Large-scale CO2 Sequestration Research Articles

Preparation activated tailings by pH swing process: Towards yielding cemented tailings backfill and in-situ CO2 mineralization

In-situ CO2 mineralization of tailings has shown great potential for large-scale CO2 sequestration, but its development is seriously limited by the low CO2 conversion rate. This study proposed an innovative pH swing process to produce activated tailings through magnesium extraction from raw tailings and subsequent leachate precipitation. By the combination of activated tailings and high-belite calcium sulfoaluminate cement, a new type of cemented activated tailings backfill (CATB) was developed. The results demonstrate that 82.33% of magnesium is extracted from raw tailings and precipitates in the form of Mg(OH)2 serving as the dominating carbonation active phase during the pH swing process. Besides the aragonite forms in the carbonated cemented raw tailings backfill (CRTB), carbonated CATB also contains calcite, nesquehonite, and hydromagnesite. Substituting activated tailings for raw tailings led to the higher CO2 absorption capability (ranging from 8.88% to 14.17% with various binder-to-tailings ratios). These indicate that the activated tailings have a promising application scenario in large scale in-situ CO2 mineralization.

Sustainable energy solutions: Well retrofit analysis and emission reduction for a net-zero future in the Intermountain West, United States of America

To achieve net-zero emissions by 2050, we need economic means of sequestering carbon dioxide (CO2) and reducing greenhouse gas emissions (GHG). We analyze the sequestration potential of the Intermountain West (I-West) region, US, as a primary energy transition hub through analysis of wellbore retrofit potential and emission reduction in both fugitive gas abatement and flare gas. We selected the I-West region due to its abundant energy sources and oil and gas production legacy. Preliminary analysis hints that well retrofits can breathe new life into a well at a fraction of the cost of a new drill. With millions of potential candidates in the US, even a modest fraction (1% or less) suitable for retrofit could accelerate the shift to large-scale CO2 sequestration. Fugitive gas, the unintentional release of wellbore gases such as methane, is a significant emissions source. Through conservative analysis, it is estimated that wellhead leakage alone may account for 5 million tonnes of carbon dioxide equivalent (CO2e) emissions. We conclude by assessing the CO2 emissions from flaring, which is the burning of associated gas during well operations, conservative analysis indicates flaring contributes another 2 million tonnes of CO2 emissions to the region. We find that with targeted retrofit and better controls on emissions sources, the I-West region can make a significant impact in the nation's push to become net-zero. This study outlines economic feasibility and actionable items to achieve the critical reductions in emissions and increases in sequestration necessary to attain net zero.

Geophysical and Geochemical Evidence for a New Mafic Magmatic Province Within the Northwest Shelf of Australia

AbstractThe formation of mafic magmatic provinces are significant geological events that can drive mass extinctions and continental rifting and can influence basin evolution, petroleum prospectivity and mineralization. Buried magmatic provinces, however, are rarely identified and difficult to define. The Northwest Shelf of Australia contains large volumes of potentially interconnected mafic igneous material across several sedimentary basins. However, limited study and a lack of surface exposure have prevented detailed description and classification of these rocks. In this study, the distribution and composition of these mafic igneous rocks are described using an integrated geophysical and geochemical approach, which included over 10,000 km line length of 2D seismic data, well log data and chemical analysis of samples from 14 wells across the Browse, Roebuck, Canning and North Carnarvon basins. Using this combined data set, we demonstrate interconnectivity of buried mafic igneous rocks across the Northwest Shelf and calculate a total surface area exceeding 280,000 km2 and a cumulative minimum volume of ∼140,000 km3. Petrology and geochemistry of samples indicate they are basaltic and doleritic with alkaline and sub‐alkaline compositions and formed in a continental rift setting. Collectively, the igneous rocks meet the criteria for classification as a mafic magmatic province (MMP) and closely match the criteria required for classification as a large igneous province (LIP). Emplacement of the newly defined Northwest Shelf MMP may represent hotspot magmatism that could have initiated rifting of the Cimmerian Block from NW Australia during the Permian and could have potential for future, large scale CO2 sequestration and storage.

