CO2-rich Conditions Research Articles

Preparation of MoSi2-particle reinforced Ni-W alloy coatings and their anti-corrosion behavior in CO2-saturated 3.5 % NaCl solution

In the process of oil and gas production, the use of Ni-W electroplated coatings as a protective layer for oil well tubing has been widely used. In this study, the effect of MoSi2 particles as reinforcing material on the properties of electrodeposited coatings was investigated in order to improve the resistance of Ni-W alloy deposits against CO2 corrosion. The purchased MoSi2 sample was subjected to detailed material characterization, including microscopic morphology, crystallographic properties, particle size distribution and dispersion in the plating solution. After the introduction of MoSi2 particles into the deposits, the diffuse phase strengthening mechanism improved the properties of alloy. By comparing the electrochemical behavior of 3.5 % NaCl solution in saturated CO2, it can be concluded that the composite coatings prepared have the best corrosion resistance when MoSi2 is added to the plating solution at 0.02 g/L. This study provides new horizons for the application of Ni-W coatings in CO2-rich environments or CCUS conditions.

Mechanical behaviour of sulphur-based Martian regolith concrete processed under CO2-rich conditions

Martian regolith holds promise as a potential construction material for future settlements on the planet's surface. However, the planet's predominantly CO2-rich atmosphere poses challenges that may impact the mechanical properties of regolith-based concrete materials. In this study, we explore the compressive and flexural characteristics of Martian regolith simulant concrete mixtures incorporating sulphur, processed under CO2-rich conditions. The results reveal that regolith simulant concrete mixtures containing 70 wt% sulphur exhibit a maximum flexural strength of 5.95 ± 0.25 MPa. Meanwhile, the highest compressive strength of 3.66 ± 0.25 MPa and elastic modulus of 9.57 ± 0.32 GPa are achieved with regolith simulant mixtures comprising 60 wt% sulphur. These findings offer crucial insights for the advancement of construction materials tailored for future Martian settlements.

Microstructural phase evolution and strength development of low-lime calcium silicate cement (CSC) paste incorporating ordinary Portland cement under an accelerated carbonation curing environment

Low-lime calcium silicate cement (CSC) is a CO2-reactive cement that utilizes the carbonation products of low- or non-hydraulic C2S, C3S2, and CS phases under H2O- and CO2-rich conditions. However, the reactivity and compressive strength of the CSC require further improvement. Therefore, this study aims to investigate the effects of blending ordinary Portland cement (OPC) as a reactive source into CSC on the initial reaction kinetics, phase evolution, and compressive strength development during carbonation curing. To assess the effects of blending CSC and OPC, CSC was substituted by OPC with the incremental ratio of 20 wt%. Notably, the CSC sample with 20 wt% OPC incorporation exhibited the highest compressive strength, which increased by up to 2.5 times compared to the pure CSC paste. Analysis of the microstructural phase evolution revealed that this significant increase in compressive strength was attributed to the strong mechanical interlocks between the rhombic CaCO3 crystals, which were reinforced by a substantial amount of vaterite.

Performance of Pozzolan-Based Reactive Magnesia Cement Mixes against Sulphate Attack

Reactive magnesia cement (RMC) has gained interest due to its lower production temperatures when compared to Portland cement. In this study, the performance of pozzolan-based RMC concrete samples against sulphate attack was examined. Cube samples, after being removed from their moulds, were stored in a CO2-rich environment to gain compressive strength. Information obtained from XRD showed the formation of Mg carbonates in different forms. The use of fly ash and slag in large volumes reduces the environmental impact of concrete, but the use of these components have been found to greatly affect the formation of Mg carbonates in RMC mixes. This is mainly due to their filler effects. The coexistence of Ca- and Mg-based products was found in the slag-RMC mixes. The concrete samples based on RMC underwent mass and strength losses when stored in a MgSO4 solution for up to 12 weeks. The removal of Mg from the microstructure of these samples was confirmed using SEM analysis. The use of the most widely used pozzolans at 50% by weight of the binder greatly affected the carbonation mechanism of the RMC mixes. This finding suggests that they should be limited in the design of Mg-based products that harden under CO2-rich conditions.

