (2) the economic recession caused by the COVID-19 pandemic, and examined whether these factors improved photosynthesis in urban trees. The historic decrease in NO2 improved leaf photosynthesis for P. yedoensis and R. pulchrum, while the COVID-19 pandemic reduced NO2 by only 0.3 ppb and did not further improve photosynthesis in these tree species. This report shows that air pollution control measures improved photosynthesis in urban trees over several years in Japan, and is valuable because it demonstrates that air pollution control measures can increase CO2 uptake by urban trees.

Sequential Pore Functionalization in MOFs for Enhanced Carbon Dioxide Capture.

The capture of carbon dioxide (CO2) is crucial for reducing greenhouse emissions and achieving net-zero emission goals. Metal-organic frameworks (MOFs) present a promising solution for carbon capture due to their structural adaptability, tunability, porosity, and pore modification. In this research, we explored the use of a copper (Cu(II))-based MOF called m CBMOF-1. After activation, m CBMOF-1 generates one-dimensional channels with square cross sections, featuring sets of four Cu(II) open metal sites spaced by 6.042 Å, allowing strong interactions with coordinating molecules. To investigate this capability, m CBMOF-1 was exposed to ammonia (NH3) gas, resulting in hysteretic NH3 isotherms indicative of strong interactions between Cu(II) and NH3. At 150 mbar and 298 K, the NH3-loaded (∼1 mmol/g) material exhibited a 106% increase in CO2 uptake compared to that of the pristine m CBMOF-1. Carbon-13 solid-state nuclear magnetic resonance spectra and density functional theory calculations confirmed that the sequential loading of NH3 followed by CO2 adsorption generated a copper-carbamic acid complex within the pores of m CBMOF-1. Our study highlights the effectiveness of sequential pore functionalization in MOFs as an attractive strategy for enhancing the interactions of MOFs with small molecules such as CO2.

Effect of carbonation curing regime on 3D printed concrete: Compressive strength, CO2 uptake, and characterization

Carbonation curing is a promising method to improve the mechanical strength and reduce the carbon emissions of 3D printed concrete (3DPC). To avoid the adverse impacts of excessive CO2 exposure, the effect of carbonation curing regimes on 3DPC was investigated in this study. The CO2 uptake and compressive strength of 3DPC with different pre-curing and carbonation durations were determined. The prolonged pre-curing and carbonation duration led to increased CO2 uptake of 3DPC, while its compressive strength reached the highest for 10–17.5-h pre-curing and 12 ∼16-h carbonation. The water loss rate, as an important factor for determining the pre-curing duration of 3DPC, is optimal at 20 %. The appropriate carbonation curing can lead to 39.9 % increase in 3-day compressive strength, but the effect on the later-age strength is weakened. Carbonation curing can improve the pore structure of 3DPC by reducing the porosity and volume fraction of harmful pores. In addition, the prolonged pre-curing and carbonation may result in excessive consumption of C3S and C2S and water loss, adversely affecting the subsequent hydration reactions and decreasing the compressive strength of 3DPC. Hence, suitable pre-curing and carbonation duration should be determined by considering the balance of mechanical strength and CO2 uptake of 3DPC.

Modeling carbon dynamics from a heterogeneous watershed in the mid-Atlantic USA: A distributed-calibration and independent verification (DCIV) approach

The terrestrial ecosystem plays a vital role in regulating regional and global carbon budgets. Ecosystem models are extensively employed to estimate carbon fluxes across different spatial scales. However, there remains a need to reduce the uncertainties associated with model parameterization and input data. To address these limitations, we assessed a distributed-calibration and independent-verification (DCIV) approach that uses (1) remotely sensed net primary production (NPP) and evapotranspiration (ET) data from the Moderate Resolution Imaging Spectroradiometer (MODIS), (2) multi-site eddy covariance net ecosystem exchange (NEE) data; and (3) field sampling of soil organic carbon (SOC) and aboveground biomass (ABG) data to improve the overall predictability of carbon fluxes for the different land use and land cover (LULC) types at a watershed scale. The DCIV approach was applied to an advanced version of the Soil and Water Assessment Tool (SWAT)-Carbon (or SWAT-C), equipped with Century-based SOC algorithms to simulate carbon dynamics for watersheds with heterogeneous vegetation. The objective of the modeling effort was to assess carbon stocks and fluxes under different land management scenarios for a 3000-acre experimental farm and forest preserve in the northeastern United States. Our study showed that a large SOC stock of at least 100 tons ha−1 is stored under mixed forest, deciduous, shrubland, and floodplain (grass). Our study also showed that converting floodplain (grass) to deciduous forest has the potential to increase CO2 uptake (-NEE) by an order of three magnitude and ABG by 77 %, leading to an increased SOC stock of 23 % after twenty years. Similarly, we found that converting ungrazed grassland to grazed pasture leads to a non-statistically decreasing trend of SOC, especially in the 0–30 cm soil layer. Thus, the methodology used in this study can be applied to improve carbon dynamic prediction from a heterogeneous watershed at a regional scale.