CO2 – brine – sandstone wettability evaluation at reservoir conditions via Nuclear Magnetic Resonance measurements

CO2-rock wettability is a key parameter which governs CO2 trapping capacities and containment security in the context of CO2 geo-sequestration schemes. However, significant uncertainties still exist in terms of predicting CO2 rock wettability at true reservoir conditions. This study thus reports on wettability measurements via independent Nuclear Magnetic Resonance (NMR) experiments on sandstone (CO2–brine systems) to quantify Wettability Indices (WI) using the United States Bureau of Mines (USBM) scale. The results show that CO2 (either molecularly dissolved or as a separate supercritical phase) significantly reduced the hydrophilicity of the sandstone from strongly water-wet (WI ≈ 1) to weakly water-wet (WI = 0.26), and associated with that the water-wetness of the rock for the two-phase systems. This was caused by additional protonation of surface silanol groups on the quartz, induced by carbonic acid. Capillary pressure and relative permeability curves and residual CO2 saturation were also measured; these results were compared with literature data, and general consistency was found. NMR T2 distribution measurements also demonstrated preferential water displacement in large pores (r > 1 µm) following scCO2 flooding, while no change was observed for smaller pores (r < 1 µm). These insights add confidence to the assessments of CO2-rock wettability and therefore reduce project risk. This work thus aids in the implementation of large-scale CO2 sequestration.

Hybrid Pd50-Ru50/MXene (Ti3C2Tx) nanocatalyst for effective hydrogenation of CO2 to methanol toward climate change control

Increase in atmospheric carbon dioxide (CO2) concentration has motivated researchers to develop large-scale CO2 sequestration and subsequent fuel conversion processes using various nanocatalysts. Herein, a 2D alloyed Pd50-Ru50 nanoparticles decorated MXene (Pd50-Ru50/MXene) nanocatalyst for efficient hydrogenation of CO2 into selective production of methanol is successfully fabricated and analyzed for its performance. HR-TEM and BET studies showed that hexagonal close-packed Pd50-Ru50 was formed with an average size of 3.2 nm and grown on the MXene nanosheets resulting in a higher specific surface area of 120 m2 g−1. Among the various catalysts studied, Pd50-Ru50/MXene showed a superior catalytic activity for hydrogenation of CO2 into selective production of CH3OH. The CO2 hydrogenation process involved the hydrolysis of NaBH4 (H2 facilitator) with ethylene glycol as CO2 capture agent. The Pd50-Ru50/MXene catalyst produced a higher CO2 conversion efficiency of 78% with a CH3OH yield of 76% (total turnover number based on Pd50-Ru50 = 2932) under mild conditions (pCO2 = 10 bar; T = 150 °C; t = 12 h). The recyclability test and morphological analysis of the spent Pd50-Ru50/MXene catalyst demonstrated its chemical stability even after prolonged usage for several hours indicating its promise for commercial-scale CO2 capture and renewable liquid fuel production.

Towards real-time monitoring: data assimilated time-lapse full waveform inversion for seismic velocity and uncertainty estimation

