Direct Air Capture

This Protocol provides the requirements and procedures for the calculation of net carbon dioxide equivalent (CO₂e) removals from the atmosphere via Direct Air Capture (DAC). This Protocol is developed for application to DAC processes (e.g., solid-sorbent processes,¹ liquid-solvent processes,² membrane processes,³ electro-chemical processes,⁴ etc.), or combinations of processes, in which a cradle-to-grave greenhouse gas (GHG) Statement can be accurately applied and in which the CO₂ captured is stored via physical⁵ or chemical⁶ trapping mechanisms for >1000 years.

The Protocol was developed in line with latest scientific understanding^7,8,9 and industry best-practices^10,11 which inform the quantification of gross CO₂ durably captured and stored via DAC, as well as the accounting of GHG emissions associated with DAC processes. Additionally, the Protocol ensures:

• Consistent procedures are used to measure and monitor all aspects of the process required to enable accurate accounting of net CO₂e removal;
• Consistent system boundaries and calculations are utilized to quantify net CO₂e removal;
• Requirements are met to ensure the CO₂ removals are additional; and
• Evidence is provided and verified by independent third parties to support all net CO₂e removal claims.

Specific standards and protocols which are utilized as the foundation of this Protocol, and which this Protocol is intended to be fully compliant with, are as follows:

• Isometric Standard; and
• ISO 14064-2: 2019 – Greenhouse Gases – Part 2: Specification with guidance at the project level for quantification, monitoring, and reporting of greenhouse gas emission reductions or removal enhancements.

Additional reference standards that inform the requirements and overall practices incorporated in this Protocol include:

• ISO 14064-3: 2019 – Greenhouse Gases – Part 3: Specification with Guidance for the verification and validation of greenhouse gas statements;
• ISO 14040: 2006 - Environmental Management - Life Cycle Assessment - Principles & Framework; and
• ISO 14044: 2006 - Environmental Management - Life Cycle Assessment - Requirements & Guidelines.

This Protocol was developed based on the current state of the art and publicly available science regarding DAC and CO₂ storage. Because DAC is still a developing approach to carbon dioxide removal (CDR), with ever-expanding published literature, the Protocol incorporates requirements that may be more stringent than some current regulations or other protocols related to DAC and CO₂ storage. The approach taken here may be altered in future versions of the Protocol as DAC and CO₂ storage technology and research advance.

This Protocol applies to projects that capture CO₂ from ambient air and store it durably according to the requirements established in the storage Modules associated with this Protocol (see Section 8). A cradle-to-grave GHG Statement must also be able to be accurately applied to all processes within the scope of the Project.

Projects that co-capture CO₂ from on-site point sources do not qualify for the generation of Credits under this Protocol, as this constitutes avoided emissions - not emissions removal. DAC projects that are co-located with industrial point sources of CO₂, defined here as being within 1km distance, are only eligible if the Project appropriately discounts measured gross CO₂ removals in an amount corresponding to the relative difference between local atmospheric CO₂ concentrations, and background atmospheric CO₂ concentrations - to ensure that only the captured fraction corresponding to non-fossil emissions is included in claimed removals. In practice, this should be achieved by measuring the concentration of CO₂ in the ambient air at the inlet to the DAC process, and discounting gross removals by an amount corresponding to the relative excess of this measurement compared to a background reading at a distance greater than 1km from the co-located industrial point source.

Only DAC projects which meet a zero emissions baseline scenario (see Section 7.2) are eligible under this Protocol. A Project may qualify for this distinction by meeting one of the following conditions:

• No capture facility existed at the capture facility location prior to the start of the project activity (greenfield capture facilities);
• New capture facilities or expanded capture facilities are installed at an existing capture facility location (expansion of existing capture facilities); or
• An existing capture facility would be decommissioned prior to the start of the project activity (refurbishment of an existing capture facility).