CO2 Dynamics in a Flexible Metal-Organic Framework with Gate-Opening Phenomenon.

As a promising porous material for CO2 adsorption and storage, elastic layer-structured metal-organic framework-11 (ELM-11) has attracted significant attention owing to its distinct gate-opening phenomenon. There is a sharp increase in CO2 uptake once reaching the gate-opening threshold pressure. To better understand this gate-opening mechanism, we investigated its transition process from the perspective of CO2 dynamics and its interaction with the framework via variable-temperature 13C solid-state nuclear magnetic resonance spectroscopy. Our findings revealed that during the gate-opening process, CO2 is initially strongly adsorbed at one site when the gate only slightly opens, while two distinct types of CO2 molecules exist when the gate fully opens. 11B, 13C, and 19F magic-angle spinning NMR, in conjunction with in-situ XANES experiments, were also conducted to probe the location of adsorption sites.

Green solvents assisted de-novo synthesis and defect-engineered UiO-66 for improved CO2 adsorption and kinetics- experimental and DFT approach

The CO2 concentration in the atmosphere is increasing at an alarming rate, which is causing distress to human society and the natural environment. Adsorption is one of the most widely used methods of removing CO2 from flue gases, which reduces its adverse effects on our environment. For adsorption purposes, a facile green solvent-assisted de-novo synthesis approach was developed to construct a UiO-66′s structure to target CO2 at low pressure due to the partial pressure of CO2 in flue gases in the atmosphere (0.01⁓0.02 MPa). In the de-novo synthesis approach, a combination of various types of modulators and deep eutectic solvents (DES) are utilized to graft structural defects and induce quantitative and dispersive deep eutectic solvents onto the UiO-66 structure, respectively. The green solvent-assisted de-novo synthesis approach helped to tune all three structural parameters and preserve extra open metal sites (Lewis acid and Bronsted basis sites) with active NH2 and OH groups for improved CO2 adsorption and kinetics under flue gas conditions (CO2/N2=15/85 %). In comparison to the parent UiO-66, de-novo synthesized ChClPropx5@UiO-66 showed increased CO2 uptake (65.04 mg g-1) by 73 % at 0.15 bar and 25 °C, and the cyclic capacity remained almost similar over 10 consecutive cycles with an almost 94 % retention rate. After 3 times of regeneration at 105 °C under N2 atmosphere, the sample reserved almost similar adsorption capacity and could be recycled without dropping CO2 uptake. The strong and rapid interaction between guest CO2 and de-novo synthesized UiO-66 was confirmed by pseudo-first-order and second-order kinetics with reaction rate constants of 0.00026 and 0.00259, respectively. Furthermore, through periodic Density Functional Theory (DFT) calculations, a variety of linker defects are engineered onto the UiO-66 structure to preserve more open metal sites. For each of the engineering defects, free energies, adsorption energies, and the interaction of CO2 molecules on defect structures with bond length (Ɩ, Å) and bond angle (θ˚) are calculated for the most stable structures of UiO-66.