SUMMARYRapid development of time-lapse seismic monitoring instrumentations has made it possible to collect dense time-lapse data for tomographically retrieving time-lapse (even continuous) images of subsurface changes. While traditional time-lapse full waveform inversion (TLFWI) algorithms are designed for sparse time-lapse surveys, they lack of effective temporal constraint on time-lapse data, and, more importantly, lack of the uncertainty estimation of the TLFWI results that is critical for further interpretation. Here, we propose a new data assimilation TLFWI method, using hierarchical matrix powered extended Kalman filter (HiEKF) to quantify the image uncertainty. Compared to existing Kalman filter algorithms, HiEKF allows to store and update a data-sparse representation of the cross-covariance matrices and propagate model errors without expensive operations involving covariance matrices. Hence, HiEKF is computationally efficient and applicable to 3-D TLFWI problems. Then, we reformulate TLFWI in the framework of HiEKF (termed hereafter as TLFWI-HiEKF) to predict time-lapse images of subsurface spatiotemporal velocity changes and simultaneously quantify the uncertainty of the inverted velocity changes over time. We demonstrate the validity and applicability of TLFWI–HiEKF with two realistic CO2 monitoring models derived from Frio-II and Cranfield CO2 injection sites, respectively. In both 2-D and 3-D examples, the inverted high-resolution time-lapse velocity results clearly reveal a continuous velocity reduction due to the injection of CO2. Moreover, the accuracy of the model is increasing over time by assimilating more time-lapse data while the standard deviation is decreasing over lapsed time. We expect TLFWI-HiEKF to be equipped with real-time seismic monitoring systems for continuously imaging the distribution of subsurface gas and fluids in the future large-scale CO2 sequestration experiments and reservoir management.

Combining CSEM or gravity inversion with seismic AVO inversion, with application to monitoring of large-scale CO2 injection

A sequential inversion methodology for combining geophysical data types of different resolutions is developed and applied to monitoring of large-scale CO2 injection. The methodology is a two-step approach within the Bayesian framework where lower resolution data are inverted first, and subsequently used in the generation of the prior model for inversion of the higher resolution data. For the application of CO2 monitoring, the first step is done with either controlled source electromagnetic (CSEM) or gravimetric data, while the second step is done with seismic amplitude-versus-offset (AVO) data. The Bayesian inverse problems are solved by sampling the posterior probability distributions using either the ensemble Kalman filter or ensemble smoother with multiple data assimilation. A model-based parameterization is used to represent the unknown geophysical parameters: electric conductivity, density, and seismic velocity. The parameterization is well suited for identification of CO2 plume location and variation of geophysical parameters within the regions corresponding to inside and outside of the plume. The inversion methodology is applied to a synthetic monitoring test case where geophysical data are made from fluid-flow simulation of large-scale CO2 sequestration in the Skade formation. The numerical experiments show that seismic AVO inversion results are improved with the sequential inversion methodology using prior information from either CSEM or gravimetric inversion.

Turbulence simultaneously stimulates small- and large-scale CO2 sequestration by chain-forming diatoms in the sea

Chain-forming diatoms are key CO2-fixing organisms in the ocean. Under turbulent conditions they form fast-sinking aggregates that are exported from the upper sunlit ocean to the ocean interior. A decade-old paradigm states that primary production in chain-forming diatoms is stimulated by turbulence. Yet, direct measurements of cell-specific primary production in individual field populations of chain-forming diatoms are poorly documented. Here we measured cell-specific carbon, nitrate and ammonium assimilation in two field populations of chain-forming diatoms (Skeletonema and Chaetoceros) at low-nutrient concentrations under still conditions and turbulent shear using secondary ion mass spectrometry combined with stable isotopic tracers and compared our data with those predicted by mass transfer theory. Turbulent shear significantly increases cell-specific C assimilation compared to still conditions in the cells/chains that also form fast-sinking, aggregates rich in carbon and ammonium. Thus, turbulence simultaneously stimulates small-scale biological CO2 assimilation and large-scale biogeochemical C and N cycles in the ocean.

