Geological Carbon Capture Research Articles

Effects of natural non-volcanic CO2 leakage on soil microbial community composition and diversity

Geological carbon capture and storage (CCS) can reduce anthropogenic CO2 emissions, but questions exist about impacts at the surface if CO2 leaks from deep storage reservoirs. To examine potential impacts on soils, previous studies have investigated the geochemistry and microbiology of volcanic soils hosting high fluxes of CO2 rich gas. This study builds on those previous investigations by considering impacts of CO2 leakage at a non-volcanic site, where deep geogenic CO2 leaks from a cracked well casing. At the site, we collected 26 soil cores adjacent to soil gas monitoring wells. Based on measured CO2 fluxes, the soil samples fall into two groups 1) high CO2 (flux = 304.6 ± 272.1 g m−2 d−1, conc. = 29.1 ± 34 %) and 2) low CO2 (flux = 15.8 ± 6.1 g m−2 d−1, conc. = 0.8 ± 0.9 %). Soil pH was significantly lower (p < 0.05) in high flux group samples (4.6 ± 0.3) than the low flux ones (5.3 ± 0.7). Beta diversity calculations using 16S rRNA gene sequences and redundancy analysis (RDA) revealed clear clustering of microbial communities relative to CO2 flux and significant correlations of community composition with pH and organic carbon content. In the high flux soils, abundant microbial groups included Acidobacteriota, Ktedonobacteria, and SC-I-84 in the phylum Proteobacteria, as well as Nitrososphaeria, a genus of ammonia oxidizing archaea. Compared to volcanic sites described previously, our non-volcanic site had slight differences in soil geochemical properties and gradual shifts in community compositions between CO2 hotspots and background locations. Moreover, the elevated abundance of SC-I-84 has not been reported in studies of volcanic sites. This study improves our ability to predict potential environmental impacts of geological CCS by expanding the range of conditions over which existing CO2 leakage has been observed.

Carbonation Reaction Mechanisms of Portlandite Predicted from Enhanced Ab Initio Molecular Dynamics Simulations

Geological carbon capture and sequestration (CCS) is a promising technology for curbing the global warming crisis by reduction of the overall carbon footprint. Degradation of cement wellbore casings due to carbonation reactions in the underground CO2 storage environment is one of the central issues in assessing the long-term success of the CCS operations. However, the complexity of hydrated cement coupled with extreme subsurface environmental conditions makes it difficult to understand the carbonation reaction mechanisms leading to the loss of well integrity. In this work, we use biased ab initio molecular dynamics (AIMD) simulations to explore the reactivity of supercritical CO2 with the basal and edge surfaces of a model hydrated cement phase—portlandite—in dry scCO2 and water-rich conditions. Our simulations show that in dry scCO2 conditions, the undercoordinated edge surfaces of portlandite experience a fast barrierless reaction with CO2, while the fully hydroxylated basal surfaces suppress the formation of carbonate ions, resulting in a higher reactivity barrier. We deduce that the rate-limiting step in scCO2 conditions is the formation of the surface carbonate barrier which controls the diffusion of CO2 through the layer. The presence of water hinders direct interaction of CO2 with portlandite as H2O molecules form well-structured surface layers. In the water-rich environment, CO2 undergoes a concerted reaction with H2O and surface hydroxyl groups to form bicarbonate complexes. We relate the variation of the free-energy barriers in the formation of the bicarbonate complexes to the structure of the water layer at the interface which is, in turn, dictated by the surface chemistry and the degree of nanoconfinement.

Practical leakage risk assessment for CO2 assisted enhanced oil recovery and geologic storage in Ohio's depleted oil fields