The Project must consider environmental and social impacts, and the Project Proponent must provide evidence that The Project will do no net environmental or social harm by complying with Section 3.7 of the Isometric Standard as well as the following requirements:

• CO₂ storage and pipelines must have monitoring systems in place to detect and identify potential CO₂ leaks, including audible alarms and regular monitoring or remote access to alarm notifications by Project Proponent staff following national/international regulations¹² (see Section 7.4.1 and the relevant storage modules for more information).
• The Project Proponent must have a CO₂ leak response plan in place that complies with local or national requirements¹² and covers the Area of Review (AOR). This plan must be shared with local communities and first responders in temporary holding, pipeline, and storage locations.
• The Project Proponent must document emissions of solvents and/or sorbents from the DAC Project and demonstrate that emissions of the following types are below regulatory limits where applicable based on solvent and/or sorbent chemistry:
  • Amines (volatilized or in aerosol form);
  • Ammonia;
  • Volatile organic compounds (VOCs);
  • Nitrosamines and nitramines;
  • Particulate matter, and
  • Other hazardous substances (as defined by the authority of the geography where the Project is located or the most stringent of relevant standards worldwide, for example by the EPA) that may be released as a result of sorbent or solvent degradation, volatilization, or aerosolization.
• Emission levels of solvents and/or sorbents must be demonstrated by using, where possible and reasonable, national or international standard test and sampling methods (i.e., NIST, ASTM, EPA), and should be completed by a qualified testing organization. Project Proponents must keep such records on file and must repeat testing when substantial changes to solvent or sorbent formulations occur or substantial changes in operating conditions occur that may impact emissions.
• Project Proponents must comply with all health and safety procedures as required by the authority of the geography where the Project is located or the most stringent of relevant standards worldwide. Proponents must demonstrate that they have addressed any specific hazards associated with the use of the proposed sorbent or solvent, and with high concentrations of CO₂.
• Demonstrate that a social risk assessment has been conducted. This must consider environmental and social justice issues for the selected storage site, including a robust Stakeholder Input Process and considerations of any direct or indirect impacts on local communities or indigenous people, including livelihoods, ancestral knowledge, and cultural heritage in line with the applicable human rights laws and United Nations declarations.
• Demonstrate a risk assessment and mitigation plan for safeguarding working conditions, especially regarding safe handling and transportation of solvents/sorbents as well as workers operating the capture and storage facility.
• The Project Proponent must monitor water consumption and water stress, in addition to implementing necessary mitigation activities to ensure water neutrality.¹³

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), 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 DAC, for example:

• Information on power purchase agreements (PPAs) or other direct long term offtake agreements for the procurement of energy (if applicable);
• GHG emissions associated with solvent/sorbent use and safe disposal; and
• Purity/concentration of CO₂ to be stored.

Projects must be validated and Project 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 Validation and Verification Body (VVB) must consider following requisite components:

1. Verify that storage sites adhere to the requirements listed in the relevant storage module;
2. Verify that the quantification approach and monitoring plan adheres to requirements of Section 7, including demonstration of required records;
3. Verify that the Environmental & Social Safeguards outlined in Section 5 are met; and
4. Verify that the Project is compliant with requirements outlined in the Isometric Standard.

The threshold for Materiality, 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 of the GHG Statement, as required by Section 2.5.7 of the Isometric Standard. Qualitative Materiality issues may also be identified and documented, such as:¹⁴

• Data and document control issues that erode the verifier’s confidence in the reported data;
• Poorly managed documented information;
• Difficulty in locating requested information; and
• Noncompliance with regulations indirectly related to GHG emissions, removals or storage.

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 minimum, site visits during validation and initial verification to the DAC Project and storage site. Verifiers should, whenever possible, observe operation of the capture and storage processes to ensure full documentation of process inputs and outputs through visual observation and validation of instrumentation, measurements, and required data quality measures.

A site visit must thereafter occur at least once every 2 years at each location.

VVBs must comply with the requirements defined in Section 4 of the Isometric Standard. In addition, teams should maintain and demonstrate expertise associated with the specific technologies of interest, including solvent/sorbent chemistry, electricity procurement, heat/power generation and the relevant CO₂ storage technology.

Competency must be demonstrated in accordance with Isometric's VVB policy, for example through the relevant sectoral scope accreditations in IAF MD 14.

CDR via DAC and subsequent storage is often a result of a multi-step process (such as capture, desorption, CO₂ transport, CO₂ temporary holding, CO₂ injection or reaction, etc.), with activities in each step sometimes managed and operated by different operators, companies, or owners. When there are multiple parties involved in the process (e.g. if capture and storage are undertaken by different entities), and to avoid double counting of net CO₂e removals, a single Project Proponent must be specified contractually as the sole owner of the Credits. 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 scenario and counterfactual utilized to assess additionality must be project-specific, and are described in Section 7.2 of this Protocol.