High-Performance Modeling of Carbon Dioxide Sequestration by Coupling Reservoir Simulation and Molecular Dynamics

Summary The present work describes a parallel computational framework for carbon dioxide (CO2) sequestration simulation by coupling reservoir simulation and molecular dynamics (MD) on massively parallel high-performance-computing (HPC) systems. In this framework, a parallel reservoir simulator, reservoir-simulation toolbox (RST), solves the flow and transport equations that describe the subsurface flow behavior, whereas the MD simulations are performed to provide the required physical parameters. Technologies from several different fields are used to make this novel coupled system work efficiently. One of the major applications of the framework is the modeling of large-scale CO2 sequestration for long-term storage in subsurface geological formations, such as depleted oil and gas reservoirs and deep saline aquifers, which has been proposed as one of the few attractive and practical solutions to reduce CO2 emissions and address the global-warming threat. Fine grids and accurate prediction of the properties of fluid mixtures under geological conditions are essential for accurate simulations. In this work, CO2 sequestration is presented as a first example for coupling reservoir simulation and MD, although the framework can be extended naturally to the full multiphase multicomponent compositional flow simulation to handle more complicated physical processes in the future. Accuracy and scalability analysis are performed on an IBM BlueGene/P and on an IBM BlueGene/Q, the latest IBM supercomputer. Results show good accuracy of our MD simulations compared with published data, and good scalability is observed with the massively parallel HPC systems. The performance and capacity of the proposed framework are well-demonstrated with several experiments with hundreds of millions to one billion cells. To the best of our knowledge, the present work represents the first attempt to couple reservoir simulation and molecular simulation for large-scale modeling. Because of the complexity of subsurface systems, fluid thermodynamic properties over a broad range of temperature, pressure, and composition under different geological conditions are required, although the experimental results are limited. Although equations of state can reproduce the existing experimental data within certain ranges of conditions, their extrapolation out of the experimental data range is still limited. The present framework will definitely provide better flexibility and predictability compared with conventional methods.

Treatment of produced water from an oilfield and selected coal mines in the Illinois Basin

If large-scale CO2 sequestration operations are implemented in oilfields or coal mines, large volumes of water (i.e., produced water) could potentially be generated that would need to be properly managed. In this work, produced water samples with total dissolved solids (TDS) values of 18,000–102,000mg/L (ppm) were collected from an oilfield, a coal-bed methane field, and a coal mine in the Illinois Basin of the United States and were treated by selected conventional pretreatment processes followed by a reverse osmosis desalination process. Pretreatment processes included coagulation by lime, ferric chloride, or aluminum sulfate; filtration by sand, walnut shells, anthracite coal, or microfiltration; and adsorption by organoclay, activated carbon, or ion-exchange resins. Selected pretreatment processes were sufficient for removing most of the contaminants, but the high sodium background of the high-TDS produced water (102,000ppm) limited the effectiveness of the ion-exchange pretreatment in removing scale-forming species. Reverse osmosis was a practical process for desalination of pretreated produced water samples tested (by reducing the TDS more than 96%) except for the high-TDS produced water. Reported bench-scale produced water treatment data might be beneficial for the design and operation of pilot-scale plants for treating produced waters with similar properties.

Ultraviolet modification of Chlamydomonas reinhardtii for carbon capture

Ultraviolet modification of Chlamydomonas reinhardtii for carbon capture Nikhil S Gopal,1 K Sudhakar2 1The Lawrenceville School, Lawrenceville, NJ, USA; 2Bioenergy Laboratory, Malauna Azad National Institute of Technology, Bhopal, India Purpose: Carbon dioxide (CO2) levels have been rising rapidly. Algae are single-cell organisms with highly efficient CO2 uptake mechanisms. Algae yield two to ten times more biomass versus terrestrial plants and can grow nearly anywhere. Large scale CO2 sequestration is not yet sustainable due to high amounts of nitrogen (N) and phosphate (P) needed to grow algae in media. Methods: Mutant strains of Chlamydomonas reinhardtii were created using ultraviolet light (2.2&ndash;3 K J/m2) and natural selection using media with 20%&ndash;80% lower N and P compared to standard Sueoka&#39;s high salt medium. Strains were selected based upon growth in media concentrations varying from 20% to 80% less N/P compared to control. Biomass was compared to wild-type control (CC-125) using direct counts, optical density dry weight, and mean doubling time. Results: Mean doubling time was 20 and 25 hours in the low N and N/P strains, respectively (vs 66 hours in control). Using direct counts, growth rates of mutant strains of low N and N/P cultures were not statistically different from control (P=0.37 and 0.70), respectively. Conclusion: Two new strains of algae, as well as wild-type control, were able to grow while using 20%&ndash;40% less N and P. Ultraviolet light-based modification of algae is an inexpensive and alternative option to genetic engineering techniques. This technique might make larger scale biosequestration possible. Keywords: biosequestration, ultraviolet, carbon sequestration, carbon capture, algae