A method for risk assessments of geological carbon capture, utilization and storage (CCUS) projects was created and the results of three risk assessments for potential CCUS projects at depleted oil fields in Ohio are presented. The risk framework described uses the bow-tie method with features, events, and processes (FEPs) to identify and assess risk posed by potential loss of integrity of legacy wells. Field-scale well integrity studies have had to rely largely on historical data to assess the potential for fluid leakage related to CCUS projects. This study uses categories of known information to develop a proxy for likelihood of leakage. Proxy categories were: Spud Date, Treatment, Well Status, Plugging and Abandonment Date, Well Type, Plug, Surface Cement, and Primary Cement. Separate risks were developed for each well and each scenario. The consequence of a leakage event was estimated based on costs to businesses and property owners for each leakage scenario. Cost categories in this framework include finding and fixing the leak, environmental remediation, CO2 injection interruption, technical remedies for damages, and legal costs. Using the likelihood of leakage calculated for each field and the cost of potential consequences, the risks for each field were estimated to be between $13 million to $63 million for the three fields of interest. The use of the bow-tie method allows easy visualization and identification of barriers that may reduce the likelihood of the top event in a risk scenario.

Dissolution and Precipitation Dynamics at Environmental Mineral Interfaces Imaged by In Situ Atomic Force Microscopy.

Chemical reactions at the mineral-solution interface control important interfacial processes, such as geochemical element cycling, nutrient recovery from eutrophicated waters, sequestration of toxic contaminants, and geological carbon storage by mineral carbonation. By time-resolved in situ imaging of nanoscale mineral interfacial reactions, it is possible to clarify the mechanisms governing mineral-fluid reactions.In this Account, we present a concise summary of this topic that addresses a current challenge at the frontier of understanding mineral interfaces and their importance to a wide range of mineral re-equilibration processes in the presence of a fluid aqueous phase. We have used real-time nanoscale imaging of liquid-cell atomic force microscopy (AFM) to observe the in situ coupling of the dissolution-precipitation process, whereby the dissolution of a parent mineral phase is coupled at mineral interfaces with the precipitation of another product phase, chemically different from the parent. These nanoscale observations allow for the identification of dissolution and growth rates through systematically investigating various minerals, including calcite (CaCO3), siderite (FeCO3), cerussite (PbCO3), magnesite (MgCO3), dolomite (CaMg(CO3)2), brushite (CaHPO4·2H2O), brucite (Mg(OH)2), portlandite (Ca(OH)2), and goethite (α-FeOOH), in various reacting aqueous fluids containing solution species, such as arsenic, phosphate, organo- or pyrophosphate, CO2, selenium, lead, cadmium, iron, chromium, and antimony. We detected the in situ replacement of these parent mineral phases by product phases, identified through a variety of analytical methods such as Raman spectroscopy, high-resolution transmission electron microscopy, and various X-ray techniques, as well as modeling by geochemical simulation using PHREEQC. As a consequence of the coupled processes, sequestration of toxic elements and hazardous species and inorganic and organic carbon, and limiting or promoting recovery of nutrients can be achieved at nano- and macroscopic scales.We also used in situ AFM to quantitatively measure the retreat rates of molecular steps and directly observe the morphology changes of dissolution etch pits on calcium phosphates in organic acid solutions present in most rhizosphere environments. By molecular modeling using density functional theory (DFT), we explain the origin of dissolution etch pit evolution through specific stereochemistry and molecular recognition and provide an energetic basis by calculating the binding energies of chemical functionalities on organic acids to direction-specific steps on mineral surfaces. In addition, we further quantified precipitation kinetics of calcium phosphates (Ca-P's) on typical mineral surfaces at the nanoscale in environmentally relevant solutions with various organic molecules, by measurements obtained from sequential images obtained by liquid-cell AFM. In situ dynamic force spectroscopy (DFS) was used to determine binding energies of single-molecules with different chemical functionalities found in natural organic matter at mineral-fluid interfaces. Quantifying molecular organo-mineral bonding or binding energies mechanistically explains phosphate precipitation and transformation. From DFS measurements, molecular-scale interactions of mineral-natural organic matter (DNA, proteins, and polysaccharides) associations were determined. With this powerful tool, single-molecule determinations of polysaccharide-amorphous iron oxide or hematite interactions provided the mechanistic origin of the phase- or facet-dependent adsorption. These systematic investigations and findings significantly contribute to a more quantitative prediction of the fate of nutrients and contaminants, chemical element cycling, and potential geological carbon capture and nuclear waste storage in aqueous environments.