Additionality determinations should be reviewed and completed every five years (aligned with the Crediting Period), at a minimum, or whenever project operating conditions change significantly, such as the following:

• Regulatory requirements or other legal obligations for project implementation change or new requirements are implemented;
• Project financials indicate Carbon Finance is no longer required, potentially due to, for example:
  • Sale of co-products that make the business viable without Carbon Finance; or
  • Reduced rates for capital access.

Any review and change in the determination of additionality should not affect the availability of Carbon Finance and Verified Credits for the current or past Crediting Periods, but if the review indicates The Project has become non-additional, this should make The Project ineligible for future Credits.¹⁵

The uncertainty in the overall estimate of the net CO₂e removal as a result of the Project must be calculated and transparently presented. The total net CO₂e removed over a Reporting Period ($RP$; see Section 7.3.1) for a Project, $CO_2e_{Removal,\ RP}$, must be conservatively determined, based on the requirements outlined in Section 2.5.7 of the Isometric Standard.

Projects must report a list of all input variables used in the net CO₂e removal calculation and their uncertainties, including:

• Emission factors utilized, as published in public and other databases used;
• Values of measured parameters from process instrumentation, such as metered heat and electricity usage, sorbent/solvent replacement periods and other equipment considerations;
• Laboratory analyses, including that required by selected storage module(s), which could include analysis of carbon content and purity of CO₂, CO₂-containing injectants or carbonated minerals; and
• Summary of data handling, processing, and error propagation approach.

The uncertainty information should at least include the minimum and maximum values of a variable. 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 uncertainty must be provided. Details of the sensitivity analysis method must be provided so that the results can be re-created. Parameters may be omitted from a full uncertainty analysis if a sensitivity analysis can demonstrate that the parameter contributes to <1% change in removal. For all other parameters, information about Uncertainty must be specified.

In accordance with Section 3.8 of the Isometric Standard, all evidence and data related to the underlying quantification of the net CO₂e removal will be available to the public through Isometric's platform. This includes:

• Project Design Document;
• GHG Statement;
• Measurements taken;
• Emission factors used; and
• Scientific literature used.

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 emission 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.

The scope of this Protocol includes the GHG sources, sinks, and reservoirs (SSRs) associated with a DAC Project.

A cradle-to-grave GHG Statement must be prepared encompassing the GHG emissions relating to the activities associated with a DAC and storage Project for net CO₂e removal, as summarized in Figure 1 and described below:

• DAC process: All activities that take place associated with capturing atmospheric CO₂;
• CO₂ transportation: All activities associated with transporting CO₂ from the DAC plant to the storage location;
• CO₂ storage: All activities that take place associated with the permanent storage of CO₂ at the storage location; and
• CO₂ monitoring: All activities related to monitoring CO₂ storage.

Emissions for processes within the system boundary should include all GHG SSRs from the construction or manufacturing of each Project and associated equipment, closure of each Project and disposal of associated equipment, and operation of each process (DAC process, CO₂ transportation, CO₂ storage, and CO₂ monitoring).

Ancillary activities (such as supplementary research and development activities and corporate administrative activities) that are associated with a Project but are not directly or indirectly related to the issuance of Credits can be excluded from the system boundary.

GHG emissions and removals associated with the Project may be as direct emissions from a process or storage system, or as indirect emissions from combustion of fuels, electricity generation, or other sources. The Project Proponent must consider all GHGs associated with the relevant SSRs, in alignment with the United States EPA’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).

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).

The above greenhouse gases must be included in emission calculations for each calculation term identified in Figure 1, according to the following guidelines:

Calculation terms shaded in blue must account for potential emissions of CO₂ and other GHGs (e.g., CH₄, and N₂O) via use of appropriate emission factors and conversion to CO₂e.

Calculation terms shaded in green must account for potential emissions of CO₂ only, as no other GHG emissions are expected from these types of sources.

The baseline scenario for a DAC Project assumes the activities associated with The Project do not take place and any associated infrastructure is not built.

