Dynamics of CO<Subscript>2</Subscript> fluxes and concentrations during a shallow subsurface CO<Subscript>2</Subscript> release

A field facility located in Bozeman, Montana provides the opportunity to test methods to detect, locate, and quantify potential CO₂ leakage from geologic storage sites. From 9 July to 7 August 2008, 0.3 t CO₂ day⁻¹ were injected from a 100-m long, ~2.5-m deep horizontal well. Repeated measurements of soil CO₂ fluxes on a grid characterized the spatio-temporal evolution of the surface leakage signal and quantified the surface leakage rate. Infrared CO₂ concentration sensors installed in the soil at 30 cm depth at 0–10 m from the well and at 4 cm above the ground at 0 and 5 m from the well recorded surface breakthrough of CO₂ leakage and migration of CO₂ leakage through the soil. Temporal variations in CO₂ concentrations were correlated with atmospheric and soil temperature, wind speed, atmospheric pressure, rainfall, and CO₂ injection rate.     

Ammonia emission from CO<Subscript>2</Subscript> capture pilot plant using aminoethylethanolamine

Amine post-combustion carbon capture technology is based on washing the flue gas with a solvent that captures CO₂. Thus, a small fraction of this solvent can be released together with the cleaned flue gas. This release may cause environmental concerns, both directly and indirectly through subsequent solvent degradation into other substances in the atmosphere. The paper presents the ammonia emission from CO₂ capture pilot plant (1 tonne CO₂ per day) using 40 wt% aminoethylethanolamine solvent, along with the efficiency of the water wash unit. In addition, the temperature effect of lean amine entering the absorber on ammonia emission was studied. Furthermore, the concentrations of other compounds such as SO₂, SO₃, NO₂, CS₂ and formaldehyde were monitored. The literature review on the NH₃ emission from a pilot plant using aminoethylethanolamine solvent has not been published. The results show that the main source of ammonia emission is the absorber and that emission (in the range 27–50 ppm) corresponds to typical NH₃ release from CO₂ capture pilot plant using an amine solvent. The emission of amines and amine degradation products is a complex phenomenon which is difficult to predict in novel solvents, and for this reason the significance of new solvents testing in a pilot scale has been highlighted.     

Energy production,economic growth and CO<Subscript>2</Subscript> emission: evidence from Pakistan

Extreme weather events present environmental and social challenges across the Eurasian steppe. In Mongolia much attention is given to drought and dzud (severe winter conditions) impact on rural livelihoods, landscapes and governance. A link between the two events, fostered by international and state agencies, speculates that drought leads to dzud; this has become the widely accepted doctrine. However, the relationship between the two events is assumed rather than analysed. Whilst there may be natural links between climate events, causality is more difficult to establish yet often claimed post-event. This paper stresses Mongolia’s destructive dzuds of 1999–2001 and 2009–2010 in examining drought frequency before dzud events. Findings question the hazard connection as just 3 of 32 examined dzud events were preceded by drought. Investigation did not document a relationship between the disasters; linkages between extreme events were implied rather than established. The human role in disaster also needs to be assessed as preparation, and response are key factors for mitigation. Study results identified a lack of causality between the disasters, suggesting more assiduous investigation of hazards is needed in Mongolia. This can clarify causal factors, identify risk and improve disaster mitigation strategies in Mongolia.     

Feasibility of CO<Subscript>2</Subscript> migration detection using pressure and CO<Subscript>2</Subscript> saturation monitoring above an imperfect primary seal of a geologic CO<Subscript>2</Subscript> storage formation: a numerical investigation

A numerical model was developed to investigate the potential to detect fluid migration in a (homogeneous, isotropic, with constant pressure lateral boundaries) porous and permeable interval overlying an imperfect primary seal of a geologic CO₂ storage formation. The seal imperfection was modeled as a single higher-permeability zone in an otherwise low-permeability seal, with the center of that zone offset from the CO₂ injection well by 1400 m. Pressure response resulting from fluid migration through the high-permeability zone was detectable up to 1650 m from the centroid of that zone at the base of the monitored interval after 30 years of CO₂ injection (detection limit = 0.1 MPa pressure increase); no pressure response was detectable at the top of the monitored interval at the same point in time. CO₂ saturation response could be up to 774 m from the center of the high-permeability zone at the bottom of the monitored interval, and 1103 m at the top (saturation detection limit = 0.01). More than 6% of the injected CO₂, by mass, migrated out of primary containment after 130 years of site performance (including 30 years of active injection) in the case where the zone of seal imperfection had a moderately high permeability (10^??17 m² or 0.01 mD). Free-phase CO₂ saturation monitoring at the top of the overlying interval provides favorable spatial coverage for detecting fluid migration across the primary seal. Improved sensitivity of detection for pressure perturbation will benefit time of detection above an imperfect seal.     