Simultaneous determination of partition coefficients of three organic compounds distributed as mixtures between SF-CO2 and water using interfaced SFE-SFC apparatus

A combined SFE-SFC system has enabled the simultaneous determination of the partition coefficient (K) values of three organic compounds distributed as mixtures between SF-CO2 and water phases. The system used a single valve SFE-SFC recirculation interface. The compounds were: o-toluidine, o-cresol and indole prepared as mixtures in aqueous solutions at concentration levels applicable to industrial process waters and of relevance to potential groundwater contamination that may arise from geological carbon capture and storage facilities. Sets of three compound K values were simultaneously obtained at temperatures 313 K, 323 K, 333 K, and five pressures from 8.62 MPa to 22.41 MPa. At each temperature, the SFE vessel pressure was incremented in controlled SF-CO2 pressure steps applied to a single stirred water sample to rapidly obtain complete series of individual K values. The instrumentation and method demonstrate considerable potential to achieve significant time savings to construct an expanded organic compound K database.

The Importance of Baseline Surveys of Near-Surface Gas Geochemistry for CCS Monitoring, as Shown from Onshore Case Studies in Northern and Southern Europe

The monitoring of the integrity of onshore geological carbon capture and storage projects will require an approach that integrates various methods with different spatial and temporal resolutions. One method proven to be quite effective for site assessment, leakage monitoring, and leakage verification is near-surface gas geochemistry, which includes soil gas concentration and gas flux measurements. Anomalous concentrations or fluxes, relative to the natural background values, can indicate the potential occurrence of a leak. However the natural background can be quite variable, especially for CO<sub>2<sub/>, due to biological production and accumulation in the soil that changes as a function of soil type, land use, geology, temperature, water content, and various other parameters. To better understand how these parameters influence natural, near-surface background values, and to examine the potential of different sampling strategies as a function of the survey goals, this paper reports results from two highly different case studies, one from northern Europe (Voulund, Denmark) and one from southern Europe (Sulcis, Sardinia, Italy). The small Voulund site, with its homogeneous soil, climate, and topography, was surveyed twice (in fall and in spring) within the EU-funded SiteChar project to examine the effects of different land use practices and seasons on baseline values. Forested land was found to have lower CO<sub>2<sub/> concentrations during both campaigns compared to cultivated and heath land, and higher CH<sub>4<sub/> values during the spring sampling campaign. Continuous monitoring probes showed much more detail, highlighting seasonal changes in soil gas CO<sub>2<sub/> concentrations linked primarily to temperature variations. The much larger Sulcis site, studied within an ENEA-funded project on potential CO<sub>2<sub/>-ECBM (Enhanced Coal Bed Methane) deployment, was surveyed at the regional scale and on detailed grids and transects for site assessment purposes. Despite the completely different soil and climate conditions, the statistical distribution of the Sulcis data was similar to that of Voulund. Much higher soil gas CO<sub>2<sub/> anomalies were found at this site, however, due to the less permeable sediments (i.e., better water retention and greater gas accumulation) and the warmer temperatures. Detailed surveys at this site highlighted various significant anomalies, some of which can be explained by near surface biological processes, whereas others, especially helium anomalies, were more difficult to explain. These results show the utility of baseline surveys, and highlight the need for follow-up studies to clarify any unexplained anomalies before any CO<sub>2<sub/> storage.

An interdisciplinary assessment of climate engineering strategies

Mitigating further anthropogenic changes to the global climate will require reducing greenhouse‐gas emissions (“abatement”), or else removing carbon dioxide from the atmosphere and/or diminishing solar input (“climate engineering”). Here, we develop and apply criteria to measure technical, economic, ecological, institutional, and ethical dimensions of, and public acceptance for, climate engineering strategies; provide a relative rating for each dimension; and offer a new interdisciplinary framework for comparing abatement and climate engineering options. While abatement remains the most desirable policy, certain climate engineering strategies, including forest and soil management for carbon sequestration, merit broad‐scale application. Other proposed strategies, such as biochar production and geological carbon capture and storage, are rated somewhat lower, but deserve further research and development. Iron fertilization of the oceans and solar radiation management, although cost‐effective, received the lowest ratings on most criteria. We conclude that although abatement should remain the central climate‐change response, some low‐risk, cost‐effective climate engineering approaches should be applied as complements. The framework presented here aims to guide and prioritize further research and analysis, leading to improvements in climate engineering strategies.