The counterfactual for DAC projects considers quantification of the CO₂ that would have been removed from ambient air via a DAC process and durably stored over the same period in the absence of the Project. As established in Section 4, the counterfactual of qualifying projects is typically considered to be zero, unless a counterfactual scenario is required in the applicable storage module.

DAC systems are typically operated continuously, with captured CO₂ being transported and durably stored using a variety of potential processes. Due to the continuous nature of DAC systems, the equations below used to calculate net CO₂e removals will pertain to all CO₂ removals and GHG emissions that occur over an interval of time. This unit of time is defined as the Reporting Period, $RP$, which represents an interval of time over which net CO₂e removals are calculated and reported for verification.

The following sections outline the process for calculating the net CO₂e removed for each Reporting Period, written hereafter as $CO_2e_{Removal,\ RP}$.

Net CO₂e removal for a process utilizing DAC must be calculated as follows for a Reporting Period, $RP$:

$$CO_2e_{Removal} = CO_2e_{Stored}\ –\ CO_2e_{Counterfactual}\ -\ CO_2e_{Emissions}$$

(Equation 1)

Where;

• $CO_2e_{Removal}$ = the total net CO₂e removed for a given $RP$, in tonnes of CO₂e.
• $CO_2e_{Stored}$ = the total CO₂ removed from the atmosphere and durably stored over the $RP$, in tonnes of CO₂e. See Section 7.4.1.
• $CO_2e_{Counterfactual}$ = the total counterfactual CO₂ removed from the atmosphere and durably stored in the absence of The Project over the $RP$, in tonnes of CO₂e. Note, unless otherwise specified in the applicable storage module, the counterfactual for DAC projects is typically zero. See Section 7.4.2.
• $CO_2e_{Emissions}$ = the total GHG emissions associated with the $RP$, in tonnes of CO₂e. See Section 7.4.3.

It should be noted that any potential reversals of CO₂ storage in the final storage location occur after Credits have been issued so are not included in this equation. See Section 5.6 of the Isometric Standard for further information. Risk of reversal information is given in Appendix 2: Risk of Reversal Questionnaire, with further information provided within the relevant storage module storage module.

Quantification of $CO_2e_{Stored}$ for the different conversion and storage options is detailed within the respective Modules.

Type: Counterfactual

Unless otherwise specified in the applicable storage module, the counterfactual ($CO_2e_{Counterfactual}$) for eligible projects is considered to be zero, as outlined in Section 4 and Section 7.2.

Type: Emissions

$CO_2e_{Emissions}$ is is the total quantity of GHG emissions associated with a given Reporting Period, $RP$. This can be calculated as:

$$CO_{2}e_{Emissions} = CO_{2}e_{Energy} + CO_{2}e_{Transportation} \\ + CO_{2}e_{Embodied} + CO_{2}e_{Misc.} CO_{2}e_{Leakage}$$

(Equation 2)

Where:

• $CO_2e_{Emissions}$ = the total GHG emissions for a given $RP$, in tonnes of CO₂e.
• $CO_2e_{Energy}$ = the total GHG emissions associated with energy consumption for a given $RP$, in tonnes of CO₂e, see Section 7.4.3.2.
• $CO_2e_{Transportation}$ = the total GHG emissions associated with transportation for a given $RP$, in tonnes of CO₂e, see Section 7.4.3.3.
• $CO_2e_{Embodied}$ = the total embodied GHG emissions allocated to a given $RP$, in tonnes of CO₂e, see Section 7.4.3.4.
• $CO_2e_{Misc.}$ = the total miscellaneous GHG emissions for a given $RP$, that cannot be categorized by $CO_2e_{Energy}$, $CO_2e_{Transportation}$, or $CO_2e_{Embodied}$, in tonnes CO₂e, see Section 7.4.3.5.
• $CO_2e_{Leakage,\ n}$= the total GHG emissions associated with the Project’s impact on activities that fall outside of the system boundary of a Project, allocated to a given $RP$, in tonnes of CO₂e, see Section 7.4.3.6.

Emissions that occur during a Reporting Period, $RP$, must be included directly and fully in that Reporting Period, and not allocated across multiple Reporting Periods.

Embodied emissions which relate to multiple Reporting Periods may be allocated to removals in line with the allocation rules set out in the Embodied Emissions Accounting Module v1.0.