Hydrology of the Forest City basin, Mid-Continent, USA: implications for CO2 sequestration in the St. Peter Sandstone

The central United States contain numerous coal-burning electric power plants that emit large amounts of CO2 for which a nearby suitable disposal site would be desirable. The results of a reconnaissance study reported here indicate that the St. Peter Sandstone in the Forest City basin has potential large-scale CO2 sequestration capacity, despite the basin’s overall relatively shallow depth. A three-dimensional stratigraphic model of the basin constructed from published well logs reveals that about 59 % of the St. Peter in the basin lies below a depth of 750 m, where CO2 would exist in a supercritical state for increased storage efficiency. Based on a porosity of 15 % and a storage efficiency factor of 5.4 %, the St. Peter in the basin could potentially sequester upto ~830 M tonnes of CO2, equating to upto 23,500 tonnes of CO2 per km2. A three-dimensional hydrologic model coupling groundwater flow, heat transport, and salinity transport provided insights into how CO2 might be transported in the basin. The results show a consistent pattern of predominantly southwestward groundwater flow in the northern part of the basin and predominantly eastward flow in the southern part of the basin. Groundwater average linear velocities are known with much less confidence, but in the St. Peter are mostly under 10 m/year and lack a strong vertical component. Mineralogical analysis shows the St. Peter to be composed almost entirely of quartz, suggesting that the St. Peter would be resistant to dissolution by CO2-enriched fluids and accompanying increases in porosity and permeability.

Residual trapping, solubility trapping and capillary pinning complement each other to limit CO2 migration in deep saline aquifers

Abstract We derive a theoretical model for the post-injection migration of a CO2 gravity current in a confined, sloping aquifer under the influence of residual trapping, solubility trapping, and capillary pinning. The resulting model consists of two coupled partial differential equations that describe the local thickness of the buoyant CO2 current and the thickness of the mound of brine saturated with dissolved CO2 as a function of time. We apply this model to a representative geological formation and provide estimates of the lifetime of the buoyant CO2 current and its maximum migration distance. Our analysis shows that residual trapping, solubility trapping, and capillary pinning complement each other in limiting the ultimate migration distance of CO2 gravity currents. The relative contribution of residual trapping, solubility trapping, and capillary pinning varies as a function of the injection volume. Our model can be used as a screening tool to evaluate the potential of deep saline aquifers for large-scale CO2 sequestration.

Can we Overcome Thermo-elastic Limits on CO2 Injection Rates in Horizontal Wells?

Large-scale CO2 sequestration projects will be prone to thermally induced fractures at injectors, because CO2 delivered by pipeline will enter the storage formation significantly cooler than reservoir temperature at typical large injection rates. Fracturing will influence plume migration and may be forbidden by regulators, so it is important to be able to predict its onset, especially since it occurs at pressures below the nominal fracture gradient. Reducing the injection pressure by constructing horizontal wells does not obviate this limitation. Based on fracture initiation criterion and heat transfer model between wellbore fluid and formation, this work provides a simple tool for evaluating this tendency and strategies to avoid it in horizontal wells.