Baseline variability in onshore near surface gases and implications for monitoring at CO2 storage sites

The measurement of gas concentrations and fluxes in the soil and atmosphere is a powerful tool for monitoring geological carbon capture and storage (CCS) sites because the analyses are made directly in the biosphere in which we live. These methods can be used to both find and accurately quantifying leaks, and are visible and tangible data for public and ecosystem safety. To be most reliable and accurate, however, the measurements must be interpreted in the context of natural variations in gas concentration and flux. Such baseline data vary both spatially and temporally due to natural processes, and a clear understanding of their values and distributions is critical for interpreting near-surface gas monitoring techniques. The best example is CO2 itself, as the production of this gas via soil respiration can create a wide range of concentrations and fluxes that must be separated from, and not confused with, CO2 that may leak towards the surface from a storage reservoir. The present article summarizes baseline studies performed by the authors at various sites having different climates and geological settings from both Europe and North America, with focus given to the range of values that can result from near surface processes and how different techniques or data processing approaches can be used to help distinguish a leakage signal from an anomalous, shallow biogenic signal.

Scientific Drilling

Summary This workshop report describes plans for scientific drill ing in the Samail ophiolite in Oman in the context of past, current, and future research. Long-standing plans to study formation and evolution of the Samail crust and upper mantle, involving igneous and metamorphic processes at an oceanic spreading center, have been augmented by recent interest in ongoing, low temperature processes. These include alteration and weathering, and the associated sub-surface biosphere supported by chemical potential energy due to disequilibrium between mantle peridotite and water near the surface. This interest is motivated in part by the possibility of geological carbon capture and storage via engineered, accelerated mineral carbonation in Oman.

Eddy Covariance Method for CO2 Emission Measurements in CCUS Applications: Principles, Instrumentation and Software

The eddy covariance method is a micrometeorological technique for direct measurements of gas transport between the surface and the atmosphere. It is widely used for quantifying CO2 emission rates from natural, urban and agricultural ecosystems, including areas of agricultural carbon sequestration. In geological carbon capture, utilization and sequestration, emerging projects utilize eddy covariance to monitor large areas where CO2 may escape from the subsurface, to detect and quantify CO2 leakage, and to improve CO2 storage efficiency. This paper describes key principles of the method, main requirements, typical instrumentation and software, and educational resources particularly useful for carbon sequestration research.

Does seaweed offer a solution for bioenergy with biological carbon capture and storage?

AbstractThe concept of combining bioenergy with carbon capture and storage (BECCS) has been identified as one mechanism to achieve energy production with a net negative atmospheric carbon emission. Conventional geological carbon capture and storage involves large capital outlay and recurring expense. Therefore there is increased interest in coupling biological carbon capture and sequestration with biomass production. Systems such as low‐input high‐diversity native grasslands and biochar production have been heralded as carbon negative biofuels. Another potential production system for bioenergy with biological carbon capture and storage (BEBCCS) is the large‐scale cultivation of seaweed (macroalgae) for biofuels. Marine biofuels offer considerable advantages over terrestrial first‐generation biofuels in terms of their low land use, fresh water and fertilizer requirements. In addition, they also offer considerable potential in the field of BEBCCS. Macroalgae rapidly accumulate biomass and as part of this process, a significant proportion (estimates range up to 60%) of the carbon they fix photosynthetically is released into the water. A proportion of this released dissolved organic carbon (DOC) is highly labile and enters the bacterial loop and is rapidly remineralized back to CO2. However, a proportion is known to be resistant to biological degradation and enters the refractory DOC pool. The marine DOC pool is the largest organic carbon pool on the planet and the refractory component is known to have a turnover period of 100s‐1000s years. The release of refractory DOC from macroalgae combined with biofuel production offers the potential for large scale carbon negative fuel production. © 2012 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Characterization of carbonic anhydrase II from Chlorella vulgaris in bio-CO2 capture

