Site For Sequestration Research Articles

PhytOC sequestration characteristics and phytolith carbon sink capacity of the karst grasslands in southwest China

Grassland is an important component of terrestrial ecosystems and plays a crucial role in the global carbon cycle. PhytOC (phytolith-occluded organic carbon) is an extremely important long-term and stable carbon pool in terrestrial ecosystems. Southwest China karst soil exhibits obvious characteristics of alkalinity, high silicon content, and rich calcium, which can significantly influence the characteristics and mechanisms of PhytOC sequestration in vegetation. To elucidate the sequestration characteristics and mechanisms of PhytOC in the karst grasslands, three typical karst grasslands of tropical shrub tussock (TST), warm-temperate shrub tussock (WST), and mountain meadow (MM) from Guizhou province of southwest China were studied. The following results and conclusions were obtained that: 1) the range of PhytOC content of aboveground plant parts, underground roots, and soil in the karst grasslands was 4.03–16.54 g·kg−1, 10.67–33.92 g·kg−1, and 0.63–1.89 g·kg−1, respectively. The underground roots are an important site for phytolith carbon sequestration in grassland ecosystems, and the PhytOC content of underground roots may be higher than that of the aboveground parts. 2) The PhytOC sequestration rate of vegetation was 7.34–15.93 kg·ha−1·yr−1, and the annual sequestration amount of PhytOC of the whole grasslands in southwest China could reach 0.48 × 103–1.48 × 103 t CO2. Compared to grasslands in non-karst regions of China, karst grasslands in southwest China have a higher sequestration rate of PhytOC in vegetation and a greater capacity for phytolith carbon sequestration. 3) Soil available silicon, pH, and stoichiometric characteristics of C, N and P nutrients significantly affected the phytolith carbon sequestration of vegetation and the soil accumulation of PhytOC in the karst grasslands. The research results are of great significance for estimating the phytolith carbon sequestration capacity of grassland ecosystems and for grassland construction and management based on enhancing carbon sequestration.

Laboratory investigation on injection of supercritical CO2 into basalt: Implication for CO2 sequestration via mineralization

Hydraulic fracturing can create a fracture network that enables fluid penetration of a basalt formation with otherwise low porosity, offering a site for rapid CO2 mineralization sequestration. Supercritical carbon dioxide (SC-CO2) is a promising fracturing fluid with unique properties, making it well-suited for unconventional oil and gas reservoir stimulation. In this study, experiments of fracturing with water and SC-CO2 were conducted under different injection schemes and formation temperatures. The frackability of basalts was investigated from the perspective of breakdown pressure and fracture morphology. The findings revealed that SC-CO2 fracturing with a low pressurization rate could become an optimized option for enhancing the stimulated effect. The potential of carbon sequestration was roughly estimated based on the area of induced fractures, suggesting that fostering a developed fracture network would aid in the in-situ mineralization and storage of carbon. The variation of element composition obtained from basalt slices containing fractures induced by SC-CO2 under different reaction conditions verified the role of water participation and time scale in the mineralization effect.

Numerical simulation of potential site for CO2 sequestration in a depleted oil reservoir in northern Thailand

Due to the effects of an anthropogenic global warming, the concern about the emissions of carbon dioxide (CO2) into the environment has increased in various industries like petroleum industry. Currently, the use of the geological storage techniques, such as carbon capture and sequestration (CCS), is the most promising way to mitigate these emissions. The objective of this study on a numerical simulation is to investigate CO2 onshore geological storage in the depleted oilfields in the North of Thailand. The geological modelling is a critical step in proving the suitability of a geologic formation for a CCS project. The simulations of the pressure build-up, CO2 plume movement and the amount of CO2 stored are the main points of this research. The development of the 3D reservoir model is performed by means of CMG-GEM, and CMG-WINPROP. This study performs how CO2 sequestration is injected with the flow rate of 1000–4000 tons/day into a reservoir with a depth of 2120-2161 m. The result indicates that CO2 moves up to the top formation. Moreover, 0.583 Mt of CO2 can be stored into the reservoir. This presents the preliminary study for the CO2 sequestration in Northern Thailand, which aids in the next phase of CCS projects in Thailand.