When the Project Proponent is planning to cease operations within a given storage site, they must project any emissions associated with activities required for post-closure monitoring, and allocate them to the remaining removals taking place at the storage site. If that is not possible, the Project Proponent should allocate those emissions to other projects and/or storage sites they conduct removal operations at, in agreement with Isometric. If for any reason emissions are not appropriately allocated, the Reversal process will be triggered in accordance with Isometric Standard to account for any remaining monitoring emissions.

In instances where monitoring activities are shared between entities, for example if multiple DAC companies use the same storage infrastructure and share monitoring activities, the emissions associated with these activities must be allocated proportionally between the entities.

GHG emissions associated with $CO_2e_{Energy}$ should include all emissions associated with electricity usage or fuel combustion.

Energy related emissions may include, but are not limited to:

• DAC Process:
  • Electricity used in process operations, including renewable energy, such as:
    • Sorbent/solvent or other regeneration process (electrically heated, electrochemical, or other);
    • electricity for pumps, motors, drives, etc;
    • electricity for instrumentation and controls; and
    • electricity for building operation and management for DAC process buildings and direct support buildings (noting that research and development and administrative facilities are not included).
  • Fuel combustion for thermal energy generation (heat/steam) such as:
    • Sorbent/solvent or other regeneration process (thermal); and
    • Heat for DAC process buildings and operations.
  • Heat utilization for thermal processes;¹⁶ and
  • Cryogenic processes for CO₂ purification or liquefaction.
• CO₂ Transportation:
  • Electricity or fuel used for operation of a pipeline or similar non-mobile CO₂ transportation process.
• CO₂ Storage:
  • Electricity used for operation of any CO₂ conversion processes, such as ex- carbonate production and handling;
  • Electricity used for injection operations, including any pumps, compressors (including for compression into supercritical CO₂), or related equipment inside the injection facility gate; and
  • Fuel used for heat generation or other purposes at the conversion or injection sites.
• CO₂ Monitoring:
  • Electricity used for monitoring equipment operation, including analyzers, instrumentation, on-site laboratories specifically for monitoring activities;
  • Electricity used for sampling pumps, sampling systems, or other similar monitoring activities;
  • Electricity used for off site analytical laboratory operation and sample analysis;
  • Electricity used for monitoring system installation (if not accounted for in Project embodied emissions) and operation, such as electricity used for temperature control of monitoring systems (heat trace);
  • Electricity for building operation & management for monitoring facility buildings;
  • Fuel used for sampling system operation, such as any pumps or heating systems;
  • Fuel used for any handling equipment, such as fork trucks or loaders, which are used during sample collection and processing; and
  • Fuel used during monitoring system installation, operation or closure, such as that used by drill rigs.

The Energy Use Accounting Module v1.2 provides requirements on how energy-related emissions must be calculated so that they can be subtracted in the net CO₂e removal calculation. It sets out the calculation approach to be followed for intensive facilities and non-intensive facilities and acceptable emission factors.

Emissions related to transportation of CO₂ or injectants for all injections during a Reporting Period must be accounted for, including the following:

• Emissions associated with transportation of captured CO₂ from the DAC process to the injection site via pipeline;
• Emissions associated with transportation of compressed gaseous or liquid CO₂, or CO₂ containing injectant (such as a carbonate slurry), or carbonated minerals via freight transportation services, such as rail, truck, or maritime transport; and
• Transportation of samples for lab analysis.

The Transportation Emissions Accounting Module v1.1 provides requirements on how transportation-related emissions must be calculated so that they can be subtracted in the net CO₂e removal calculation. It sets out the calculation scope, approach to be followed, and acceptable emissions factors.

Embodied GHG emissions associated with the manufacturing, delivery, and installation of all equipment and consumables used in the DAC process must be accounted for in each $RP$. The Project Proponent must identify all equipment and consumables used in the DAC process, identify appropriate cradle-to-grave emission factors, and allocate the emissions to removals appropriately in line with the Embodied Emissions Accounting Module v1.0.