Determinants of the increased CO<Subscript>2</Subscript> emission and adaption strategy in Chinese energy-intensive industry

Climate change has not only brought about many natural hazards but also threaten the sustainable development of industry. This study is to investigate the adaptive implications for energy-intensive industries of China in response to climate change impacts. For this purpose, a deep and comprehensive analysis on the change of CO₂ emission for 6 energy-intensive sectors is explored over the period of 2000–2007. A Log-Mean Divisia Index based on time series is also introduced in our study to identify the key factors toward the change of CO₂ emission. It is shown that there were 146.1 million metric tons carbon increased in energy-intensive industries from 2000 to 2007. And the excessive growth of industrial output and increasingly fossil-intensive energy consumption structure were the main driving forces for the increased CO₂ emission. Nevertheless, energy intensity change and declining emission coefficient of electricity played negative role in the growing trend of CO₂ emission. On the basis of these four determinants (namely industrial output, energy intensity, fuel mix effect, and emission coefficient), it is suggested that both economic motives and technologically feasible approaches should be implemented to control the scale of excessive productions and improve energy efficiency toward the energy-intensive industries. And more importantly, strengthening energy-intensive sectors’ awareness of climate change adaptation should be given stronger emphasis as long-term work with the help of some propaganda campaigns for instance.     

Human impact on the historical change of CO<Subscript>2</Subscript>degassing flux in River Changjiang

The impact of water quality changes in River Changjiang (formally known as the Yangtze River) on dissolved CO₂ and silicate concentrations and seasonal carbon flux in the past several decades (1960s–2000) was evaluated, based on monitoring data from hydrographic gauge. It was found that dissolved CO₂ and silicate in Changjiang decreased dramatically during this decades, as opposed to a marked increase in nutrient (e.g. NO₃ ^-) concentrations. Our analyses revealed that dissolved CO₂ in Changjiang was over-saturated with the atmosphere CO₂, and its concentration had showed a declining trend since the 1960s, despite that fluvial DIC flux had maintained stable. Analysis results also suggested that the decrease in dissolved CO₂ concentration was attributed to changes on the riverine trophic level and river damming activities in the Changjiang drainage basin. Due to the economic innovation (e.g. agriculture and industry development) across the Changjiang watershed, fertilizers application and river regulations have significantly altered the original state of the river. Its ecosystem and hydrological condition have been evolving toward the "lacustrine/reservoir" autotrophic type prevailing with plankton. Accordingly, average CO₂ diffusing flux to the atmosphere from the river had been reduced by three-fourth from the 1960s to 1990s, with the flux value being down to 14.2 mol.m^-2.yr^-1 in the 1990s. For a rough estimate, approximately 15.3 Mt of carbon was degassed annually into the atmosphere from the entire Changjiang drainage basin in the 1990s.     

The Role of CaCO<Subscript>3</Subscript> Reactions in the Contemporary Oceanic CO<Subscript>2</Subscript> Cycle

The present analysis adjusts previous estimates of global ocean CaCO₃ production rates substantially upward, to 133 × 10¹² mol yr^?1 plankton production and 42 × 10¹² mol yr^?1 shelf benthos production. The plankton adjustment is consistent with recent satellite-based estimates; the benthos adjustment includes primarily an upward adjustment of CaCO₃ production on so-called carbonate-poor sedimentary shelves and secondarily pays greater attention to high CaCO₃ mass (calcimass) and turnover of shelf communities on temperate and polar shelves. Estimated CaCO₃ sediment accumulation rates remain about the same as they have been for some years: ~20 × 10¹² mol yr^?1 on shelves and 11 × 10¹² mol yr^?1 in the deep ocean. The differences between production and accumulation of calcareous materials call for dissolution of ~22 × 10¹² mol yr^?1 (~50 %) of shelf benthonic carbonate production and 122 × 10¹² mol yr^?1 (>90 %) of planktonic production. Most CaCO₃ production, whether planktonic or benthonic, is assumed to take place in water depths of <100 m, while most dissolution is assumed to occur below this depth. The molar ratio of CO₂ release to CaCO₃ precipitation (CO₂↑/CaCO₃↓) is <1.0 and varies with depth. This ratio, Ψ, is presently about 0.66 in surface seawater and 0.85 in ocean waters deeper than about 1000 m. The net flux of CO₂ associated with CaCO₃ reactions in the global ocean in late preindustrial time is estimated to be an apparent influx from the atmosphere to the ocean, of +7 × 10¹² mol C yr^?1, at a time scale of 10²–10³ years. The CaCO₃-mediated influx of CO₂ is approximately offset by CO₂ release from organic C oxidation in the water column. Continuing ocean acidification will have effects on CaCO₃ and organic C metabolic responses to the oceanic inorganic C cycle, although those responses remain poorly quantified.     