Chemical Composition of Wet Atmospheric Deposition in a Natural Urban Reserve, Conservation of Green Urban Areas: a Mexico City Case Study

Green areas are essential for life in cities and for the conservation of ecosystem services in the case of megacities such as Mexico City. Green areas mitigate air pollution, reduce the temperature, and promote infiltration to feed the aquifers that, in the case of Mexico City, supply 68% of the water. Additionally, food production and recreational usage are important for the population. In the years 2017 and 2018, the chemical composition of wet deposition in the southern part of Mexico City was analyzed, daily and weekly. The study area is located in the greenest part of Mexico City, an important site for water recharge and carbon sequestration. Mexico City, like other megacities of high- and low-income countries, faces serious problems of air pollution. The purpose of this study was to measure the amount of total nitrogen and sulfur that is available in a natural reserve located inside the National Autonomous University of Mexico, and conductivity, pH, rain volume, and anions and cations were analyzed as well. Eighteen months of data were analyzed in order to understand the atmospheric deposition in and anthropogenic influence on an urban green natural area from the southern part of the city. Although both stations are less than 2 km apart, there are significant differences in their chemical composition; however, no differences were found for precipitation and pH, indicating that each station provides a local contribution, depending on local events and sources. Samples included rain events match for both sampling sites, with 67% of the samples in the same rain event match. Nonetheless, when only volume is compared for each year, both tests showed no significant difference (pv = 0.520). Throughout the year, various rainfall rates occur at the CU-CCA and REPSA stations, and the rainy season presents during the May–October period; the median value registered for both monitoring stations was 780 mL, and maximal rainfall was 4780 mL presenting at the CU-CCA station.

Biomineralisation and metal sequestration in a crustacean ectoparasite infecting the gills of a freshwater fish

It has been suggested that parasites are effective bioindicators as they are sensitive to environmental changes and, in some cases, accumulate trace elements in higher concentrations than their hosts. Accumulated elements sequester in different organs. In monogenean and crustacean ectoparasites, sclerotised structures and egg yolk appear to be the preferred site for element sequestration. In this study, the sequestration of trace elements; Mg, Al, Ca, Fe, Cu, and Zn in Lamproglena clariae was studied from two rivers. Adult L. clariae were collected from the gills of Clarias gariepinus from Lake Heritage in the Crocodile River and in the Vaal River below the Vaal Dam, South Africa. Collected parasites were flash frozen in liquid nitrogen and sectioned with a cryomicrotome. Sections were treated with Phen-Green to observe fluorescent signals. Trace elements in the parasite were analysed using a scanning electron microscope with an energy-dispersive spectroscope (SEM–EDS). Results showed more intense fluorescence signals in the exoskeleton compared to tissues, and in the egg yolk. Analysis by SEM–EDS confirmed the presence of elements in the parasite from both sites. Levels of Al were higher in L. clariae from the Vaal River than those from Lake Heritage, and Fe was higher in L. clariae from Lake Heritage. Element distribution patterns in the parasite matched those in the water from the sites. Unlike other crustaceans, regulation of metals in adult females of L. clariae does not occur through moulting, but high levels occurred in the yolk.