Natural Gas Hydrates – A Review of the Resources Offshore Nigeria and around the Globe

Natural gas hydrates are ice-like materials which exist in permafrost regions and in the continental margins of oceans. They constitute a huge unconventional reservoir of natural gas around the globe including offshore Nigeria. The paper is a review of this important global resource with particular focus on the Nigerian deposits. The reasons for the interest on hydrates are discussed including the potential for the recovery of large quantities of methane, the climate change and ocean floor instability that may result from their dissociation. They may also be exploited for large-scale CO2 sequestration. The geographical distribution of hydrates deposits on earth, the thermodynamics of why they occur in those particular places and source of the methane gas that is eventually enchlathrated into hydrates are discussed. The natural gas in the Nigerian hydrate is essentially biogenic in origin and is almost pure methane (more than 99% methane). The hydrates exist in finely disseminated or massive aggregate forms within clay-rich sediment.

The Wabamun Area Sequestration Project (WASP): A multidisciplinary study of gigaton scale CO2 storage in a deep saline carbonate aquifer

The Wabamun Area Sequestration Project (WASP) is a major integrated, multidisciplinary study investigating the potential for large-scale CO2 sequestration (>20 Mt/yr) in a deep saline aquifer in the Wabamun Lake area, southwest of Edmonton, Alberta, Canada. Four large coal-fired power plants in the region produce on the order of 30 Mt CO2/yr, with the goal being to inject 1 Gt of these emissions over 50 years. The WASP project establishes the viability of the Devonian Nisku Formation carbonate for large-scale injection. Storage capacity is thought to be between 0.2 and 0.3 Gt using conventional drilling and reservoir pressure management methods, while the injection potential may be increased to >0.4 Gt using more advanced strategies. Geostatistical manipulation of existing well log data, core-derived rock properties, and available seismic data allowed construction of static geologic models that were used for simulation of CO2 injection into the target formation. Important considerations include interactions of dissolved H2S in the aquifer brine with injected CO2; the geomechanics of the target formation and caprock seal; and the likely need for pressure management schemes to optimize injectivity without compromising seal integrity or large-scale aquifer behaviour. Future work should include more complete and up-to-date sampling of the caprock seal and entire injection formation interval; better aquifer brine samples for geochemical analysis; and in-situ test programs for assessing the geothermal effects on fracturing and the leakage rates through abandoned well bore cements and casings.

Preparing for a carbon constrained world; overview of the United States regional carbon sequestration partnerships programme and its Southwest Regional Partnership

Abstract The Southwest Carbon Partnership (SWP), one of seven United States Department of Energy-funded Regional Carbon Sequestration Partnerships, has been tasked with assessing the CO 2 sequestration potential within the southwestern United States. Carbon dioxide is considered a ‘greenhouse’ gas and is emitted, in large volumes, by the burning of fossil fuels and other industrial processes. CO 2 capture from point source emitters and subsequent geological sequestration is being considered as a viable short- to intermediate-range mitigation option to combat the phenomena of global warming. Significant fossil fuel reserves and consumers exist within the seven member states of the SWP and, as such, the Partnership is dedicating a large amount of resources to the challenges posed by large-scale CO 2 sequestration. Three distinct phases of work have been or will be performed by the SWP: a Characterization Phase to identify carbon capture and sequestration potential; a Validation Phase to test small-scale field injection of CO 2 ; and a Deployment Phase to test commercial-scale field injection of CO 2 . Each phase presents challenges and opportunities to the refinement of the best approach to safe and efficient geological storage of CO 2 within the SW region of the United States.

Impact of intentionally injected carbon dioxide hydrate on deep‐sea benthic foraminiferal survival