Mechanistic Interpretations and Insights for the Oxidative Dehydrogenation of Propane via CO2 over Cr2O3/Al2O3 Catalysts

Oxidative dehydrogenation (ODH) of alkanes using carbon dioxide as a soft oxidant has recently emerged as a potentially attractive alternative to steam cracking for the production of light olefins. To elucidate reaction pathways and their dependence on the operating conditions, CO2-assisted propane dehydrogenation over a redox-active Cr2O3/Al2O3 catalyst was examined in a packed bed reactor as a function of temperature, Cr2O3/CO2 feed ratio, and residence time. Previous ODH studies have largely focused on CO2-rich conditions with the aim of preventing coke formation. However, at T = 600 °C the present study finds that the use of propane-rich conditions (1 ≤ C3H8/CO2 ≤ 2.5) maximizes propylene production and selectivity while maintaining catalyst stability. It is postulated that the selective Mars van Krevelen dehydrogenation process is optimized at these ratios. Excess CO2 apparently promotes nonselective dehydrogenation and dry reforming pathways that generate additional CO, adversely impacting catalyst stability via the Bouduard reaction. This hypothesis is supported by complementary investigations of the reverse water gas shift reaction and thermodynamic analysis. The findings and methodology presented here are likely applicable to related ODH processes with other alkanes and redox-active catalysts.

Evaluation of the carbon sequestration potential of steel slag in China based on theoretical and experimental labile Ca

Mineral carbonation with steel slag reduces greenhouse gas emissions and steel slag stockpiles. The mineral carbonation potential of steel slag was investigated by comparing fresh and weathered steel slag. Brownmillerite was discovered to be the most abundant inactive Ca-bearing mineral in steel slag, and the theoretical labile Ca was calculated using this information. The experimental labile Ca was studied using flow-through and batch experiments at ambient and CO2-rich conditions; the theoretical and experimental labile Ca agree well and are both at around 80%, indicating high mineral carbonation reactivity. The experimental results are also well supported by PHREEQC modeling, charge balance, and mass balance. We discovered that each ton of steel slag can capture approximately 250 kg of CO2. Furthermore, 450 Mt CO2 could be directly captured via steel slag CO2 mineralization. We offer dependable experimental and analytical methods for evaluating the mineral carbonation potential of steel slag.

Early age properties of alkali-activated cement and class G cement under different saturation conditions in oil well applications

This experimental study evaluates the early-age properties of one-part alkali-activated cement (AAC) and class G cement (GC) under three subsurface curing conditions of water, brine, and carbon dioxide (CO2)-saturated water. The novel one-part AAC used in this study consist of fly ash and slag as the mineral precursors activated by a waste glass/sodium hydroxide-based solid alkali activator. The fresh and hardened properties of AAC and GC were characterised using rheology, strength, and microstructural tests. AAC showed relatively lower flow and setting time than GC under ambient conditions. Both the yield stress and plastic viscosity of AAC were reduced at elevated temperatures. AAC showed comparable strengths under water, higher strengths under brine, and lower strengths under CO2 saturation conditions compared to GC. Microstructural tests of GC evidenced the precipitation of chloride salt and leaching of Portlandite under brine conditions. A higher total porosity of AAC was reported with poorly crystalline calcium carbonate deposits under CO2 saturation. The early strength of one-part AAC should be improved by using suitable additives before their use for oil well-cementing, especially in CO2-rich conditions.

Introduction of cross-linking agents to enhance the performance and chemical stability of polyethyleneimine-impregnated CO2 adsorbents: Effect of different alkyl chain lengths

Polyethyleneimine (PEI)-functionalized silica-based CO2 adsorbents are well known to irreversibly form urea during the regeneration process at high temperatures and under CO2-rich atmospheric conditions. The formation of urea is a critical drawback that substantially reduces the cyclic performance of PEI-functionalized adsorbents. In this study, epoxy cross-linkers were introduced to PEI to suppress the formation of urea. Pristine PEI and epoxy cross-linked PEI were impregnated into mesostructured cellular foam silica using a dry impregnation method. In particular, epoxy cross-linkers with different alkyl chain lengths were used, and the effect of the alkyl chain length of the cross-linkers on the chemical stability and CO2 adsorption performance of adsorbents was scrutinized. The suppression of urea formation improved as the alkyl chain length of the cross-linkers increased. The adsorbent functionalized with epoxy cross-linked PEI exhibited an approximately three times higher working capacity (0.71 mmol g−1) than the adsorbent functionalized with pristine PEI (0.23 mmol g−1) after 40 rapid cycles comprising adsorption at 100 °C with 15% CO2 balanced by N2 for 10 min and regeneration at 130 °C with 100% CO2 for 5 min. It is believed that the alkyl chain of the cross-linkers acted as a spacer that could hinder the urea formation, enhancing the chemical stability and CO2 adsorption performance of PEI-functionalized adsorbents.