Fault Slip Tendency Analysis for a Deep-Sea Basalt CO2 Injection in the Cascadia Basin

Offshore basalts, most commonly found as oceanic crust formed at mid-ocean ridges, are estimated to offer an almost unlimited reservoir for CO2 sequestration and are regarded as one of the most durable locations for carbon sequestration since injected CO2 will mineralize, forming carbonate rock. As part of the Solid Carbon project, the potential of the Cascadia Basin, about 200 km off the west coast of Vancouver Island, Canada, is investigated as a site for geological CO2 sequestration. In anticipation of a demonstration proposed to take place, it is essential to assess the tendency of geologic faults in the area to slip in the presence of CO2 injection, potentially causing seismic events. To understand the viability of the reservoir, a quantitative risk assessment of the proposed site area was conducted. This involved a detailed characterization of the proposed injection site to understand baseline stress and pressure conditions and identify individual faults or fault zones with the potential to slip and thereby generate seismicity. The results indicate that fault slip potential is minimal (less than 1%) for a constant injection of up to ~2.5 MT/yr. This is in part due to the thickness of the basalt aquifer and its permeability. The results provide a reference for assessing the potential earthquake risk from CO2 injection in similar ocean basalt basins.

Sealing capability of the Eocene–Miocene Horda and Lark formations of the Nini West depleted oil field – implications for safe CO2 storage in the North Sea

The Nini West depleted oil field in the Siri Canyon, Danish North Sea, is considered a potential storage site for safe sequestration of CO2 to fulfill Denmark's ambition to reduce CO2 emissions using carbon capture storage (CCS) technologies. The Paleocene Nini West sandstone reservoir is overlain by several caprocks forming a 900 m thick seal complex composed of the regionally distributed Eocene–Miocene Horda and Lark formations. The integrity and capacity of the seal complex has been evaluated using a multidisciplinary analytical approach integrating organic and inorganic compositional data, physical properties, wireline logs, and mud gas data. The seal complex consists of clay-dominated mudstones with a relatively homogenous lithology constituting a tight seal. Mud gas logs are introduced as a novel proxy for seal integrity in a CCS context, and they show only very limited vertical gas migration has occurred from the reservoir into the basal part of the seal. Average porosities range from ∼15–20% and both measured and modelled average permeabilities range from only 0.11–0.39 μD. The seal mudstones have narrow unimodal pore throat size distributions, and 40% of the samples have extremely small median pore throat radius r50. The seal has high supercritical (sc)CO2 displacement pressures, and it can hold back a vertical column of scCO2 of minimum ∼600 m providing a comfortable seal safety column-overhead. The current findings have relevant application to other depleted oil fields and saline aquifers with similar seals in the larger Central Graben area in the North Sea.

Sediment deformation triggered by underlying magma intrusion

Magma intrusion often uplifts and deforms overlying strata to produce forced folds. How the amplitude changes of forced folds through time reflect the transverse thickness changes in the deformed sedimentary strata, and can thus shed light on the processes driving deformation. For example, we expect the original morphology of intrusion-induced forced folds to reflect the shape and emplacement history of the underlying magma body. However, in sedimentary basins, the geometry of forced fold above ancient, buried magma body is a function of intrusion-induced uplift and post-emplacement compaction. Few studies have attempted to separate such syn- and post-intrusion deformation, meaning we poorly understand how burial-related compaction can modify forced fold geometry. This paper deals with the forced folds which are presently buried to depths of 2350–2600 m and caused by underlying magma intrusions, using high-resolution 3D seismic data and well data from the Pearl River Mouth Basin, northern South China Sea. The contribution of differential compaction (compaction-related deformation) was estimated by calculating sediment compaction curve, which allows the reconstruction of original syn-emplacement fold amplitude. This study shows that during magma emplacement, overlying strata greatly thin due to shear compaction. Moreover, burial can increase the amplitude of forced fold, improving their potential for capturing and storing fluids, and making it attractive site for hydrocarbon accumulation or carbon sequestration.