Origin of the patchy emission pattern at the ZERT CO<Subscript>2</Subscript> release test

A numerical experiment was carried out to test whether the patchy CO₂ emission patterns observed at the Zero Emissions Research and Technology release facility are caused by the presence of packers that divide the horizontal injection well into six CO₂-injection zones. A three-dimensional model of the horizontal well and cobble–soil system was developed and simulations using TOUGH2/EOS7CA were carried out. Simulation results show patchy emissions for the seven-packer (six-injection-zone) configuration of the field test. Numerical experiments were then conducted for the cases of 24 packers (23 injection zones) and an effectively infinite number of packers. The time to surface breakthrough and the number of patches increased as the number of packers increased suggesting that packers and associated along-pipe flow are the origin of the patchy emissions. In addition, it was observed that early breakthrough occurs at locations where the horizontal well pipe is shallow and installed mostly in soil rather than the deeper cobble. In the cases where the pipe is installed at shallow depths and directly in the soil, higher pipe gas saturations occur than where the pipe is installed slightly deeper in the cobble. It is believed this is an effect mostly relevant to the model rather than the field system and arises through the influence of capillarity, permeability, and pipe elevation of the soil compared to the cobble adjacent to the pipe.     

Sealing efficiency analysis for shallow-layer caprocks in CO<Subscript>2</Subscript> geological storage

The CO₂ migrated from deeper to shallower layers may change its phase state from supercritical state to gaseous state (called phase transition). This phase transition makes both viscosity and density of CO₂ experience a sharp variation, which may induce the CO₂ further penetration into shallow layers. This is a critical and dangerous situation for the security of CO₂ geological storage. However, the assessment of caprock sealing efficiency with a fully coupled multi-physical model is still missing on this phase transition effect. This study extends our previous fully coupled multi-physical model to include this phase transition effect. The dramatic changes of CO₂ viscosity and density are incorporated into the model. The impacts of temperature and pressure on caprock sealing efficiency (expressed by CO₂ penetration depth) are then numerically investigated for a caprock layer at the depth of 800 m. The changes of CO₂ physical properties with gas partial pressure and formation temperature in the phase transition zone are explored. It is observed that phase transition revises the linear relationship of CO₂ penetration depth and time square root as well as penetration depth. The real physical properties of CO₂ in the phase transition zone are critical to the safety of CO₂ sequestration. Pressure and temperature have different impact mechanisms on the security of CO₂ geological storage.     

The effect of alkalis and polymerization on the solubility of H<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> in alkali-rich silicate melts