Geomechanical and petrographic assessment of a CO2 storage site: Application to the Acorn CO2 Storage Site, offshore United Kingdom

Extraction or injection of fluids within the subsurface causes fluctuations of fluid pressures and thus stress conditions. It is paramount to have knowledge of the geomechanical strength of a system’s lithologies, and the factors that control it, in order to maintain optimal conditions during extraction/injection. If the yield strengths of the reservoir or caprock are overcome, particularly in the near-wellbore region where stress is amplified, these fluctuations could potentially compromise the system, through compactional or dilatational failure. Here we have used a novel combination of methods to determine the geomechanical and petrographic properties of the reservoir and caprock lithologies to assess suitability of the proposed Acorn CO2 Storage Site, offshore north-east Scotland, for long-term injection and storage of CO2.The Acorn CO2 Storage Site has a highly porous and transmissible sandstone reservoir, with bulk mineralogy that will be stable under CO2-rich conditions, making it ideal for receiving at least 152 MT CO2 injected over ∼20 years and storage of >1000 years post-injection, as part of the ACT-Acorn Development Plan. However, due to the high porosity and low cementation of the sandstone reservoir, it has low yield strength and is vulnerable to disaggregation and porosity-reduction if injection rates are too high and stress/pressure conditions exceed their yield strength. The results presented here provide quantitative constraints on the porosity reduction expected should yield occur and place limits on CO2 injection rates. The shale caprock, with a high swelling clay content and very low permeability, present ideal Carbon Capture and Storage seal properties.

On the controls of mineral assemblages and textures in alkaline springs, Samail Ophiolite, Oman

Interactions between meteoric water and ultramafic rocks in the Oman Ophiolite generate waters of variable physicochemical characteristics. The discharge of these waters forms complex alkaline pool networks, in which mineral precipitation is triggered by mixing, evaporation, and uptake of atmospheric CO2. A systematic and co-localized sampling of waters and solids in two individual spring sites allowed us to determine the saturation state of a range of minerals and correlate them to the different water and precipitate types. We subdivided the waters of the spring sites into three distinctive types: i) Mg-type; moderately alkaline (7.9<pH<9.5), Mg2+–HCO3−-rich waters, ii) Ca-type; hyperalkaline (pH>11.6), Ca2+–OH−-rich waters, and iii) Mix-type; alkaline to hyperalkaline (9.6 < pH < 11.5) waters with intermediate chemical composition. We first report the occurrence of hydrated magnesium (hydroxy-) carbonate phases in Mg-type waters. Nesquehonite forms in these waters via evaporation and transforms into dypingite and hydromagnesite under CO2-rich conditions. In Ca-type waters, the coupling of atmospheric CO2 uptake with evaporation leads to the formation of a calcitic crystalline crust on the air-water interface. The crusts are aragonite- and brucite-bearing, where Mg-type and Ca-type waters discharge and vigorously mix at the same pool. Unlike the Mg-type and Ca-type waters, the pools of Mix-type waters host massive aragonite-dominated deposits due to high Mg/Ca ratio that favors the growth of aragonite over calcite. The hydrodynamics during mixing spatially control brucite precipitation and restrict its formation and accumulation around specific mixing zones, where a continuous supply of Mg of inflowing Mg-type waters takes place. Crystal morphologies record the effect on the values of supersaturation and supersaturation rates in the pools due to mixing processes, evaporation and CO2 uptake. In Ca-type waters, CO2 uptake and evaporation dictate the textural characteristics of calcite both in crystalline crusts and rock coatings. Textural evolution of aragonite from crystalline sheaves to spheroidal shapes underlines the different supersaturation rates of calcium carbonate crystallization in flocculent material of Mix-type waters. Geochemical models of mixing between Mg-type and Ca-type waters revealed the evolution of mineral saturation indices under various mixing proportions, and their relation to the observed mineralogy and geochemistry of the pool waters. The thorough documentation of mineral assemblages and crystal morphologies enabled us to provide a more detailed account of how water composition, mixing, and mineral precipitation co-evolve in the alkaline spring systems, where CO2 is sequestered.