Human pericentromeric tandemly repeated DNA is transcribed at the end of oocyte maturation and is associated with membraneless mitochondria-associated structures

Most of the human genome is non-coding. However, some of the non-coding part is transcriptionally active. In humans, the tandemly repeated (TR) pericentromeric non-coding DNA—human satellites 2 and 3 (HS2, HS3)—are transcribed in somatic cells. These transcripts are also found in pre- and post-implantation embryos. The aim of this study was to analyze HS2/HS3 transcription and cellular localization of transcripts in human maturating oocytes. The maternal HS2/HS3 TR transcripts transcribed from both strands were accumulated in the ooplasm in GV-MI oocytes as shown by DNA–RNA FISH (fluorescence in-situ hybridization). The transcripts’ content was higher in GV oocytes than in somatic cumulus cells according to real-time PCR. Using bioinformatics analysis, we demonstrated the presence of polyadenylated HS2 and HS3 RNAs in datasets of GV and MII oocyte transcriptomes. The transcripts shared a high degree of homology with HS2, HS3 transcripts previously observed in cancer cells. The HS2/HS3 transcripts were revealed by a combination of FISH and immunocytochemical staining within membraneless RNP structures that contained DEAD-box helicases DDX5 and DDX4. The RNP structures were closely associated with mitochondria, and are therefore similar to membraneless bodies described previously only in oogonia. These membraneless structures may be a site for spatial sequestration of RNAs and proteins in both maturating oocytes and cancer cells.

Numerical simulation of calcite vein formation and its impact on caprock sealing efficiency – Case study of a natural CO2 reservoir

For the long-term CO2 geological storage, the evolution of the caprock sealing efficiency has received increasing attention. In this paper, the Huangqiao CO2 gas field in Jiangsu Province, China, where the calcite veins have been found in the lower part of mudstone caprock, is considered as a natural analogue site for CO2 geological sequestration (CCS). To ascertain the dynamic formation process of calcite vein and its impact on the evolution of caprock sealing efficiency, a one-dimensional model was designed to represent the fractured reservoir-caprock system. Numerical simulations were performed using the multiphase reactive transport program TOUGHREACT. Sensitivity analyses of fracture permeability and calcite reaction rate were made. The simulation results illustrate that calcium bicarbonate decomposes to form calcium carbonate and release CO2 from solution due to the pressure decay as the CO2-rich fluids migrate upwards along the fracture. The formation of calcite vein decreases the porosity and permeability significantly, which can enhance the integrity and sealing efficiency of caprock. Sensitivity analyses indicate that the formation of calcite vein is facilitated by the fast fluid flow, and calcite vein tends to form in the vicinity of reservoir-caprock interface under the slow-flow condition as the decrease of fracture permeability. Information currently available in Huangqiao CO2 gas field and some other area describing the formation of calcite vein shows good agreement with our simulation results. The mudstone caprock with fractures and faults is able to keep CO2 from leaking for a long time as the case of Huangqiao area. The methods and analyses presented here may be useful for CO2 storage sites with similar conditions.

Delineation of early Jurassic aged sand dunes and paleo-wind direction in southwestern Wyoming using seismic attributes, inversion, and petrophysical modeling

Moxa Arch is a potential site for carbon sequestration in the state of Wyoming, recognized by the US Department of Energy. In this paper, we primarily focus on improving our understanding of the geology, including lithofacies and depositional environment, of Nugget Sandstone-a potential carbon storage reservoir, by integrating results from three different techniques including seismic attributes, seismic inversion, and petrophysical modeling. The Nugget Sandstone formation is primarily an eolian sandstone, deposited in the early Jurassic and is present throughout southwestern Wyoming. Seismic attribute analysis indicates the presence of NW-SE trending elongated geological features in the Nugget Sandstone interval. Based on our seismic and well log analyses, we interpret these features to be eolian sand dunes, which is consistent with the previous publications indicating a general NE-SW paleo-wind direction at the time of the deposition of Nugget Sandstone and other equivalent formations in Wyoming and Utah. The petrophysical analysis indicates that the Nugget Formation is mostly composed of quartz; however, clay and evaporites such as anhydrite and halite are also present. The acoustic impedance, derived from well logs, indicates that high porosity dunal sandstones correspond to low impedance values whereas interdunal evaporites are characterized by high impedance values. Combined analysis of seismic attribute coherence and inverted P-impedance discriminates the dunal and interdunal deposits in 3D seismic data volume; the low coherence defines the extent of low impedance dunal deposits. Detailed analysis of the curvature attribute from the seismic data indicates a dominant paleo-wind direction of approximately N225°.

