Ocean Alkalinity Enhancement from Coastal Outfalls
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This Protocol provides the requirements and procedures for the calculation of net carbon dioxide equivalent (CO₂e (The amount of CO₂ emissions that would cause the same integrated radiative forcing or temperature change, over a given time horizon, as an emitted amount of GHG or a mixture of GHGs. One common metric of CO₂e is the 100-year Global Warming Potential.)) removal from the atmosphere via Ocean Alkalinity Enhancement (OAE) from coastal outfalls. OAE is a marine Carbon Dioxide Removal (CDR) (Activities that remove carbon dioxide (CO₂) from the atmosphere and store it in products or geological, terrestrial, and oceanic Reservoirs. CDR includes the enhancement of biological or geochemical sinks and direct air capture (DAC) and storage, but excludes natural CO₂ uptake not directly caused by human intervention.) technique that has a potential co-benefit of locally mitigating ocean acidification1 and mimics Earth’s natural process for regulating atmospheric carbon dioxide (CO₂).
Over geologic timescales, there are various processes that act to regulate atmospheric CO₂, such as the weathering cycle2 and deep ocean neutralization of sediments3. Silicate rock weathering reactions remove carbon dioxide from the atmosphere to produce chemically stable bicarbonate and carbonate ions. Riverine transport subsequently brings the bicarbonate and carbonate ions to the ocean where they are stored on multi-millennial timescales.
OAE aims to speed up this natural process by adding CO₂-reactive alkalinity to the surface ocean to shift CO₂ in the ocean to bicarbonate and carbonate ions, which results in a CO₂ deficit in the surface ocean. A net reduction of atmospheric CO₂ concentrations occurs via air-sea gas exchange. This is achieved by reducing the natural rate of ocean CO₂ outgassing, or by increasing the amount of atmospheric CO₂ absorbed and stored as dissolved inorganic carbon (DIC) in the ocean. The class of approaches that fall under OAE use CO₂-reactive alkalinity: 1) as naturally contained in rocks and minerals, 2) as synthetically derived from rocks, brine or seawater via various processes (e.g. electrochemistry or calcination), or 3) as available in or derived from certain industrial waste streams. These alkaline materials can be added in dissolved, solid or mixed (slurry) form to the ocean that releases alkalinity upon dissolution. Details of applicable projects under this Protocol are described in Section 4.
OAE has high scaling potential because it intentionally leverages the vast surface area and mixing of the ocean. This choice necessitates a different carbon removal quantification approach than closed-system CDR pathways. OAE projects release alkalinity to the open environment, where the alkaline plume mixes and moves with local hydrodynamics, rapidly diluting and spreading the affected seawater chemistry and air-sea gas exchange over large temporal and spatial scales (potentially spanning several hundred square kilometers and over months to years). Due to rapid dilution and the range of spatial and temporal scales encompassed by OAE, direct measurements of air-sea CO₂ fluxes pose significant analytical and logistical challenges at this time. Thus, quantification of atmospheric CO₂ removal currently relies on state of the art biogeochemical ocean models, which have been extensively validated against observations and whose uncertainties have been quantified. More details on model requirements are found in the Air-Sea CO₂ Uptake Module v1.01, and the quantification approach is described in Section 78.1. Net removal of CO₂e is determined through a GHG Assessment (The process by which all emissions associated with a Project's Removal or Reduction process, including leakages, are accounted for.) (see Section 78.2).
Evaluations of the commercial feasibility of OAE are ongoing and in early stages. Although abiotic marine CDR methods such as OAE have promising potential in terms of scalability and efficacy at removing CO₂, scientific understanding around these approaches is currently an active area of research4, 5, 6. As of this writing, there are fewer than 10 OAE field trials that have occurred or are in the planning stages5, including trials by OAE projects7 and academic researchers, which are often carried out collaboratively8, 9. The results of these early stage projects will no doubt shape the future trajectory of OAE and marine CDR, as well as advance fundamental science in oceanography.
As the first community-level OAE Protocol for quantifying net CO₂e removal, this Protocol aims to start building consensus around Monitoring, Reporting and Verification (MRV) (The multi-step process to monitor the Removals or Reductions and impacts of a Project, report the findings to an accredited third party, and have this third party Verify the report so that the results can be Certified.) approaches that are both rigorous and operationally feasible. The guiding principle for this Protocol is to provide a high level of scientific rigor and safety guardrails for early stage OAE trials and deployments, while also balancing operational feasibility and leaving flexibility for innovation. Furthermore, projects should share data relevant for scientific research to facilitate scientific advances in OAE (see Section 5.6).
Note that throughout this Protocol, use of the word "must" indicates a requirement, whereas "should" indicates a recommendation.
Specific standards and protocols that are utilized as the foundation of this Protocol, and for which this Protocol is intended to comply with, are the following:
Additional reference standards that inform the requirements and overall practices incorporated in this Protocol include:
Additional standards, methodologies and protocols that were reviewed, referenced and informed the development of this Protocol include:
This Protocol was developed based on the current state of the art, publicly available science regarding OAE. This Protocol will be updated in future versions as the science underlying OAE evolves and the overall body of knowledge and data across all processes is increased, for example regarding feedstock supply, conversion, ecosystem impacts and durable storage.
This Protocol will be reviewed at a minimum every 2 years and/or when there is an update to scientific published literature which would affect net CO₂e removal quantification or the monitoring and modeling guidelines outlined in this Protocol.
OAE projects can be categorized by the source of CO₂-reactive alkalinity (e.g. electrochemistry, mining or grinding), which is relevant to project System Boundary (see Section 7.2), and by the phase of alkalinity used (e.g. solid, liquid, slurry), which is relevant for quantifying dissolution in the ocean (Section 7.4.1.2). This Protocol applies to projects or processes which enhance Total Alkalinity (Defined as an excess of proton acceptors over proton donors, which functionally describes the ability of a solution to neutralize acids to the CO₂ equivalence point.) in the surface ocean via discharge from coastal outfalls by one of the following processes:
This Protocol applies to projects and associated operations that meet all of the following project conditions. The project:
The following topics are covered briefly in this Protocol due to their inclusion in the Isometric Standard, which governs all Isometric Protocols. See in-text references to the Isometric Standard for further guidance.
For each specific project to be evaluated under this Protocol, the Project Proponent must document project characteristics in a Project Design Document (PDD) (The document that clearly outlines how a Project will generate rigorously quantifiable Additional high-quality Removals or Reductions.) as outlined in Section 3.2 of the Isometric Standard. The PDD will form the basis for project verification and evaluation in accordance with this Protocol, and must include consideration of processes unique to each OAE project such as:
Projects must be validated and net CO₂e removals verified by an independent third party, consistent with the requirements described in this Protocol as well as in Section 4 of the Isometric Standard.
The VVB must adhere to these requisite components:
The threshold for Materiality (An acceptable difference between reported Removals/emissions or Reductions/emissions and what an auditor determines is the actual Removal/emissions or Reduction/emissions.), considering the totality of all omissions, errors and mis-statements, is 5%, in accordance with Section 4.3 of the Isometric Standard.
Verifiers should also verify the documentation of uncertainty (A lack of knowledge of the exact amount of CO₂ removed by a particular process, Uncertainty may be quantified using probability distributions, confidence intervals, or variance estimates.) of the GHG statement (A document submitted alongside Claimed Removals and/or Reductions that details the calculations associated with a Removal or Reduction, including the Project's emissions, Removals, Reductions and Leakages, presented together in net metric tonnes of CO₂e per Removal or Reduction.) as required by Section 2.5.7 of the Isometric Standard. Qualitative Materiality (An acceptable difference between reported Removals/emissions or Reductions/emissions and what an auditor determines is the actual Removal/emissions or Reduction/emissions.) issues may also be identified and documented, such as10:
Project validation and verification must incorporate site visits to project facilities in accordance with the requirements of ISO 14064-3, 6.1.4.2, including, at a minimum, site visits during validation and initial verification. Validators should, whenever possible, observe project operations to ensure full documentation of process inputs and outputs through visual observation (see Section 4 of the Isometric Standard).
A site visit must occur at least once every 2 years at each dosing location.
Verifiers and validators must comply with the requirements defined in Section 4 of the Isometric Standard. For this OAE Protocol, in addition to a primary certified Validation and Verification Body (VVB) (Third-party auditing organizations that are experts in their sector and used to determine if a project conforms to the rules, regulations, and standards set out by a governing body. A VVB must be approved by Isometric prior to conducting validation and verification.), independent third party consultants may be required for tasks that require subject matter expertise such as the evaluation of suitable ocean models and analysis required in Section 7. These consultants may be subcontracted out by the VVB or separately contracted by Isometric. Consultants must have relevant experience with the ocean models used in this Protocol, as demonstrated through work experience, post-graduate degrees, research projects, peer-reviewed papers, or equivalent experience.
All VVBs are approved by Isometric independently and impartially based on alignment with Isometric's Conflict of Interest policy, rotation of VVB policy, oversight on quality and the following requirements:
CDR via OAE can often be a result of a multi-step process, with activities in each step managed and operated by a different operator, company or owner. When there are multiple parties involved in the process, a single Project Proponent must be specified contractually as the sole owner of Credits to avoid double counting of net CO₂e removal. Contracts must comply with all requirements defined in Section 3.1 of the Isometric Standard.
The Project Proponent must be able to demonstrate additionality through compliance with Section 2.5.3 of the Isometric Standard. The baseline scenarios and counterfactuals (An assessment of what would have happened in the absence of a particular intervention – i.e., assuming the Baseline scenario.) utilized to assess additionality must be project-specific, and are described in Section 7 of this Protocol.
Additionality determinations must be reviewed and completed every 2 years, at a minimum, or whenever project operating conditions change significantly, such as the following:
Any review and change in the determination of additionality shall not affect the availability of Carbon Finance and Credits (A publicly visible uniquely identifiable Credit Certificate Issued by a Registry that gives the owner of the Credit the right to account for one net metric tonne of Verified CO₂e Removal or Reduction. In the case of this Standard, the net tonne of CO₂e Removal or Reduction comes from a Project Validated against a Certified Protocol.) for the current or past Crediting Periods (The period of time over which a Project Design Document is valid, and over which Removals or Reductions may be Verified, resulting in Issued Credits.), but, if the review indicates the project has become non-additional, this shall make the project ineligible for future Credits12.
The uncertainty in the overall estimate of net CO₂e removal as a result of the project must be accounted for. The total net CO₂e removal for a specific Reporting Period must be determined with high confidence, and projects must conduct an uncertainty analysis for the net CO₂e removal calculation in compliance with requirements outlined in Section 2.5.7 of the Isometric Standard.
Projects must report a list of all key variables used in the net CO₂e removal calculation and their uncertainties, as well as a description of the uncertainty analysis approach, including:
The uncertainty information should at least include the minimum and maximum values of each variable that goes into the net CO₂e removal calculation (see Section 7.4 for more details). More detailed uncertainty information should be provided if available, as outlined in Section 2.5.7 of the Isometric Standard.
In addition, a sensitivity analysis that demonstrates the impact of each input parameter’s uncertainty on the final net CO₂e removal uncertainty must be provided. Details of the sensitivity analysis method must be provided such that a third party can reproduce the results. Input variables which contribute < 1% change in the net CO₂e removal may be omitted from an uncertainty analysis. For all other parameters, information about uncertainty must be specified.
For more details on model uncertainty, model skill and sensitivity analysis of ocean models, see the Air-Sea CO2 Uptake Module v1.01 and Appendix 2.
In accordance with the Isometric Standard, all evidence and data related to the underlying quantification of net CO₂e removal and environmental monitoring will be available to the public through Isometric’s Science Platform. That includes:
The Project Proponent can request certain information to be restricted (only available to authorized Buyers, the Registry and VVB) where it is subject to confidentiality. This includes emissions factors from licensed databases. However, all other numerical data produced or used as part of the quantification of net CO₂e removal will be made available.
[/R-HDG5-0]In addition, in compliance with the Guide on Data Reporting and Sharing for Ocean Alkalinity Enhancement Research13 and FAIR Principles14, the Project Proponent should publicly disseminate deployment data that is relevant to scientific research (e.g. ocean monitoring measurements, ocean model results), such as through open data repositories.