Acceleration of hydrogen production during water-olivine-CO2 reactions via high-temperature-facilitated Fe(II) release

The effects of temperature on hydrogen (H2) production in the alteration of olivine [(Mg,Fe)2SiO4] have been investigated under both CO2-rich (0.5 mol/L NaHCO3) and CO2-free conditions at 225–300 °C. Under CO2-rich conditions, H2 production rates showed strong temperature dependence, where the rate drastically increased for ≥275 °C, while the rate in CO2-free conditions was less temperature-dependent. At 300 °C under CO2-rich conditions, the H2 generation rate was 3 times faster than that under CO2-free conditions, and a considerable amount of CO2 was simultaneously stored as magnesite [(Mg,Fe)CO3]. Increasing the temperature under CO2-rich conditions promoted olivine consumption, while suppressing both brucite [(Mg,Fe)(OH)2] formation and incorporation of Fe(II) into secondary minerals, thus facilitating Fe(II) release and oxidation to produce H2. It has been revealed for the first time that H2 production during water-olivine-CO2 reactions is markedly accelerated via high-temperature-facilitated Fe(II) release.

NaHCO3-promoted olivine weathering with H2 generation and CO2 sequestration in alkaline hydrothermal system

Hydration of Fe(II) bearing minerals, such as olivine ((Mg,Fe)SiO4), potentially generate hydrogen (H2). However, because of the low Fe(II) dissolution rate, the H2 production rate is usually low. We have recently proposed a novel system to promote H2 production and simultaneous CO2 storage in hydrothermal conditions via NaHCO3-enhanced olivine weathering. The present study reports the role of NaHCO3 on both H2 production from olivine hydration and on minerals generations on laboratory experiments in CO2-rich (0.5 mol/L NaHCO3) and CO2-free hydrothermal conditions at pH range of 8-11. The highest H2, HCOOH yields and carbonation rate reached at the CO2-rich experiment with lower alkaline pH at 8.25. The addition of high concentration NaHCO3 decreased pH from 10.92 to 8.25, whereas olivine and brucite dissolutions were accelerated. Thus, more Fe(II) was released from olivine and brucite, and H2 production was accelerated. At higher pH range, olivine dissolution was promoted, but brucite dissolution was suppressed in both CO2-rich and CO2-free conditions. This study suggests H2 production was promoted with the presence of HCO3−, but not the pH variation. The consumption of Fe(II)-bearing brucite was important in enhancing H2 production during olivine hydration process.

Enhanced hydrogen production with carbon storage by olivine alteration in CO2-rich hydrothermal environments

Here we report a novel experimental study on simultaneous hydrogen (H2) production and CO2 storage. A high concentration of NaHCO3 (source of CO2) is utilized to promote H2 generation from olivine (Mg,Fe)2SiO4) hydration, and then CO2 is reduced to formic acid (HCOOH) or sequestrated in magnesite (MgCO3) in a hydrothermal system. The effects of NaHCO3 concentration (0–1.0 mol/L) and initial pH (8–11) on H2 production and CO2 storage were experimentally lab-scale tested at 300 °C. Both reaction pathways and reaction rates changed with variation of the reaction conditions. Under CO2-rich conditions, olivine consumption was promoted with the absence of Fe(II)-bearing brucite (Mg,Fe(OH)2), by which more Mg and Fe ions were released. Thus, the production of H2 and carbonation processes were significantly accelerated. The highest H2 generation rate reached 3.13 mmol/kgolivine·h, which is more than 15 times higher than previously reported. The HCOOH yield was 129.1 mmol/kgolivine and magnesite ((Mg,Fe)CO3) generation reached a maximum of 19.2 wt% in 72 h. The enhancement of H2 production at lower pH is primarily attributed to the presence of HCO3−, rather than the pH changes caused by NaHCO3 addition. The system proposed here has significant potential to be applied at the field-scale.

Hydrotalcites and hydrated Mg-carbonates as carbon sinks in serpentinite mineral wastes from the Woodsreef chrysotile mine, New South Wales, Australia: Controls on carbonate mineralogy and efficiency of CO2 air capture in mine tailings

