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Cited by 657CO2 Sequestration and Geologic InteractionsClimate Change and GeoengineeringOcean Acidification Effects and Responses

Assessing ocean alkalinity for carbon sequestration

Open access
Renforth, Phil, Henderson, Gideon·2017·Reviews of Geophysics
DOI 10.1002/2016rg000533
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Abstract

Over the coming century humanity may need to find reservoirs to store several trillions of tons of carbon dioxide (CO 2 ) emitted from fossil fuel combustion, which would otherwise cause dangerous climate change if it were left in the atmosphere. Carbon storage in the ocean as bicarbonate ions (by increasing ocean alkalinity) has received very little attention. Yet recent work suggests sufficient capacity to sequester copious quantities of CO 2 . It may be possible to sequester hundreds of billions to trillions of tons of C without surpassing postindustrial average carbonate saturation states in the surface ocean. When globally distributed, the impact of elevated alkalinity is potentially small and may help ameliorate the effects of ocean acidification. However, the local impact around addition sites may be more acute but is specific to the mineral and technology. The alkalinity of the ocean increases naturally because of rock weathering in which >1.5 mol of carbon are removed from the atmosphere for every mole of magnesium or calcium dissolved from silicate minerals (e.g., wollastonite, olivine, and anorthite) and 0.5 mol for carbonate minerals (e.g., calcite and dolomite). These processes are responsible for naturally sequestering 0.5 billion tons of CO 2 per year. Alkalinity is reduced in the ocean through carbonate mineral precipitation, which is almost exclusively formed from biological activity. Most of the previous work on the biological response to changes in carbonate chemistry have focused on acidifying conditions. More research is required to understand carbonate precipitation at elevated alkalinity to constrain the longevity of carbon storage. A range of technologies have been proposed to increase ocean alkalinity (accelerated weathering of limestone, enhanced weathering, electrochemical promoted weathering, and ocean liming), the cost of which may be comparable to alternative carbon sequestration proposals (e.g., $20–100 tCO 2 −1 ). There are still many unanswered technical, environmental, social, and ethical questions, but the scale of the carbon sequestration challenge warrants research to address these.

AI snapshot

Written from the paper’s full text.

TL;DR

This review assesses increasing ocean alkalinity as a carbon sequestration route, storing CO₂ as bicarbonate and carbonate ions in the ocean. It finds potentially large capacity and costs that may be comparable to conventional mitigation, but major uncertainties remain about environmental impacts, carbonate precipitation feedbacks, and governance.

Key findings

  • The ocean already stores ≈38,000 Gt C, and the paper suggests it may be possible to sequester hundreds of billions to trillions of tonnes of C without surpassing post-industrial average carbonate saturation states in the surface ocean.
  • Adding Ca²⁺ or Mg²⁺ can sequester close to 2 moles of C per mole of cation; at 400 ppmv, S = 35, T = 17°C, η = 0.831, implying 0.83 moles of C stored per mole of H⁺ consumed, or 1.66 per mole of Ca²⁺ or Mg²⁺ added. Carbonate mineral dissolution gives smaller net uptake of 0.4 to 0.7.
  • If used as the sole destination for all anthropogenic CO₂ over 100–500 years, ocean alkalinity would increase from 2.3 mEq kg⁻¹ to ~3 mEq kg⁻¹, with calcite saturation between 5 and 7.5; average calcite saturation is unlikely to surpass pre-industrial levels, but localized impacts around addition sites may be more acute.
  • Proposed technologies include ocean liming, accelerated weathering of limestone, electrochemical splitting, and enhanced weathering; the paper reports costs/energy broadly comparable to alternatives, e.g. 1–10 GJ tCO₂⁻¹ and $50–150 tCO₂⁻¹ in the conclusions, with the abstract citing $20–100 tCO₂⁻¹.

Methods

  • This is a review and synthesis of the inorganic ocean carbon sink, covering alkalinity chemistry, ocean carbon cycle processes, modeling studies, mineral-based technologies, environmental impacts, and regulation.
  • It draws on published literature, box models and spatially resolved models (e.g. 3-box, Paquay and Zeebe, Ilyina et al., Keller et al., Ferrer-González and Ilyina), technoeconomic comparisons, and proposed experimental scenarios in Table 2.
  • No new primary experiments or field data collection are reported; the analysis is narrative and comparative, with quantitative estimates taken from cited studies and model outputs.

Limitations

  • Stated: many technical, environmental, social, and ethical questions remain unanswered; research is needed to understand impacts and feasibility, and local impacts are specific to the mineral and technology used.
  • Stated: carbonate precipitation at elevated alkalinity is poorly constrained, reaction kinetics are poorly constrained, cost estimates are largely speculative, and monitoring may require years to detect alkalinity changes above background seasonal variability.
  • Evident: the review relies heavily on models and desk-top or bench-scale studies; upscaling to billions of tons CO₂ per year is described as a considerable challenge, and model assumptions such as instant complete olivine dissolution or uniform alkalinity addition limit real-world inference.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1002/2016rg000533

Cites

218 of 218 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 214 cited sources checked · 0 supported · 0 flagged

  • Findingnone given

    Dissolution of a mole of Ca2+ or Mg2+ sequesters close to 2 moles of carbon.

    “Dissolution of a mole of Ca 2+ or Mg 2+ sequesters close to 2 moles of C (see section 2).”
    Quote in the paperNot a substantial claim
  • Findingcitation

    In practice the uptake is 1.4 to 1.7 molecules because of the presence of some CO3 2-, a reduction of uptake efficiency by 15%-30%, depending on temperature, salinity and pCO2.

    “In practice the uptake is 1.4 to 1.7 molecules because of the presence of some CO3 2-, (i.e. a reduction of uptake efficiency, η, by 15% -30%), depending on temperature, salinity and pCO2 (equation 23; see supporting information for derivation [Dickson, 1990]).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Dickson, 1990

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  • Findingreasoning

    Fully compensating for present anthropogenic emission of 10 Gt C a-1 requires addition of 20 Gt Ca2+ a-1.

    “Addition of sufficient Ca 2+ to fully compensate for present anthropogenic emission of 10 Gt C a -1 therefore requires addition of 20 Gt Ca 2+ a -1 .”
    Quote in the paperSubstantial claim
  • Findingown data

    The increased alkalinity flux in the right-hand panels prevents the significant changes in atmospheric CO2 and ocean pH seen in the left-hand figures.

    “The increased alkalinity flux in the right hand panels prevents the significant changes in atmosphere CO2 and ocean pH seen in the left-hand figures.”
    Quote in the paperSubstantial claim
  • Findingreasoning

    Even considering the surface ocean alone, the annual addition is less than a 0.3% increase in total Ca2+.

    “Even if considering the surface ocean alone this annual addition is less than a 0.3% increase in total Ca 2+ .”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. 180
  • May combine two claims. 129

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingcitation

    A solution:gas flow ratio of 8 was sufficient to capture 85% of the CO2 from a 10% gas at 1 atm.

    “He showed that a solution:gas flow ratio of 8 was sufficient to capture 85 % of the CO2 from a 10 % gas at 1 atm.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rau 2011

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  • May combine two claims.

    Findingreasoning

    Because the dissolution of CaCO3 releases a carbon atom, the net impact of such dissolution on CO2 uptake is smaller (0.4 to 0.7) than Ca2+ ions released from silicate weathering, but dissolving CaCO3 in seawater leads to uptake of CO2 from the atmosphere.

    “Because the dissolution of CaCO3 releases a C atom, the net impact of such dissolution on CO2 uptake is smaller (0.4 to 0.7) than Ca 2+ ions released from silicate weathering, but it is important to note the rather counter-intuitive fact that dissolving CaCO3 in seawater leads to uptake of CO2 from the atmosphere.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    For pCO2 = 400 ppmv, S = 35%, and T = 17°C, η = 0.831, implying that 0.83 moles of carbon are stored per mole of H+ consumed, or 1.66 per mole of Ca2+ or Mg2+ added to the ocean.

    “For pCO2 = 400 ppmv, S = 35 %, and T = 17°C, η = 0.831.This implies that 0.83 moles of carbon are stored per mole of H + consumed, or 1.66 per mole of Ca 2+ or Mg 2+ added to the ocean.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The model shows the scale of change in alkalinity in the surface and deep ocean resulting from alkalinity addition, and significant changes in lysocline depth arising from both anthropogenic carbon emission and alkalinity addition.

    “They also show the scale of change in alkalinity in the surface and deep ocean that results from this intervention, and the significant changes in lysocline depth that arise both from anthropogenic C emission, and from alkalinity addition.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The right-hand panels illustrate long-term effects on ocean saturation due to continued addition of alkalinity.

    “The right hand panels also illustrate the long-term effects on ocean saturation due to continued addition of alkalinity.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    Adding one mole of Ca2+ to a single-box ocean causes an increase in HCO3- and CO3 2- and the uptake of approximately 1.7 moles of CO2.

    “Assuming addition of Ca 2+ : adding one mole of Ca 2+ to a single-box ocean causes an increase in HCO3 - and CO3 2-and the uptake of ≈1.7 moles of CO2 (see section 2.3).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    Figure 8 shows the decrease in Ωcalcite that has already occurred due to anthropogenic CO2 emissions, and the further decrease expected as CO2 emissions continue.

    “This figure shows the decrease in Ωcalcite that has already occurred due to anthropogenic CO2 emissions, and the further decrease expected as CO2 emissions continue.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Recent work suggests sufficient capacity to sequester copious quantities of CO2 by increasing ocean alkalinity.

    “Yet, recent work suggests sufficient capacity to sequester copious quantities of CO2.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Renforth et al. [2013] suggest that ocean liming has similar energy and financial requirements to other air capture technologies.

    “In this context, the techno-economic feasibility of Ocean Liming was re-examined by Renforth et al., [2013], who suggest similar energy and financial requirements to other air capture technologies.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Renforth et al., 2013

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    Premisecitation

    The pledged contributions under the Paris Agreement are insufficient to prevent a 2°C temperature rise.

    “While 136 countries have ratified the agreement, the pledged contributions are insufficient to prevent a 2°C temperature rise [Rogelj et al. 2016].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rogelj et al. 2016

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Many future scenarios that keep climate change below 2°C do so not only by limiting the use of carbon, but by using technology to limit the impact of carbon use on the atmospheric concentration.

    “Many future scenarios that keep climate change below 2°C do so not only by limiting the use of carbon, but by using technology to limit the impact of carbon use on the atmospheric concentration.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Fuss et al., 2014

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    • cites McLaren 2012

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Spreading natural minerals on the land surface potentially allows the naturally corrosive chemistry in soil pore waters to be used to accelerate dissolution kinetics.

    “On one hand, spreading natural minerals on the land surface [reviewed by Hartmann et al., 2013] potentially allows the naturally corrosive chemistry in soil pore waters [Manning and Renforth 2013] to be used to accelerate dissolution kinetics.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Hartmann et al., 2013

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    • cites Manning and Renforth 2013

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Manning [2008] and Manning et al. [2013] suggest that solution chemistry in soil pore-waters may promote the precipitation of carbonate minerals, which has been demonstrated widely in anthropogenic soils.

    “Alternatively, Manning [2008] and Manning et al., [2013] suggest that solution chemistry in soil pore-waters may promote the precipitation of carbonate minerals, which has been demonstrated widely in anthropogenic soils [Renforth et al., 2009;Washbourne et al., 2015Washbourne et al., , 2012]].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Manning 2008

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    • cites Manning et al., 2013

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Both Kheshgi [1995] and Renforth et al. [2013] recognized that the production of lime from limestone may not be the most efficient process for increasing ocean alkalinity due to the large energy and CO2 burden of calcination.

    “However, both Kheshgi [1995] and Renforth et al., [2013] recognized that the production of lime from limestone may not be the most efficient process for increasing ocean alkalinity due to the large energy and CO2 burden of calcination.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Kheshgi 1995

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    • cites Renforth et al., 2013

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Chou et al. [2015] found lower carbon sequestration efficiencies of <50% in a two-stage AWL reactor.

    “Chou et al., [2015] investigated the operation of a two stage AWL reactor in which gas-liquid equilibration occurs prior to solid-liquid equilibration, and found lower carbon sequestration efficiencies of <50 %.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Chou et al., 2015

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  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Carbon storage in the ocean as bicarbonate ions by increasing ocean alkalinity has received very little attention.

    “Carbon storage in the ocean as bicarbonate ions (by increasing ocean alkalinity) has received very little attention.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The oceans contain approximately 38,000 Gt C, some 45 times more than the present atmosphere, and oceanic uptake has already consumed close to 40% of anthropogenic carbon emissions.