Azimuthal anisotropy analysis of multiazimuth P-wave seismic data — An example from the Rock Springs Uplift, Wyoming, USA

Our study area in Rock Sprigs Uplift, Wyoming, lies close to the carbon dioxide ([Formula: see text])-producing Jim Bridger power plant, and hence it is a good site for carbon sequestration. Two subsurface reservoirs within this area are being analyzed for their capability of long-term carbon storage. The presence and orientation of fractures within a reservoir and the associated seal govern the efficiency and long-term effectiveness of [Formula: see text] storage. The presence of natural fractures gives rise to seismic anisotropy that is related to the fracture orientation and density. This work analyzed P-wave multiazimuth seismic amplitude and well data from a potential carbon sequestration site for the anisotropy analysis. Using prestack waveform inversion, accurate azimuthal velocities were obtained for offset-to-angle transformation and to compute azimuthal angle gathers. These angle gathers were then stacked for each azimuth and analyzed for azimuthal anisotropy to estimate the fracture orientation and relative fracture density. Finally, by corroborating the results of the seismic azimuthal analysis with well data, it was confirmed that the results from the azimuthal analysis of the angle stacks are related to the fracture orientation and density.

Decision analysis for robust CO2 injection: Application of Bayesian-Information-Gap Decision Theory

Care must be taken when choosing a site for geological CO2 sequestration to ensure that the CO2 remains sequestered for many years, and that the environment is not harmed. Making a decision between sites for sequestration is not without its challenges because, as in the case of many subsurface problems, there are a lot of uncertainties. A method for making decisions under various types and severities of uncertainties, Bayesian-Information-Gap Decision Theory (BIG DT), is coupled with a numerical multiphase flow model for CO2 injection. The framework is used to make a decision between two CO2 sequestration sites; data are collected during a test injection and are used by the framework to assess the robustness of each site against failure by either leakage or induced seismic activity. A discussion of how the data are used to decide on a site follows. The results show that at the two synthetic sites examined here, the one with the less leakage potential is preferred. This indicates that the potential for leakage is more prone to violate decision goals at these sites than the potential for overpressurization.

Field-based simulation of a demonstration site for carbon dioxide sequestration in low-permeability saline aquifers in the Ordos Basin, China

Saline formations are considered to be candidates for carbon sequestration due to their great depths, large storage volumes, and widespread occurrence. However, injecting carbon dioxide into low-permeability reservoirs is challenging. An active demonstration project for carbon dioxide sequestration in the Ordos Basin, China, began in 2010. The site is characterized by a deep, multi-layered saline reservoir with permeability mostly below 1.0 × 10−14 m2. Field observations so far suggest that only small-to-moderate pressure buildup has taken place due to injection. The Triassic Liujiagou sandstone at the top of the reservoir has surprisingly high injectivity and accepts approximately 80 % of the injected mass at the site. Based on these key observations, a three-dimensional numerical model was developed and applied, to predict the plume dynamics and pressure propagation, and in the assessment of storage safety. The model is assembled with the most recent data and the simulations are calibrated to the latest available observations. The model explains most of the observed phenomena at the site. With the current operation scheme, the CO2 plume at the uppermost reservoir would reach a lateral distance of 658 m by the end of the project in 2015, and approximately 1,000 m after 100 years since injection. The resulting pressure buildup in the reservoir was below 5 MPa, far below the threshold to cause fracturing of the sealing cap (around 33 MPa).