[/G-V56R-0]Following the Isometric Standard, Credits issued under Isometric's OAE Protocol are contingent on the implementation, transparent reporting and independent verification of comprehensive safeguards. These safeguards encompass a wide range of considerations, including environmental protection, social equity, community engagement and respect for cultural values. The process mandates that safeguard plans be incorporated into all major project phases, with detailed reports made accessible to stakeholders. Adherence to and verification of environmental and socio-economic safeguards is a condition for all Crediting Projects.
For additional guidance and resources, we refer Project Proponents to the Guide to Best Practices in Ocean Alkalinity Enhancement Research Chapter 10 (Legal considerations relevant to research on Ocean Alkalinity Enhancement)15 and Chapter 11 (Social considerations and best practices to apply to engaging publics on ocean alkalinity enhancement)16, and the Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration Chapter 2.1 Legal and Regulatory Landscape and Chapter 2.2 Social Dimensions and Justice Considerations5.
Due to the novelty of marine CDR projects
The minimum requirements for coastal projects are:
Project Proponents must identify jurisdictional authorities, including local rightsholders, of the water body of the project site and affected areas.
[/G-J5FZ-0]Project Proponents must observe ratified provisions in international conventions where relevant. Many existing international conventions are more applicable to open ocean marine CDR and so are not likely applicable to projects covered by this Protocol. Some examples of potential relevant international conventions are: the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (“London Convention”), the Protocol to that Convention (“London Protocol”), the Convention on Biological Diversity, the United Nation Convention on the Law of the Sea, the International Convention for the Prevention of Pollution from Ships, the Basel Convention and the European Union Marine Strategy Framework Directive.
[/G-5TBM-0]Environmental and social risk assessment in adherence with Section 3.7 of the Isometric Standard must be completed to identify potential risks, followed by the development of tailored mitigation plans. These plans must encompass specific actions to avoid, minimize or rectify identified impacts. Effective implementation of these measures must also be accompanied by a robust monitoring plan to detect negative impacts and stop projects when necessary (see Section 10).
The Project Proponent must conduct an environmental risk assessment which adheres to Section 3.7.1 of the Isometric Standard.
Specific risks to be considered for OAE are listed below. The list will be updated in future iterations of the Protocol as new research emerges.
Potential risks associated with feedstocks include land use impacts from sourcing, production, preparation, storage, and distribution, such as land degradation, land occupation, dust pollution, deforestation and localized watershed contamination.
[/G-P3SQ-0]Potential marine environmental risks associated with OAE are listed below. Not every risk is applicable to every project, and the severity of these risks vary based on site specificities, type of OAE project (e.g. electrochemical or mineral), and the intensity and duration of alkalinity enhancement. The following list is a minimum set of risks for all OAE projects to which Isometric and the supplier can add risks on a case by case basis, which would be included in the PDD:
In addition, the following risks are applicable to some OAE projects and should be included in the PDD if relevant:
When assessing marine environmental risks, it is important to holistically consider the context, for instance keeping in mind the project impacts in relation to the risk of climate change. It is unrealistic to aim for a project to prove zero changes to the ocean ecosystem because of some of the following reasons:
However, it is important to try to minimize as much as possible any large and/or adverse impacts, which is the goal of this Protocol.
The Project Proponent must conduct a social risk assessment which adheres to Section 3.7.2 of the Isometric Standard on Social Impacts.
Marine CDR projects must conduct an environmental justice review, which considers the historical inequities in the distribution of coastal amenities and disamenities prior to site selection.
[/G-H2CP-0]Per Section 3.5 of the Isometric Standard, Project Proponents must demonstrate active stakeholder engagement throughout project planning and operation, ensuring that all risk mitigation strategies contribute to sustainable project outcomes.
Local stakeholders situated in the vicinity of the project site may contribute an in-depth understanding of the local system and provide invaluable insights and recommendations on the potential risks, necessary safeguards and specific monitoring needs. Relevant local stakeholders may include local members of academia, Indigenous groups, environmental groups, citizen associations and other users of the marine space, such as commercial and recreational fishermen, shellfish farmers, boaters and recreational users.
[/G-4Q8B-0]The Stakeholder input process must adhere to requirements outlined in Section 3.5 of the Isometric Standard, and evidence of these meetings must be submitted in the PDD.
Project Proponents must include in the PDD a plan for information sharing, emergency response and conditions for stopping or pausing a deployment. Plans for pausing or stopping a deployment must be in place in instances where:
The Reporting Period for OAE represents an interval of time over which removals are calculated and reported for verification. OAE projects may operate continuously or with discrete dosing periods. For discrete projects, the Reporting Period may encompass a single dosing period, while continuous projects may allocate dosing into multiple Reporting Periods. The total net CO₂e removal is calculated using a combination of measurements and multi-scale modeling for a specified Reporting Period, and is written hereafter as [math: CO_2e_{Removal, RP}].
GHG emission calculations must include all emissions related to the project activities that occur within the Reporting Period. This includes: (a) any emissions associated with project establishment allocated to the Reporting Period (See Section 7.4.4.1), (b) any emissions that occur within the Reporting Period (See Section 7.4.4.2), (c) any anticipated emissions that would occur after the Reporting Period that have been allocated to the Reporting Period (See Section 7.4.4.3) and (d) leakage emissions that occur outside of the project boundary as a result of induced market changes that are associated with the Reporting Period (See Section 7.4.4.4).
In line with the Isometric Standard, this Protocol requires that Removal Credits are issued ex-post (after net Removal from the atmosphere via air-sea gas exchange has been achieved). Credits may be issued (1) incrementally over time based on the incremental air-sea equilibration achieved over a Reporting Period, or (2) all at once after full or near-complete equilibration.26 Note for option (2), there is no requirement as to what percent equilibration has been achieved; any net removals up to the time point chosen can be credited. The Crediting timeline, corresponding Reporting Periods and allocation of emissions to Reporting Periods must be agreed upon with Isometric, and listed in the PDD.
The scope of this Protocol includes GHG sources, sinks and reservoirs (SSRs) associated with an OAE CDR project.
A cradle-to-grave GHG Statement must be prepared encompassing the GHG emissions relating to the activities outlined within the system boundary.
GHG emissions and removals associated with The systemProject boundarymay be direct emissions (Emissions that are produced by a specific CDR process and are directly controllable.) from a process, or indirect emissions from combustion of fuels, electricity generation, or other sources. Emissions must include all GHG SSRs controlledwithin bythe system boundary, from the construction or manufacturing of each physical site and associated equipment, closure and disposal of each site and associated equipment, and operation of each process, including embodied emissions (Life cycle GHG emissions associated with production of materials, transportation, and construction or other processes for goods or buildings.) of equipment and consumables used in the project. The Project Proponent is responsible for identifying all sources of emissions directly or indirectly related to the project, including but not limited to the GHG SSRs in Figure 1 and Table 1.
[Image: **Figure 1** Process flow diagram showing system boundary for OAE projects]
Figure 1 Process flow diagram showing system boundary for OAE projects
The system boundary must include all GHG SSRs from activities related to the batch of Credits delivered within the Reporting Period associated with the establishment of the project, operations and end-of-life activities that occur after the Reporting Period.
Any emissions from sub-processes or process changes that would not have taken place without the involvement of the CDR process, such as subsequent transportation and refining,Project must be fully considered in the system boundary. ThisAny allowsactivity that ultimately leads to the issuance (Credits are issued to the Credit Account of a Project Proponent with whom Isometric has a Validated Protocol after an Order for accurateVerification considerationand Credit Issuance services from a Buyer and once a Verified Removal or Reduction has taken place.) of additionalCredits should be included in the system boundary.
The system boundary must include all relevant GHG SSRs controlled, incrementalrelated emissionsand inducedaffected by the CDRProject, processincluding but not limited to the SSRs set out in Figure 1 and Table 1.
If any GHG SSRs within Table 1 are deemed not appropriate to include in the system boundary (e.g., electrochemical OAE processes may not require feedstock), they may be excluded provided that robust justification and appropriate evidence is provided in the PDD.
Figure 1.Process flow diagram showing system boundary for OAE projects
[Image: OAE System Boundary table]
Table 1. Scope of activities and GHG SSRs to be included by the removalOAE CDR project
Activity | GHG source, sink or reservoir | GHG | Scope | Timescale | ||
|---|---|---|---|---|---|---|
Establishment of project | Equipment | All | Embodied | Before | ||
Equipment and materials transport to site | All GHGs | Transport emissions associated with transporting materials and equipment to The Project site(s) (lifecycle Module A4). | ||||
Construction and installation | All GHGs | Emissions related to construction and installation of the project site(s) (lifecycle Module A5). To include energy use for construction, installation and groundworks, as well as waste processing activities and emissions associated with land use change. | ||||
Initial surveys and feasibility studies | All GHGs | To include any embodied, energy use and transport emissions associated with surveys required for establishment of the project site. | ||||
Misc. | All GHGs | Any SSRs not captured by categories above. | ||||
Operations | Feedstock | All GHGs |
| |||
Feedstock raw material extraction and manufacturing including rock quarrying, crushing, grinding and drying. | Over each Reporting Period - must be accounted for in the relevant Reporting Period (See Section 8.5.2) | |||||
Feedstock transport | All GHGs | Feedstock transport from source | ||||
OAE | All GHGs |
| ||||
consumables For electrochemical processing this must include consideration of acid transport, neutralization and disposal. | ||||||
Sampling required for MRV | All GHGs | Pre-dosing, during dosing and post-dosing monitoring, including transportation to collect samples, shipping of samples for laboratory analysis and sample processing. | ||||
Staff travel | All GHGs | Flight, car, train or other travel required for the project operations, | ||||
Surveys | All GHGs | Equipment, energy use and transport associated with surveys e.g. | ||||
CO₂ stored | CO₂ | The gross amount of CO₂ removed and durably stored from an OAE | ||||
Misc. | All GHGs |
| ||||
Any SSRs not captured by categories above. | ||||||
End-of-Life | End-of-life emissions | All GHGs | To include anticipated end-of-life emissions (lifecycle modules | After Reporting Period - must be accounted for in the first Reporting Period or amortized in line with allocation rules (See Section | ||
Sampling required long term monitoring for MRV | All GHGs | Ongoing monitoring, including transportation to collect samples, shipping of samples for laboratory analysis and sample processing. | ||||
Long term ongoing monitoring and surveys | All GHGs | Anticipated equipment, energy use and transport associated with ongoing monitoring and surveys e.g. ecological surveys. | ||||
Misc. | All GHGs | Any emissions source, sink or reservoir not captured by categories above. |
The Project Proponent must consider all GHGs associated with SSRs, in alignment with the United States Environmental Protection Agency’s definition of GHGs, which includes: carbon dioxide (CO₂), methane (CH4), nitrous oxide (N2O) and fluorinated gasses such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3). For CO₂ capture and acid CO₂ spillage, only CO₂ shall be included as part of the quantification. For all other activities all GHGs must be considered. For example, CO₂, CH4 and N2O are all associated with diesel consumption.
All GHGs must be quantified and converted to CO2e in the GHG Statement using the 100-yr Global Warming Potential (GWP) for the GHG of interest, based on the most recent volume of the IPCC Assessment Report (currently the Sixth Assessment Report)28.
Miscellaneous GHG emissions are those that cannot be categorized by the GHG SSR categories provided in Table 1. The Project Proponent is responsible for identifying all sources of emissions directly or indirectly related to project activities and must report any outside of the SSR categories identified as miscellaneous emissions.
Emissions associated with a project's impact on activities that fall outside of the system boundary of a project must also be considered. This is covered under Leakage in Section 78.4.43.4.
In line with the GHG Accounting Module v1.1, Systemthe BoundaryProject Considerations
Ancillarymust:
Ancillaryall activities (such as supplementary research and development activities and corporate administrative activities) that areGHGs associated with aSSRs, projectin butalignment are not directly or indirectly related towith the issuanceUnited States Environmental Protection Agency’s definition of CreditsGHGs canwhich includes: carbon dioxide (CO₂), methane (CH4), nitrous oxide (N20) and fluorinated gasses such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3). For CO2 stored, only CO2 shall be excludedincluded fromas part of the systemquantification. boundary.
SecondaryFor Impactsall onother GHGactivities Emissions
OAEall mayGHGs havemust additionalbe impacts on GHG emissions beyond the scope of this Protocolconsidered. For example, therethe release of CO2, CH4, and N2O is expected during diesel consumption;
In some instances, OAE project activities may be potentialintegrated forinto additionalexisting CO₂activities. uptake from increased primary production and biological carbon export,Activities or increased dimethylsulfide production due to increased pH.29 These potential secondary climate effects are uncertain at this time and are not included in the system boundary.