    “The oceans contain ≈38,000 Gt C, some 45 times more than the present atmosphere, and oceanic uptake has already consumed close to 40% of anthropogenic C emissions [Sabine and Tanhua, 2010].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Sabine and Tanhua, 2010

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Rau and Caldeira [1999] point out that the once-through cooling water consumed within some power stations equates to around 400 tons per ton of CO2 emitted, thus lowering the additional water requirements of AWL.

    “However, Rau and Caldeira [1999] point out that the once-through cooling water consumed within some power stations equates to around 400 tons per ton of CO2 emitted, thus lowering the additional water requirements of AWL.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rau and Caldeira 1999

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Caldeira and Rau [2000] suggested that the cost and environmental impact of AWL compares favorably to direct injection of CO2 in the deep ocean.

    “Caldeira and Rau [2000] suggested the cost and environmental impact compares favorably to direct injection of CO2 in the deep ocean.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Caldeira and Rau 2000

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    The local impact around ocean alkalinity addition sites may be more acute but is specific to the mineral and technology.

    “However, the local impact around addition sites may be more acute but is specific to the mineral and technology.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    The dissolution of minerals in a carbonic acid solution is relatively slow compared to stronger acids.

    “The dissolution of minerals in a carbonic acid solution is relatively slow compared to stronger acids.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The key limitation of AWL is the amount of water required, in which thousands of tons of seawater are needed per ton of CO2 sequestered.

    “The key limitation of this process is the amount of water required, in which thousands of tons of seawater are needed per ton of CO2 sequestered.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    The ocean naturally stores a very large quantity of carbon as dissolved carbonate and bicarbonate ions.

    “The ocean naturally stores a very large quantity of carbon as dissolved carbonate and bicarbonate ions”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Contacting carbonate minerals, seawater and power station flue gas (10% CO2 at 1 atm) would result in increased alkalinity in the effluent discharged back to the ocean.

    “Therefore, contacting carbonate minerals, seawater and power station flue gas (10 % CO2 at 1 atm), would result in increased alkalinity in the effluent discharged back to the ocean.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The representative concentration pathway that results in a likely temperature rise by 2100 below 2°C is RCP2.6, which suggests a cumulative emission of 880 Gt C.

    “The representative concentration pathway (RCP) that results in a likely temperature rise by 2100 below 2°C is RCP2.6 (Figure 1, see [van Vuuren et al., 2011]), which suggests a cumulative emission of 880 Gt C”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites van Vuuren et al., 2011

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The products of mineral dissolution, including increased alkalinity of rainwater, are transported to the ocean via runoff, rivers and shallow groundwater.

    “Notionally, the products of dissolution (including increased alkalinity of rainwater) are transported to the ocean via runoff, rivers and shallow groundwater.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Reactions in the open environment could have a time constraint on the order of years, 10^5-10^6 times longer than in engineered reactors, because of the much larger volume.

    “Reactions in the open environment could have a time constraint on the order of years (10 5 -10 6 times longer) because of the much larger volume.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The use of enhanced ocean alkalinity for carbon storage was first proposed by Kheshgi [1995].

    “The use of enhanced ocean alkalinity for C storage was first proposed by Kheshgi [1995].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kheshgi 1995

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Rau and Caldeira [1999] suggested that the dissolution of carbonate minerals exposed to waste flue gas CO2 and seawater (Accelerated Weathering of Limestone; AWL) could increase ocean alkalinity.

    “An alternative proposal was developed independently by Rau and Caldeira [1999], who suggested that the dissolution of carbonate minerals (e.g., CaCO3) exposed to waste flue gas CO2 and seawater (Accelerated Weathering of Limestone; AWL) as a means for increasing ocean alkalinity.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rau and Caldeira 1999

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    Premisecitation

    Rau (2011) provided results from a bench-scale experiment demonstrating high levels of CO2 sequestration largely as a function of the solution/gas volume ratio within the reactor.

    “Rau (2011) provided results from the operation of a bench-scale experiment, which demonstrated high levels of CO2 sequestration largely as a function of the solution/gas volume ratio within the reactor.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rau 2011

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Raising the partial pressure of CO2 to >5,000 μatm at a total pressure of 1 atm in contact with seawater creates the conditions in which carbonate minerals can spontaneously dissolve.

    “Raising the partial pressure of CO2 to >5,000 µatm (at a total pressure of 1 atm) in contact with seawater, creates the conditions in which carbonate minerals can spontaneously dissolve.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    When globally distributed, the impact of elevated alkalinity is potentially small and may help ameliorate the effects of ocean acidification.

    “When globally distributed, the impact of elevated alkalinity is potentially small, and may help ameliorate the effects of ocean acidification.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    The high energy costs of creating lime, and research focus on other forms of climate change mitigation, meant that the proposal was largely disregarded in the 1990s and early 2000s.

    “The high energy costs of creating lime, and research focus on other forms of climate change mitigation, has meant that the proposal was largely disregarded in the 1990's and early 2000's.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    These inorganic removal processes are distinct from the biological pump, in which organic material is produced and settles to the deep ocean, equating to a carbon flux of about 10 Gt C a-1.

    “It is important to note that these processes are distinct from”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Seawater in the surface ocean is supersaturated with respect to calcite by a factor of about 4 times (and aragonite by about 2.5 times), but the presence of other elements in seawater prevents inorganic precipitation of calcite in almost all oceanic settings.

    “Seawater in the surface ocean is supersaturated with respect to calcite by a factor of about 4 times (and aragonite by about 2.5 times), but the presence of other elements in seawater prevent inorganic precipitation of calcite in almost all oceanic settings [Berner 1975].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Berner 1975

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  • May combine two claims.

    Premisereasoning

    Many species of plant and animal have developed chemical approaches to overcome this limitation and precipitate CaCO3 as calcite or aragonite, leading to removal of Ca2+ and alkalinity from the surface ocean.

    “Many species of plant and animal have, however, developed chemical approaches to overcome this limitation and precipitate CaCO3 as calcite or aragonite, leading to removal of Ca 2+ (and alkalinity) from the surface ocean.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    If carbonate minerals dissolve on land and subsequently re-precipitate, there is no net effect on CO2, but if the Ca2+ reaches the ocean, the resulting increase in alkalinity leads to uptake of CO2.

    “If carbonate minerals (e.g., in limestone) dissolve on land and subsequently re-precipitate, there is no net effect on CO2, but if the Ca 2+ reaches the ocean, the resulting increase in alkalinity leads to uptake of CO2.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Biological activity also accelerates weathering.

    “Biological activity also accelerates weathering [e.g., Cockell 2011]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Cockell 2011

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    These weathering reactions are exothermic, but proceed slowly due to the significant kinetic limitation created by the strong bonding found in silicate minerals.

    “These weathering reactions are exothermic, but do proceed slowly due to the significant kinetic limitation created by the strong bonding found in silicate minerals.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Seawater has a high alkalinity (2.5 mEq kg-1) which, coupled to the large volume of the ocean, makes oceanic inorganic carbon by far the largest carbon reservoir in the ocean-atmosphere-biosphere system (approximately 42,000 Gt C).

    “Seawater has a high alkalinity (2.5 mEq kg -1 ) which, coupled to the large volume of the ocean, make oceanic inorganic C by far the largest C reservoir in the ocean-atmosphere-biosphere system (≈42,000 Gt C; [Ciais et al., 2014]).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Ciais et al., 2014

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  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Interpretationcitation

    If ocean HCO3- and CO3 2- were the sole repository of the carbon, then such an approach may be limited by the saturation state or environmental pH limits of the rain/river water.

    “If ocean HCO3 - and CO3 2-were the sole repository of the carbon, then others argue that such an approach may be limited by the saturation state or environmental pH limits of the rain/river water [Köhler et al., 2011].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Köhler et al., 2011

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The principle factors controlling weathering rate are the temperature, run-off, and the available surface area (i.e. the grainsize of the rock or mineral).

    “The principle factors controlling weathering rate are the temperature, run-off (to provide water to remove reaction products), and the available surface area (i.e. the grainsize of the rock or mineral [West et al., 2005]).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites West et al., 2005

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    These minerals break down slowly at the surface in a variety of reactions together referred to as chemical weathering.

    “These minerals break down slowly at the surface in a variety of reactions together referred to as chemical weathering.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Such alkalinity-induced changes in partitioning of carbon between atmosphere and ocean are thought to play an important role in controlling climate change on timescales of 1 ka and longer.

    “Such alkalinity-induced changes in partitioning of C between atmosphere and ocean are thought to play an important role in controlling climate change on timescales of 1 ka and longer [e.g., Zeebe 2012].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Zeebe 2012

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    On geological timescales, the removal flux of CO2 by silicate weathering is balanced by volcanic sources of CO2 from the Earth interior.

    “On geological timescales, this removal flux is balanced by volcanic sources of CO2 from the Earth interior.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    As alkalinity increases, more dissociation of carbonic acid occurs, and greater amounts of carbon are held in solution as HCO3- and CO3 2-.

    “As alkalinity increases, more dissociation of carbonic acid occurs, and greater amounts of C are held in solution as HCO3 -and CO3 2-(see Box 1 for details).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisereasoning

    On timescales longer than the circulation of the ocean (i.e. >1 ka), carbonate compensation alters the alkalinity of the whole ocean and acts as a natural buffer to offset changes in atmospheric CO2 created by imbalances elsewhere in the carbon cycle.

    “On timescales longer than the circulation of the ocean (i.e.>1 ka), carbonate compensation alters the alkalinity of the whole ocean and acts as a natural buffer to offset changes in atmospheric CO2 created by imbalances elsewhere in the C cycle.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Many silicate minerals were formed at high temperature and are unstable in the presence of water at the temperature and pressure conditions of the surface Earth.

    “Many silicate minerals were formed at high temperature and are unstable in the presence of water at the temperature and pressure conditions of the surface Earth.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S4 (based). May combine two claims.

    Interpretationreasoning

    There is nothing that warrants the exclusion of ocean alkalinity enhancement proposals from research and policy development, particularly considering that mineral weathering and ocean alkalinity production is the primary mechanism whereby nature will eventually consume and store anthropogenic CO2.

    “However, at this stage, there is nothing that warrants their exclusion from research and policy development, particularly considering that mineral weathering and ocean alkalinity production is the primary mechanism whereby nature will eventually consume and store anthropogenic CO2.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Other silicate minerals involve a full array of elements and produce a range of other endproducts, frequently including clay minerals, but are often characterized by the consumption of CO2.

    “Other silicate minerals involve a full array of elements and produce a range of other endproducts, frequently including clay minerals, but, as above, are often characterized by the consumption of CO2 (see Table 1 for examples).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Köhler et al. [2013] suggest that crushing and grinding to a diameter of 1 μm is necessary for olivine particles to dissolve within the mixed layer.

    “For instance, Köhler et al., [2013] investigated the direct addition of olivine particles to the surface ocean.As it is imperative that the added particles dissolve within the mixed layer, they suggest that crushing and grinding to a diameter of 1 µm is necessary.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Köhler et al., 2013

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Several inter-related processes are responsible for inorganic removal of CO2 from the atmosphere: weathering of silicate and carbonate rocks, reaction with carbonate sediments, and the alkalinity, or buffering capacity, of the ocean.

    “Several inter-related processes are responsible for inorganic removal of CO2 from the atmosphere: weathering of silicate and carbonate rocks, reaction with carbonate sediments, and the alkalinity, or buffering capacity, of the ocean.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The temperature dependence of weathering rate provides a long-term negative feedback on climate change to keep Earth's long-term climate in a relatively narrow range.

    “Nevertheless, such changes in the weathering/volcanism balance are fundamental in controlling the climate system, and the temperature dependence of weathering rate provides a long-term negative feedback on climate change to keep Earth's long-term climate in a relatively narrow range [Berner et al., 1983].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Berner et al., 1983

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The biological pump plays a critical role in the carbon cycle and is the focus of carbon-sequestration schemes involving ocean fertilization.

    “That process also plays a critical role in the C cycle and is the focus of C-sequestration schemes involving ocean fertilization [e.g., Wallace et al., 2010;Williamson et al., 2012].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Wallace et al., 2010

      Not checked in the free run.

    • cites Williamson et al., 2012

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisenone given

    Imbalances between the input and removal fluxes of alkalinity can result in changes in global oceanic alkalinity and therefore the capacity of the ocean to store carbon.