A preliminary site selection system for a CO2-AGES project and its application in China

Because of the high costs involved in CO2 sequestration in deep saline formations, it has been difficult for its widespread application in the short term. Recently, however, a new technology called “combined geothermal production–CO2 sequestration technology” has made the technique more attractive not only by increasing the CO2 storage capacity, but also by decreasing the operational costs, through the utilization of geothermal energy, either directly or for the purpose of producing electricity. A CO2-aided (or CO2-involved) geothermal extraction system (CO2-AGES) is presented, based on existing technologies and the new ideas of “combined geothermal production-CO2 sequestration” introduced in this paper. This system can be used to extract geothermal energy from sedimentary aquifer formations (low–medium temperature) at different stages. The purpose of this paper is to set up an evaluation system for selecting a suitable site for this CO2-AGES system. There are both similarities and differences in the procedure needed for selecting a site for a conventional pure CO2 sequestration and for this CO2-AGES system. Both are carried out at different scales, including basin, region and target formation scales. The biggest difference is the temperature gradient, which plays an opposite role in the two systems. By using the preliminary ranking and screening method presented in this paper, it can be shown that the Bohaiwan, Songliao and Qiangtang basins have the highest potential for the application of this CO2-AGES technology. However, if CO2 sequestration is considered alone, the Ordos, Tarim and Bohaiwan basins should be selected as the best three operational sites in China. While preliminary evaluation methods can provide some useful information on the selection of the best sites for the “combined geothermal production–CO2 sequestration technology”, more detailed work is still required because of the strong uncertainties that exist in the determination of the upper and lower boundaries for each indicator.

Monitoring CO2 Storage at Cranfield, Mississippi with Time-Lapse Offset VSP – Using Integration and Modeling to Reduce Uncertainty

Abstract A time-lapse Offset Vertical Seismic Profile (OVSP) data set was acquired as part of a subsurface monitoring program for geologic sequestration of CO2. The storage site at Cranfield, near Natchez, Mississippi, is part of a detailed area study (DAS) site for geologic carbon sequestration operated by the U.S. Dept. of Energy's Southeast Regional Carbon Sequestration Partnership (SECARB). The DAS site includes three boreholes, an injection well and two monitoring wells. The project team selected the DAS site to examine CO2 sequestration multiphase fluid flow and pressure at the interwell scale in a brine reservoir. The time-lapse (TL) OVSP was part of an integrated monitoring program that included well logs, crosswell seismic, electrical resistance tomography and 4D surface seismic. The goals of the OVSP were to detect the CO2 induced change in seismic response, give information about the spatial distribution of CO2 near the injection well and to help tie the high-resolution borehole monitoring to the 4D surface data. The VSP data were acquired in well CFU 31-F1, which is the ∼3200 m deep CO2 injection well at the DAS site. A preinjection survey was recorded in late 2009 with injection beginning in December 2009, and a post injection survey was conducted in Nov 2010 following injection of about 250 kT of CO2. The sensor array for both surveys was a 50-level, 3-component, Sercel MaxiWave system with 15 m (49 ft) spacing between levels. The source for both surveys was an accelerated weight drop, with different source trucks used for the two surveys. Consistent time-lapse processing was applied to both data sets. Time-lapse processing generated difference corridor stacks to investigate CO2 induced reflection amplitude changes from each source point. Corridor stacks were used for amplitude analysis to maximize the signal-to-noise ratio (S/N) for each shot point. Spatial variation in reflectivity (used to ‘map’ the plume) was similar in magnitude to the corridor stacks but, due to relatively lower S/N, the results were less consistent and more sensitive to processing and therefore are not presented. We examined the overall time-lapse repeatability of the OVSP data using three methods, the NRMS and Predictability (Pred) measures of Kragh and Christie (2002) and the signal-to-distortion ratio (SDR) method of Cantillo (2011) . Because time-lapse noise was comparable to the observed change, multiple methods were used to analyze data reliability. The reflections from the top and base reservoir were identified on the corridor stacks by correlation with a synthetic response generated from the well logs. A consistent change in the corridor stack amplitudes from pre- to post-CO2 injection was found for both the top and base reservoir reflections on all ten shot locations analyzed. In addition to the well-log synthetic response, a finite-difference elastic wave propagation model was built based on rock/fluid properties obtained from well logs, with CO2 induced changes guided by time-lapse crosswell seismic tomography ( Ajo-Franklin et al., 2013 ) acquired at the DAS site. Time-lapse seismic tomography indicated that two reservoir zones were affected by the flood. The modeling established that interpretation of the VSP trough and peak event amplitudes as reflectivity from the top and bottom of reservoir is appropriate even with possible tuning effects. Importantly, this top/base change gives confidence in an interpretation that these changes arise from within the reservoir, not from bounding lithology. The modeled time-lapse change and the observed field data change from 10 shotpoints are in agreement for both magnitude and polarity of amplitude change for top and base of reservoir. Therefore, we conclude the stored CO2 has been successfully detected and, furthermore, the observed seismic reflection change can be applied to Cranfield's 4D surface seismic for spatially delineating the CO2/brine interface.