Considerations for Waste Input Emissions
Embodied emissions associated with system inputs considered as waste products can be excluded from the system boundary provided the appropriate criteria are met. For energy inputs, for example the useportions of waste heat, refer to the Energy Accounting Module v1.2. For other waste inputs, the following criteria shall be considered.
If EC1 in Table 2 is satisfied then this is sufficient to exclude embodied emissions from the system boundary. Market leakage emissions associated with waste inputs may also be excluded from the system boundary as compliance with EC1 would result in no change to the waste producer behavior (no market leakage) and indicates there are no alternative users of the waste product (no replacement emissions).
Table 2. Waste input emissions exclusion criteria, EC1
If EC2 and EC3 in Table 3 are both satisfied then this is sufficient to exclude embodied emissions from the system boundary. Market leakage emissions associated with waste inputs may also be excluded from the system boundary as compliance with EC2 and EC3 would result in no significant change to the waste producer behavior (no market leakage) and there are no alternative use cases for the waste product (no replacement emissions).
Table 3. Waste input emissions exclusion criteria, EC2 and EC3
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Considerations for Project Activities Integrated into Separate Practices
The project may be reliant on processes occuring separately from the CDR activity, for example, direct addition of compounds to wastewater or other industrial outfalls that discharge into the ocean. GHG SSRs associated with the OAE project, which relate to activities that were already occurring in the baseline and would continuehave continued to occur without the OAE project, may be omitted from the system boundary, subject providedto thatthe evidenceconditions thatset below.
For the purpose of this provision, an "activity" may refer to an operational sub-unit, such as an individual trip leg, a single pass of field equipment, or a discrete processing step, where such sub-units can be cleanly delineated by equipment, timing, and physical scope. Where a pre-existing activity is partially modified by the project (for example, a transport trip whose route is extended to include project-specific stops, or a field operation whose pass is lengthened to include project inputs), the activity must be partitioned into:
An activity, or portion of an activity, may only be excluded where the Project Proponent can demonstrate all of the following:
Evidence supporting these conditions must be provided.
Any impacts onin the separatePDD. This processmust thatinclude wouldeither:
And separatethe facilityfollowing:
Where these conditions are met, only the emissions associated with heavierthe loadsactivity foras incorporatingit OAEwould processes,have shalloccurred in the baseline may be consideredexcluded. Any incremental emissions attributable to the project must remain within the system boundary.
The separateand facilitybe mustaccounted notfor considerin the OAErelevant processemissions within their GHG accounting to avoid double counting of removalssub-section.
The baseline scenario for OAE projects assumes the activities associated with the OAE project do not take place and any infrastructure is not built. The counterfactual for OAE projects considers the CO2 that would have been removed from or outgassed to the atmosphere and stored in the ocean in the baseline scenario, over the same domain. The counterfactual for OAE is therefore the natural background ocean uptake and outgassing of CO₂ over the same spatial and temporal domain as the project intervention. In some cases, OAE may affect natural alkalinity fluxes from sediments;3024 this is discussed further in Section 78.43.2.
The Reporting Period, RP, for OAE represents an interval of time over which removals are calculated and reported for verification. OAE projects may operate continuously or with discrete dosing periods. For discrete projects, the Reporting Period may encompass a single dosing period, while continuous projects may allocate dosing into multiple Reporting Periods.
GHG emission calculations must include all emissions related to the project activities that occur within the Reporting Period. This includes
The total net CO₂e removal is calculated using a combination of measurements and multi-scale modeling for a specified Reporting Period, and is written hereafter as [math: CO_2e_{Removal, RP}]. The final net CO2e removal quantification must be conservatively determined, giving high confidence that at a minimum, the estimated amount of CO2e was removed.
In line with the Isometric Standard, this Protocol requires that Removal Credits are issued ex-post. Credits may be issued once CO₂ has been durably stored in the identified storage reservoir.
Net CO₂e removal for OAE for each Reporting Period, RP, must be calculated so as to give high confidence that the estimated net CO₂e was removed.
[/R-5CGF-1]This should include additional equations if applicable, definition of terms, emissions allocation method and how the time-evolution of CO₂ uptake is accounted for.
[/G-VQHJ-0]The net CO₂e removal equation is:
[math: CO_2e_{Removal, RP} = CO_2e_{Stored, RP} - CO_2e_{Counterfactual, RP} - CO_2e_{Emissions, RP}]
Equation 1
Where
Increasing the Total Alkalinity of the ocean results in a decrease in the concentration of dissolved CO₂ in the ocean, which prompts re-equilibration of the atmospheric and oceanic carbon reservoirs through increasing the flux of CO₂ from the atmosphere to the ocean, or reducing the outgassing of CO₂ from the ocean to the atmosphere. To make this explicit, the gross CO₂ removal [math: CO_2e_{Stored, RP}] relies on quantifying the air sea CO₂ fluxes:
Equation 2 Where, Similarly, the counterfactual is given by Equation 3 Where, It is useful to define the following term to represent the net ocean uptake of atmospheric CO₂ (or a reduction in ocean outgassing of CO₂) relative to the counterfactual scenario. Note that throughout this Protocol, [math: \Delta] will be used to symbolize a difference between the OAE scenario and counterfactual scenario: Equation 4 Substituting Equations 2-4 into Equation 1 allows Equation 1 to be re-written as Equation 5 Equation 5 is the primary form of the removal quantification equation that will be used throughout the rest of the Protocol. The [math: \Delta CO_2e_{AirSeaFlux, RP}] term encapsulates both the gross removal term and the counterfactual term. The following sections provide details on how each of the terms in Equation 5 are calculated. Quantification of uncertainty is required for each term in Equation 5 in line with [math: CO_2e_{Stored,RP} = CO_2e_{AirSeaFlux, Intervention, RP} ]
[math: CO_2e_{Counterfactual, RP} = CO_2e_{AirSeaFlux, Counterfactual, RP}][math: \Delta CO_2e_{AirSeaFlux, RP} = CO_2e_{AirSeaFlux,Intervention, RP} - CO_2e_{AirSeaFlux, Counterfactual, RP}]
[math: CO_2e_{Removal, RP} = \Delta CO_2e_{AirSeaFlux, RP} - CO_2e_{Emissions, RP} ][G-FCD7-0, Projects must describe how the uncertainty is quantified for each term in the net carbon removal equation. ]Section 2.5.7 of the Isometric Standard. See Section 5.5.1 for more details.
Type: Ocean Storage
Gross CO2 removal via OAE occurs at a wide range of spatial and temporal scales. The quantification framework for the gross CO2 removal requires explicit characterization of four spatio-temporal regimes depicted in Figure 2. At the smallest scales, alkalinity is released into the ocean at the dosing location, causing a decrease in the seawater pCO2. Over seconds to hours, in the mixing zone (A regulatory concept describing the spatial area surrounding the discharge infrastructure where water quality criteria can be exceeded.), the plume mixes and moves as its initial momentum is dissipated. Over hours to years, the pCO2-depleted water within the surface mixed layer, which may have spread over several hundred kilometers, facilitates additional oceanic carbon uptake from the atmosphere or reduction in outgassing via air-sea gas exchange. Air-sea gas exchange may span the coastal and open ocean domain. In the coastal domain, the pCO2-depleted water moves and mixes due to nearshore processes such as tides, coastal currents, and waves, while in the open ocean domain, the altered water is primarily transported horizontally by regional to basin-scale currents and vertically by upwelling and/or downwelling.
Figure 2 Schematic of the four spatio-temporal regimes that need to be characterized for the calculation of the gross CO₂ removal. Shown in this example, alkalinity discharged at depth generates a buoyant plume which initially rises and mixes in the mixing zone. Seawater CO2 depletion following alkalinity addition generates a pCO2-deficient plume which is transported by various processes across a range of scales in the coastal and open ocean domains. Air-sea gas equilibration in the coastal and open ocean domains facilitate additional CO₂ uptake or reduces natural ocean outgassing, leading to a net reduction of atmospheric CO2. The spatial scales encompassed by each domain will vary depending on the site and intended activity. Note: a buoyant plume at depth is used for illustrative purposes. Other coastal discharge infrastructure such as surface outfalls can be used.
This Protocol requires [math: \Delta CO_2e_{AirSeaFlux, RP}] to be determined in three steps, corresponding to the different spatio-temporal regimes. These steps are summarized below and detailed in the subsequent sections:
See Appendix 3: Supplementary Figures for a graphical summary of these steps.
All models used for quantification must be validated in line with Section 2.5.5 of the Isometric Standard. For numerical ocean models used in this Protocol, additional requirements and guidance are provided in Appendix 2 and the Air-Sea CO2 Uptake Module v1.1.
Note that the quantification framework for [math: \Delta CO_2e_{AirSeaFlux, RP}] is written for projects that raise TA but not DIC. Projects whose primary alkalinity source is carbonate feedstocks, i.e. feedstocks that contain carbon and upon dissolution would increase the amount of DIC in the ocean (but not as a result of CO2 removal from the atmosphere), will require some adjustments to the above quantification approach. The same general steps can be followed, but with alterations to account for the DIC that is added in addition to alkalinity. Adjustments to the quantification approach must be agreed upon with Isometric.
Relevant Regime: alkalinity dosing location
The effluent measurements are taken from the outflow pipe prior to release to the ocean. Measurements must be described in the PDD, and include details about sampling methods, sampling frequency, instrument calibration, data reporting and quality assurance/quality control. Analysis and reporting of monitoring data and measurement uncertainties should occur for every Reporting Period (see Section 78.1 for definition of a Reporting Period).
These descriptions must include at a minimum:
Electrochemical OAE approaches
Projects must describe how the following parameters are continuously monitored throughout the dosing period: alkalinity dosing rate, the total time-duration of discharge and the timeseries of volumetric flow rate.
[/G-PP4H-0]If projects are using electrochemical OAE approaches, they must include a description of how uncertainty in the amount of alkalinity over a Reporting Period mustwill be reported.
Mineral OAE approaches
The total quantity of alkalinity determined by dry feed material weight must be measured prior to discharge. The total time-duration of discharge, timeseries of mass flow rate and timeseries of volumetric flow rate must be continuously monitored throughout the dosing period to determine and calibrate the upper bound on the alkalinity dosing rate. The upper bound is only realized if full dissolution occurs within the mixed layer, but the alkalinity addition based on particle dissolution and sinking must be further quantified in the coastal dynamics domain (see Step 2 below and Appendix 2 for more details).
[/G-XZVV-0]In the outflow pipe, the fraction of solid and dissolved alkalinity must be measured or estimated. Whenever possible, Project Proponents should validate their initial particle dissolution kinetics via direct sampling from the effluent pipe (e.g., collecting a grab sample from the effluent pipe, followed by immediate filtration and analysis of the filter and the filtrate for relevant cation content).
[/G-HMQG-0]The uncertainty in the amount of feedstock released to the ocean over a Reporting Period must be disclosed.
[/G-59K5-0]Measurement approaches should be cross-referenced with relevant standards where applicable following Appendix 1 of the protocol.
[/G-RYET-0]Relevant Regime: mixing zone and coastal domain
A coastal dynamics study is needed to characterize transport and mixing of the alkaline plume by ambient currents and turbulence. This enables upscaling of the initial alkalinity dosing, which may occur over a small region of space, to a time-variable alkalinity forcing function applied to the ocean model used to quantify air-sea CO₂ uptake. In addition, processes such as calcification that result in losses of alkalinity should be quantified, and the losses must be subtracted from the alkalinity forcing function applied to the ocean model used in Step 3. See Section 78.43.2 for more details on alkalinity losses.
In the ocean model, alkalinity addition should be applied as a 3-D interior forcing. Typically, to maximize the atmospheric CO2 drawdown effect, alkalinity should be added at or close to the surface ocean, but this may not always be the case. Thus, the vertical distribution of the alkalinity is important to carefully characterize for the forcing function. Laterally, the shape of the alkalinity forcing can be represented as a Gaussian or similar parametric form. The results of the coastal dynamics study should be the time-variable 3D alkalinity forcing function to be applied to the model used for quantifying CO2 uptake, along with its uncertainty.
A few different options for determining the time-variable alkalinity forcing function are outlined below. The choice of an appropriate approach depends on the specifics of the project site and OAE project.