    “Imbalances between the input and removal fluxes of alkalinity can result in changes in global oceanic alkalinity and therefore the capacity of the ocean to store C.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisereasoning

    If the cations from silicate weathering are transported to the ocean they increase the alkalinity, and lead to transfer of CO2 to HCO3- and CO3 2-.

    “If, on the other hand, the cations are transported to the ocean they increase the alkalinity, and lead to transfer of CO2 to HCO3 -and CO3 2-.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    Remineralization of settling organic carbon at depth releases CO2 and decreases the pH of seawater.

    “Remineralization of settling organic C at depth releases CO2 and decreases the pH of seawater.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The total removal of CO2 from the atmosphere by natural weathering of silicate minerals may be as high as approximately 0.25 Gt C a-1 but is poorly constrained due to difficulty in separating fluxes from weathering silicates and carbonates, and may be significantly smaller.

    “The total removal of CO2 from the atmosphere by natural weathering of silicate minerals may be as high as ≈0.25 Gt C a -1 [Suchet and Probst 1995;Gaillardet et al., 1999;Hartmann et al., 2009] but is poorly constrained due to difficulty in separating fluxes from weathering silicates and carbonates, and may be significantly smaller [Liu et al., 2011].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Suchet and Probst 1995

      Not checked in the free run.

    • cites Gaillardet et al., 1999

      Not checked in the free run.

    • cites Hartmann et al., 2009

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given

    It is highly unlikely that any of the proposed ocean alkalinity enhancement approaches will form humanity's sole response to climate change.

    “It is highly unlikely that any of the above proposals (e.g., Figure 2) will form humanity's sole response to climate change.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Seasonal variation of up to 80-110 μeq kg-1 are also seen, resulting from changes in vertical mixing, riverine inputs, and especially primary production.

    “Seasonal variation of up to 80-110 µeq kg -1 are also seen, resulting from changes in vertical mixing [Lee et al., 2006], riverine inputs [Cai et al., 2010], and especially primary production [Wolf-Gladrow et al., 2007].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Lee et al., 2006

      Not checked in the free run.

    • cites Cai et al., 2010

      Not checked in the free run.

    • cites Wolf-Gladrow et al., 2007

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The deep ocean is characterized by dissolution of CaCO3 and an increase in alkalinity.

    “The deep ocean is characterized by dissolution of CaCO3 and an increase in alkalinity (Figure 3 B ;and Andersson [2014]).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Andersson 2014

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Ilyina et al.'s model, pH was generally returned to values similar to pre-industrial in much of the ocean, but was elevated around application regions, and calcite saturation increased to Ωcalcite approximately 20.

    “Similarly, pH was generally returned to values similar to pre-industrial in much of the ocean, but was elevated around application regions, and calcite saturation similarly increased (Ωcalcite ≈ 20).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Ilyina et al., [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    No single model is yet accepted to explain glacial-interglacial atmospheric pCO2 cycles, but it is clear that the CO2 removed from the atmosphere during glacials was stored in the ocean.

    “No single model is yet accepted to explain glacial-interglacial atmospheric pCO2 cycles, but it is clear that the CO2 removed from the atmosphere during glacials was stored in the ocean.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    Carbonate compensation at the PETM buffered a significant fraction of the change in CO2 and occurred on a timescale of less than 10,000 years.

    “This carbonate compensation buffered a significant fraction of the change in CO2 and occurred on a timescale of <10,000, short geologically, but still a slow response relative to human timescales.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisereasoning

    The major way in which alkalinity changes become important is changes in precipitation and particularly dissolution of CaCO3 (i.e. through carbonate compensation).

    “So the major way in which alkalinity changes become important is changes in precipitation and particularly dissolution of CaCO3 (i.e. through carbonate compensation).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Geochemical proxies have been developed to reconstruct past aspects of the ocean carbonate system, with two, measured in marine carbonates, seeing the greatest use: carbonate B isotope composition systematically reflects changing concentrations of B species with pH, and an empirical relationship is observed between carbonate B/Ca and the concentration of CO3 2-.

    “Geochemical proxies have been developed to reconstruct past aspects of the ocean carbonate system, with two, measured in marine carbonates, seeing the greatest use: carbonate B isotope composition systematically reflects changing concentrations of B species with pH, and an empirical relationship is observed between carbonate B/Ca and the concentration of CO3 2-.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Carbonate precipitation is a key feature in the physiology of a large number of ocean dwelling organisms.

    “Carbonate precipitation is a key feature in the physiology of a large number of ocean dwelling organisms [Addadi et al., 2006;Müller 2011].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Addadi et al., 2006

      Not checked in the free run.

    • cites Müller 2011

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    At the PETM, the large increase in CO2 in the ocean resulting from carbon release led to significant decreases in ocean pH and shoaling of the lysocline to increase ocean alkalinity.

    “At the PETM, the large increase in CO2 in the ocean resulting from C release led to significant decreases in ocean pH and shoaling of the lysocline to increase ocean alkalinity [Zachos et al., 2005].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zachos et al., 2005

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    The oceanic residence time of Ca2+ with respect to riverine input is greater than 1000 ka, on which timescale the balance between volcanic degassing and sedimentary removal of carbon becomes a dominant control.

    “The oceanic residence time of Ca 2+ with respect to riverine input is greater than 1000 ka (Figure 3A), on which timescale the balance between volcanic degassing and sedimentary removal of C becomes a dominant control.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    The models shown in Figure 8 demonstrate potential advantages to ocean saturation state of alkalinity addition.

    “The models shown on this figure demonstrate the potential advantages to ocean saturation state of alkalinity addition.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Some studies suggest increased risk to coral ecosystems when Ωaragonite falls below 3, corresponding to Ωcalcite approximately 4.5, in the open ocean surrounding reefs.

    “For instance, some studies suggest increased risk to coral ecosystems when Ωaragonite falls below 3 (Ωcalcite ≈ 4.5) in the open ocean surrounding reefs [Ricke et al., 2013].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Ricke et al., 2013

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    Spontaneous nucleation is strongly inhibited in seawater, and carbonate production is thought to be largely biologically controlled, although there is no estimate of the relative proportions.

    “However, spontaneous nucleation is strongly inhibited in seawater, and carbonate production is thought to be largely biologically controlled, although there is no estimate of the relative proportions.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In Ilyina et al.'s model, alkalinity increased to between 2.3 and 3.0 mEq kg-1 for most of the ocean, rising up to 5.5 mEq kg-1 in the North Atlantic and North Pacific where alkalinity addition was imposed.

    “Alkalinity increased, as expected, to between 2.3 and 3.0 mEq kg -1 for most of the ocean, but rising up to 5.5 mEq kg -1 in the north Atlantic and North Pacific where alkalinity addition was imposed.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Ilyina et al., [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationreasoning

    Such higher alkalinity would increase storage of CO2 in the ocean, and contribute to the decrease of atmospheric pCO2 known to be a significant cause of glacial cooling.

    “Such higher alkalinity would increase storage of CO2 in the ocean, and contribute to the decrease of atmospheric pCO2 known to be a significant cause of glacial cooling.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning

    Through studying natural changes in ocean alkalinity, it may be possible to constrain future changes in ocean chemistry from artificial changes in ocean alkalinity.

    “Through studying these natural changes in ocean alkalinity, it may be possible to constrain future changes in ocean chemistry from artificial changes in ocean alkalinity.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Olivine also contains iron as fayilite, Fe2SiO4, which may also fertilize biological activity.

    “Olivine also contains iron (as fayilite, Fe2SiO4), which may also fertilize biological activity.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several processes may have led to higher ocean alkalinity during the glacial periods of the Pleistocene.

    “Several processes may have led to higher ocean alkalinity during the glacial periods of the Pleistocene (e.g., the last glacial, 20 ka ago).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The simple one-box approach demonstrates the possibility of substantial uptake of carbon to the ocean with relatively small changes in the ocean, but also the scale of effort required to effect significant alkalinity addition.

    “This simple one-box approach demonstrates the possibility of substantial uptake of C to the ocean with relatively small changes in the ocean, but also the scale of the effort required to effect significant alkalinity addition.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    The resulting decrease in CaCO3 precipitation, and probable erosion and dissolution of old reefs, would increase global ocean alkalinity.

    “The resulting decrease in CaCO3 precipitation, and probable erosion and dissolution of old reefs, would increase global ocean alkalinity [Opdyke and Walker 1992].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Opdyke and Walker 1992

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    A small-number box model demonstrates the expectation that long-term alkalinity addition could compensate for anthropogenic carbon addition and could prevent the associated decrease in ocean pH.

    “Such a model demonstrates the expectation that long-term alkalinity addition could compensate for anthropogenic C addition, and could prevent the associated decrease in ocean pH.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    Changes in ocean circulation in the Atlantic leading to sluggish deep waters containing substantially more re-mineralized CO2 would lower deep-water pH to raise the lysocline, and thereby add alkalinity by dissolution of CaCO3.

    “Another process, but operating in the deep ocean, stems from changes in ocean circulation in the Atlantic leading to sluggish deep waters containing substantially more re-mineralized CO2.This would lower deep-water pH to raise the lysocline, and thereby add alkalinity by dissolution of CaCO3 [Boyle 1988;Sigman et al., 2010].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Boyle 1988

      Not checked in the free run.

    • cites Sigman et al., 2010

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given

    The handful of modeling studies investigating intentional increase of ocean alkalinity have been useful in broadly defining the relationship between carbon sequestration extent and the impact on the ocean carbonate system.

    “The handful of modeling studies investigating an intentional increase of ocean alkalinity have been useful in broadly defining the relationship between carbon sequestration extent and the impact on the ocean carbonate system.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In Ferrer-Gonzalez and Ilyina's model, despite uniform alkalinity addition, the ocean response was more marked in the Arctic, where pH climbed to 8.6 and Ωcalcite was approximately 10, and in the tropics where Ωcalcite was also high.

    “Despite imposing a uniform distribution of alkalinity addition, the ocean response was more marked in some regions, notably the Arctic, where pH climbed to 8.6 and Ωcalcite ≈ 10, and the tropics where Ωcalcite was also high.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Ferrer-Gonzalez and Ilyina [2016]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Lower glacial sea level would leave less continental shelf area for formation of carbonate reefs.

    “One such process, operating in the surface ocean, is that lower glacial sea level would leave less continental shelf area for formation of carbonate reefs.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Spatially resolved modeling indicates general success of alkalinity addition in generating ocean uptake of CO2, but highlights challenges imposed by extreme ocean changes such as elevated pH and carbonate saturation in regions of alkalinity addition.

    “As for the simple box models, this spatially-resolved modeling, indicates the general success of alkalinity addition in generating ocean uptake of CO2, but highlights clearly the challenges imposed by extreme ocean changes (e.g., elevated pH and carbonate saturation) in regions of alkalinity addition.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation

    Alkalinity changes may have played a role in the storage of CO2 in the ocean during glacials.

    “Alkalinity changes may have played a role in this storage (see Sigman and Boyle [2000] for a summary of glacial-interglacial pCO2 mechanisms).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Sigman and Boyle 2000

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Köhler et al.'s model predicts that while there is elevated alkalinity, there is a decrease in CaCO3 export and an increase in organic carbon export due to the fertilization effect of dissolved silica on diatoms.

    “Surprisingly, while there is elevated alkalinity, the model predicts a decrease in CaCO3 export and an increase in organic carbon export due to the fertilization effect of dissolved silica on diatoms.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Köhler et al., [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Barker et al. [2006] suggest that elevated organic carbon export associated with carbonate production at the surface may offset any CO2 release, either through sequestration of organic carbon into sediments or the interior ocean, or through enhanced dissolution of sediments from increased oxidation of organic carbon.

    “Barker et al., [2006] suggest that elevated organic carbon export associated with carbonate production at the surface, may offset any CO2 release, either through sequestration of organic carbon into sediments/interior ocean, or through enhanced dissolution of sediments from increased oxidation of organic carbon.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Barker et al., [2006]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    The residence time of dissolved inorganic carbon in the whole ocean is around 100 ka, which would effectively form a permanent storage reservoir on human timescales.

    “The residence time of dissolved inorganic carbon in the whole ocean is around 100 ka, which would effectively form a permanent storage reservoir on human timescales.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The long-term negative feedback is unlikely to completely reverse the effectiveness of alkalinity input because the fluxes of carbonate in the natural cycle are smaller than those required on human timescales.

    “However, it is unlikely to completely reverse the effectiveness of alkalinity input because the fluxes of carbonate in the natural cycle are smaller than those that those required on human timescales.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    Olivine dissolution increases total alkalinity with a molar 1:4 olivine/alkalinity ratio but also releases silicon.