Post-crosslinking knitting strategy for triazine-functionalized ionic hypercrosslinked polymers: Enhanced CO2 adsorption and conversion

Pore engineering has gained significant recognition as a pivotal strategy to tailor the structure and functionality of porous materials. In this study, a post-crosslinking knitting strategy was employed to fabricate a series of triazine-functionalized ionic hypercrosslinked polymers (IHCPs) using low specific surface area ionic polymers as precursors and external crosslinkers α,α′-dichloro-p-xylene (DCX) and α,α′-dibromo-p-xylene (DBX) through the Friedel Crafts alkylation reaction. This post-crosslinking knitting methodology increases the specific surface area of the resulting IHCPs, leading to enhanced CO2 adsorption capabilities (reaching 1.92 mmol·g−1 at 1 bar and 273 K), enhanced a remarkable 5.6-fold increase in CO2 uptake compared to the original ionic polymers. Of particular interest, inclusion of –NH– groups in PTA-2-DBX exhibits a synergistic catalytic effect facilitated by hydrogen bonding interactions that enable efficient conversion of CO2 into various cyclic carbonates under solvent- and cocatalyst-free conditions with yields exceeding 99 %. Furthermore, PTA-2-DBX demonstrates excellent recyclability while maintaining its activity even after five consecutive cycles. This study offers an effective approach for modulating pores in ionic polymers while highlighting the promising applications of triazine-functionalized IHCPs as dual-functional materials for both CO2 capture and conversion.

Pre-treatment of waste hydrated cement used for replacement of fine aggregate using amine-based CO2 solvent

In the realm of construction and demolition (C&D) waste, a small fraction of hydrated cement waste is typically repurposed to generate supplementary cementitious material or filler for concrete. However, the conventional method of utilizing it in powder form demands significant energy consumption to achieve the necessary fineness. Therefore, this study proposes a method to use a waste-hydrated cement paste as a fine aggregate as well as the pre-treatment method to enhance its properties. The pre-treatment involves carbonating hydrated cement in a fully CO2-dissolved amine-based CO2 solvent, specifically a monoethanolamine (MEA) solution. This process eliminates vulnerable phases, such as calcium hydroxide, resulting in a higher compressive strength of mortar when incorporating the treated hydrated cement as fine aggregate. Notably, the use of fully CO2-dissolved 1% and 10% MEA solutions during carbonation demonstrates superior performance and increased CO2 uptake. Additionally, the developed pre-treatment method uses MEA CO2 solvent directly, commonly utilized for CO2 capture in industrial flue gas. It is an alternative for solvent regeneration without the need for a heating process, potentially reducing overall energy consumption.

Rare earth oxide promoted Ru/Al2O3 dual function materials for CO2 capture and methanation: An operando DRIFTS and TGA study

Dual-function materials (DFMs) combine sorbent and catalytic components to perform selective CO2 capture and subsequent hydrogenation. This study explores the performance of rare-earth oxides (REOs) as CO2 adsorption sites on Ru/Al2O3. REOs increase CO2 uptake by upwards of +60 % by enhancing the overall catalyst surface basicity and favoring metal–support interactions. Thermogravimetric analysis during CO2 adsorption-hydrogenation cycles exhibited significant catalytic activity and enhanced stability of Ru-REO/Al2O3 at temperatures as low as 200 °C. This leads to methane production of 50–85 µmol g−1, surpassing recently reported values obtained for alkali and alkali-earth promoted Ru-based materials operated at 250 °C. The highest performing studied DFM, RuNd2O3/Al2O3, achieved 85 % CO2 capture efficiency and steadily produced methane in cyclic operation (+120 % CO2 uptake relative to Ru/Al2O3). Operando DRIFTS revealed that the dominant mechanism for methane formation is the hydrogenation of ruthenium carbonyls, which are stabilized by REOs. Upon CO2 exposure, surface carbonates and bicarbonate species form more abundantly on DFMs than on Ru/Al2O3. This confirms that REOs enhance the adsorption and retention of carbonates, which generate additional promoter-related reaction pathways during low-temperature hydrogenation. These findings are crucial in the advancement of sustainable, wider operation range carbon capture and utilization technologies.

Carbon dioxide removal through ecosystem restoration: Public perceptions and political participation

We compare public perceptions of restoring different ecosystems to increase CO2 uptake in Germany, through focus groups and a general population survey. Among focus group participants forests were highly popular, peatlands evoked negative associations, and seagrass was largely unknown. Nevertheless, the restoration of all ecosystems was viewed positively. We contrast these reactions to those of survey respondents who had not received additional information on restoration. They voiced narrower, less diverse opinions centering around afforestation. Further, focus group participants preferred expert-led restoration decisions, citing low trust in politicians’ technical competence. Contrary to common policy recommendations, also beyond the German context, participants did not emphasize the need of citizen participation and were not strongly concerned about land use conflicts or compensation of affected user groups. The results imply that the public underestimates the political complexity of negotiation processes in ecosystem governance, which are becoming increasingly relevant in the international policy landscape.