Carbonic anhydrase II (CA II) can catalyze the reversible hydration reaction of CO(2) at a maximum of 1.4 × 10(6) molecules of CO(2) per second. The crude intracellular enzyme extract containing CA II was derived from Chlorella vulgaris. A successful CO(2) capture experiment with the presence of calcium had been conducted on the premise that the temperature was conditioned at a scope of 30-40°C, that the biocatalyst-nurtured algal growth period lasted 3days, and that pH ranged from7.5 to 8.5. Ions of K(+), Na(+), Ca(2+), Co(2+), Cu(2+), Fe(3+), Mg(2+), Mn(2+), and Zn(2+) at 0.01, 0.1, and 0.5M were found to exhibit no more than 30% inhibition on the residual activity of the biocatalyst. It is reasonable to expect that calcification catalyzed by microalgae presents an alternative to geological carbon capture and sequestration through a chain of fundamental researches carried on under the guidance of sequestration technology.

The New Proposed EU Legislation on Geological Carbon Capture and Storage (CCS): A First Impression of the Commission’s Proposed Framework on CCS

The New Proposed EU Legislation on Geological Carbon Capture and Storage (CCS): A First Impression of the Commission’s Proposed Framework on CCS

The impact of carbon capture and storage on overall mitigation policy

Policy makers, as well as many economists, recognize geological carbon capture and storage (CCS) as an option for avoiding costly emission reductions. While an extreme perspective is to envision CCS as a magic bullet to solve the issue of climate change, a more balanced economics perspective would situate this approach within a portfolio of mitigation actions. CCS can be implemented with two purposes: it can act as a substitute for other technological efforts to reach a given environmental target and it offers the potential for additional emission reductions to reach a ‘safer’ climate target. In order to balance these two possible ways of utilizing CCS and to assess their respective effects on early policy strategies, we have undertaken a twofold numerical experiment. First, a cost-efficiency analysis was undertaken, where the sole effect of CCS was substitution for other efforts. This was followed by a cost—benefit analysis where both purposes had to be balanced. We find that future availability of CCS i...

The impact of carbon capture and storage on overall mitigation policy

Policy makers, as well as many economists, recognize geological carbon capture and storage (CCS) as an option for avoiding costly emission reductions. While an extreme perspective is to envision CCS as a magic bullet to solve the issue of climate change, a more balanced economics perspective would situate this approach within a portfolio of mitigation actions. CCS can be implemented with two purposes: it can act as a substitute for other technological efforts to reach a given environmental target and it offers the potential for additional emission reductions to reach a ‘safer’ climate target. In order to balance these two possible ways of utilizing CCS and to assess their respective effects on early policy strategies, we have undertaken a twofold numerical experiment. First, a cost-efficiency analysis was undertaken, where the sole effect of CCS was substitution for other efforts. This was followed by a cost—benefit analysis where both purposes had to be balanced. We find that future availability of CCS is less of a reason to relax near-term abatement efforts than what could be inferred from previous analyses. Moreover, the cost—benefit analysis indicates that environmental targets should be more ambitious when CCS is included in the picture.

Carbon Capture and Sequestration: How Much Does this Uncertain Option Affect Near-Term Policy Choices?

Policy makers as well as many economists recognize geological Carbon Capture and Sequestration (CCS) as a key option to avoid costly emission reduction. While an extreme perspective is to envision CCS as a magic bullet to solve the issue of climate change, the economics perspective is more balanced and see it as a part of a portfolio of mitigation actions. Besides, as any novel mitigation technology, CCS can be implemented with a twofold purpose; on one side it can substitute some other technological efforts to reach a given environmental target. On the other side, it offers the opportunity to go for additional emission reductions and reach a safer climate target. In order to balance these two possible utilizations of CCS and assess their respective effects on early policystrategies, we undertake a twofold numerical experiment. First, a cost-efficiency analysis is undertaken where CCS sole effect is substitution of other efforts. This is followed by a cost-benefit analysis where both purposes have to be balanced. We find that future availability of CCS is less a reason to relax near-term abatement efforts than what could be inferred from previous analyses. Moreover, cost-benefit analysis indicates that the environmental target should be more ambitious when CCS is included in the picture.