    “Olivine (forsterite rich, Mg2SiO4) dissolution increases total alkalinity with a molar 1:4 olivine/alkalinity ratio) but also releases silicon.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    One study indicates higher alkalinity in the glacial ocean, though this is not observed in all ocean regions.

    “One such study indicates higher alkalinity in the glacial ocean [Rickaby et al., 2010], though this is not observed in all ocean regions [Zeebe and Marchitto 2010].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Rickaby et al., 2010

      Not checked in the free run.

    • cites Zeebe and Marchitto 2010

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    A deeper CCD will lead to an increase in the extent of sediment exposed to elevated saturation states, and notionally an increase in calcification and export, and thus increase the net removal of CaCO3 from the ocean.

    “A deeper CCD will lead to an increase in the extent of sediment exposed to elevated saturation states, and notionally an increase in calcification and export, and thus increase the net removal of CaCO3 from the ocean.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Phytoplanktonic calcifiers are responsible for a considerable proportion of particulate inorganic carbonate production in the surface ocean.

    “Phytoplanktonic calcifiers are responsible for a considerable proportion of particulate inorganic carbonate production in the surface ocean.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Initial studies by Pytkowicz [1965] suggest that highly elevated saturation states were required to spontaneously precipitate calcium carbonate from seawater, confirmed to be between Ωcalcite approximately 19 and 25 by Morse and He [1993].

    “But initial studies by Pytkowicz [1965] suggest that highly elevated saturation states were required to spontaneously precipitate calcium carbonate from seawater, confirmed to be between Ωcalcite ≈ 19 and 25 by Morse and He [1993].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Pytkowicz [1965]

      Not checked in the free run.

    • cites Morse and He [1993]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The hydrated calcium carbonate polymorph ikaite has been found to be stable at near zero temperatures.

    “Although, the hydrated calcium carbonate polymorph ikaite (CaCO3 .6H2O) has been found to be stable at near zero temperatures [Lu et al., 2012].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Lu et al., 2012

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Coral species that have little control on calcifying fluid chemistry generally follow an abiotic relationship between Ω and calcification rate.

    “Those that have little control generally follow an abiotic relationship between Ω and calcification rate (Figure 11, see below).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    The dissolution of carbonate minerals is an important component of the natural carbon cycle, at 0.1-0.2 Gt C a-1, which may be impacted by elevated alkalinity.

    “The dissolution of carbonate minerals is an important component of the natural carbon cycle (0.1 -0.2 Gt C a -1 ), which may be impacted by elevated alkalinity.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    The marine snow product has a defined PIC:POC ratio, typically 1:4.

    “The 'marine snow' product has a defined PIC: particulate organic carbon (POC) ratio (the ratio between particulate inorganic and organic carbon, typically 1:4).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Species of coral express a wide degree of control on the chemistry of their calcifying fluids.

    “Species of coral express a wide degree of control on the chemistry of their calcifying fluids.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    The rate of dissolution follows an abiotic relationship with Ω, which will likely be impeded by elevated alkalinity.

    “Generally, the rate of dissolution follows an abiotic relationship with Ω, which will likely be impeded by elevated alkalinity.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Although coral reefs constitute only a small proportion of the ocean, they are responsible for up to 50% of global CaCO3 production.

    “Although coral reefs constitute only a small proportion of the ocean they are responsible for up to 50% of the global CaCO3 production [Mackenzie and Andersson 2013;Smith and Kinsey 1976].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Mackenzie and Andersson 2013

      Not checked in the free run.

    • cites Smith and Kinsey 1976

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Corals are responsible for carbonate production, but are also a site for dissolution, for example through raised pCO2 from respiration.

    “While corals are responsible for carbonate production, they are also the site for dissolution (e.g., through raised pCO2 from respiration).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Schneider et al. [2011] found that alkalinity levels increased by around 0.1 and 0.05 mEq kg-1 for S. Herrmanni and H. leucospilota respectively, with 70-85% due to accelerated dissolution of carbonate and the remainder due to ammonia secretion.

    “In these experiments, alkalinity levels increased by around 0.1 and 0.05 mEq kg -1 for S. Herrmanni and H. leucospilota respectively (70-85 % due to the accelerated dissolution of carbonate, the remainder due to ammonia secretion).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Schneider et al., [2011]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Research investigating species and ecosystem response to ocean acidification has produced variable results.

    “As such, research investigating species and ecosystem response to ocean acidification has produced variable results [Ries et al., 2009].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Ries et al., 2009

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The response of corals to elevated saturation states is poorly constrained.

    “The response of corals to elevated saturation states is poorly constrained.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Increased biological carbon export and subsequent remineralization could decrease dissolved oxygen content in the water column or result in increased weathering in underlying sediments.

    “However, increased biological carbon export (and subsequent remineralization) could decrease the dissolved oxygen content in the water column (see section 7), or result in increased weathering in underlying sediments [Barker et al., 2006].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Barker et al., 2006

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Temperature is thought to control the mineralogy of the precipitating phase; in seawater, calcite nucleates at temperatures below 8°C, and above this aragonite is the precipitating phase.

    “Temperature is thought to control the mineralogy of the precipitating phase.In seawater, calcite nucleates at temperatures <8°C, and above this aragonite is the precipitating phase [Morse et al., 1997].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Morse et al., 1997

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Some coral species have evolved a capacity for buffering against lower Ω.

    “Whereas, some coral species have evolved a capacity for buffering against lower Ω [McCulloch et al., 2012].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites McCulloch et al., 2012

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Rickaby et al.'s experiments there was little change in particulate inorganic carbon production for Gephyrocapsa oceanica and C. pelagicus at pCO2 = 1,800 ppmv and Ωcalcite = 13, whereas variations in organic carbon fixation were detected.

    “In these experiments there was little change in particulate inorganic carbon production (for Gephyrocapsa oceanica and C. pelagicus at pCO2 = 1,800 ppmv, and Ωcalcite = 13), whereas variations in organic carbon fixation were detected.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rickaby et al., 2010

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Premisecitation

    Others suggest that carbonate precipitation on re-suspended sediment is the cause of whiting events.

    “Others suggest that carbonate precipitation on re-suspended sediment to be the cause of the whiting events [Bustos-Serrano et al., 2009;Morse et al., 2003].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Bustos-Serrano et al., 2009

      Not checked in the free run.

    • cites Morse et al., 2003

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Bach et al.'s results for Emiliania huxleyi decouple the impact of AT and [CO2] on inorganic carbon production, and suggest a plateau at around AT = 4.9 mEq kg-1.

    “By undertaking two experimental regimes in which pCO2 is manipulated while allowing pH to vary or maintaining it at a constant value, the results decouple the impact of AT and [CO2] on inorganic carbon production, and suggest a plateau at around AT = 4.9 mEq kg -1 .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Bach et al., [2011]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Increasing the concentration of magnesium relative to calcium is thought to increase the stoichiometric solubility constant of calcite, resulting in a decrease in the [Ca2+][CO3 2-] ion activity product.

    “Increasing the concentration of magnesium relative to calcium is thought to increase the stoichiometric solubility constant of calcite resulting in a decrease in the [Ca 2+ ] [CO3 2-] ion activity product (IAP, equation 25; adapted from Mucci and Morse [1983])”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Mucci and Morse [1983]

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Bijma et al. [2002] suggest a linear relationship between shell mass and [CO3 2-], expressed as SW = 29.5 + 0.051[CO3 2-].

    “Bijma et al., [2002] suggest a linear relationship between shell mass and [CO3 2-] (SW = 29.5 + 0.051[CO3 2-]), which can be expressed as a function that relates the change in relative growth rate (ΔR) to the change saturation state (%ΔR = 2.0 ΔΩcalcite, assuming constant [Ca 2+ ] = 10 mmoles kg -1 , current Ωcalcite = 4.8, pKsp = 5.62, current core-top shell mass of 38 µg).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Bijma et al., [2002]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    SO4 2- is present at concentrations of approximately 28 mmoles kg-1 in seawater, but substantially smaller concentrations are sufficient to impede carbonate formation.

    “SO4 2-is present at concentrations of approximately 28 mmoles kg -1 in seawater, but substantially smaller concentrations are sufficient to impede carbonate formation [Busenberg and Plummer 1985].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Busenberg and Plummer 1985

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The relationship in equation 26 is thought to be valid between phosphate concentrations of 1 and 100 μmoles kg-1.

    “This relationship is thought to be valid between phosphate concentrations of 1 and 100 µmoles kg -1 .”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    It is possible that a lower abiotic precipitation rate is presently masked by a larger biological signal.

    “However, it is possible that a lower abiotic precipitation rate is presently masked by a larger biological signal.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Walter and Morse [1985] determined the surface area of shallow seawater sediments to be between 0.1 and 24.0 m2 g-1, although samples were limited to size fraction greater than 37 μm.

    “Walter and Morse [1985] determined the surface area of shallow seawater sediments to be between 0.1 and 24.0 m 2 g -1 , although samples were limited to size fraction >37 μm, which would exclude smaller particles with a larger surface area to mass ratio.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Walter and Morse [1985]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    After dewatering, precipitated magnesite could be fed into a kiln/slaking system to produce brucite (Mg(OH)2), which could be used for ocean liming.

    “After dewatering, the precipitated magnesite could be fed into a kiln/ slaking system to produce brucite (Mg(OH)2) (equation 29), which could be used for ocean liming (equation 30).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Renforth and Kruger [2013]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Pokrovsky [1998] investigated the induction time required for spontaneous CaCO3 (aragonite) nucleation, which is proportional to the saturation state.

    “In extended duration experiments Pokrovsky [1998] investigated the induction time required for spontaneous CaCO3 (aragonite) nucleation, which is proportional to the saturation state (equation 27)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Pokrovsky [1998]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In equation 27, A is 7.207 and n is -3.784 for a [Mg2+]/[Ca2+] ratio of 5.3 at 20°C.

    “Where A is 7.207 and n is -3.784 for [Mg 2+ ]/[Ca 2+ ] ratio of 5.3 at 20°C (Figure 13).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Pokrovsky [1998]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Kheshgi [1995] first proposed adding lime (CaO) or portlandite (Ca(OH)2) to the surface ocean.

    “Kheshgi [1995] first proposed adding lime (CaO) or portlandite (Ca(OH)2) to the surface ocean.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kheshgi [1995]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Morse and He [1993] suggest that a calcite saturation state of greater than 19 is required for nucleation in seawater at 25°C.

    “Morse and He [1993] suggest that a calcite saturation state of >19 is required for nucleation in seawater at 25°C.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Morse and He [1993]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Renforth et al. [2013] also explored steam flash calcination and solar calcination, both of which could potentially reduce the costs of lime production to 4 and 2 GJ t CO2 respectively.

    “Renforth et al., [2013] also explored the use of steam flash calcination and solar calcination, both of which could potentially reduce the costs of lime production (4 and 2 GJ t CO2 respectively).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Renforth et al., [2013]

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    This could equate to a carbonate formation rate of between 0.01 and 14.3 Gt C y-1 in the surface ocean for a volumetric surface area between 10^-6.3 and 10^-3.2 m2 l-1.

    “This could equate to a carbonate formation rate of between 0.01 and 14.3 Gt C y -1 in the surface ocean (~300x10 6 km 2 , 60 m deep) for a volumetric surface area between 10 -6.3 and 10 -3.2 m 2 l -1 .”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Renforth and Kruger [2013] investigated the possibility of using forsterite-rich olivine (Mg2SiO4) as a feedstock for a coupled mineral carbonation ocean liming process.

    “Renforth and Kruger [2013] investigated the possibility of using forsterite rich olivine (Mg2SiO4) as a feedstock for a coupled mineral carbonation ocean liming process (Figure 15).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Renforth and Kruger [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Assuming the lower end member, abiotic precipitation would increase from 0.01 to 0.4 Gt C y-1 for an increase in Ωcalcite from its current value to 10, a 20% increase of carbonate production.

    “While biological carbonate precipitation depends on numerous factors, the abiotic precipitation follows a predicable relationship with Ω, and (assuming the lower end member) would increase from 0.01 to 0.4 Gt C y -1 for an increase in Ωcalcite from its current value to 10 (a 20% increase of carbonate production).”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The lower end member of the abiotic precipitation rate range is used for the projected increase in carbonate production.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Renforth et al. [2013] suggested that lime or dolime production in an oxy-fuel fired kiln with CCS, together with associated energy costs of raw material preparation and ocean disposal, would require between 6 and 10 GJ per net ton of CO2 sequestered.