Strengthening effect of mechanical vibration on the carbonation properties of steel slag compact

This study examines the impact of mechanical vibration on the carbonation process of steel slag, a substantial byproduct of steel production. Employing a methodical experimental design that modulates mechanical vibration frequencies, the research reveals that mechanical vibration markedly influences carbonation, with an optimal frequency of 180 Hz leading to a 27.5 % increase in compressive strength of steel slag compact and an increase in CO2 uptake of 6.8 %. The application of vibration appears to catalyze the conversion of calcium-rich minerals into well-formed rhombohedral calcite, which emerges as the predominant carbonation product. Mechanism analysis suggests that vibration-induced particle redistribution creates new reaction surfaces, thereby accelerating the carbonation process. However, the effect is more pronounced in early stages, with diminishing returns as carbonation progresses. These pivotal findings propose an innovative strategy to augment the efficiency of carbonation and the inherent material properties of steel slag, thereby fostering a more sustainable approach to the utilization of industrial byproducts.

Predicting multi-annual green roof net ecosystem exchange using machine learning

Green roofs are an urban mitigation strategy to increase CO2 uptake by green infrastructure. Reliable quantification of multi-year net ecosystem exchange (NEE) is essential for evaluating carbon balance, but proves challenging due to lack of long-term data and transferability of models. Machine learning can effectively predict NEE and identify non-linear patterns for spatially and temporally upscaling. For the first time, we developed Random Forest (RF) models using long-term eddy covariance (EC) data from 2015 to 2020 from an extensive green roof at Berlin-Brandenburg Airport (BER) to understand the influence of meteorological predictors on NEE prediction and transferability. A simple (M1), extended (M2) and optimized (M3) model based on different combinations of predictors were built. M3 performed best, deviating by −13 % from the observed uptake of −132.4 gC m−2 a−1 (R2 of 0.74), with M2 (R2 = 0.73) showing similar results. Key predictors were volumetric water content (VWC) and solar radiation flux densities. The models showed robust performance under pronounced environmental conditions. Drought in 2018 introduced significant uncertainties, whereas higher VWC in 2019 and 2020 led to enhanced performance. All models tended to overestimate CO2 assimilation and underestimate respiration of the green roof. M1 deviated by −58 % from observed NEE over the entire period, indicating transferability of M1 to other locations is not feasible, whereas transferability of M2 and M3 showed better potential for broader application with minimal calibration. This study highlights the importance of water-related variables and available energy and demonstrates that RF, incorporating NEE process understanding, can effectively predict NEE.

Towards sustainable construction: Performance evaluation of slag-cenosphere geopolymers under different NaOH concentrations

The incorporation of industrial wastes into construction materials, such as geopolymers, is highly desirable to improve their environmental impact. The choice of source materials, such as slag and cenosphere, and the amount of activator used significantly impact the properties of geopolymers. For instance, including high-reactivity precursors and optimizing activator composition may enhance mechanical strength and durability. However, no studies have evaluated the effect of cenosphere addition on the properties of geopolymer composites. This research study aims to unveil the synthesis of a binary geopolymer material by integrating slag and cenosphere as precursors, activated by sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). Geopolymer composites were prepared to assess the impact of cenosphere addition (by substituting the slag with cenosphere in different percentages of 25, 50, and 75 %) and NaOH concentration (specifically 6 M, 9 M, and 12 M) on the material's properties. Additionally, one conventional mortar with a water-to-cement ratio of 0.5 was also prepared. Compressive strength, ultrasonic pulse velocity (UPV), electrical resistivity, water absorption, density, and thermogravimetric analysis were conducted. Results showed that increasing the cenosphere percentage increased the water absorption and decreased the compressive strength, UPV, electrical resistivity, and density compared to the geopolymer mixture with 100 % slag content. However, up to 50 % substitution of cenosphere, the geopolymer mix performed better than conventional mortar. Notably, results suggest a potential increase in CO2 uptake due to the addition of cenosphere, further enhancing the environmental performance of geopolymer composites. The findings of this study suggest the potential use of slag-cenosphere geopolymer as an alternative and sustainable construction material.