Cobalt(II) sequestration on fungal biogenic manganese oxide enhanced by manganese(II) oxidase activity

We examined the ability of biogenic manganese oxide (BMO) formed in the cultures of a Mn(II) oxidizing fungus, Acremonium strictum strain KR21-2, to sequester Co(II) and found that the newly formed BMO effectively sequestered Co(II) under aerobic conditions with virtually no release of Mn(II). Under anaerobic conditions, smaller amounts of Co(II) were sequestered and a significant amount of Mn(II) was released. Similar trends were observed when the BMOs were poisoned with 50mM NaN3 or heated at 85°C for 1h. X-ray absorption near-edge structure spectroscopy and two-step extraction confirmed that oxidation of Co(II) to Co(III) occurs with BMOs with higher oxidation efficiency under aerobic conditions. These results demonstrate that BMOs can reoxidize Mn(II) through the Mn(II) oxidase associated with the BMO phase and can subsequently provide a new reaction site for Co sequestration. The ability of BMO to sequester Co(II) was also found to be long lasting in 20mM 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES) buffer (pH 7.0) containing no nutrients to maintain fungal growth, because sequential treatment of BMOs with the Co(II) solution every 24h for at least 8days led to Co(II) sequestration. In addition, Co accumulation in the solid phase was eventually 2.48-fold relative to the accumulation of Mn oxide (molar ratio). X-ray diffraction results suggest that the continuing Co(II) oxidation by newly formed BMOs results in the formation of heterogenite (β-CoOOH) aggregates. Assays using the concentrated Mn(II) oxidase crude solution showed that the preformed Mn oxide phase was important for further Mn(II) oxidation in coexisting Co(II). The fact that the coexisting Co(II) was less inhibitory to Mn(II) oxidation if the preformed Mn oxide phase was present suggests a possible electron path from Co(II) to the final electron acceptor O2 through BMO and Mn(II) oxidase in BMO/enzyme aggregation. These results suggest that fungal BMOs supporting Mn(II) oxidase activity can serve as an effective Co(II) sequestering material, without the need for additional nutrients.

Techno-economic optimization of IGCC integrated with utility system for CO2 emissions reduction—Maximum power production in IGCC

Environmental legislation, with its increasing pressure on the energy sector to control greenhouse gases, is a driving force to reduce CO2 emissions. In this paper, pre-combustion CO2 capture through integration of a site utility system with an integrated gasification combined cycle (IGCC) is investigated as an option to provide a compressed CO2-rich stream from a process site for sequestration. This work presents a two-step procedure for integration and optimization of a site utility system with an IGCC plant: (i) screening and optimization of IGCC plant performance parameters; (ii) integration and optimization of the utility system of the site with the IGCC plant. In the first step, an optimization approach applies the results of screening studies based on rigorous simulation of the IGCC. Having fixed the inlet fuel flow rate, the IGCC design parameters (including oxygen consumption, diluent flow rate and turbine exit pressure) are optimized for maximum power generation. Energy flows between the IGCC and CO2 compression train are considered. In the second step, the economic and operating performance of the utility system integrated with the IGCC plant are modeled and optimized for minimum operating cost to find the most appropriate level of integration. In a case study illustrating the approach, 94% of the fuel is gasified; additional power generation offsets the operating costs of pre-combustion CO2 capture.