[/R-CP7S-0]For mineral OAE, the feedstock sinking and dissolution impacts the amount of TA added, the timing of when TA is elevated, and the vertical and lateral distribution of TA addition. The maximum possible dissolved alkalinity addition is achieved if full mineral dissolution occurs in the water column, but the dissolved alkalinity addition may be reduced if feedstock particles sink out of the mixed layer before dissolving or accumulate on the sea bed and interact with natural alkalinity fluxes. Therefore, unless the feedstock is "fast dissolving," the dissolution and sinking of the feedstock in the ocean needs to be robustly demonstrated through coastal modeling and/or measurements. See Section 9: Pre-deployment requirements for more details on feedstock characterization.
[/G-CKAF-0]Ways to determine the time-variable alkalinity forcing function include:
Hybrid approaches that combine multiple options above, or alternative novel approaches are welcome provided they are well-described and justified, and will be assessed by Isometric on a case-by-case basis. For any of the upscaling approaches used, the uncertainty of the resulting alkalinity forcing function must be determined. For some projects, a DIC forcing function may also need to be obtained using a similar approach.
Project Proponents must consider and disclose the following in the PDD when determining the time-variable alkalinity forcing function:
Relevant Regime: coastal domain and open-ocean domain
Once the alkalinity forcing function for the model used to quantify air-sea CO2 uptake is obtained, [math: \Delta CO_2e_{AirSeaFlux, RP}] can be calculated according to the Air-Sea CO2 Uptake Module v1.1. Note that the Air-Sea CO2 Uptake Module provides details on how to calculate [math: \Delta CO_{2, AirSeaFlux}(t)] at a point in time [math: t]. The removal over a Reporting Period, RP, spanning the time period from [math: t_1] to [math: t_2] is given by [math: \Delta CO_{2, AirSeaFlux, RP} = \Delta CO_{2, AirSeaFlux}(t_2) - \Delta CO_{2, AirSeaFlux}(t_1)].
Air-Sea CO2 Uptake Module
In addition to satisfying all the Module requirements, two additional sense checks must be reported in the PDD:
The air-sea CO2 equilibration must be quantified over the coastal domain, the open-ocean domain, or both. However, it is not required for air-sea gas exchange to be quantified over the initial transport and mixing of the alkaline plume in the coastal domain. This represents a more conservative approach to quantifying CO₂ uptake as the initial air-sea exchange is expected to be large due to the enhanced pCO₂ deficit before full dilution, and there are increased uncertainties regarding air-sea flux parameterizations in coastal areas on short timescales.3226 . If quantification of Removals in the coastal domain is desired, then the coastal domain model must meet the requirements of the Air-seaSea CO₂ Uptake Module v1.1.
The requirements of the Air-Sea CO₂ Uptake Module v1.1 apply for all domains over which Removals are quantified i.e. if quantification of Removals occurs over the coastal domain, then the coastal domain model must meet the requirements of the module.
[/G-46FW-0]In addition, appropriate care must be taken to ensure connectivity and no double counting of Removals between the coastal and open-ocean domains. This could be accomplished for example with multiscale nested models, or appropriate upscaling of the coastal CO₂ uptake as an additional DIC forcing in the open-ocean model. These approaches must be described in the PDD and will be assessed on a case-by-case basis.
[/G-QVBH-0]Relevant Regime: alkalinity dosing location and coastal domain
There are some known processes that could reduce the TA added and subsequently reduce [math: \Delta CO_2e_{AirSeaFlux, RP}]. These are referred to as “losses”, and they must be accounted for in the removal quantification such that the appropriate quantity of TA is represented in the models encompassing air-sea gas exchange. If it cannot be justified that these losses are negligible, it is expected that these alkalinity losses are quantified and subtracted from the alkalinity forcing function as part of Step 2 of the quantification approach (Section 78.43.1.2), since the models used to quantify the air-sea CO₂ removal vary in the degree to which they represent the losses, if at all3327.
Upon alkalinity discharge in the ocean, the following processes can cause losses of TA that may reduce the efficiency of OAE:
Understanding these and potential other loss terms is an active area of scientific research, and the list of known losses in this Protocol and quantification approach will be updated as research evolves.
In the PDD, Project Proponents must describe the risk of these losses, as well as either (1) a justification of why the losses are negligible or (2) a strategy for quantifying them. Due to the difficulty and uncertainty in quantifying the impact of these processes at this time, acceptable treatment of loss terms in this Protocol include:
Losses considered must include: secondary precipitation, biotic calcification, and changes in counterfactual alkalinity release from interactions with sediments.
[/G-EVMR-0]Data, measurements and evidence used in the quantification of losses must be publicly disclosed. Specific example recommendations for each loss term are discussed below.
[/G-2GGD-0]Secondary Precipitation
Secondary precipitation of calcium carbonate in seawater following alkalinity enhancement would remove alkalinity and could cause CO₂ outgassing. In the open ocean, abiotic calcium carbonate precipitation is rare because spontaneous nucleation is strongly inhibited in seawater3428, 3529, 3630, and most carbonate production is thought to be biologically mediated3731. There are very few areas of the ocean where spontaneous carbonate precipitation is observed (e.g. the Great Bahama Bank and the Persian Gulf3832). Such locations typically have exceptionally high saturation states (i.e. [math: \Omega_{CaCO_3}] > 19)3933. In coastal areas, higher suspended particulates may increase nucleation. Early research suggests there is a relationship between increased alkalinity loss with higher TSS in the receiving water body4034. Thus, the risk of secondary precipitation is most pronounced in the mixing zone and coastal domain, where the pH and TA perturbation from OAE is highest and TSS is elevated.
Limiting pH and the aragonite saturation state has been shown to be effective at avoiding this result, and laboratory research to characterize the critical thresholds that trigger precipitation under close-to-natural conditions are ongoing4135, 4236, 4337, 4438. Furthermore, precipitation dynamics occur on a timescale between minutes to hours4135, 4337, which suggests that dilution could be an effective risk mitigation strategy4539.
An example avoidance strategy is setting a pH threshold, with consideration of TA, TSS and dilution at the site, and continuous monitoring of pH, TA, and TSS to ensure that conditions for secondary precipitation are avoided. Thresholds should be justified by academic literature or laboratory analysis of site-relevant characteristics. In some cases, secondary precipitation can be identified by an observed increase in turbidity. Monitoring of turbidity is recommended, however it may be difficult to isolate a signal from secondary precipitation over natural fluctuations.
Biotic Calcification
Increases in biotic calcification also remove alkalinity and can cause CO₂ outgassing. The carbonate chemistry conditions promoted by OAE could promote calcification due to the lowered H+/ elevated saturation state4640, 4741, 4842, 1917. Early stage research manipulating Total Alkalinity with the aim of simulating OAE has found no significant increase in biologically produced calcium carbonate at elevated alkalinity in the ocean4943, 5044 . However, the Black Sea, a naturally elevated alkalinity environment, harbors extensive blooms of the coccolithophores 5145, 5246, a major group of calcifying plankton. This is thought to be due to the favorable carbonate chemistry promoted by the elevated alkalinity regime1917. This is still an area where more research is needed, particularly through mesocosm and field trials. The risk of alkalinity loss due to biotic calcification may be project and location specific. Recently published meta-analyses synthesizing data from ocean acidification studies for OAE supports this claim that species and functional group specificity is likely 5347. Coastal areas with significant benthic calcification of CaCO3 sediments may be especially susceptible to this feedback.
One potential avoidance strategy is for Project Proponents to set thresholds on pH and TA and monitor for changes in ocean biota. Thresholds should be justified by academic literature or laboratory analysis of site-relevant characteristics. For example, a recent study used lab experiments on representative species of two biogeochemically important phytoplankton functional groups to assess sensitivity to biotic calcification under limestone-inspired OAE conditions4943. This study suggests pH < 9 and [math: \Delta]TA < 1000 μmol/kg as thresholds below which biotic calcification was avoided under the particular conditions studied. Similar studies targeting site relevant water chemistry, OAE perturbation, and calcifying population can be used to determine relevant site and project specific thresholds.
Interactions with Sediments
Early research suggests that OAE may reduce natural alkalinity fluxes from sediments5448. This risk may be exacerbated by mineral OAE projects which result in alkalinity enrichment in sediments, and the potential impacts on the net removal calculation is highly uncertain at this time. More research in this area is needed and the Protocol will be updated with future advancements.
A recommended avoidance strategy for mineral OAE projects is to limit accumulation of alkalinity on the sea bed through careful selection of rapidly dissolving feedstock, dosing rate and project sites with full water column mixing and/or sufficient resuspension due to shear forces at the sea bed. Potential monitoring approaches may include sediment sampling, measuring particle settling and accumulation rates. Alternatively, acceptable evidence for quantification could include numerical modeling of particle transport in receiving waters, sediment sampling, sediment transport modeling, measuring benthic alkalinity fluxes, measuring changes in net calcification at the sea bed and sediment diagenesis modeling.
Type: Counterfactual
For OAE, the ocean baseline air-sea CO₂ fluxes are already accounted for (see Equations 3-5) and are incorporated in the [math: \Delta CO_2e_{AirSeaFlux, RP}] term in Equation 5. A reminder of the notation used throughout this Protocol is that [math: \Delta] represents a difference between the OAE intervention and counterfactual scenarios.
Type: Emissions
[math: CO_2e_{Emissions, RP}] is the total GHG emissions associated with a Reporting Period, [math: {RP}]. This can be calculated as:
[math: CO_2e_{Emissions,\ RP} = CO_2e_{Establishment,\ RP} + CO_2e_{Operations,\ RP} + CO_2e_{End-of-Life,\ RP} + CO_2e_{Leakage,\ RP}]
Equation 6
Where
The following sections set out specific quantification requirements for each variable.
GHG emissions associated with project establishment should include all historic emissions incurred as a result of project establishment, including but not limited to the SSRs set out in Table 1.
Project establishment emissions occur from the point of project inception up untilto the firstmoment Reporting Period. Establishment emissions may be accounted for in the following ways, with the allocation method selected and justified by the Project Proponent:
The anticipated lifetime7 of the projectGHG shouldAccounting beModule basedv1.1.
Refer to Section 7 of the GHG Accounting Module for guidance on reasonable justification and should be included in the Project Design Document (PDD) to be assessed as part of project validationamortization.
Allocation of project establishment emissions to removals must be reviewed at each Crediting Period renewal and any adjustments made. If the Project Proponent is not able to comply with the allocation schedule described in the PDD e.g. due to changes in delivered volume or anticipated project lifetime, the Project Proponent must notify Isometric as early as possible in order to adjust the allocation schedule for future removals. If that is not possible, the Reversal process will be triggered in accordance with the Isometric Standard, to account for any remaining emissions.
GHG emissions associated with [math: CO_2e_{Operations, RP}] must include all emissions associated with operational activities, including but not limited to the SSRs set out in Table 1.
[math: CO_2e_{Operations, RP}] emissions occur over the Reporting Period for the deployment being credited and are applicable to the current deployment only. [math: CO_2e_{Operations, RP}] emissions must be attributed to the Reporting Period in which they occur, this includes neutralization and disposal of acid waste generated as part of an electrochemical OAE project. Allocation may be permitted in certain instances, on a case by case basis in agreement with Isometric.
[math: CO_2e_{End-of-Life, RP}] includes all emissions associated with activities that are anticipated to occur after the Reporting Period, but are directly or indirectly related to the Reporting Period. For example, this could include ongoing sampling activities for MRV for the specific deployment (directly related), or end-of-life emissions for the project facility (indirectly related to all deployments).
GHG emissions associated with [math: CO_2e_{End-of-Life, RP}] may occur from the end of the Reporting Period onwards, and typically through to completion of project site deconstruction and any other end-of-life activities.
GHG emissions associated with activities that are directly related to each deployment must be quantifiedestimated asupfront part of that Reporting Period. GHG emissions associated with activities that are indirectly related to all deployments may beand allocated in the same waysway as set out infor calculation of [math: CO_2e_{Establishment, RP}].
Given the uncertain nature of [math: CO_2e_{End-of-Life, RP}] emissions, assumptions must be revisited at each Crediting Period and any necessary adjustments made. Furthermore, if there are unexpected [math: CO_2e_{End-of-Life, RP}] emissions associated with a Reporting Period, or the project as a whole, that occur after the project has ended, then the Reversal process will be triggered to compensate for any emissions not accounted for.