Optimizing restoration duration to maximize CO2 uptake on the Tibetan Plateau

Grasslands cover one-third of the terrestrial area, though half of them have been degraded and primarily due to overgrazing. The Tibetan Plateau (TP) is home to the largest area of alpine grassland on Earth, experiencing a typical degradation-restoration story over the past three decades. With the large-scale implementation and long-term duration of ecological projects aimed at restoring degraded grasslands by fencing across the TP, there is considerable uncertainty regarding the direction and magnitude of changes in the carbon (C) sink function. To address this, we combined ten pairs of systematic field observations at the site scale with literature compilation, aiming to clarify whether restoration still contributes to C uptake and its driving factors. Our results show that after a decade of restoration, living biomass was enhanced by over 80 %, and litter accumulation increased by 3.68 ± 1.25 times across all ecosystem types, although these changes were barely reflected in soil C. Litter caused consistent negative impacts on CO2 uptake across all vegetation types, despite restoration having increased CO2 uptake by half in alpine steppes and alpine meadows. This negative impact was more evident in alpine wetlands, where the quantity of litter was double the living biomass. The thick layer of litter produced a shading effect that further limited the photosynthetic yield of living plants, regulating the restoration-induced CO2 gain or loss. Combining 246 cases across the TP further highlights the need to shorten the duration of restoration to maximize CO2 uptake while also benefitting sustainability, which is deserving of attention from both the scientific community and policy-makers.

Postsynthetically Modified Alkoxide‐Exchanged Ni2(OR)2BTDD: Synergistic Interactions of CO2 with Open Metal Sites and Functional Groups

AbstractPostsynthetic modifications (PSMs) of metal–organic frameworks (MOFs) play a crucial role in enhancing material performance through open metal site (OMS) functionalization or ligand exchange. However, a significant challenge persists in preserving open metal sites during ligand exchange, as these sites are inherently bound by incoming ligands. In this study, for the first time, we introduced alkoxides by exchanging bridging chloride in Ni2Cl2BTDD (BTDD=bis (1H‐1,2,3,–triazolo [4,5‐b],–[4′,5′‐i]) dibenzo[1,4]dioxin) through PSM. Rietveld refinement of synchrotron X‐ray diffraction data indicated that the alkoxide oxygen atom bridges Ni(II) centers while the OMSs of the MOF are preserved. Due to the synergy of the existing OMS and introduced functional group, the alkoxide‐exchanged MOFs showed CO2 uptakes superior to the pristine MOF. Remarkably, the tert‐butoxide‐substituted Ni_T exhibited a nearly threefold and twofold increase in CO2 uptake compared to Ni2Cl2BTDD at 0.15 and 1 bar, respectively, as well as high water stability relative to the other exchanged frameworks. Furthermore, the Grand Canonical Monte Carlo simulations for Ni_T suggested that CO2 interacts with the OMS and the surrounding methyl groups of tert‐butoxide groups, which is responsible for the enhanced CO2 capacity. This work provides a facile and unique synthetic strategy for realizing a desirable OMS‐incorporating MOF platform through bridging ligand exchange.

From abandoned mines to carbon sinks: Assessing the CO2 storage capacity of Austrian low-rank coal deposits

This study represents the first assessment of CO2 storage potential in Austrian coal seams. Coal samples were taken from Fohnsdorf and Leoben abandoned coal mines, with particular emphasis on the Fohnsdorf coal since Leoben coal reserves were largely mined during previous coal production. Several methods were used to compare coal characteristics, including Rock-Eval pyrolysis (RE), organic petrography, and low-pressure N2 and CO2 sorption measurements. Both Fohnsdorf and Leoben coal samples show low sulfur and ash yields, as well as correspondingly high total organic carbon (TOC) contents. The pyrolysis Tmax and vitrinite reflectance values agree with a low coal rank for both sites. According to the N2 adsorption measurements at 77 K, low-lying mire coals from Fohnsdorf show a higher BET-specific surface area (BET-SSA) and BJH pore volume compared to raised-mire coals from Leoben. However, sapropelic shales and high-ash coals from Leoben show the highest BET-SSA and BJH pore volumes of all investigated samples and considerably exceed the N2 adsorption volumes of pure coals from both locations (N2 uptake up to 16 cm3/g; avg. for all samples 5.4 cm3/g). In contrast, the mean adsorbed CO2 uptake measured at 273 K and ∼ 1 bar followed the order of Fohnsdorf low-lying mire coals > Leoben raised-mire coals > Leoben sapropelic coals and shales, ranging at ∼0.8 mmol/g, ∼0.7 mmol/g, and ∼ 0.2 mmol/g, respectively. This shows that BET-SSA and BJH equations did not allow for adequate estimation of CO2 adsorption capacity trends in the investigated sample set. Furthermore, based on the existence of a hysteresis loop between CO2 adsorption and desorption branches for all investigated samples, the occurrence of weak chemisorption phenomena during CO2 adsorption is indicated. This effect helps to increase CO2 uptake and storage safety since the chemisorption process is not fully reversible upon pressure decrease. Ultimately, the theoretical CO2 sequestration potential of the remaining unmined Fohnsdorf coal reserves was estimated at 4.65 million tons, with an additional potential for enhanced coal bed methane production due to the gas-rich nature of Fohnsdorf coals with an estimated 1.2 billion m3 of CH4 in place.