    “They suggested that lime or dolime production in an oxy-fuel fired kiln with CCS, together with the associated energy costs of raw material preparation and ocean disposal, would require between 6 and 10 GJ per net ton of CO2 sequestered.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Renforth et al., [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    It is possible that spontaneous nucleation occurs in the surface ocean but is masked by a larger biological signal, and an increase in carbonate saturation state may accelerate these processes to have a significant impact on the overall carbon cycle.

    “Similar to seeded precipitation, it is possible that spontaneous nucleation occurs in the surface ocean, but is masked by a larger biological signal, and an increase in carbonate saturation state may accelerate these processes to have a significant impact on the overall carbon cycle.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    pKc* is thought to vary between 6.59 and 6.27 for [Mg2+]/[Ca2+] between 0 and 20.

    “pKc* is thought to vary between 6.59 and 6.27 for [Mg 2+ ]/[Ca 2+ ] between 0 and 20.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Pokrovsky [1998] suggests an induction time of around 2 months for Ωaragonite approximately 4, decreasing to around 1 week for Ωaragonite approximately 7, and 9 hours for Ωaragonite = 15.

    “Rather than a threshold saturation state to induce carbonate precipitation, Pokrovsky [1998] suggests an induction time of around 2 months for Ωaragonite ≈ 4 decreasing to around 1 week for Ωaragonite ≈ 7, and 9 hours for Ωaragonite = 15.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Pokrovsky [1998]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The evolved CO2 is recycled back into the mineral carbonation reactor.

    “The evolved CO2 is recycled back into the mineral carbonation reactor.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Renforth and Kruger [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Rau [2008] suggests addition of the high pH solution to the ocean as the mechanism for ocean alkalinity increase.

    “however Rau [2008] suggests the addition of the high pH solution to the ocean as the mechanism for ocean alkalinity increase.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rau [2008]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    This raw material requirement will increase once inefficiencies are accounted for.

    “This requirement will increase once inefficiencies are accounted for.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation

    It is possible that the portfolio of climate change mitigation technologies will contain considerably more than 7 or 19 different measures.

    “It is possible that the portfolio of climate change mitigation technologies will contain considerably more than 7 or 19 different measures”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    AWL could be relevant to air capture if applied to mitigation of CO2 from electricity production via biomass combustion.

    “AWL could be relevant to air capture if applied to mitigation of CO2 from electricity production via biomass combustion (i.e. an alternative storage mechanism for biomass energy carbon capture and storage).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Davies [2015] proposed an MgCl2 rich brine thermally decomposed into magnesium oxide and hydrochloric acid, requiring around 0.8 GJ electrical and 13 GJ thermal energy per t CO2 sequestered.

    “An approach was proposed by Davies [2015], in which an MgCl2 rich brine is thermally decomposed into magnesium oxide and hydrochloric acid, which requires around 0.8 GJ of electrical and 13 GJ of thermal energy per t CO2 sequestered.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Davies [2015]

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The energy requirements for the CaCO3 electrolyte method may be around 5 GJ(electrical) per t CO2 consumed, which to be CO2-emissions-negative must be powered by non-fossil-derived electricity.

    “The energy requirements for this may be around 5 GJ(electrical) per t CO2 consumed, which to be CO2-emissions-negative must be powered by non-fossil-derived electricity.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    A once-through seawater cooled, 500 MW plant pumps some 20 m3 s-1 of seawater, meaning around 6% of the plant's CO2 could theoretically be converted to seawater alkalinity without new pumping.

    “However, a once-through seawater cooled, 500 MW plant pumps some 20 m 3 s -1 of seawater, meaning that around 6% of the plant's CO2 could theoretically be converted to seawater alkalinity without new pumping.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The required seawater flow for a 500 MW coal plant is two orders of magnitude greater than the largest seawater reverse osmosis facilities (1-5 m3 s-1) and an order of magnitude greater than the largest sewage treatment works (e.g., Atotonilco el Alto, 35 m3 s-1).

    “which is, for example, two orders of magnitude greater than the largest seawater reverse osmosis facilities (1 -5 m 3 s -1 [Lior 2012]), and an order of magnitude greater than the largest sewage treatment works (e.g., the Atotonilco el Alto treatment plant, 35 m 3 s -1 [Mendoza 2012]).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Lior 2012 source

      Not checked in the free run.

    • cites Mendoza 2012

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The majority of cement production capacity was created in China, which had an annual compound production growth of 11.5% between 2000 and 2012.

    “The majority of this production capacity was created in China, which had an annual compound production growth of 11.5 % between 2000 and 2012 [USGS, 2014].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites USGS, 2014

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Pacala and Socolow [2004] chose annual emissions 'wedges' of 1 Gt C a-1 by 2050, each wedge mitigating around 14% of their business as usual CO2 emissions scenario, by upscaling known mitigation strategies.

    “For instance, Pacala and Socolow [2004] chose annual emissions 'wedges' of 1 Gt C a -1 by 2050 (each wedge mitigating around 14% of their business as usual CO2 emissions scenario) by upscaling known mitigation strategies.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Pacala and Socolow [2004]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationnone given

    While predicted financial and energy costs are variable and largely speculative, they suggest a level of competitiveness with 'conventional' methods of mitigation.

    “While the predicted financial and energy costs are variable, and at this stage largely speculative, they suggest a level of competitiveness with 'conventional' methods of mitigation.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Using produced Mg(OH)2 to increase ocean alkalinity notionally reduces overall cost by ~60-80% from additional CO2 draw-down per mole of base added.

    “and notionally reduces the overall cost by ~60 -80 % (from additional CO2 draw-down per mole of base added).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    The volume ratio between liquid and gas in the reactor has a strong influence on capture efficiency; too little water gives insufficient carbonate solubility to remove CO2 from the gas phase.

    “The volume ratio between liquid and gas in the reactor has a strong influence on capture efficiency, too little water in the reactor and there is insufficient carbonate solubility to remove CO2 from the gas phase.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    Seawater, natural or artificial brines could be the source of the electrolyte, which would negate the use of freshwater/desalination, although this would require treatment of H2 and Cl2 produced.

    “Seawater, natural or artificial brines could be the source of the electrolyte, which would negate the use of freshwater/desalination (although this would require the treatment of H2 and Cl2 produced)”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The chlor-alkali method has been used industrially for over 100 years to produce NaOH from seawater and brines.

    “This chlor-alkali method has been used industrially for over 100 years to produce NaOH from seawater and brines [Brinkmann et al., 2014].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Brinkmann et al., 2014

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Rau [2008] proposed an alternative method that uses a CaCO3 solution as the electrolyte, in which acid conditions produced around the anode dissolve CaCO3.

    “Rau [2008] proposed an alternative method that uses a CaCO3 solution as the electrolyte (Figure 18), in which acid conditions produced around the anode dissolve CaCO3.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rau [2008]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The Davies [2015] proposal is probably most suitable for treatment of desalination reject brines using solar energy, with global potential on the order of 1 Mt CO2 a-1.

    “As Davies [2015] suggests, this proposal is probably most suitable for the treatment of desalination reject brines using solar energy, the global potential of which is on the order of 1 Mt CO2 a -1 .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Davies [2015]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    The global cement industry extracts around 7 billion tons of raw material, which are ground and processed in a kiln, and the finished product (4.2 billion tons of cement a-1) is distributed locally.

    “The global cement industry extracts around 7 billion tons of raw material (mainly limestone, shale and/or clay), which are ground and processed in a kiln, and the finished product (4.2 billion tons of cement a -1 ), is distributed locally.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A minimum cost of <$10 per t CO2 for AWL is suggested via use of waste limestone and recycled once-through power plant cooling seawater.

    “While there is considerable potential for AWL, (Rau et al, [2007] suggests a minimum cost of <$10 per t CO2 via use of waste limestone and recycled once-through power plant cooling seawater)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rau et al, [2007]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given

    Assuming no efficiency losses, the energy requirements of electrolysis (1.8 GJ per t CO2) are completely met by the exergy destruction in the fuel cell and during acid neutralization (1.9 GJ per t CO2).

    “Assuming no efficiency losses, the energy requirements of electrolysis (1.8 GJ per t CO2) is completely met by the exergy ('available' energy) destruction in the fuel cell and during acid neutralization (1.9 GJ per t CO2).”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: There are no efficiency losses in electrolysis, fuel cell generation, and acid neutralization.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The wedge approach has conceptually defined the scale at which a mitigation technology should be able to achieve.

    “A consequence of the wedge approach is that it has conceptually defined the scale at which a mitigation technology should be able to achieve.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    For technologies that store CO2 in another part of the Earth system or in geological reservoirs, the capacity of the sink may be limited, and total storage requirements could be on the order of trillions of t of C.

    “This is particularly important when considering technologies that propose to store CO2 in another part of the Earth system (or in geological reservoirs), where the capacity of the sink may be limited, and the total requirements of storage could be on the order of trillions of t of C.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    In 1960 global cement production was around 0.3 Gt, in 2014 it was 4.2 Gt.

    “In 1960 global cement production was around 0.3 Gt, in 2014 it was 4.2 Gt.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Mg(OH)2 will likely need to be relatively pure for ocean liming to minimize biological impact from Fe and Si that may be present.

    “However, it is likely that the Mg(OH)2 will need to be relatively pure for ocean liming to minimize biological impact from Fe and Si that may be present.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In the CaCO3 electrolyte method, CO3 2- ions migrate towards the anode, protonate, and degas as CO2; Ca2+ cations migrate towards the cathode to produce a high pH Ca(OH)2 rich solution.

    “In such a solution the CO3 2-ions would migrate towards the anode, protonate, and degas as CO2.The Ca 2+ cations would migrate towards the cathode to produce a high pH Ca(OH)2 rich solution.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Rau [2008]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Humanity could emit between 880 (RCP 2.6) and ~thousands of Gt C by the end of the century.

    “Humanity could emit between 880 (RCP 2.6) and ~thousands of Gt C by the end of the century (section 1).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Many mitigation measures could well be more feasible at hundreds of Mt C a-1 scale, solving 1-5% of emission mitigation requirements.

    “many of them could well be more feasible at hundreds of Mt C a -1 scale (solving 1 -5 % of the emission mitigation requirements).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    71% of US power stations are located within 100 km of limestone deposits, and 200 are adjacent to the coast.

    “Langer et al., [2009] suggest that 71% of US power stations are located within 100 km of limestone deposits, and 200 are adjacent to the coast.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Langer et al., [2009]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Davis et al. [2013] used 19 wedges (9 to stabilize emissions and 10 to reduce to zero), although the wedge size remains the same.

    “Refining this approach to include projected efficiency improvements and the most up to date emission pathways, Davis et al., [2013] used 19 (9 to stabilize emissions and 10 to reduce to zero), although the wedge size remains the same.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Davis et al., [2013]

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given

    The olivine-based approach avoids the CO2 burden of decomposing a carbonate raw material, and MgCO3 decarbonates at a lower temperature than CaCO3.

    “The value of this approach is that it avoids the CO2 burden of decomposing a carbonate raw material, and MgCO3 decarbonates at a lower temperature than CaCO3.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The Revelle Factor has increased by around 15% on pre-industrial levels and will increase by 30-50% for a doubling of CO2.

    “The RF has increased by around 15 % on pre-industrial levels and will increase by 30-50 % for a doubling of CO2 [Hauck and Völker 2015].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Hauck and Völker 2015

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Almost 50% of historic anthropogenic CO2 emissions have been absorbed into the ocean.

    “Almost 50 % of historic anthropogenic CO2 emissions have been absorbed into the ocean [Sabine et al., 2004].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Sabine et al., 2004

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The first order impact of increasing [CO3 2-] and [HCO3-] in seawater is probably minimal.

    “The first order impact of increasing [CO3 2-] and [HCO3 -] in seawater is probably minimal.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Initial experiments suggested that a reduction in [CO3 2-] and therefore a reduction in the saturation state of carbonate minerals would lead to a reduction in carbonate formation of calcifying organisms.

    “Initial experiments [Riebesell et al., 2000] suggested that a reduction in [CO3 2-] and therefore a reduction in the saturation state of carbonate minerals, would lead to a reduction in carbonate formation of calcifying organisms.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Riebesell et al., 2000

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Infrastructure development during the industrial revolution expanded at about 5%, tractor production in the U.S. during the height of agricultural mechanization grew at 16%, post-war U.K. road infrastructure grew at 15%, and recent cement production grew at 12%.