[math: CO_2e_{Leakage, RP}] includes emissions associated with a projectProject's impact on activities that fall outside of the system boundary of aThe projectProject. It includes increases in GHG emissions as a result of theThe projectProject displacing emissions or causing a knock onsecondary effect that increases emissions elsewhere. As an example, creating a market for feedstocks may generate new revenue in the source sector that alters producer behavior in ways that result in additional GHG emissions.
ItFor isOAE the Project Proponent's responsibility to identify potential sources ofProjects, leakage emissions, however,associated forwith anfeedstock OAEreplacement projectand theconsumables followingreplacement must be considered as a minimum.
GHG emissions accounting must be undertaken in alignment with the GHG Accounting Module v1.1, which ensures a consistently rigorous standard in how GHG emissions are quantified and reported between different CDR Projects and approaches. This includes:
Refer to the GHG Accounting Module for guidance on GHG accounting requirements. The Energy Use Accounting Module 1.3 provides requirements on how energy-related emissions must be [mathModule: CO_2e_{Leakage,ghg-accounting RP}v1.1]attributedcalculated tofor The Project so that they can be subtracted in the Reportingnet PeriodCO2e inremoval which they occurcalculation. Allocation may be permitted in certain instances, on a case by case basis in agreement with Isometric.
This sectionIt sets out specificthe requirementscalculation relatingapproach to quantificationbe offollowed energyfor useintensive asfacilities partand ofnon-intensive thefacilities GHGand Statementacceptable emission factors.
Energy Emissionsemissions associatedare withthose energyrelated usage result from the consumption ofto electricity or fuel.
Examples of electricity usage. They may include, but are not limited to:
Examples of fuel consumption may include, but are not limited to:
TheRefer to the Energy Use Accounting Module for guidance on fuel and energy emissions calculations.
The GHG Accounting Module v1.21 provides requirements on how energy-relatedtransportation and embodied emissions must be calculated infor aThe CDR projectProject so that they can be subtracted in the net CO₂eCO2e removal calculation. It sets out the calculation approach to be followed for intensive facilities and non-intensive facilities and acceptable emissions factors.
Refer to Energy Use Accounting Module for the calculation guidelines.
This section sets out specific requirements relating to quantification of transportation emissions as part of the GHG Statement.
Emissions associated with transportation includes transportation of products and equipment as part of a Reporting Period’s activities. Examples may include, but are not limited to:
The Transportation Emissions Accounting Module provides requirements on how transportation-related emissions must be calculated in a CDR project so that they can be subtracted in the net CO₂e removal calculation. It sets out the calculation approach to be followed and acceptable emissions factors.
Refer to Transportation Emissions Accounting Module for the calculation guidelines.
This section sets out specific requirements relating to quantification of embodied emissions as part of the GHG Statement. Embodied emissions are those related to energy use or other emissions during the manufacturelife cycle impact of equipment and materialsconsumables. used in a process, andThey may apply to all terms in Equation 1.
Examples of project-specific materials and equipment that must be considered as part of the embodied emission calculation include, but are not limited to:
TheTransportation Embodiedemissions Emissionsare Accountingthose Modulerelated setsto outtransportation of products and equipment. They may include, but are not limited to:
Refer to EmbodiedSection Emissions4.1 and Section 4.2 of the GHG Accounting Module for theguidance calculationon guidelinesembodied and transportation emissions calculations.
The long term storage reservoir of the CO₂ removed through OAE is as Dissolved Inorganic Carbon (DIC) in the ocean. The durability and reversal risks of this storage reservoir are discussed in the following Module.
Ocean DIC Storage Module
As outlined in SectionRisk 2.5.9of Reversal section of the Isometric Standard, the Bufferbuffer Poolpool (A common and recognized insurance mechanism among Registries allowing Credits to be set aside (in this case by Isometric) to compensate for Reversals which may occur in the future.) is a mechanism used to insure against Reversal risks that may be observable and attributable to a particular project through monitoring.
In BasedRiver onAlkalinity present understandingEnhancement, reversalscarbon inis thestored globalas oceandissolved Dissolvedinorganic Inorganic Carboncarbon (DIC) reservoir will not be directly observable with measurements and attributable to a particular project. Reversals of DIC in the ocean, a vast and well-mixed reservoir where storage durability is aexpected system-wide storage uncertainty that shouldto be addressedbetween through10,000 furtherand scientific100,000 researchyears. Projects applicable toAs this Protocolconstitutes arean generallyopen categorizedsystem aswith havingno adirectly Veryobservable Low Risk Level of Reversal according toreversals, the Isometric Standard Riskclassifies AssessmentProjects Questionnaire.operating Riskunder this Protocol as “No observable risk” for the purposes of reversal information is given in Appendix 4:the Risk of Reversal Questionnaireassessment, withand furthersuch informationProjects providedare withinnot therequired relevantto storagecomplete modulea Risk of Reversal questionnaire.
Following theThis Isometricresults Standardin Sectiona 2.5.9,0% buffer storage uncertainty pool for openProjects systems is primarily accounted within the removal quantification. For projects applicable tousing this Protocol, safeguards are in place to minimize risks of reversals (e.g. due to acid leakage) and areStorage accounted for in Section 7Module. The approach for quantifying theThis reversal risk and the stability of the ocean DIC reservoir will be reassessed at the renewal of the Crediting Period (The period of time over which a Project Design Document is valid, and updatedover aswhich Removals or Reductions may be Verified, resulting in Issued Credits.), or when new scientific research and understandingknowledge arisesare produced.
For more details on Reversals, refer to Sectionsthe 2.5.9Reversals and 5.6Buffer Pools Section of the Isometric Standard.
All
Project Proponents must provide a site description including the dominant circulation and modes of variability, as well as the frequency of various environmental conditions. At minimum, information must be provided on seasonal patterns, predominant currents in relation to tidal ranges, atmospheric forcing (winds and air temperature), periods of maximum stratification, periods of upwelling or downwelling and periods when receiving water quality conditions may be more critical for ecological health. For some sites, it may also be necessary to include discussion on riverine inputs, groundwater inputs, waves, sediment transport and ice presence.
Project Proponents must disclose other marine CDR activities which are co-located at the site.
Currently, there is minimal research on co-located marine CDR projects. Due to nonlinear interactions, attribution and prediction of air-sea CO2CO2 uptake and environmental impacts for co-located projects is more challenging. Project co-location includes projects with overlapping mixing zones, spatially and temporally, and may extend to projects with overlapping regions of air-sea CO2CO2 uptake. Collaboration on quantification and environmental monitoring efforts is recommended for co-located projects. The level of interaction between projects is expected to decrease as the alkalinity perturbation becomes more dilute away from the alkalinity dosing location. Guidance on robust quantification and responsible environmental safeguarding for multiple projects operating in the same area will be updated with the latest research.
Project Proponents must develop a conceptual model of plume transport and dispersion, such as through producing a mixing zone model (which is usually a standard requirement in ocean discharge permits, see Appendix 2). The mixing zone model will estimate initial alkalinity dispersal and inform the spatial extent of monitoring efforts.
[/R-EYJ2-0]Sensitivity analysis is required to demonstrate adherence to water quality limits at the boundary of the mixing zone under varying environmental conditions.
Project Proponents must select alkalinity dosing rates that result in alkalinity release that adhere to safety thresholds and minimize water contamination and accumulation on the sea bed (if applicable).
[/R-2KDQ-0]It is recommended that safe alkalinity dosing rates are determined through modeling.
[/G-4RTP-0]Alkalinity dosing schedule should gradually ramp up to the intended dosing rate for continuous discharge.
Additional
Project Proponents must characterize aspects of feedstock in accordance with the Isometric Rock and Mineral Feedstock Characterization Module v1.2. These include major and trace elemental abundance, mineralogy, particle size distribution, and surface area. Furthermore
Feedstock dissolution rate must be characterzed using feedstock specific dissolution rate constants, feedstock particle size and surface area as inputs. Feedstock dissolution kinetic parameters may be drawn from peer-reviewed scientific literature, publicly available reputable scientific sources, and/or empirical data collected by the Project Proponent. "Fast dissolving" feedstocks are defined as those in which dissolution happens within minutes in the water column and before particles settle on the seabed. Evidence of fast dissolving feedstocks must be disclosed in the PDD, for example as demonstrated through dissolution experiments and/or models of particle sinking speeds.
Additional
If projects are using electrochemical OAE approaches, Project Proponents must provide detailed information on the neutralization and disposal route for acid byproduct (e.g. HCl). Spillage of acid byproduct would exacerbate local ocean acidification, and counteract carbon dioxide removal achieved by the OAE project. Such spillages must be disclosed and applied against the net CO2e removal as required in Section 7.2.
If projects are using electrochemical OAE approaches, Project Proponents must identify and provide detailed information on the storage and disposal of hazardous by-products (e.g. chlorine gas, hydrogen gas).
[/R-9X51-0]A monitoring plan must be established prior to project activities and described in the PDD. The aims of the monitoring plan are to demonstrate permit compliance, monitor environmental conditions, conduct ongoing measurement for quantification, and establish processes for adaptive management to ensure that projects stop if negative impacts are identified.
[/R-XJ0P-0]Thresholds on parameters for monitoring are used to determine safe limits for discharge and identify negative environmental impact. Two types of thresholds are used:
The monitoring plan must include details about monitoring duration, frequencies, location, sample collection methods, analytical methods, thresholds (if applicable), data reporting and quality assurance/quality control. Analysis and reporting of monitoring data and measurement uncertainties should occur for every Reporting Period (see Section 78.1 for definition of a Reporting Period).
Analytical methods for discrete bottle samples must follow the Guide to Best Practices for Ocean CO₂ Measurement for carbonate chemistry parameters and Sampling and Sample-handling Protocols for GEOTRACES Cruises for trace metals (for more recommended analytical methods, see Appendix 1).
[/G-1ZQY-0]Projects must report how data gaps will be handled.
[/G-99F8-0]Monitoring guidance and requirements will be updated in alignment with advances in sensor technology which enhance the capacity for measurement and monitoring.
Monitoring must span pre-deployment, throughout dosing and post-dosing.
[/G-KC9A-0]For pre-deployment environmental monitoring, Project Proponents must provide a baseline characterization of monitored water chemistry and ecological parameters at the site, which should be sufficiently long and well-resolved to characterize background ocean variability. The exact duration and frequency of monitoring will depend on the parameters being measured, as well as site and project specific factors.
[/G-714Z-0]Listed below are considerations for determining and justifying the monitoring frequency and duration, and some illustrative examples can be found in Appendix 1.
The duration of pre-deployment monitoring should consider:
Likewise, post-dosing environmental monitoring should consider:
The monitoring frequency should reflect what is necessary to provide sufficient information about the effluent and receiving waters. Some factors which may influence the frequency and intensity of the monitoring plan include:
The environmental monitoring plan must cover the following general locations listed below. This Protocol does not prescribe exact monitoring locations. Project Proponents are responsible for determining appropriate monitoring locations. It is recommended that Project Proponents use models to plan and optimize sampling design5549. A diagram of the monitoring locations, including the location in the water column, must be included in the monitoring plan submitted in the PDD (an example is shown in Figure 3).
Projects must justify why a control site has or has not been established as part of the monitoring plan.
[/G-NMKK-0][Image: **Figure 4** Plan view of monitoring locations]
Figure 3 Plan view showing example monitoring map, where T = temperature, S = salinity, DO = Dissolved Oxygen, TSS = Total Suspended Solids, and Chl-a = chlorophyll-a. Bold text indicates required measurements, otherwise measurements are recommended. See Table 4 for justification and more details of environmental monitoring measurements. *Alkalinity may be calculated from measurement of a third carbonate system variable e.g. pCO₂, with routine bottle samples of alkalinity to check alkalinity calculations are consistent with measurement.
Effluent prior to discharge
These monitoring requirements apply to all credited OAE projects under this Protocol. They represent the minimum common measurement requirements for all projects. Additional measurements may be needed depending on project and site specifics
Effluent prior to discharge
Project Proponents must monitor effluent characteristics prior to ocean discharge through ongoing measurement of pH, alkalinity, temperature and salinity of the effluent. ]
Project must monitor effluent characteristics prior to ocean discharge through ongoing measurement of pH, alkalinity, temperature and salinity of the effluent.