AbstractSequestration of carbon dioxide (CO2) in the ocean is being considered as a feasible mechanism to mitigate the alarming rate in its atmospheric rise. Little is known, however, about how the resulting hypercapnia and ocean acidification may affect marine fauna. In an effort to understand better the protistan reaction to such an environmental perturbation, the survivorship of benthic foraminifera, which is a prevalent group of protists, was studied in response to deep‐sea CO2 release. The survival response of calcareous, agglutinated, and thecate foraminifera was determined in two experiments at ∼3.1 and 3.3 km water depth in Monterey Bay (California, USA). Approximately 5 weeks after initial seafloor CO2 release, in situ incubations of the live–dead indicator CellTracker Green were executed within seafloor‐emplaced pushcores. Experimental treatments included direct exposure to CO2 hydrate, two levels of lesser exposure adjacent to CO2 hydrate, and controls, which were far removed from the CO2 hydrate release. Results indicate that survivorship rates of agglutinated and thecate foraminifera were not significantly impacted by direct exposure but the survivorship of calcareous foraminifera was significantly lower in direct exposure treatments compared with controls. Observations suggest that, if large scale CO2 sequestration is enacted on the deep‐sea floor, survival of two major groups of this prevalent protistan taxon will likely not be severely impacted, while calcareous foraminifera will face considerable challenges to maintain their benthic populations in areas directly exposed to CO2 hydrate.

Risk Assessment for future CO2 Sequestration Projects Based CO2 Enhanced Oil Recovery in the U.S.

Abstract This paper is the first of a series that attempts to assess the possible health and safety risks associated with large scale CO2 sequestration in deep brine reservoirs. The approach is based on analysis of available data on the operational track record from CO2 transportation and injection associated with enhanced oil recovery (CO2-EOR) in the US. This paper is particularly concerned with identification of the main business risks facing a company engaged in geological sequestration. Such risks include both the operational risks of capturing, compressing, transporting and injecting CO2, as well as the risk of accidental, rapid CO2 release from wells (including an analysis of blow out data from CO2 injection wells, worked over wells as well as abandoned wells). Observations of the outcomes from accidents in real pipelines and CO2 injection wells in CO2-EOR projects provide the most concrete basis to predict the future safety of the above ground operations of CO2 sequestration in deep brine reservoirs.

Extracellular acid–base regulation during short-term hypercapnia is effective in a shallow-water crab, but ineffective in a deep-sea crab

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 334:1-9 (2007) - doi:10.3354/meps334001 Extracellular acid–base regulation during short-term hypercapnia is effective in a shallow-water crab, but ineffective in a deep-sea crab Eric F. Pane*, James P. Barry Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, USA *Email: epane@mbari.org ABSTRACT: Rising levels of atmospheric carbon dioxide could be curbed by large-scale sequestration of CO2 in the deep sea. Such a solution requires prior assessment of the impact of hypercapnic, acidic seawater on deep-sea fauna. Laboratory studies were conducted to assess the short-term hypercapnic tolerance of the deep-sea Tanner crab Chionoecetes tanneri, collected from 1000 m depth in Monterey Canyon off the coast of central California, USA. Hemolymph acid– base parameters were monitored over 24 h of exposure to seawater equilibrated with ~1% CO2 (seawater PCO2 ~6 torr or 0.8 kPa, pH 7.1), and compared with those of the shallow-living Dungeness crab Cancer magister. Short-term hypercapnia-induced acidosis in the hemolymph of Chionoecetes tanneri was almost uncompensated, with a net 24 h pH reduction of 0.32 units and a net bicarbonate accumulation of only 3 mM. Under simultaneous hypercapnia and hypoxia, short-term extracellular acidosis in Chionoecetes tanneri was completely uncompensated. In contrast, Cancer magister fully recovered its hemolymph pH over 24 h of hypercapnic exposure by net accumulation of 12 mM bicarbonate from the surrounding medium. The data support the hypothesis that deep-sea animals, which are adapted to a stable environment and exhibit reduced metabolic rates, lack the short-term acid–base regulatory capacity to cope with the acute hypercapnic stress that would accompany large-scale CO2 sequestration. Additionally, the data indicate that sequestration in oxygen-poor areas of the ocean would be even more detrimental to deep-sea fauna. KEY WORDS: CO2 · Deep sea · Physiology · Decapod crustacea · Acid–base regulation · Chionoecetes tanneri · Cancer magister Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 334. Online publication date: March 26, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.