Carbon dioxide sequestration in mortars with excavated soil: Engineering performances and environmental benefits

Globally, substantial volume of excavated soils is generated during construction and demolition activities, which can be utilized in the manufacturing stabilized earth-based construction materials. Furthermore, increasing amount of CO2 is being released into the environment from growing industrial operations that can sequestered in earth-based materials without compromising the engineering properties. This article attempts to explore the effect of CO2 sequestration through accelerated carbonation curing on engineering properties, micro-structure and phase composition of cement-lime stabilized soil mortars. Lateritic soil (clay content of 42 %) is used to replace 25 % and 50 % of natural sand by mass. The experimental findings demonstrate an increase in CO2 uptake by 15–23 % and 33–40 % due to addition of 25 % and 50 % soil respectively compared to control (0 % soil). Precipitation of meta-stable calcium carbonates majorly contributes to the total CO2 uptake, accounting for 62–69 % and 78–87 % of the carbonates formed in 25 % soil-mortars and 50 % soil mortars. These are substantially higher compared to 40–50 % in the case of control mixes. The mentioned finding is attributed to the formation of additional calcium-silicate-hydrate and calcium-aluminate-hydrate due to clay-lime reaction, that binds CO2 and precipitate meta-stable polymorphs of calcium carbonate. Addition of lime and carbon sequestration are found to substantially enhance 1-day strength of cement-soil and cement-lime-soil mortars by 31–36 %, although no prominent effect at 7-day and 28-day marks are observed. Furthermore, capillary water absorption at 28-day age is reduced by 18–31 % in lime-added cement-soil mortars compared to the ones without lime, that reduces moisture sensitivity of the mortars. Overall, the carbon sequestered mortars demonstrate satisfactory strength (20–37 MPa) and water absorption performance of the stabilized mortars for masonry applications, which will provide a promising means to manufacture low-carbon and more durable construction products.

Micro kinetic analysis of the CO2 hydrate formation and dissociation with L-tryptophan in brine via high pressure in situ Raman spectroscopy for CO2 sequestration

Hydrate-based CO2 sequestration (HBCS) is widely recognized as a promising, long-term, and stable approach for CO2 sequestration, but its slow formation kinetics in saline systems pose a significant challenge. In order to address this challenge, this experimental study investigated the potential of L–Tryptophan (L–Trp) as a CO2 hydrate kinetic promoter in deionized water and brine systems. A high-pressure reactor coupled with in situ Raman spectroscopy was used to examine macro-level kinetics and micro-level Raman spectra. The CO2 hydrate formation experiments were conducted at 3.5 MPa and 275.15 K, with different L–Trp concentrations (0–3000 ppm) in deionized water (DI) and brine systems. Raman spectra were monitored throughout the hydrate formation process, identifying distinct peaks corresponding to dissolve CO2, CO2 hydrates, and water activity. The experimental results indicate that the addition of 1000 ppm L–Trp in deionized water significantly enhances CO2 uptake by 3.6–fold and promotes hydrate formation kinetics by 3.3–fold compared to the system without L–Trp. In the brine system (3.5 wt% NaCl), the optimal L–Trp concentration was found to be 2000 ppm, leading to a 1.5-fold increase in CO2 uptake. Remarkably, L–Trp not only enhances the formation kinetics but also facilitates dissociation and CO2 recovery in DI water. Nevertheless, the presence of NaCl hinders the promoting effect of L–Trp on the dissociation kinetics. These findings represent a significant advancement in feasible HBCS technology for CO2 sequestration.