[/G-WYAX-0]Temperature and salinity are required for determining physical characteristics of the effluent, and pH and alkalinity are monitored to demonstrate compliance with the dosing rate allowed under official permitting and described in the PDD.
[/G-GK6J-0]Measurements of pH and alkalinity may also be used to inform and validate mineral dissolution rates, if applicable.
[/G-QWXW-0]Since frequent alkalinity samples may be difficult to sustain in practice, and there are no ready-to-deploy alkalinity sensors available at this time, alkalinity may be calculated from measurements of two carbonate system variables (e.g. pH and pCO2), with routine bottle samples of alkalinity to check calculations of alkalinity are consistent with measurement. It is a known limitation of using pH and pCO2 measurements to constrain the full carbonate system that uncertainty can be high5650.
Project Proponents are responsible for ensuring that the effluent monitoring location provides a representative and well-mixed characterization of the effluent.
[/G-Z6N6-0]It is also recommended that Project Proponents measure a third carbonate system variable (pCO2 or DIC) to assess the initial state of carbonate system disequilibrium at the point of discharge.
[/G-JVGV-0]When reporting calculated carbonate chemistry variables in the PDD, justification of state of equilibrium, equilibrium constants used in carbonate chemistry speciation software and number of carbonate chemistry parameters used for calculations must be disclosed.
[/G-6GCG-0]Effluent must adhere to the pH safety threshold allowed under official permitting. The safety threshold must be met at the location indicated on permit allowances (such as at the end of the pipe prior to, or in the ocean after initial mixing). Regardless of where the safety threshold is applied, Project Proponents should calculate the corresponding in-pipe threshold, such that ongoing compliance can be monitored.
[/G-T585-0]Mixing Zone
These monitoring requirements apply to all credited OAE projects under this Protocol. They represent the minimum common measurement requirements for all projects.
[/R-4VR0-0]The area where initial dilution takes place is often called the mixing zone (or "a reasonable mixing zone" or "zone of initial dilution"), typically on the scale of O(100m), depending on the scale of discharge. A mixing zone is a regulatory concept, which describes a spatial area surrounding the discharge infrastructure where water quality criteria can be exceeded.5751 Permits which allow for a mixing zone require water quality criteria to be met at the edge of a mixing zone. A mixing zone is simplified representation of initial mixing, the true spatial extent of initial mixing changes dynamically with environmental conditions.
Detection of a measurable signal may be difficult beyond the mixing zone, especially for small-scale deployments. Increased sampling efforts may be necessary for accurate assessment within the mixing zone due to heterogeneous effects of turbulence. Beyond the mixing zone, receiving waters will display less turbulent variability, which can provide more representative measurements of the impact of alkalinity addition. Thus, environmental monitoring should be focused on the edge of the mixing zone. A spatially distributed array of sensors may provide more comprehensive coverage of the mixing zone and plume transport.
Project
Projects must monitor temperature, salinity, two carbonate chemistry parameters (pH, TA, DIC, pCO2), DO, turbidity and TSS at the edge of the mixing zone.
[/G-DT3T-0]Temperature and salinity are necessary for determining physical conditions, and should be collocated with other measured quantities.
[/G-N3V4-0]Two carbonate chemistry parameters (pH, TA, DIC, pCO2) must be monitored to characterize the carbonate system for the purpose of monitoring water quality, determining local carbonate saturation state and informing loss term estimates (see Section 7.4.2).
[/G-8RPS-0]An additional third carbonate system measurement is recommended to assess the local state of carbonate disequilibrium.
[/G-G2E3-0]DO, turbidity and TSS are water quality indicators. Action thresholds are placed on pH, TSS and DO (see Section 10.5: Determination of Action Thresholds).
[/G-WDJE-1]Chl-a and dissolved inorganic nutrients are also recommended.
[/G-34YY-0]Burst sampling is recommended for parameters monitored with autonomous sensors within the mixing zone. By sampling at a high frequency, burst sampling can provide insights into the turbulent mixing processes and contributes to greater statistical certainty in the temporal variability and distributions of the monitored parameter.
[/G-3Q9R-0]Additional measurements may be needed depending on project and site specifics, alkalinity loss strategy, and environmental risk mitigation plan.
[/R-RGKN-0]There are additional required or recommended monitoring procedures for different types of OAE projects.
There are additional required or recommended monitoring procedures for different types of OAE projects.
[/R-7AP3-0]Intake
For projects with intake pipes, Project Proponents must take actions to mitigate risk of adversely harming marine biota originally contained in the seawater, and assess the realized ecological impacts of impingement and entrainment in the intake pipe due to pumping, and treatment of seawater prior to and during electrochemical treatment. Such impacts can be determined though demographic or conditional mortality approaches2018.
Biological and ecological monitoring in deployment area
Project Proponents are recommended to conduct periodic ecological surveys to monitor phytoplankton community abundance and composition, benthic community abundance and diversity and presence and potential interactions with species of special concern (IUCN listed, commercially exploited or keystone species). Functional diversity should be considered in addition to taxonomic diversity. Survey sites should include the immediate vicinity of the discharge pipe and specific benthic habitats within the affected area of the OAE project activities to be identified and determined on a site-by-site basis.
Action thresholds are not imposed on ecological indicators due to the difficulty of establishing ecological baselines and attributing ecological changes. Data collection remains imperative for establishing a foundation for future analysis and enabling the assessment of cumulative and chronic impacts of OAE.
[/G-HRDJ-0]Ecological data must be made publicly available, and the location of where data is stored publicly must be included in the PDD.
[/G-5D97-0]Additional requirements for mineral OAE
Project Proponents must assess accumulation of feedstock on the seabed, which may require a combination of sediment measurements and coastal dynamics modeling.
[/G-S24W-0]When undertaking mineral OAE Project Proponents are required to monitor heavy metal and trace elements concentrations, both within the water column and sediments. The elemental composition of mineral feedstocks and sediments should be analyzed in line with Section 3.45.1 of the Rock and Mineral Feedstock Characterization Module v1.2.
The concentration of heavy metals and trace elements in water and sediments must not exceed the limits established by the local authority where the project is located. In the absence of local regulations, the Project Proponent must adhere to standards set by the Isometric Standard and United States Environmental Protection Agency (US EPA). It is the responsibility of the Project Proponent to report adherence to local, regional and national regulatory standards within the PDD submitted to the projects VVB.
[/G-0BW6-0]If heavy metal contamination is already present in the sediments before starting the project (as identified in the baseline scenario), the project may still be considered for this Protocol. This is contingent on the Project Proponent providing evidence of existing contamination via detailed elemental and geochemical characterization.
[/G-M0QV-0]As projects scale beyond pilot projects and get closer to approaching operational capacity, Project Proponents are recommended to monitor trace metal concentration in the tissue of representative benthic organisms.
[/G-7NKG-0]Project Proponents may also be required to conduct sediment sampling to validate estimates for losses due to secondary precipitation and counterfactual alkalinity fluxes through analysis for changes in CaCO3 content, brucite precipitation, and natural alkalinity fluxes (see Section 7.4.2).
[/G-VAF5-0]Measurements for model validation and model inputs
Measurements are also essential for model validation, which must be demonstrated prior to using the model for quantification of CO2 uptake (see Appendix 2 Mixing Zone and Coastal Dynamics Modeling, and Section 43.16 in Air-Sea CO2 Uptake Module v1.1).
Furthermore, ocean data (such as winds, currents, tides, waves, turbulent mixing etc.) are inputs to the model used to quantify air-sea CO2 uptake. This data may originate from data collected at the field site by the project, or data made available from other sources such as government agencies.
It is recommended that Project Proponents measure air-sea carbon flux to validate modeled carbon flux in the model used to quantify air-sea CO2 uptake. At this time, there are no existing sensors which can directly measure CO2 flux. Methods for integrating proxy and/or tracer measurements into a quantification for CO2 uptake should be validated via intercomparison. Methods may include gradient method, eddy covariance, flux chambers or dual tracer regression, and modeled uptake.
Table 4 below summarizes the required and recommended monitoring parameters. Required measurements indicate the minimum common set of measurements needed for all projects under this Protocol. Additional required measurements may be necessary based on specifics of the project, site, alkalinity loss quantification strategy, and environmental risk mitigation plan. The exact monitoring plan must be described in the PDD.
Use of calibrated in situ sensors for continuous monitoring with discrete water samples for validation is recommended (see Appendix 1). Analytical methods for discrete bottle samples must follow the Guide to Best Practices for Ocean CO₂ Measurement5852 for carbonate chemistry parameters and Sampling and Sample-handling Protocols for GEOTRACES Cruises5953 for trace metals (for more recommended analytical methods, see Appendix 1). Guidance for measurements and sampling strategy will be updated as innovations in measurement develop.
Table 4. Summary of required and recommended measurements for monitoring. Required measurements indicate the minimum common set of measurements needed for all projects under this Protocol. Additional required measurements may be necessary based on specifics of the project, site, alkalinity loss quantification strategy, and environmental risk mitigation plan. The exact monitoring plan must be described in the PDD.
Location | Parameter | Requirement Scope | Reason for Measurement | Methods | Frequency |
|---|---|---|---|---|---|
Effluent | pH | Required for all projects | Required for demonstrating compliance with the pH threshold described in the PDD and quantification of alkalinity losses via secondary precipitation | pH sensor or discrete bottle samples | Ongoing throughout deployment |
Alkalinity | Required for all projects | Required for demonstrating compliance with the dosing rate described in the PDD | Discrete bottle samples May also be calculated from measurement of a third carbonate system variable e.g. pCO₂, with routine bottle samples of alkalinity to ground truth whether calculated alkalinity is consistent with measurement | ||
Temperature | Required for all projects | Required for determining physical conditions and making calculations to fully constrain the seawater carbonate system | Sensor | ||
Salinity | Required for all projects | Required for determining physical conditions and making calculations to fully constrain the seawater carbonate system | Sensor | ||
Alkalinity dosing rate for all projects | Required for all projects | Required for determining the total alkalinity introduced as a result of the project activity, needed as an input to the mixing zone and coastal models for alkalinity upscaling | Sensor or calibrated based on dry feed weight of feedstock and flow rate | ||
Flow rate | Required for all projects | Required for determining physical conditions of discharge and ensuring accurate representation of discharge in mixing zone model for alkalinity upscaling | Flow meter | ||
Fraction of dissolved alkalinity | Required for mineral OAE projects | Required for determining the fraction of solid and dissolved alkalinity to be input into the coastal model | Grab sample and subsequent filtering and analysis | ||
Edge of mixing zone | Temperature | Required for all projects | Required for determining physical conditions and making calculations to fully constrain the seawater carbonate system | Sensor | (a) at high frequency when ramp-up is occurring and shortly after any dosing rate changes are made |
Salinity | Required for all projects | Required for determining physical conditions and making calculations to fully constrain the seawater carbonate system | Sensor | ||
Any two carbonate system paramters | Required for all projects | Required to constrain the seawater carbonate system, monitor water quality and local carbonate saturation state | Sensor (for pH or pCO₂) or discrete bottle samples | ||
Third carbonate system paramters | Recommended for all projects | Recommended to assess the local state of carbonate disequilibrium | Sensor (for pH or pCO₂) or discrete bottle samples | ||
Dissolved Oxygen | Required for all projects | Required as indicator of general ecosystem health | Sensor | ||
Total Suspended Solids | Required for all projects | Required for monitoring water quality and quantification of alkalinity losses due to secondary precipitation. Risk of elevated total suspended solids is higher with mineral OAE projects | Discrete bottle samples and filtering directly onto pre-weighed filter and subsequent measurement of mass change through drying (for example, in an oven) | ||
Turbidity | Required for all projects | Recommended as part of ecosystem monitoring because elevated turbidity can impact photosynthesis and benthic ecosystem health, and be an indicator of secondary precipitation. Risk of elevated turbidity is higher with mineral OAE projects. | Sensor or discrete water sample | ||
Chlorophyll-a | Recommended for all projects, may be required as part of project-specific environmental risk mitigation strategy | Recommended as an indicator of general ecosystem health (phytoplankton primary productivity) | Sensor or discrete water sample | ||
Dissolved inorganic nutrients | Recommended for all projects, may be required as part of project-specific environmental risk mitigation strategy | Recommended as an indicator of general ecosystem health (available nutrients for primary productivity) and nutrient limitation impacts from secondary precipitation. | In situ sensor or discrete water sample via mooring or routine boat sampling | ||
Deployment area | Plankton community | Recommended for all projects, may be required as part of project-specific environmental risk mitigation strategy | Recommended periodically for monitoring of ecosystem health, documentation of shifting baseline ecology and contributions to primary research | Plankton tow or other methods | At agreed upon intervals, before, during and after deployment |
Benthic community | Recommended for all projects, may be required as part of project-specific environmental risk mitigation strategy | Recommended periodically for monitoring of ecosystem health, documentation of shifting baseline ecology and contributions to primary research Recommended for water and tissue samples in keystone biological species to track potential trace and heavy metal accumulation | Benthic survey or other methods | ||
Trace metal concentration | Recommended for all projects, may be required as part of project-specific environmental risk mitigation strategy | Recommended for water and tissue samples in keystone biological species to track potential trace and heavy metal accumulation | Discrete bottle and tissue sampling | ||
Sediments in mixing zone or in areas of accumulation | Trace metal concentration and sediment composition | Required for mineral OAE with feedstock and dosing rates that measurably increase sediment concentrations | Required for sediments to track potential trace and heavy metal accumulation Recommended to validate estimates for losses due to secondary precipitation and counterfactual alkalinity fluxes through analysis for changes in CaCO3 content, brucite precipitation, and natural alkalinity fluxes | Sediment sampling | |
Throughout OAE facility | Marine biota samples | Required for projects with seawater intakes | Required to quantify the impact of seawater processing on resident marine biota | Demographic mortality survey, conditional mortality survey, or other methods |
Action thresholds can be absolute or relative, and can be determined by regulatory limits, relative to natural variability based on historical data or relative to a control site. For example, the action threshold on pH could be pH < 9 or ±0.2 relative to natural variability or to a control site, whichever is more conservative. Action thresholds may vary seasonally, and should be consistent with monitoring requirements under official permitting.