The effect of alkalis on the solubility of H₂O and CO₂ in alkali-rich silicate melts was investigated at 500 MPa and 1,250 °C in the systems with H₂O/(H₂O + CO₂) ratio varying from 0 to 1. Using a synthetic analog of phonotephritic magma from Alban Hills (AH1) as a base composition, the Na/(Na + K) ratio was varied from 0.28 (AH1) to 0.60 (AH2) and 0.85 (AH3) at roughly constant total alkali content. The obtained results were compared with the data for shoshonitic and latitic melts having similar total alkali content but different structural characteristics, e.g., NBO/T parameter (the ratio of non-bridging oxygens over tetrahedrally coordinated cations), as those of the AH compositions. Little variation was observed in H₂O solubility (melt equilibrated with pure H₂O fluid) for the whole compositional range in this study with values ranging between 9.7 and 10.2 wt. As previously shown, the maximum CO₂ content in melts equilibrated with CO₂-rich fluids increases strongly with the NBO/T from 0.29 wt % for latite (NBO/T = 0.17) to 0.45 wt % for shoshonite (NBO/T = 0.38) to 0.90 wt % for AH2 (NBO/T = 0.55). The highest CO₂ contents determined for AH3 and AH1 are 1.18 ± 0.05 wt % and 0.86 ± 0.12 wt %, respectively, indicating that Na is promoting carbonate incorporation stronger than potassium. At near constant NBO/T, CO₂ solubility increases from 0.86 ± 0.12 wt % in AH1 [Na/(Na + K)] = 0.28, to 1.18 ± 0.05 wt % in AH3 [Na/(Na + K)] = 0.85, suggesting that Na favors CO₂ solubility on an equimolar basis. An empirical equation is proposed to predict the maximum CO₂ solubility at 500 MPa and 1,100–1,300 °C in various silicate melts as a function of the NBO/T, (Na + K)/∑cations and Na/(Na + K) parameters: \({\text{wt}}\% \;{\text{CO}}_{2} = - 0.246 + 0.014\exp \left( {6.995 \cdot \frac{\text{NBO}}{T}} \right) + 3.150 \cdot \frac{{{\text{Na}} + {\text{K}}}}{{\varSigma {\text{cations}}}} + 0.222 \cdot \frac{\text{Na}}{{{\text{Na}} + {\text{K}}}}.\) This model is valid for melt compositions with NBO/T between 0.0 and 0.6, (Na + K)/∑cation between 0.08 and 0.36 and Na/(Na + K) ratio from 0.25 to 0.95 at oxygen fugacities around the quartz–fayalite–magnetite buffer and above.     

CO<Subscript>2</Subscript> fluid inclusions in Jack Hills zircons

The discovery of Hadean to Paleoarchean zircons in a metaconglomerate from Jack Hills, Western Australia, has catalyzed intensive study of these zircons and their mineral inclusions, as they represent unique geochemical archives that can be used to unravel the geological evolution of early Earth. Here, we report the occurrence and physical properties of previously undetected CO₂ inclusions that were identified in 3.36–3.47 Ga and 3.80–4.13 Ga zircon grains by confocal micro-Raman spectroscopy. Minimum P–T conditions of zircon formation were determined from the highest density of the inclusions, determined from the density-dependence of the Fermi diad splitting in the Raman spectrum and Ti-in-zircon thermometry. For both age periods, the CO₂ densities and Ti-in-zircon temperatures correspond to high-grade metamorphic conditions (≥5 to ≥7 kbar/~670 to 770 °C) that are typical of mid-crustal regional metamorphism throughout Earth’s history. In addition, fully enclosed, highly disordered graphitic carbon inclusions were identified in two zircon grains from the older population that also contained CO₂ inclusions. Transmission electron microscopy on one of these inclusions revealed that carbon forms a thin amorphous film on the inclusion wall, whereas the rest of the volume was probably occupied by CO₂ prior to analysis. This indicates a close relationship between CO₂ and the reduced carbon inclusions and, in particular that the carbon precipitated from a CO₂-rich fluid, which is inconsistent with the recently proposed biogenic origin of carbon inclusions found in Hadean zircons from Jack Hills.     

The regional pressure impact of CO<Subscript>2</Subscript> storage: a showcase study from the North German Basin

A regional scale, showcase saline aquifer CO₂ storage model from the North German Basin is presented, predicting the regional pressure impact of a small industrial scale CO₂ storage operation on its surroundings. The intention of the model is to bridge the gap between generic and site-specific, studying the role of fluid flow boundary conditions and petrophysical parameters typically found in the North German Basin. The numerical simulation has been carried out using two different numerical simulators, whose results matched well. The most important system parameters proved to be the model’s hydrological boundary conditions, rock compressibility, and permeability. In open boundary aquifers, injection-induced overpressures dissipate back to hydrostatic level within a few years. If a geological flow barrier is present on at least one side of the aquifer, pressure dissipation is seriously retarded. In fully closed compartments, overpressures can never fully dissipate, but equilibrate to a compartment-wide remnant overpressure. At greater distances to the injection well, maximum fluid pressures are in the range of a few bar only, and reached several years to decades after the end of the actual injection period. This is important in terms of long-term safety and monitoring considerations. Regional pressure increase impacts the storage capacities of neighbouring sites within hydraulically connected units. It can be concluded that storage capacities may be seriously over- or underestimated when the focus is on a single individual storage site. It is thus necessary to assess the joint storage capacities and pressure limitations of potential sites within the same hydraulic unit.     