Techno-economic assessment of hydrogen production from underground coal gasification (UCG) in Western Canada with carbon capture and sequestration (CCS) for upgrading bitumen from oil sands

This paper examines the techno-economic viability of hydrogen production from underground coal gasification (UCG) in Western Canada, for the servicing of the oil sands bitumen upgrading industry. Hydrogen production for bitumen upgrading is predominantly achieved via steam methane reforming (SMR); which involves significant greenhouse gas (GHG) emissions along with considerable feedstock (natural gas) cost volatility. UCG is a formidable candidate for cost-competitive environmentally sustainable hydrogen production; given its negligible feedstock cost, the enormity of deep coal reserves in Western Canada and the favourable CO2 sequestration characteristics of potential UCG sites in the Western Canadian sedimentary basin (WCSB). Techno-economic models were developed for UCG and SMR with and without CCS, to estimate the cost of hydrogen production including delivery to a bitumen upgrader. In this paper, at base case conditions, a 5% internal rate of return (IRR) differential between UCG and SMR was considered so as to account for the increased investment risk associated with UCG. The cost of UCG hydrogen production without CCS is estimated to be $1.78/kg of H2. With CCS, this increases to range of $2.11–$2.70/kg of H2, depending on the distance of the site for CO2 sequestration from the UCG plant. The SMR hydrogen production cost without CCS is estimated to be $1.73/kg of H2. In similar fashion to UCG, this rises to a range of $2.14 to $2.41/kg of H2 with the consideration of CCS. Lastly, for hydrogen production without CCS, UCG has a superior cost competitiveness in comparison to SMR for an IRR differential less than 4.6%. This competitive threshold rises to 5.4% for hydrogen production with CCS.

Estimating CO2 plume size: A correlation for site screening

Plume size is an important factor in the consideration of a site for CO2 sequestration. Flow model simulations are the accepted means of estimating plume size, but the development of geologic and numerical flow models requires a significant quantity of data, analyses and staff resources. These may not be readily available. Additionally, a proper geologic model should reflect all of the available rock and fluid properties and a general understanding of the dominant mechanisms influencing CO2 injection and movement in the injection interval. The time and resources required for flow model simulations can be substantial.During site screening, when multiple sites are being considered, rigorous modeling of the geology of a site may be impractical and cost prohibitive. In such a situation, a reliable correlation tool that would provide a comparative indication of plume size at different sites and provide a hierarchy of site choices for additional tests and analyses or for advanced geologic modeling would be desirable.A right circular cylinder was used with a range of Monte Carlo-derived storage efficiency factors to estimate CO2 plume size (lateral extent). The cylinder was described using net thickness and effective porosity. The storage efficiency factor included four displacement efficiency terms, which were areal, vertical, gravity, and microscopic displacement efficiency. For site screening, it was assumed that there was more certainty in thickness and porosity at a specific site than for basin-scale (regional) screening. Consequently, the correlations in this paper require the cumulative mass of injected CO2, net thickness, and effective porosity.The plume size correlations were compared with 13 flow model simulations where net thickness, cumulative CO2 injection, and permeability were varied. Plume size values obtained from the 13 models compared very well with the plume size values obtained from the right circular cylinder correlations. Additionally, the storage efficiency values from each model compared well with the storage efficiency values obtained using the Monte Carlo simulations. The method was applied to published data on the Sleipner CO2 storage field and gave relatively good results considering the elliptical shape of the Sleipner CO2 plume.