Control site guidance
Establishing a control site can help isolate the impacts of ocean alkalinity enhancement from baseline variability. However, finding a control site is challenging due to various factors. Firstly, an ideal control site will have a clear separation between perturbation and control, where the only difference between the two locations is the alkalinity addition. Spatially, this means that the correlation scale between relevant parameters should exceed the separation distance (distance between pertubed site and control site), while simultaneously, perturbation mixing zones must be smaller than the site separation.
However, environmental noise introduces variability, muddling the clean separation of perturbation and control. Furthermore, balancing the size of perturbations with instrument detection limits is crucial; large perturbations risk contaminating the control site, while smaller ones may be challenging to detect amidst background noise. These challenges underscore the difficulty in validating a control site. Thus, for this Protocol, deploying instruments or collecting samples at a control site is determined on a site by site basis as outlined in the PDD and is not universally required.
Violations are determined based on the threshold type, and specificities of the site, permit and intended activities. For example, exceedance of safety thresholds may be determined by daily mean or max values and exceedance of action thresholds in the mixing zone may be determined by weekly and/or monthly mean or max values. All violations need to be reported, and gaps in monitoring data must be justified.
Credits cannot be issued for time periods without sufficient in-pipe effluent measurements. The handling of data gaps must be reported in the PDD. Removal activity from discharges that occur during time periods of safety threshold violations will not be eligible for Crediting. Action threshold violations must trigger adaptive management plans. Failure to adequately address environmental risks or remediate any harm will lead to a project being subject to Credit cessation.
Isometric would like to thank the following contributors to this Protocol and relevant Modules:
Isometric would like to thank the following reviewers of this Protocol and relevant Modules:
Alkalinity dosing location
The point source at which alkalinity is discharged into the surface ocean.
Counterfactual
A quantification of what would have happened in the absence of a particular intervention, i.e. assuming the baseline conditions.
Deployment area
The area over which ecological and biological indicators should be monitored for changes due to chronic exposure to alkalinity enhancement, determined on a project-specific basis in the PDD. This is likely to be smaller than the coastal modeling domain but larger than the mixing zone.
DIC
Dissolved inorganic carbon
Dosing Period
The period of time over which alkalinity or feedstock is discharged into the ocean.
EPA
Environmental Protection Agency
GHG
Greenhouse gas
GWP
Global Warming Potential: Calculations should use the 100-yr GWP for the GHG of interest, based on the most recent volume of the IPCC Assessment Report, currently the Sixth Assessment Report4. Current 100-yr GWPs are: CO2 = 1; CH4= 27.9; N2O = 273
ISO
International Organization for Standardization
Mixing Zone
A regulatory concept describing the spatial area surrounding the discharge infrastructure where water quality criteria can be exceeded.
MRV
Monitoring, Reporting and Verification
PDD
Project design document
Reporting Period
The Reporting Period (RP) for OAE represents an interval of time over which removals are calculated and reported for verification. See Section 78.1 for full details.
Surface ocean
The ocean mixed layer, whose depth can vary depending on time and location.
Total Alkalinity
Defined as an excess of proton acceptors over proton donors, which functionally describes the ability of a solution to neutralize acids to the CO₂ equivalence point.
VVB
Validation and verification body
While quantification of Carbon Dioxide Removal (CDR) associated with Ocean Alkalinity Enhancement (OAE) relies heavily on ocean models, field measurements play an important role in:
Broadly, field measurements may include moored in situ sensors, ship-based or autonomous transecting and profiling, discrete bottle sampling, field surveys, aerial imaging and remote sensing. There is significant variability in the specific instruments and field methods that may be used to conduct collect data.
Project Proponents must provide thorough documentation on planned and completed field campaigns, including details on the campaign design (spatial and temporal coverage, sampling density, data collection techniques, instrument resolution), metadata, data processing, analytical and statistical techniques, instrument calibration and data quality control. In the sections that follow, we highlight some recommended references and best practices to ensure high quality data generation from field measurements.
Collecting discrete bottle samples alongside continuous autonomous sensor measurements is recommended. Both measurement types offer advantages, for example autonomous sensors can offer wider temporal coverage, while bottle samples are crucial for ground truthing absolute values. Additionally, bottle samples can be used to calibrate drift of long term autonomous sensor deployments.
To facilitate accessibility, transparency and interoperability of research relevant data, data collected from field campaigns must adhere to FAIR data principles14. Project Proponents should follow the data standards and controlled vocabularies described in Guide to Best Practices in Ocean Alkalinity Research: Chapter 13 (Data reporting and sharing for ocean alkalinity enhancement research)6054. Metadata should be complete according to the NOAA ocean acidification metadata template6155.
Note on alkalinity and pH measurements
Alkalinity is used in multiple fields that may have different terminology and definitions. For example, total or titration alkalinity is widely used in oceanography, whereas charge balance alkalinity is commonly used in freshwater systems and by geologists6256. This protocol uses the oceanographic community terminology when referring to measurements taken in the ocean, where total alkalinity (TA) for seawater is defined following Dickson 1981 based on acid titration to the CO2 equivalence point6357. However, alternative definitions of alkalinity that may be more appropriate for specific projects (e.g. for non-seawater systems, such as effluent from a wastewater stream) should be specified in the PDD.
There are also different scales used for pH measurements which may differ by over 0.16458. For example, the National Bureau of Standards (NBS) scale is suitable for freshwater systems and waters with low ionic strength, while for seawater, the total hydrogen ion scale is more commonly used6559. This protocol recommends the total hydrogen ion scale for seawater pH measurements, following the SOPs below in the Guide to Best Practices for Ocean CO2 Measurements. Care should be taken to account for differences in pH scales, such as when comparing pH measurements against regulatory thresholds.
For discrete bottle samples, we refer Project Proponents to the Best Practice Data Standards for Discrete Chemical Oceanographic Observations6660. Additional considerations for discrete bottle sampling of carbonate chemistry are discussed in Guide to Best Practices in Ocean Alkalinity Research: Chapter 2 (Seawater carbonate chemistry considerations for ocean alkalinity enhancement research: theory, measurements and calculations)6761.
Recommended analytical methods for bottle samples include:
Parameter | Recommended Method |
|---|---|
Carbonate Chemistry parameters (pH, DIC, TA) | |
Nutrients |
|
| Methods of Seawater Analysis | |
Salinity | |
Dissolved Oxygen | |
Chl-a | |
TSS | |
Trace metals |
The following methods are approved by the Clean Water Act, EPA:
For autonomous instruments, Project Proponents are recommended to follow manufacturer provided user manuals for instrument preparation, maintenance, calibration and quality control. Environmental and deployment factors which may affect the quality and interpretation of data, (e.g. instrument orientation, interference, presence of bubbles, sediment, and biology) must be described.
Adoption of innovative sensor technologies is encouraged. For novel sensors, additional information that would typically be available from a manufacturer would also have to be provided. These include detection range, resolution, accuracy, performance under different environmental conditions (i.e. temperature ranges) and response time. The expected measurement conditions must be within the sensor’s range.
Project Proponents must perform instrument calibration before deployment, and recalibrate instruments at an interval recommended by the manufacturer. Calibration curves or equations for the instrument or sensor must be documented. Post-deployment calibration is recommended to account for instrument drift over the deployment duration.
Project Proponents must develop a maintenance plan for moored instruments deployed longer than 30 days. This should include plans to clean or replace sensors that may be impacted by biofoul, such as optical sensors, conductivity cells or flow through sensors.
Data processing techniques must be documented, including quality control, filtering, despiking and statistical analysis. The recommended quality control process differs between instruments. Data should be reported using quality control flags consistent with International Oceanographic Data and Information Exchange (IODE)6862.
The quality control manuals for autonomous instruments prepared by the Integrated Ocean Observing System are a recommended resource.
Quality control checks could include:
Data Analysis Methods for Physical Oceanography is a recommended resource for statistical analysis methods6963.
Tracer studies track effluent using a tracer that is either naturally present or added. They can be useful for OAE projects to:
Ideal tracers are not harmful to the environment, have near zero background concentration, are conservative or decay very slowly in relation to the duration of field work, mix freely and can be measured in the field at low concentrations. As such, examples of tracers that may be used in OAE are fluorescent dyes (i.e. rhodamine dye) and gas tracers (SF6, CH3, SF5, 3He).
Fluorescent dye tracers, such as rhodamine dye, are preferable because they can be detected from aerial imaging or high frequency in situ sensors. Rhodamine dye degrades in days to weeks, and can be helpful for characterizing near-field mixing. Gas tracers have a lifespan on the order of years, and can be useful for large scale experiments, however, they have high global warming potential.
Tracers can be injected into the effluent to increase the ability to track the effluent. Alternatively, the tracer dye can be released directly into the water column as a slug release, to help constrain localized dispersion characteristics for coastal models.
If a tracer study is conducted to characterize alkaline plume transport in the coastal domain, the sampling plan must include vertical profiling along transects. A sufficient number of studies are required to produce a sensitivity analysis. Sampling plan, data analysis and interpretation will be evaluated on a case by case basis. See the LOC-NESS project for an example of an OAE tracer study design and accompanying sensing suite.
The US EPA Operating Procedure7064 and USGS Procedure for Dye Tracer Measurements7165 are recommended resources.
The following checklist can be referenced for tracer release studies using rhodamine dye to validate a coastal model or characterize alkaline plume transport.
Study planning:
Materials preparation:
Release:
Sampling (ship-based or underway system):
Data quality and interpretation:
Below are some hypothetical examples that are for illustrative purposes only, to demonstrate some of the site and project considerations when determining the appropriate monitoring duration and frequency for a particular parameter and use case.
Example 1
A project is monitoring for changes in ocean pH near the discharge site to make sure the change in pH does not exceed a threshold of +/-0.2 of the natural variability of pH. The dosing period is 1 week, and the residence time of the region where pH sensors are deployed is 1 day. At this site, it is known from previous studies and published literature that the dominant temporal modes of variability for pH are diurnal and seasonal, due to biological activity.
Monitoring duration: Because the activity and dosing period are much shorter than the seasonal variability in this case, it is not necessary for the baseline characterization to span a full year to resolve the seasonal cycle. Instead, the baseline monitoring for a few days before deployment is sufficient. There is ongoing monitoring during the 7 day dosing period, and the post-dosing monitoring for pH should additionally span at least the residence time. To be conservative and to collect additional safety data though, the project decides to extend post-dosing monitoring for 1 week.
Monitoring frequency: To resolve the diurnal cycle variability, sampling should be conducted at a higher frequency than daily, e.g. sampling at minimum every 6 hours would result in at least 4 measurements per day and would be sufficient here. Luckily, the project uses continuous pH sensors, which allows them to sample much more frequently to fully resolve the diurnal cycle.