Carbon mineralisation of ultramafic mine tailings can reduce net emissions of anthropogenic carbon dioxide by reacting Mg-silicate and hydroxide minerals with atmospheric CO2 to produce carbonate minerals. We investigate the controls on carbonate mineral formation at the derelict Woodsreef chrysotile mine (New South Wales, Australia). Quantitative XRD was used to understand how mineralogy changes with depth into the tailings pile, and shows that hydromagnesite [Mg5(CO3)4(OH)2·4H2O], is present in shallow tailings material (<40 cm), while coalingite [Mg10Fe3+2(CO3)(OH)24·2H2O] and pyroaurite [Mg6Fe3+2(CO3)(OH)16·4H2O] are forming deeper in the tailings material. This indicates that there may be two geochemical environments within the upper ∼1 m of the tailings, with hydromagnesite forming within the shallow tailings via carbonation of brucite in CO2-rich conditions, and pyroaurite and coalingite forming under more carbon limited conditions at depth. Radiogenic isotope results indicate hydromagnesite and pyroaurite have a modern (F14C > 0.8) atmospheric CO2 source. Laboratory-based anion exchange experiments, conducted to explore stable C isotope fractionation in pyroaurite, shows that pyroaurite δ13C values change with carbon availability, and 13C-depleted signatures are typical of hydrotalcites in C-limited environments, such as the deep tailings at Woodsreef. Quantitative XRD and elemental C data estimates that Woodsreef absorbs between of 229.0–405.1 g CO2 m−2 y−1.

Double-Layer Structured CO2 Adsorbent Functionalized with Modified Polyethyleneimine for High Physical and Chemical Stability.

CO2 capture using polyethyleneimine (PEI)-impregnated silica adsorbents has been receiving a lot of attention. However, the absence of physical stability (evaporation and leaching of amine) and chemical stability (urea formation) of the PEI-impregnated silica adsorbent has been generally established. Therefore, in this study, a double-layer impregnated structure, developed using modified PEI, is newly proposed to enhance the physical and chemical stabilities of the adsorbent. Epoxy-modified PEI and diepoxide-cross-linked PEI were impregnated via a dry impregnation method in the first and second layers, respectively. The physical stability of the double-layer structured adsorbent was noticeably enhanced when compared to the conventional adsorbents with a single layer. In addition to the enhanced physical stability, the result of simulated temperature swing adsorption cycles revealed that the double-layer structured adsorbent presented a high potential working capacity (3.5 mmol/g) and less urea formation under CO2-rich regeneration conditions. The enhanced physical and chemical stabilities as well as the high CO2 working capacity of the double-layer structured adsorbent were mainly attributed to the second layer consisting of diepoxide-cross-linked PEI.

Ab Initio Thermodynamics of Hydrated Calcium Carbonates and Calcium Analogues of Magnesium Carbonates: Implications for Carbonate Crystallization Pathways

Formation of calcium carbonate and its hydrates are important for a wide variety of geological, biological, and technological concerns. Recent studies have determined that formation of anhydrous crystalline calcite, aragonite, and vaterite can involve a complex series of nonclassical pathways in which the hydrated polymorphs monohydrocalcite (CaCO3·H2O), ikaite (CaCO3·6H2O), and amorphous calcium carbonate (ACC) play key roles and in some instances are stable or metastable endproducts. The stages of nucleation and crystallization along these pathways are not well understood, nor is how what is learned in an aqueous environment transfers to CO2-rich conditions. In this work ab initio thermodynamics based on density-functional theory and experimental chemical potentials for H2O-rich and CO2-rich systems are used to determine the stability of calcium carbonate polymorphs as a function of environmental conditions. In water-saturated supercritical CO2, formation of ikaite and monohydrocalcite are both highly e...

Syngas production from ethanol dry reforming over Rh/CeO2 catalyst

Carbon dioxide reforming of ethanol over Rh/CeO2 catalyst was deeply investigated at different reaction temperatures of 450–700°C and reactant ratios (CO2/ethanol from 1 to 3) under atmospheric pressure. The obtained results indicated that Rh/CeO2 catalyst presented a promising activity and stability for syngas production from renewable bio-ethanol instead of conventional methane. Typically, CO2-rich conditions (CO2/ethanol=3) were favorable for reaction process and dynamic coke cleaning, which led to remarkably stable performance over 65h on stream. The strong redox capacity of CeO2 support might also accelerate CO2 activation and prevent the carbon accumulation over the catalyst surface. Additionally, tunable H2/CO ratios were available by changing the CO2/ethanol ratios. The results from characterization of samples before and after catalytic tests allowed to establish the relationship between textural properties and catalytic performance.