Project Proponents must account for all embodied emissions in equipment and facilities, including but not limited to, the following:

• Equipment, including:

  • DAC Process:

    • DAC Process equipment, including fans, scrubbers, adsorbers, or other contact and/or sorbent regeneration equipment;
    • Sorbent, solvent, or other material handling systems, such as pumps, conveyors, augers, feed bins, and related equipment;
    • Heat transfer equipment;
    • Captured CO₂ purification equipment;
    • CO₂ compression and storage equipment (on-site); and
    • Preparation or mixing equipment for sorbents, solvents, or other materials.

  • CO₂ transportation:

    • Equipment used for transportation of CO₂, including pipelines, and any pumps or compressors.

  • CO₂ storage:

    • Ex-situ CO₂ conversion or reaction equipment (i.e. for carbonate production), including all vessels, pumps, storage, and other process equipment;
    • Closed-system temporary holding of CO₂ at the injection site; and
    • CO₂ injection equipment, including compressors, pumps, and all wellbore equipment and materials.

  • Monitoring:

    • Monitoring wells and all associated materials (steel casing, concrete, etc.);
    • On-line analyzers, measurement equipment, or other such devices; and
    • Buildings and associated equipment utilized for monitoring purposes (e.g., on-site laboratories).

  • General equipment used along the value chain:

    • Pumps, piping, and related equipment;
    • Storage tanks;
    • Support structures, facilities, and infrastructure, including steel platforms, framing, supports, concrete footings, building structures, offshore rigs where applicable etc.; and
    • Instrumentation, controls, and other process management equipment.

Heat generation equipment and heat transfer equipment must be accounted for, but embodied emissions may already be accounted for by emission factors used for fuel combustion - which are often reported from cradle-to-gate. Project Proponents should evaluate whether embodied emissions from equipment such as boilers are included in the energy emissions calculations, and if not, account for the embodied emissions here.

Project Proponents must account for all embodied emissions in DAC process consumables including but not limited to the following:

• DAC Process:
  • Sorbents or solvents, including emissions associated with:
    • Sorbent production including any CO₂ emissions released directly from sorbent production, such as emissions of CO₂ from calcination of limestone; and
    • Proper disposal of used sorbents.
  • Heat transfer fluids such as thermal oils or refrigerants.
• CO₂ storage:
  • Feedstock or reactants used in the conversion of CO₂ to other products for storage; and
  • Dilutents or additives used to support or improve injection of CO₂ or CO₂-containing product.
• Monitoring:
  • Gases, reagents, or other materials used for operation of monitoring equipment, analytical testing, calibration of monitoring equipment and on-site analyzers; and
  • Consumable sampling equipment or supplies that are used in significant quantities.
• General consumables used along the value chain:
  • Gasses such as nitrogen used for process operations, instrumentation, purges, or other operations;
  • Water, including full cradle-to-grave emissions associated with:
    • Delivery of process water (including cooling water), including embodied emissions associated with water production equipment, such as new wellbores, pumps, and piping, and all energy usage for delivery; and
    • Disposal or treatment of used or waste process water (including cooling water), including emissions associated with wastewater treatment.
  • Water treatment chemicals used in cooling or process water.

In instances where infrastructure or equipment is shared between entities, for example if multiple DAC companies use the same storage infrastructure and associated activities, the emissions associated with these activities must be allocated proportionally between the entities.

The Embodied Emissions Accounting Module v1.0 sets out the calculation approach to be followed including allocation of embodied emissions, life cycle stages to be considered, and requirements for data sources and emission factors.

GHG emissions associated with $CO_2e_{Misc.}$ should include all Project emissions that cannot be categorized by $CO_2e_{Energy}$, $CO_2e_{Transportation}$, or $CO_2e_{Embodied}$. The Project Proponent is responsible for identifying all sources of emissions directly or indirectly related to Project activities, including associated with any activities additional to those set out in Section 7.1. The Project Proponent must report such emissions as $CO_2e_{Misc.}$.

Examples include, but are not limited to:

• Direct emissions of non-CO₂ GHGs due to process leaks or fugitive emissions, releases, or GHG containing tailgas from:
  • Conversion processes;
  • Degradation of sorbents or solvents; and
  • Any other source of potential GHG emissions not of the CO₂ collected from the ambient air or not addressed in $CO_2e_{Energy}$, $CO_2e_{Transportation}$, or $CO_2e_{Embodied}$ terms.
• Waste processing associated with all aspects of the DAC process, CO₂ transport, CO₂ storage and monitoring; and
• Staff travel associated with the Project.