    “For instance, infrastructure development during the industrial revolution expanded at about 5%, tractor production in the U.S. during the height of agricultural mechanization grew at a rate of 16%, post-war U.K. road infrastructure grew at a rate of 15%, and recent cement production grew at a rate of 12% ([DECC 2015;Hilbert and López 2011;Roth and Divall 2015;Renforth et al., 2011; USGS 2014]),”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites DECC 2015

      Not checked in the free run.

    • cites Hilbert and López 2011

      Not checked in the free run.

    • cites Roth and Divall 2015

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Harvey [2008] suggests a fleet of 3000 ships would be required to add 4 Gt of CaCO3.

    “For the addition of material to the ocean Harvey [2008] suggests a fleet of 3000 ships would be required to add 4 Gt of CaCO3.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Harvey [2008]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In marine aquaria, calcium reactors or Kalkwasser are widely used to prevent problematic decreases in pH caused by respiration and nitrification.

    “In marine aquaria, 'calcium reactors' (that cycle the aquarium water through a bed of crushed limestone), or 'Kalkwasser' (a solution of Ca(OH)2), are widely used to prevent problematic decreases in pH caused by respiration and nitrification.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Tullock and Earle-Bridges 2002

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given

    While upscaling transport and infrastructure could be challenging, upscaling the extraction and processing components would probably be more limiting.

    “While upscaling transport and infrastructure to cope with additional movement of material could be challenging, upscaling the extraction and processing components would probably be more limiting.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    It may be possible to extract Mg or Ca from a silicate mineral to create pure oxides or hydroxides, minimizing Si and Fe added to the ocean, but the technology to do this has yet to be developed.

    “It may be possible to extract the Mg or Ca from a silicate mineral (thus minimizing Si and Fe added to the ocean) to create pure oxides or hydroxides, however the technology to do this has yet to be developed.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Capacity of material transport over land is likely substantially more than global shipping capacity (10's of billions of tons).

    “Capacity of material transport over land is likely to be substantially more (10's of billions of tons).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    Given the abundance of mineral resource, it may be possible to optimize a technology to minimize transport requirements.

    “Given the abundance of mineral resource, it may be possible to optimize a technology to minimize transport requirements.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    If 50 Mt a-1 of spare capacity was available and convertible in existing industries, then the upscaling period would be 26 years for 1 Gt (based on 12% growth).

    “Hypothetically, if 50 Mt a -1 of spare capacity was available (and convertible) in existing industries, then the upscaling period would be 26 years for 1 Gt (based on 12% growth)”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The capacity for CO2 uptake is inversely proportional to the Revelle Factor, and the Revelle Factor is currently between 9 and 15.

    “The capacity for CO2 uptake is inversely proportional to RF, and is currently between 9 and 15 [Sabine et al., 2004].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Sabine et al., 2004

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    It is conceivable that in some confined environments, or under rapid application rates, the ambient pH may be sufficiently elevated to impact ocean biology.

    “It is conceivable that in some confined environments, or under rapid application rates, the ambient pH may be sufficiently elevated to impact ocean biology.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    If alkalinity addition were more rapid than the rate of CO2 gas to liquid transfer, there would be an increase in [CO3 2-] and [OH-] and a decrease in [CO2(aq)].

    “For instance, if alkalinity addition were more rapid than the rate of CO2 gas to liquid transfer, there would be an increase in [CO3 2-] and [OH -] and a decrease in [CO2 (aq)].”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Substantial research in the last 20 years has unearthed a complex relationship between ocean chemistry and ecosystem impact.

    “Substantial research has been undertaken in the last 20 years, which has unearthed a complex relationship between ocean chemistry and ecosystem impact [Fabry et al., 2008;Rost et al., 2008].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Fabry et al., 2008

      Not checked in the free run.

    • cites Rost et al., 2008

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    A mineral carbon sequestration technology may have an energy footprint of GJ per ton of material, and it may be possible to move material 10s or 100s of km over land and 1000s km over the ocean before significantly impacting the energy or carbon balance.

    “However, a mineral carbon sequestration technology may have an energy foot print of GJ per ton of material, it may be possible to move material 10s or 100s of km over land and 1000s km over the ocean before significantly impacting the energy or carbon balance of the technology.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Alkalinity is typically maintained between 3-6 mEq kg-1 in marine aquaria.

    “As such, alkalinity is typically maintained between 3-6 mEq kg -1 [Tullock and Earle-Bridges 2002].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Tullock and Earle-Bridges 2002

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    It is possible that a particle could sink out of the wake and dissolve in the less turbulent part of the mixed layer, creating areas of elevated alkalinity.

    “It is possible that a particle could sink out of the wake and dissolve in the less turbulent part of the mixed layer, creating areas of elevated alkalinity.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    With appropriate policy/market drivers, an expansion of >20% may be possible, but 10-15% may be more realistic, and consistent with historic industrial development.

    “With appropriate policy/market drivers, an expansion of >20 % may be possible, but 10-15 % may be more realistic, and consistent with historic industrial development.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Global shipping capacity is around 8 billion tons a-1, the utilization of which broadly follows fluctuations in international trade.

    “Global shipping capacity is around 8 billion tons a -1 (the utilization of which broadly follows fluctuations in international trade [UNCTAD 2012]).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites UNCTAD 2012

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    The consequences of this alkalinity increase on marine ecosystems is poorly understood, but it may provide a competitive advantage for calcifying organisms.

    “The consequences of this alkalinity increase on marine ecosystems is poorly understood, but it may provide a competitive advantage for calcifying organisms [Henderson et al., 2008].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Henderson et al., 2008

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    As suggested by modeling results in section 5, the globally distributed effects of an increase in ocean alkalinity would be elevated alkalinity, pH or Ωcalcite.

    “As suggested by modeling results in section 5, the globally distributed effects of an increase in ocean alkalinity would be elevated alkalinity, pH or Ωcalcite.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Renforth et al. [2013] suggest a fleet of 100 ships would be required to add 1 Gt of Ca(OH)2, largely due to solubility differences of the materials added.

    “Renforth et al., [2013] suggest a fleet of 100 ships would be required to add 1 Gt of Ca(OH)2 (the difference between these studies is largely a result of the solubility different of the materials added).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Renforth et al., [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Addition of alkalinity may induce transient elevated pH and/or lower [CO2(aq)] around the point of addition, except AWL, which would likely result in elevated [CO2(aq)] around the reactor outlet.

    “However, addition of alkalinity may induce transient elevated pH and/or lower [CO2 (aq)] around the point of addition (except AWL, which would likely result in elevated [CO2 (aq)] around the reactor outlet).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    There is considerable literature on the potential environmental impact of ocean fertilization, including increased production of N2O and CH4, lower dissolved oxygen, and nutrient driven ecosystem structural changes.

    “There is considerable literature on the potential environmental impact of ocean fertilization, including increased production of other more potent greenhouse gasses (N2O and CH4, [Fuhrman and Capone 1991]), lower dissolved oxygen, and nutrient driven ecosystem structural changes [Lampitt et al., 2008].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Fuhrman and Capone 1991

      Not checked in the free run.

    • cites Lampitt et al., 2008

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Increasing the pCO2 in equilibrium with the ocean increases [CO2(aq)] in solution and decreases [CO3 2-].

    “Increasing the pCO2 in equilibrium with the ocean increases [CO2(aq)] in solution, and decreases [CO3 2-].”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The recent accumulation of anthropogenic CO2 in the atmosphere has caused a decrease in surface ocean pH by 0.1 units.

    “The recent accumulation of anthropogenic CO2 in the atmosphere has caused a decrease in surface ocean pH by 0.1 units [Doney et al., 2009].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Doney et al., 2009

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Feng et al. [2016] suggest it may be possible to influence carbonate chemistry at a regional scale (e.g., South China Sea, the Great Barrier Reef).

    “Feng et al., [2016] suggest that it may be possible to influence carbonate chemistry at a regional scale (e.g., South China Sea, the Great Barrier Reef).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Feng et al., [2016]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Locke et al. [2009] suggest Crangon septemspinosa is sensitive to Ca(OH)2 addition, with 100% mortality for ~100 mg l-1 addition after 14 days.

    “Locke et al., [2009] suggest Crangon septemspinosa (a common shrimp species) is sensitive to Ca(OH)2 addition, with 100% mortality for ~100 mg l -1 addition after 14 days.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Locke et al., [2009]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The issue of marine geoengineering was recently addressed under the London Convention and London Protocol, treaties that regulate marine pollution from the dumping of wastes or other matter at sea.

    “Within this context, the issue of marine geoengineering was recently addressed under the London Convention and London Protocol [IMO 2003] (LC/LP), treaties that regulate marine pollution from the dumping of wastes or other matter at sea.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites IMO 2003

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    Although the amendment to the London Protocol is not yet in force, there remains a possibility that addition of alkalinity to the ocean could be regulated later as a placement of matter into the sea for marine geoengineering purposes.

    “Hence, though the amendment to the London Protocol is not yet in force, there remains a possibility that the addition of alkalinity to the ocean could be regulated at a later date as a placement of matter into the sea for marine geoengineering purposes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    The texts of the London Convention and Protocol exclude 'placement of matter for a purpose other than the mere disposal thereof, provided that such placement is not contrary to the aims of this Protocol' from the definition of dumping and would therefore apparently exclude the addition of alkalinity to the ocean from falling under these regimes.

    “The texts of these instruments excludes the 'placement of matter for a purpose other than the mere disposal thereof, provided that such placement is not contrary to the aims of this Protocol' from the definition of dumping and would therefore apparently exclude the addition of alkalinity to the ocean from falling under these regimes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Lime and hydrated lime have been used for almost a century to control invasive species in shellfish aquaculture.

    “Lime and hydrated lime have been used for almost a century to control invasive species in shellfish aquaculture (see Locke et al., [2009], and references therein).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Locke et al., [2009]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The 1982 United Nations Convention on the Law of the Sea lays down the legal framework for almost all matters relating to the seas and oceans.

    “The 1982 United Nations Convention on the Law of the Sea (LOSC [UN 1982]) lays down the legal framework for almost all matters relating to the seas and oceans.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites UN 1982

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Bivalves appear to have less control on the pH within their blood, and are possibly more sensitive to environmental changes, although control may be unnecessary for anything other than shell formation.

    “Bivalves appear to have less control on the pH within their blood, and are possibly more sensitive to environmental changes [Byrne and Dietz 1997], although control may be unnecessary for anything other than shell formation [Booth et al., 1984].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Byrne and Dietz 1997

      Not checked in the free run.

    • cites Booth et al., 1984

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Switzer et al. [2011] report that the addition of Ca(OH)2 was effective at controlling the invasive species Didemnum vexillum on commercial oysters.

    “For instance, Switzer et al., [2011] report that the addition of Ca(OH)2 was effective at controlling the invasive species of Didemnum vexillum (carpet sea squirt) on commercial oysters.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Switzer et al., [2011]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    The provisions of the LOSC are generally applicable, setting out territorial and economic claims of sovereign states, responsibilities for protection of the marine environment, marine scientific research, and dispute resolution.

    “Nevertheless, the provisions of the LOSC are generally applicable, setting out the territorial and economic claims of sovereign states, responsibilities for the protection of the marine environment, marine scientific research, and dispute resolution.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    Carbon storage as alkalinity falls within the definition of marine geoengineering.

    “On the face of it, carbon storage as alkalinity falls within the definition of 'marine geoengineering' as 'a deliberate intervention in the marine environment to manipulate natural processes, including to counteract anthropogenic climate change and/or its impacts, and that has the potential to result in deleterious effects, especially where those effects may be widespread, long-lasting or severe.'”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    Addition to coastal waters would fall under national or regional administration, whereas open ocean addition would require international oversight.

    “Addition to coastal waters would fall under national (or regional) administration, whereas open ocean addition would require international oversight.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    During the European Iron Fertilization Experiment, 7 tons of material was rapidly (within 1 day) spread over a 167 km2 patch (10-4.4 kg m-2), which over the following 14 days increased to 740 km2 (10-5 kg m-2).

    “During the European Iron Fertilization Experiment [Smetak et al., 2007], 7 tons of material was rapidly (within 1 day) spread over a 167 km 2 patch (10 -4.4 kg m -2 ), which over the following 14 days increased to 740 km 2 (10 -5 kg m -2 ).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Smetak et al., 2007

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Fish and mammals have developed renal compensation to excrete excess alkalinity, but prolonged exposure may have a chronic impact.