Quantification of CO2-cement-rock interactions at the well-caprock-reservoir interface and implications for geological CO2 storage

Wellbore integrity is a key risk factor for geological CO2 storage. A primary purpose of this study is to analyze the impacts of CO2 leakage through wellbore cement and surrounding caprock with a gap (annulus) in between. Key parameters for cement-CO2 interactions were verified with a cement core sample from the SACROC Unit exposed to CO2 for 30 years. These parameters and other data served as the basis of reactive transport model simulations. The case study example for this analysis is the Farnsworth CO2 enhanced oil recovery (EOR) unit (FWU) in the northern Anadarko Basin in Texas. Specific objectives of this study are: (1) to analyze impacts on wellbore integrity under CO2-rich conditions within an operational time scale; and (2) to predict mechanisms of chemical reactions associated with cement-CO2-brine interactions.Simulation results suggest that cement tortuosity and diffusion coefficient are the two most important parameters that dictate cement carbonation penetration distance. Portlandite (Ca(OH)2) reacts with CO2 and forms calcite, reducing porosity, in turn directly impacting CO2 leakage rates by infilling pathways. Simulated calcium-silicate-hydrate (CSH) degradation is limited, suggesting that a wellbore will maintain its integrity and structure under the considered conditions. Simulations also suggest that sulfate concentration <2500mg/L in the leaking brine would not cause monosulfate degradation. Without an existing fracture, CO2 will likely not enter the caprock, and the cement would not degrade accordingly. For the FWU specifically, the wellbore cement would likely keep its structure and integrity after 100 years. However, if a fracture exists at the cement-caprock interface, calcite dissolution in the limestone caprock fracture could occur and increase the fracture volume, a concern for caprock integrity.

Nucleobase and amino acid formation through impacts of meteorites on the early ocean

The emergence of life's building blocks on the prebiotic Earth was the first crucial step for the origins of life. Extraterrestrial delivery of intact amino acids and nucleobases is the prevailing hypothesis for their availability on prebiotic Earth because of the difficulties associated with the production of these organics from terrestrial carbon and nitrogen sources under plausible prebiotic conditions. However, the variety and amounts of these intact organics delivered by meteorites would have been limited. Previous shock–recovery experiments have demonstrated that meteorite impact reactions could have generated organics on the prebiotic Earth. Here, we report on the simultaneous formation of nucleobases (cytosine and uracil) found in DNA and/or RNA, various proteinogenic amino acids (glycine, alanine, serine, aspartic acid, glutamic acid, valine, leucine, isoleucine, and proline), non-proteinogenic amino acids, and aliphatic amines in experiments simulating reactions induced by extraterrestrial objects impacting on the early oceans. To the best of our knowledge, this is the first report of the formation of nucleobases from inorganic materials by shock conditions. In these experiments, bicarbonate was used as the carbon source. Bicarbonate, which is a common dissolved carbon species in CO2-rich atmospheric conditions, was presumably the most abundant carbon species in the early oceans and in post-impact plumes. Thus, the present results expand the possibility that impact-induced reactions generated various building blocks for life on prebiotic Earth in large quantities through the use of terrestrial carbon reservoirs.

Seasonal cycle of CO2 from the sea ice edge to island blooms in the Scotia Sea, Southern Ocean

The Scotia Sea region contains some of the most productive waters of the Southern Ocean. It is also a dynamic region through the interaction of deep water masses with the atmosphere. We present a first seasonally-resolved time series of the fugacity of CO2 (fCO2) from spring 2006, summer 2008, autumn 2009 and winter (potential temperature minimum) along a 1000km transect from the pack ice to the Polar Front to quantify the effects of biology and temperature on oceanic fCO2. Substantial spring and summer decreases in sea surface fCO2 occurred in phytoplankton blooms that developed in the naturally iron-fertilised waters downstream (north) of South Georgia island (54–55°S, 36–38°W) and following sea ice melt (in the seasonal ice zone). The largest seasonal fCO2 amplitude (ΔfCO2) of −159μatm was found in the South Georgia bloom. In this region, biological carbon uptake dominated the seasonal signal, reducing the winter maxima in oceanic fCO2 by 257μatm by the summer. In the Weddell–Scotia Confluence, the southern fringe of the Scotia Sea, the shift from wintertime CO2-rich conditions in ice covered waters to CO2 undersaturation in the spring blooms during and upon sea ice melt created strong seasonality in oceanic fCO2. Temperature effects on oceanic fCO2 ranged from ΔfCO2 sst of ~55μatm in the seasonal ice zone to almost double that downstream of South Georgia (98μatm). The seasonal cycle of surface water fCO2 in the high-nutrient low-chlorophyll region of the central Scotia Sea had the weakest biological control and lowest seasonality. Basin-wide biological processes dominated the seasonal control on oceanic fCO2 (ΔfCO2 bio of 159μatm), partially compensated (43%) by moderate temperature control (ΔfCO2 sst of 68μatm). The patchwork of productivity across the Scotia Sea creates regions of seasonally strong biological uptake of CO2 in the Southern Ocean.