Investigating the sensitivity factors of household indirect CO<Subscript>2</Subscript> emission from the production side

Indirect emission from household consumption, which is affected by technologies of production sectors, is the significant contributor to national CO₂ emission. Input–output model is preferred when direct and indirect transactions and emissions are considered simultaneously. Based on input–output model, this study applies the sensitivity analysis to indirect emission from rural and urban domestic consumption, respectively. It allows us to investigate the influences of the technology change both at the transaction level and at the sector level. In addition, multi-years symmetrical input–output tables are adopted to obtain dynamic analysis in order to study the variation trend of the influences. At the transaction level, the technology change of production and supply of electric power and heat power self-supplied intermediate inputs exerts the most significant influence on indirect emission from both rural and urban consumption. At the sector level, indirect emissions from rural and urban consumption are both the most sensitive to the technology change of chemistry industry. Furthermore, there are more key transactions selected under consideration of rural domestic consumption compared with the urban. Additionally, the influencing degree and variation trends of the same technology change would be different between rural and urban situation. According to the above findings, policy recommendations aiming at achieving emission abatement from household consumption are provided in detail.     

CO<Subscript>2</Subscript> leakage through an abandoned well: problem-oriented benchmarks

The efficiency and sustainability of carbon dioxide (CO₂) storage in deep geological formations crucially depends on the integrity of the overlying cap-rocks. Existing oil and gas wells, which penetrate the formations, are potential leakage pathways. This problem has been discussed in the literature, and a number of investigations using semi-analytical mathematical approaches have been carried out by other authors to quantify leakage rates. The semi-analytical results are based on a number of simplifying assumptions. Thus, it is of great interest to assess the influence of these assumptions. We use a numerical model to compare the results with those of the semi-analytical model. Then we ease the simplifying restrictions and include more complex thermodynamic processes including sub- and supercritical fluid properties of CO₂ and non-isothermal as well as compositional effects. The aim is to set up problem-oriented benchmark examples that allow a comparison of different modeling approaches to the problem of CO₂ leakage.     

Analytical model for screening potential CO<Subscript>2</Subscript> repositories

Assessing potential repositories for geologic sequestration of carbon dioxide using numerical models can be complicated, costly, and time-consuming, especially when faced with the challenge of selecting a repository from a multitude of potential repositories. This paper presents a set of simple analytical equations (model), based on the work of previous researchers, that could be used to evaluate the suitability of candidate repositories for subsurface sequestration of carbon dioxide. We considered the injection of carbon dioxide at a constant rate into a confined saline aquifer via a fully perforated vertical injection well. The validity of the analytical model was assessed via comparison with the TOUGH2 numerical model. The metrics used in comparing the two models include (1) spatial variations in formation pressure and (2) vertically integrated brine saturation profile. The analytical model and TOUGH2 show excellent agreement in their results when similar input conditions and assumptions are applied in both. The analytical model neglects capillary pressure and the pressure dependence of fluid properties. However, simulations in TOUGH2 indicate that little error is introduced by these simplifications. Sensitivity studies indicate that the agreement between the analytical model and TOUGH2 depends strongly on (1) the residual brine saturation, (2) the difference in density between carbon dioxide and resident brine (buoyancy), and (3) the relationship between relative permeability and brine saturation. The results achieved suggest that the analytical model is valid when the relationship between relative permeability and brine saturation is linear or quasi-linear and when the irreducible saturation of brine is zero or very small.     

Preparation of carbon molecular sieves and its impregnation with Co and Ni for CO<Subscript>2</Subscript>/N<Subscript>2</Subscript> separation

The carbon molecular sieves (CMSs) prepared by carbonaceous materials as precursors are effective in CO₂/N₂ separation. However, selectivity of these materials is too low, since hydrocarbon cracking for developing the desired microporosity in carbonaceous materials has not been done effectively. Hence, in this study, cobalt and nickel impregnation on the precursor was conducted to introduce catalysts for hydrocarbon cracking. Cobalt and nickel impregnation, carbonization under N₂ atmosphere, and chemical vapor deposition (CVD) by benzene were conducted on the extruded mixtures of activated carbon and coal tar pitch under different conditions to prepare CMSs. The best CMS prepared by carbon deposition on the cobalt-impregnated samples exhibited CO₂ adsorption capacity of 54.79 mg/g and uptake ratio of 28.9 at 0 °C and 1 bar. In terms of CO₂ adsorption capacity and uptake ratio, CMSs prepared by carbon deposition on non-impregnated and cobalt-impregnated samples presented the best results, respectively. As benzene concentration and CVD time increased, equilibrium adsorption capacity of CO₂ decreased, and uptake ratio increased. Cobalt was found to be the best catalyst for benzene cracking in the CVD process.