    “Fish and mammals have developed renal compensation in order to excrete excess alkalinity [Wood et al., 1999], but prolonged exposure may have a chronic impact.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Wood et al., 1999

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Locke et al. [2009] suggests that targeted lime addition to these environments may be able to minimize the impact of ocean acidification or improve water quality in anaerobic estuaries from excess nutrient load.

    “However, Locke et al. [2009] suggests that targeted lime addition to these environments may be able to minimize the impact of ocean acidification or improve water quality in anaerobic estuaries from excess nutrient load.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Locke et al. [2009]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The experiments (pH 8.5 to 8.8, pCO2 200 to 80 μatm, Ωcalcite = 7 to 13) demonstrated respiratory alkalosis possibly in response to lower levels of aqueous CO2.

    “The experiments (ranging from pH 8.5 to 8.8, pCO2 200 to 80 µatm, Ωcalcite = 7 to 13) demonstrated respiratory alkalosis possibly in response to lower levels of aqueous CO2.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Cripps et al., [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    Carbon storage as alkalinity, as a novel marine activity, is not explicitly addressed in the Convention.

    “Carbon storage as alkalinity, as a novel marine activity, is not explicitly addressed in the Convention.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Over the last 35 years ocean alkalinity data were collected as part of 42 cruises at 23,000 stations.

    “Over the last 35 years ocean alkalinity data were collected as part of 42 cruises at 23,000 stations (see CDIAC's ocean carbon data collection http://cdiac.ornl.gov/oceans/).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites CDIAC's ocean carbon data collection

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    The LOSC provides for the development of specific and detailed norms under the Convention for new and emerging marine activities.

    “The LOSC also provides for the development of specific and detailed norms under the Convention for new and emerging marine activities.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The addition of alkalinity to the ocean would likely operate under a complicated regulatory framework.

    “Therefore, the addition of alkalinity to the ocean would likely operate under a complicated regulatory framework.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    The amendments need ratification by two-thirds of Contracting Parties to come into force, which would provide a legally binding mechanism to regulate ocean fertilization, with the possibility of regulating other marine geoengineering activities in the future.

    “The amendments need to be ratified by 2/3rds of the Contracting Parties to come into force, which would provide a legally binding mechanism to regulate ocean fertilization, with the possibility of regulating other marine geoengineering activities in the future.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Fertilizing biological activity through the addition of iron and silicon (or increased export through ballasting) may increase dissolved oxygen in the photic zone, but reduce it in the waters below due to remineralization of exported organic carbon.

    “Fertilizing biological activity through the addition of iron and silicon (or increased export through ballasting) may increase dissolved oxygen in the photic zone, but reduce it in the waters below due to remineralization of exported organic carbon [Fuhrman and Capone 1991].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Fuhrman and Capone 1991

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Dissolved oxygen in the ocean is controlled by biogenic production at the surface, respirative removal from remineralization of sinking organic matter, ocean-atmosphere gas exchange, and circulation.

    “Dissolved oxygen in the ocean is controlled by a number of mechanisms including the biogenic production at the surface, respirative removal from remineralization of sinking organic matter, ocean-atmosphere gas exchange, and circulation [Joos et al., 2003].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Joos et al., 2003

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    It is possible that oxygen consumption from iron oxidation can be easily mitigated with suitable addition rates, and exploiting rapid dilution in the mixed layer.

    “It is therefore possible that oxygen consumption from iron oxidation can be easily mitigated with suitable addition rates, and exploiting rapid dilution in the mixed layer.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Ecosystems could be exposed to the risk of rapid changes in chemistry should the addition be halted.

    “Ecosystems could also be exposed to the risk of rapid changes in chemistry should the addition be halted.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Henderson et al. [2008] suggest that changes within the structure of primary producers could have important implications for the function of whole marine ecosystems.

    “Henderson et al., [2008] suggest that changes within the structure of these primary producers, could have important implications for the function of whole marine ecosystems.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Henderson et al., [2008]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Hypoxia alters benthic ecosystem structure and function, in which smaller taxa are more resilient than larger.

    “Hypoxia alters benthic ecosystem structure and function, in which smaller taxa are more resilient than larger [Levin et al., 2009].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Levin et al., 2009

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The collection of data from scientific cruises would likely form an important part of an ocean alkalinity monitoring system.

    “The collection of data from scientific cruises would likely form an important part of an ocean alkalinity monitoring system.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Interpretationreasoning

    The addition rate would have to be sufficient to overcome mixing of the local seawater with the ambient environment, but not sufficient to detrimentally impact ecosystems.

    “The addition rate would have to be sufficient to overcome mixing of the local seawater with the ambient environment, but not sufficient to detrimentally impact ecosystems.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The deleterious anthropogenic impact on dissolved oxygen is a concern and could increase the extent of oxygen minimum zones.

    “The deleterious anthropogenic impact on dissolved oxygen is a concern and could increase the extent of oxygen minimum zones [Stramma et al., 2008].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Stramma et al., 2008

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Transient reductions in aqueous CO2 caused by alkalinity addition could inhibit photosynthesis, and thus alter the function and structure of phytoplankton communities.

    “Therefore, transient reductions in aqueous CO2 caused by alkalinity addition could inhibit photosynthesis, and thus alter the function and structure of phytoplankton communities.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The scope of the London Convention and Protocol includes ocean fertilization activities because of significant risk that such placement would be contrary to the aims of both instruments.

    “scope of the London Convention and Protocol includes ocean fertilization activities' due to significant risk that such placement would be contrary to the aims of both the London Convention and the London Protocol.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Cripps et al. [2013] investigated the impact of Ca(OH)2 addition on Carcinus maenas.

    “In a single species experiment, Cripps et al., [2013] investigated the impact of Ca(OH)2 addition on Carcinus maenas (a globally distributed crab species).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Cripps et al., [2013]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The source of alkalinity may be derived from carbonate or silicate minerals.

    “The source of alkalinity may be derived from carbonate or silicate minerals.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Up-scaling these processes to have an impact on anthropogenic CO2 emissions, on the order of billions of tons CO2 per year, is a considerable challenge, as it is for mineral carbonation.

    “However, up-scaling these processes to have an impact on anthropogenic CO2 emissions (i.e.billions of tons CO2 a -1 ) is a considerable challenge (as it is for mineral carbonation).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Raised alkalinity in the ocean may change the rate of carbonate mineral production, both biogenic and abiological.

    “However, raised alkalinity in the ocean may change the rate of carbonate mineral production (both biogenic and abiological), but more experimental work is required to constrain this change.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    A range of techniques have been proposed for increasing ocean alkalinity, exploiting numerous reaction pathways.

    “A range of techniques have been proposed for increasing ocean alkalinity, which exploit numerous reaction pathways (Table 1).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Table 1

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    While some components of these processes already operate at a large scale, such as lime production, generally the overall technologies have not developed beyond desk-top technoeconomic assessment or bench scale laboratory work.

    “While some components of these processes already operate at a large scale (e.g., the production of lime), generally the overall technologies have not developed beyond desk-top technoeconomic assessment or bench scale laboratory work.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Because the particulate organic to inorganic carbon ratio is greater than 1, the effect of increased carbonate production and ballasting may result in additional drawdown of atmospheric CO2.

    “As the particulate organic to inorganic carbon ratio is >1, the effect may result in the additional drawdown of atmospheric CO2.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The particulate organic to inorganic carbon ratio is greater than 1.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Direct addition of silicate minerals to the ocean may fertilize biological activity through the co-dissolution of nutrients such as iron and silicon, although it may be possible to extract magnesium or calcium prior to addition.

    “Direct addition of the latter to the ocean may fertilize biological activity through the co-dissolution of nutrients (e.g., iron and silicon), although it may be possible to extract the magnesium or calcium prior to addition.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Rapid uncontrolled changes in pH, carbonate saturation state, and dissolved aqueous CO2 may have detrimental effects on ocean ecosystems.

    “However, rapid uncontrolled changes in pH, carbonate saturation state, and dissolved aqueous CO2 may have detrimental effects on ocean ecosystems.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Extensive research has been conducted over the last 20 years to understand the impact of ocean acidification on marine biota and the global carbon cycle.

    “Extensive research has been conducted over the last 20 years to understand the impact of ocean acidification on marine biota and the global carbon cycle[Doney et al., 2009].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Doney et al., 2009

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Automated monitoring systems are becoming increasingly common, currently omit alkalinity or carbonate system measurements, but will likely include these in the near future.

    “However, automated monitoring systems are becoming increasingly common, which currently omit alkalinity or carbonate system measurements, but will likely include these in the near future [GOOS 2006].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites GOOS 2006

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisenone given

    The modification of the ocean, a global commons, raises issues surrounding regulation, monitoring, and the distribution of impact.

    “Finally, the modification of the ocean (a global commons) raises issues surrounding regulation, monitoring, and the distribution of impact.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    It may also be possible to use faster dissolving carbonate minerals for alkalinity addition, with a CO2:rock mass ratio of about 0.5.

    “It may also be possible to use faster dissolving carbonate minerals for alkalinity addition (CO2: rock mass ratio ~0.5).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    Research investigating the change of shell mass with carbonate ion concentration suggests a growth rate change between 10% and 80% for calcite saturation state of 7, which is considerably less than the expected abiological increase of 140%.

    “Research investigating the change of shell mass with carbonate ion concentration suggest a growth rate change between 10 -80% for calcite saturation state of 7, which is considerably less than the expected abiological increase of 140 %.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The expected abiological increase in calcite saturation state of 7 is 140%.

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    It may be possible to ameliorate the effects of ocean acidification by controlled addition of alkalinity to sensitive environments, maintaining the saturation state of calcite at an appropriate value.

    “On one hand, it may be possible to ameliorate the effects of ocean acidification (i.e.maintaining the saturation state of calcite at an appropriate value) by controlled addition to sensitive environments.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    It is possible that increased carbonate production and ballasting will also increase the export of organic carbon.

    “It is possible that increased carbonate production and ballasting will also increase the export of organic carbon.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    Elevated CO2 in the atmosphere lowers carbonate ion concentration in the ocean, which puts stress on shell forming organisms, a process called ocean acidification.

    “Elevated CO2 in the atmosphere lowers [CO3 2-] in the ocean, which puts stress on shell forming organisms ('ocean acidification').”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Considering these changes as an upper end member, it is unlikely that the average saturation state of calcite will surpass its pre-industrial level, although some environments may be more sensitive than others.

    “Considering these changes as an upper end member, it is unlikely that the average saturation state of calcite will surpass its pre-industrial level, although some environments may be more sensitive than others.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The addition of alkalinity is common in several marine environments, such as aquaria and shellfish production.

    “While the addition of alkalinity is common in several marine environments (e.g., in aquaria and shellfish production), more research is needed to constrain the wider ecosystem response.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    The London Convention/Protocol was created to limit dumping of materials in the ocean, and has been amended, yet to be ratified, to include marine geoengineering proposals.

    “The London Convention/Protocol was created to limit dumping of materials in the ocean, and has been amended (yet to be ratified) to include marine geoengineering proposals.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The residence time for alkalinity in the ocean is on the order of 100-1,000 ka, and it would form, for all practical purposes, a permanent sink for anthropogenic CO2.

    “As such, the residence time for alkalinity in the ocean is on the order of 100 -1,000 ka, and would form, for all practical purposes, a permanent sink for anthropogenic CO2.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Transient localized impact around the point of alkalinity addition could be substantial.

    “Transient localized impact around the point of alkalinity addition could be substantial.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    It may be possible to achieve CO2:rock mass ratios greater than 1 using ultrabasic minerals, which is larger than the approximately 0.6 mass ratio for solid carbonate formation.

    “It may be possible to achieve CO2:rock mass ratios >1 using ultrabasic minerals (larger than the ~0.6 mass ratio for solid carbonate formation).”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The CO2:rock mass ratio for solid carbonate formation is approximately 0.6.

  • May combine two claims.

    Premisenone given

    Most research on ocean acidification omits investigation of elevated saturation states and primarily focuses on manipulating CO2(aq) rather than alkalinity.

    “Most of this research omits the investigation of elevated saturation states (e.g., Figure10, which is not exhaustive, but indicative), and primarily focuses on manipulating [CO2 (aq)] rather than alkalinity.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    In the global carbon cycle, up to 2 Gt C per year is incorporated into carbonate shells in the ocean, of which only less than 0.3 Gt C per year makes it into the lithosphere.