Example 2
An environmental risk of a mineral OAE project that the local community is concerned about is bioaccumulation of metals in a nearby oyster farm. To address this, the project is monitoring the concentration of trace metals in oyster tissues before and after the project activity. The project is dosing feedstock particles into the ocean for 1 week, but some of the feedstock will accumulate on the seafloor and it can take up to 3 months for the particles to fully dissolve. The farm grows oysters in the ocean for 1 year before harvesting.
Monitoring frequency: The accumulation of any metals in oysters will take some time, especially because it will take a few months after project dosing completes for the feedstock particles to dissolve. Thus it was decided to sample the oysters once a month for the first 3 months following the project since that is the period during which particle dissolution is expected to occur, and then once a season after that.
Monitoring duration: In this case, the community would like to know the impacts on the oysters that are being harvested for food. So the post-deployment monitoring lasts for 1 year post-dosing (taking seasonal samples) to span the oysters growth cycle and to ensure that metal concentrations do not exceed the local food safety regulatory limits. A control sample was collected from a number of oysters pre-deployment.
Characterization of alkaline plume transport and spread is required in the mixing zone and coastal domain. Modeling in the mixing zone is required by standard permitting processes to demonstrate adherence to water quality criteria and environmental safeguarding. The output of the mixing zone model can be used in a coastal model to determine the time and depth-dependent interior alkalinity forcing to the open-ocean model used to simulate air-sea gas exchange.
Mixing is a multi-scale phenomenon, and a model or series of models may be required to upscale the near point source alkalinity dosing into an interior alkalinity forcing function to the full domain where air-sea gas exchange is modeled.
In the initial dilution region (or mixing zone), transport and mixing is dominated by the differences in velocity and density between the discharge and the receiving water. Typically, effluent is discharged at a higher velocity than ambient currents, which generates turbulent mixing. Ocean outfalls tend to be at depth and discharge less dense effluent than the receiving water (ie. freshwater discharging into marine waters). The relative density difference affects the rise rate, where the discharge surfaces or the position of the plume in the water column if trapped beneath the surface. Figure A2-1 shows the cross-section of the initial jet motion of a submerged buoyant jet discharged into stratified water7266.
Initial dilution continues until energy dissipation brings the plume velocity to match the receiving water, and the plume is at a depth where it has the same density as the receiving water. Once this point is reached, the effluent plume typically moves horizontally with the receiving waters and ambient turbulence causes further dispersion.
Figure A2-1 Initial transport and dispersion of buoyant plume discharged at depth into stratified waters. Inspired by Jirka et al. (1979)7266. Note: other coastal discharge infrastructure, such as surface outfalls or where a plume is not buoyant may also be used.
Dilution Capacity
Dilution capacity of a receiving water is the effective volume of receiving water available to dilute the discharge. Dilution capacity can be variable due to environmental conditions. For example, stratification reduces the effective volume of receiving water by constraining vertical mixing, and tides affect the total volume of water in the receiving body. For environmental safeguarding, the worst-case scenario for mixing must be evaluated with a sensitivity analysis. This typically coincides with low tide and strong stratification, although it can be significantly altered by other environmental factors.
Relevant Environmental Factors in Receiving Waters
The marine environment is dynamic, with stratification, atmospheric forcing, tidal flows and freshwater inputs, varying on a range of timescales from diurnal to seasonal. In the marine environment, coastal circulation is often dominated by local wind and waves interacting with bathymetry. In shallow waters, ocean waves also affect mixing and dilution. Buoyancy-driven currents can also exist along coastlines. Estuaries are further impacted by freshwater inflow, tidal activity, stratification, groundwater and benthic activities.
The majority of projects will have a density difference between effluent and marine receiving waters, and as such it is advised to couple a mixing zone model with a coastal model.
A mixing zone model represents the discharge plume when it is dominated by its own momentum and buoyancy, whereas the coastal model represents the plume's transport and dispersal once it is dominated by ambient dynamics.
Commercial mixing zone models, such as CORMIX or Visual Plumes, can be used to determine initial plume dispersion. We note that mixing zone models assume sufficient dilution capacity of the receiving water such that the ambient conditions are not affected by the discharge. The tracer concentration from a mixing zone model can be used as an input in the coastal model.
At minimum, the coastal model must accurately reproduce the hydrodynamic processes of the study area and behavior of a non-reactive tracer. Opting to do a simpler model such as 1D or 2D is only permissible in certain cases and must be thoroughly justified. A summary of acceptable models in included in Table A2-1. Commercially available modeling software can be used. Biogeochemistry is not required for coastal dynamics modeling, due to the relatively short time-scales of the coastal dynamics model compared to time-scales of air-sea gas exchange.
Table A2-1. Options for coastal model
Coastal model | Use case |
|---|---|
1D hydrodynamic model | Laterally well mixed |
2D hydrodynamic model | Minimal variability in one horizontal direction |
3D hydrodynamic model ie. Delft3D, MIKE 3, TELEMAC 3D, FVCOM | Stratification is non-uniform and dynamic density differences between effluent and receiving water |
Nested hydrodynamic models | Upscaling alkalinity release to subsequently larger grid scales and model |
Particle tracking for Mineral OAE projects
Explicit representation of particle transport and dissolution is highly recommended for mineral OAE projects to determine the depth and time dependent alkalinity forcing. Realistic distributions of particle size, dissolution rates, particle density and particle shape are needed to accurately represent particle motions and sinking velocities. Modeling wave transport may be required depending on the site.
The model domain should be large enough to ensure that boundary condition influences are negligible in the vicinity of the plume. The model resolution should be chosen to appropriately resolve near-field dynamics.
Table A2-2 and Table A2-3 summarizes the typical input data required for the mixing zone model and coastal model respectively. Project Proponents are required to report all inputs to model runs.
If projects are using existing ocean outfalls, the outfall specifications must be determined (Table A2-2). For new infrastructure, modeling should be done to optimize outfall and diffuser design to maximize initial dilution and/or minimize environmental accumulation.
Since field campaigns span a limited time period, distributions of observed quantities are unlikely to represent historical maxima and minima. It is advised that inputs for environmental variables are based on statistical analysis of all historical data available.
Any parameterizations used to represent physical dynamics in the model must be disclosed in the PDD.
Table A2-2. Mixing Zone inputs
Parameters related to effluent | Outflow location |
Volumetric flow rate | |
Density | |
Parameters related to discharge infrastructure | Diameter and length of outfalls |
Diameter and length of diffusers | |
Angles of port orientations from horizontal | |
Port diameters | |
Depth | |
Number of ports | |
Port spacing | |
Parameters related to receiving water | Depth |
Velocity | |
Density Stratification |
Table A2-3. Coastal model inputs
Parameters related to discharge | Mixing zone modeling results represented as inputs to coastal |
Boundary conditions | Tidal heights at model boundaries |
Atmospheric forcing | |
Freshwater inputs | |
Predominant current speed and direction | |
Temperature, salinity, density, stratification | |
Initial conditions | Predominant current speed and direction |
Temperature, salinity, density, stratification | |
Other locally important factors | Ocean waves, ice |
Parameters related to particles (for mineral OAE) | Particle size distribution |
Dissolution rate (modeled) | |
Particle shape | |
Particle density | |
Model domain parameters | Bathymetry |
Bottom roughness coefficient | |
Eddy viscosity coefficient | |
Grid resolution and model grid | |
Model domain size | |
Time step | |
Simulated time duration |
Coastal dynamics models must demonstrate capability to represent hydrodynamic processes of the site through comparison with independent field data. The model can be calibrated using a subset of field observations, and validated by applying the calibrated model to one or more historical events and demonstrating a reasonably high level of agreement between model and observations. Project Proponents should refer to Section 43.16 in the Air-Sea CO2 Uptake Module v1.1 for guidance on model validation.
In addition to validating baseline physical dynamics, it is advantageous to ensure that the model can replicate the OAE perturbation. Evaluating the physical transport of alkalinity release can be accomplished through a tracer study, such as dye injection into effluent. Validating the biogeochemical response to the OAE perturbation involves tracking the spatial extent and relative changes in carbonate chemistry parameters. Achieving such validation would necessitate starting with a validated baseline model. Next, this validated baseline would have to be utilized to design an efficient sampling plan. Following that, an OAE perturbation with a discernible signal above background environmental variability must be produced. Additionally, sufficient instrumentation and sampling resources would be required to provide the necessary spatial and temporal coverage for observing the evolution of carbonate chemistry parameters following an OAE perturbation. This is an iterative cycle which consists of models and measurements informing each other. Although recommended, validation of the biogeochemical response at the project-level is not required, with the anticipation that ongoing scientific inquiry and field trials will advance a comprehensive system-wide validation of biogeochemical modeling for OAE. Where possible, it is recommended that individual processes (such as air-sea CO2 flux) are validated through comparison with measurements collected from the field.
See Appendix 12 for guidance on ocean sampling and high quality data generation.
A sensitivity analysis is required to develop a distribution of alkalinity forcing functions. If the coastal dynamics model is not able to replicate realistic tidal and atmospheric forcing that is representative of the Reporting Period, then the sensitivity analysis must span a wider variety of historical conditions and the following parameters should be varied in ensemble scenarios:
The result of the sensitivity analysis should be a range of expected, best and worst case conditions for alkalinity distribution within the water column (from the coastal model), and water quality conditions (from the mixing zone model).
All stages of modeling from conceptualization to results interpretation must be reported.
Model runs must be retained and reported in the PDD.
This Appendix contains supplementary figures to further clarify parts of the Protocol.
Figure A3-1 illustrates some of the quantification options described in Section 7.4.1. All projects must measure the alkalinity or feedstock dosing rate at the effluent (Step 1), and all projects must quantify the net CO₂ removal as a result of air-sea gas exchange in an appropriate ocean model (Step 3). To upscale the point source alkalinity dosing into a 3-dimensional alkalinity forcing that can be applied to the model used to quantify air-sea CO₂ uptake, Project Proponents have flexibility to choose from a number of options (Step 2).
Figure A3-1 Example of quantification options described in Section 7.4.1.
Projects applicable to this Protocol are generally categorized as having No Observable Risk of Reversal according to the Isometric Standard Risk Assessment Questionnaire. This results in a 0% buffer pool for Projects using this Protocol and Storage Module. However, if a Project identifies project-specific factors which impact the Risk of Reversal, they are required to complete the Risk of Reversal Questionnaire below.
This risk assessment identifies the pathway specific risk factors relevant to a carbon removal project. The relevant risk factors identified as part of a risk assessment are included in the monitoring plan requirements for the project, with details included in the Project Design Document. Project specific risk factors inform the required duration of monitoring along with the monitoring requirements set out in the Protocol and the requirements set out in the Monitoring Section of the Isometric Standard.
The risk score, as determined by the Risk of Reversal Questionnaire, will determine a project’s buffer pool contribution. Projects must re-assess their reversal risk at the renewal of each crediting period, or if monitoring identifies a reversal-related risk, or if an actual reversal event takes place. In any event, projects should reassess their reversal risk at a minimum every 5 years.
The Risk of Reversal Questionnaire questions that pertain to this protocol, drawn from the programme-level Risk of Reversal Questionnaire defined in Appendix B: Risk Reversal Questionnaire of the Isometric Standard, include the following:
No. in Isometric Standard Questionnaire | Question | If answered “Yes” | If answered “No” |
|---|---|---|---|
1 | Is a reversal directly observable with a physical or chemical | Proceed to questions 2- | Proceed to questions 8- |
8 | Is there 10+ years of monitoring and/or lab data demonstrating low project risk? | Minus up to 2 to Risk Score | |
9 | Does this pathway have a documented history of reversals in excess of proposed buffer pool size? | Add 2 to Risk Score | |
10 | Is there one or more project-specific factors that merit a high risk level? | Add up to 2 to Risk Score |
Note the Risk Score at any step cannot be negative.
Risk Score Categories:
Project specific risk factors will depend on the form of carbon being stored (i.e., organic vs. inorganic), the method of storage (e.g., mineralization, encapsulation), the location of carbon storage (e.g., subsurface, ocean), and the proximity of that carbon to potential agents of reversal.
For projects with carbon storage as inorganic carbon, the presence of the following risk factors must be reflected in the risk score corresponding to question 10:
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