    “In the global carbon cycle, up to 2 Gt C a -1 is incorporated into carbonate shells in the ocean, of which only <0.3 Gt C a -1 makes it into the lithosphere.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    An increased carbonate production or decrease in remineralization will lower, or reverse, the effectiveness of ocean alkalinity carbon storage.

    “An increased carbonate production or decrease in remineralization will lower, or reverse, the effectiveness of ocean alkalinity carbon storage.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    Carbonate mineral precipitation is strongly inhibited in seawater and is almost exclusively produced from biological activity.

    “Carbonate mineral precipitation is strongly inhibited in seawater, and is almost exclusively produced from biological activity.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    Increased alkalinity will likely reduce the rate at which carbonate is re-mineralized in sediments, increase the depth of the ocean in which carbonate minerals are thermodynamically unstable (the lysocline), and thus increase carbonate burial.

    “Increased alkalinity will also likely reduce the rate at which carbonate is re-mineralized in sediments, and increase the depth of the ocean in which carbonate minerals are thermodynamically unstable ('lysocline'), and thus increase carbonate burial.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    If ocean alkalinity were used as the sole destination of all anthropogenic CO2 emissions over the next 100-500 years, ocean alkalinity would increase from current levels of 2.3 mEq kg-1 to about 3 mEq kg-1, resulting in a calcite saturation level between 5 and 7.5.

    “If it were used as the sole destination of all anthropogenic CO2 emissions over the next 100 -500 a, then ocean alkalinity would increase from current levels of 2.3 mEq kg -1 to ~3 mEq kg -1 (resulting in a calcite saturation level of between 5 and 7.5).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Current ocean alkalinity is 2.3 mEq kg-1.
251 of 251

  • The authors state this as an assumption.

    The growth time for Orbulina universa remains relatively constant, so shell mass is directly analogous to calcification rate.

    “Assuming the growth time for the organism remains relatively constant, the shell mass is directly analogous to calcification rate.”

  • The authors state this as an assumption.

    The proportional change in shell mass is representative of the proportional change in growth rate.

    “However, assuming the proportional change is representative of the proportional change in growth rate, the range of values are substantially less than what would be expected from exclusively abiotic controlled kinetics (~138 % rate change over the same increase in Ωcalcite, see below).”

  • The authors state this as an assumption.

    The composition of particulate inorganic carbon is aragonite or Mg-calcite with molecular mass between 97 and 100 g(carbonate) mol-1 and up to 20% MgCO3.

    “Assuming the composition of the PIC is aragonite or Mg-calcite (molecular mass between 97 and 100 g(carbonate) mol -1 , and assuming up to 20% MgCO3), the concentration of carbonate minerals in the open surface ocean may be between 5.6 and 23.4 μg l -1 .”

  • The authors state this as an assumption.

    The lower end member of the abiotic precipitation rate range is used for the projected increase in carbonate production.

    “While biological carbonate precipitation depends on numerous factors, the abiotic precipitation follows a predicable relationship with Ω, and (assuming the lower end member) would increase from 0.01 to 0.4 Gt C y -1 for an increase in Ωcalcite from its current value to 10 (a 20% increase of carbonate production).”

  • The authors state this as an assumption.

    The rate of olivine dissolution is instant and complete in the modeling.

    “A complication in this relates to the rate of olivine dissolution required, which are assumed to be instant and complete in the modeling.”

  • The paper relies on this without support.

    The use of produced Mg(OH)2 to increase ocean alkalinity has not been explored.

    “The use of the produced Mg(OH)2 to increase ocean alkalinity has not been explored.”

  • The authors state this as an assumption.

    There are no efficiency losses in electrolysis, fuel cell generation, and acid neutralization.

    “Assuming no efficiency losses”

  • The paper relies on this without support.

    The limited technoeconomic assessment of these processes largely focuses on deriving overall energy and carbon balances, and there has been little optimization.

    “The limited technoeconomic assessment of these processes largely focus on deriving overall energy and carbon balances, and there has been little optimization.”

  • The paper relies on this without support.

    Some reaction kinetics are poorly constrained (particularly for artificial materials), resulting in considerable uncertainty in the design of the flow sheet.

    “Furthermore, some of the reaction kinetics are poorly constrained (particularly for artificial materials), resulting in considerable uncertainty in the design of the flow sheet.”

  • The authors state this as an assumption.

    Alkalinity addition effects are modeled assuming instantaneous dissolution within the rapidly mixed wake of a ship.

    “This assumes instantaneous dissolution within the rapidly mixed wake of a ship.”

  • The authors state this as an assumption.

    The dilution formula assumes that the density difference between the disposed chemical and seawater is minimal.

    “equation 32 assumes that the density difference between the disposed chemical and seawater is minimal, and thus has greater relevance to the disposal of liquid.”

  • The paper relies on this without support.

    Storage of large volumes of CO2 may be necessary to prevent dangerous climate change.

    “Storage of large volumes of CO2 may be necessary to prevent dangerous climate change.”

  • The paper relies on this without support.

    The ocean currently stores around 38,000 Gt C, equivalent to about 140,000 Gt CO2, in the form of ocean alkalinity.

    “The ocean currently stores around 38,000 Gt C (equivalent to ~140,000 Gt CO2) in this way”

  • The paper relies on this without support.

    Current ocean alkalinity is 2.3 mEq kg-1.

    “current levels of 2.3 mEq kg -1”

  • The paper relies on this without support.

    The particulate organic to inorganic carbon ratio is greater than 1.

    “As the particulate organic to inorganic carbon ratio is >1”

  • The paper relies on this without support.

    The CO2:rock mass ratio for solid carbonate formation is approximately 0.6.

    “larger than the ~0.6 mass ratio for solid carbonate formation”

  • The paper relies on this without support.

    The expected abiological increase in calcite saturation state of 7 is 140%.

    “expected abiological increase of 140 %”
17 of 17

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • OAE induces dynamic shifts in the carbonate chemistry in seawater that may impact marine organism physiology, community composition, and trophic interactions during and/or after equilibration with the atmosphere.

    “OAE induces dynamic shifts in the carbonate chemistry in seawater that may impact marine organism physiology, community composition, and trophic interactions during and/or after equilibration with the atmosphere (Oschlies et al., 2023; Renforth and Henderson, 2017).”

    From Biogeochemical responses to ocean alkalinity enhancement in the North China Sea (2026) · cites this paper as Renforth and Henderson, 2017

    Section 7.2 (page unavailable) says alkalinity addition may transiently change seawater chemistry, inhibit photosynthesis, and alter phytoplankton community structure; it also discusses possible physiological effects in marine animals. The Conclusions describe possible wider ecosystem effects, but the paper does not specifically address trophic interactions, so that part of the attributed claim is not established by our copy. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

  • Ocean Alkalinity Enhancement (OAE) has been proposed as a promising marine carbon dioxide removal strategy.

    “Ocean Alkalinity Enhancement (OAE) has been proposed as a promising marine carbon dioxide removal strategy.”

    From Biogeochemical responses to ocean alkalinity enhancement in the North China Sea (2026) · cites this paper as Renforth and Henderson, 2017

  • OAE operates by increasing seawater total alkalinity (TA), thereby increasing the ocean's capacity to absorb atmospheric CO2 and promoting the conversion of dissolved CO2 into bicarbonate (HCO3-) and carbonate (CO3 2-) ions.

    “OAE operates by increasing seawater total alkalinity (TA), thereby increasing the ocean's capacity to absorb atmospheric CO 2 and promoting the conversion of dissolved CO 2 into bicarbonate (HCO 3 -) and carbonate (CO 3 2) ions (Bach et al., 2019; Renforth and Henderson, 2017).”

    From Biogeochemical responses to ocean alkalinity enhancement in the North China Sea (2026) · cites this paper as Renforth and Henderson, 2017

  • Because seawater is typically oversaturated with respect to CaCO3, precipitated CaCO3 may constitute a long-term loss of alkalinity from the water column.

    “Because seawater is typically oversaturated with respect to CaCO3, precipitated CaCO3 may constitute a long-term loss of alkalinity from the water column. 41,42”

    From A framework for understanding efficiency losses of Ocean Alkalinity Enhancement (2026) · cites this paper as [42]

  • Ocean losses of CO2 are due to re-equilibration of DIC upon discharge to the ocean.

    “These losses of CO 2 are due to re-equilibration of DIC upon discharge to the ocean.”

    From Quantified Carbon Dioxide Removal from an Alkalinity Addition Field Trial in the Kvina River, Norway (2026) · cites this paper as Renforth and Henderson (2017)

    Section 1.2 describes CO2-bearing effluent discharged to the ocean, and section 7.2 says dissolved CO2 may be elevated near an accelerated-weathering reactor outlet. Neither passage says CO2 is lost because DIC re-equilibrates after discharge. Searches for re-equilibration, degassing, and discharge-related CO2 losses found no passage establishing that mechanism. (LLM, conf=0.72)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

  • Calcium increase is not less than 0.3%

    Minor

    The paper elsewhere gives the current calcium concentration as 10 mmoles kg -1. An increase of 0.9 mmoles kg -1 is 9% of that concentration, not less than 0.3%.

    Reported 0.3 · recomputed 9

  • Reported alkalinity-measurement precision is off by a factor of ten

    Minor

    Relative to the paper's stated seawater alkalinity of 2.5 mEq kg -1, a precision of 0.005 mEq kg -1 is 0.2%, not 0.02%.

    Reported 0.02 · recomputed 0.2

  • Existing cooling-water flow covers about 2%, not 6%, of CO2 output

    Minor

    The stated 20 m 3 s -1 of existing cooling-water flow is about 2.2% of the stated 900 m 3 s -1 required to treat all the plant's CO2, rather than 6%.

    Reported 6 · recomputed 2.222222

3 of 3

Cites

Flagged first, then by citations

2 of the 220 references couldn’t be matched to a known paper.

Research works printed but not linked: 12

  1. Booth C. E., 1984, Acid‐base balance in the sea mussel Mytihrs edulis. 1. Effects of hypoxia and air exposure on the hemolymph acid‐base status, Mar. Biol. Lett., 5, 347
  2. CEFIC, 2011, Guidelines for Measuring and Managing CO2 Emission From Freight Transport Operations, 1
  3. Ciais P., 2014, Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, 465
  4. DECC, 2015, Digest of UK Energy Statistics’, 1
  5. Drever J. I., 1988, The Geochemistry of Natural Waters
  6. Edenhofer O., 2014, Climate Change 2014: Mitigation of Climate Change, Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change
  7. 10.2307/30060218 · DOI
  8. 10.2307/30066391 · DOI
  9. Roth R., 2015, From Rail to Road and Back Again?: A Century of Transport Competition and Interdependency, Modern Economic and Social History
  10. USGS, 2014, USGS Minerals Yearbook ‐ Cement, 16.1
  11. White A. F., 1995, Chemical weathering rates of silicate minerals, Reviews in mineralogy, Mineral. Soc. Am., 31, 1
  12. Zeebe R. E., 2001, CO2 in Seawater: Equilibrium, Kinetics, Isotopes

Cited by

Sorted by citations

Related

Authors
Renforth, P., & Henderson, G.
Affiliations
  • Cardiff University (GB)
  • University of Oxford (GB)
Corresponding author
Renforth, Phil
ORCID
Venue
Reviews of Geophysics
Publisher
American Geophysical Union (AGU)
Published
2017-07-27
Volume
55
Issue
3
Pages
636-674
ISSN
  • 0096-1043 (ISSN-L)
  • 8755-1209
  • 1944-9208
DOI
10.1002/2016rg000533
OpenAlex
W2625135129
Cited by
655
References
220
Citations by year
2026: 123 · 2025: 117 · 2024: 122 · 2023: 127 · 2022: 67 · 2021: 47 · 2020: 18 · 2019: 12 · 2018: 19 · 2017: 3
FWCI
7.96
Type
journal article
Language
en
Open access
Licence
Locations
  • Reviews of Geophysics (publishedVersion, cc-by)
  • ORCA Online Research @Cardiff (Cardiff University) (acceptedVersion)
Funders
  • U.S. Department of Energy
  • Carnegie Institution of Washington
  • University of Oxford
  • Cardiff University
Topics
  • Physical Sciences › Environmental Science › Environmental Engineering › CO2 Sequestration and Geologic Interactions
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate Change and Geoengineering
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Ocean Acidification Effects and Responses
Keywords
ocean alkalinity, ocean carbon sequestration, CO2 sequestration, bicarbonate, carbonate saturation state, ocean acidification, enhanced weathering, accelerated weathering, carbonate precipitation, silicate weathering, limestone weathering

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-10.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-10.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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