Quantification of $CO_2e_{Misc. Project}$ in a given $RP$ should be undertaken in line with the requirements set out in the Energy Use Accounting Module, the Transportation Emissions Accounting Module, and the Embodied Emissions Accounting Module, where appropriate.

Quantification of emissions associated with direct emissions of non-CO₂ GHGs requires two primary measurements, the measurement of the total quantity of emissions and the analysis of emissions for CO₂ and other GHG content. This can be calculated as follows:

$$CO_{2}e_{MiscProject} = \sum_{t=1}^{T} m_{em,t} \cdot\ C_{GHG,t} \cdot\ GWP_{GHG}$$

(Equation 3)

Where:

• $m_{em,t}$ = the mass of miscellaneous emission(s) (in tonnes) during period $t$.
• $C_{GHG,t}$ = the measured concentration as weight percent (%wt) of the relevant GHGs in the miscellaneous emission(s).
• $GWP_{GHG}$ = the global warming potential of the relevant GHGs for a 100-year time interval.
• $t$ = the time index, ranging from 1 to $T$.
• $T$ = $RP/Δt$, the number of time units in Reporting Period, $RP$.
• $Δt$ = the time interval the average is taken over.

The total quantity of direct emissions can be measured by various acceptable methods, including:

• Use of calibrated flow meters to provide continuous volumetric or mass flow measurement of a release from a process. Any flow meter must be calibrated for the composition and density of tail gas, or use appropriate conversion factors;¹⁷
• Use of flow data and curves from tail gas emissions testing and pressure drop measurement (i.e. pitot tubes) in the tail gas stream. Such testing data should be produced by a qualified emissions testing company, accredited to the Stack Testing Accreditation Council for ASTM D7036, ISO 17025, or approved by the authority of the geography where the Project is located or the most stringent of relevant standards worldwide. Testing should be completed under representative process operating conditions;
• Calculation of tail gas amount by a carbon material balance calculated based on direct measurement of other process streams;
• Measurement of a storage vessel pressure and temperature at beginning and end of a defined period within the Reporting Period, $RP$. Calculation of total mass of gas can be completed based on gas composition data and temperature and pressure data to determine if release has occurred; and
• Weight of a storage vessel as determined by calibrated weigh scale or load sensor at beginning and end of a defined period within the Reporting Period, $RP$.

The concentration of CO₂ or other GHGs in emissions must be measured directly via one of the following methods:

• On-line analyzer measurement of CO₂ or GHG concentration, such as on-line gas chromatography, non-dispersive infrared (NDIR) detector, or similar. Analyzers must be calibrated regularly using NIST-traceable certified gas standards with concentrations of CO₂ and GHGs within +/- 30% of expected average tail gas concentration;^18,19
• Use of concentration data from process stream tail gas emissions testing. Such testing data should be produced by a qualified emissions testing company, accredited to the Stack Testing Accreditation Council for ASTM D7036, ISO 17025, or approved by the authority of the geography where the Project is located or the most stringent of relevant standards worldwide. Emissions data should only be used when process operating conditions during Reporting Period are similar to the conditions under which testing was completed; and
• Measurement of stream composition by approved test methods, including national and international standards, such as NIST, ASTM, or other, which target the GHG of concern and are completed by a qualified laboratory;
  • Analyses must be completed at least quarterly.

The Project Proponent must maintain the following records as evidence supporting calculation of emissions from the DAC or CO₂ conversion process:

• All raw data and data processing or calculation records for measurements and calculations of emissions;
• Results of any emissions tests used to determine emission rates of GHGs from process streams or flow measurements of gas flow from DAC or related processes, including signed report from accredited emissions testing entity;
• Flow rate data from flow meters (including pitot tubes) for each period of interest, including flow meter data recorded in data acquisition systems, manual operation logs, or other records indicating date, time, and flow rate, as well as meter identification number or ID; and
• Documentation of any known evidence of releases, such as:
  • pressure relief valve activation (open/close position, or safety valve failure and replacement record);
  • observed change in weight of storage vessels; and
  • visual observation of release records with followup measurements and documentation of release.

Records of all data and analyses must be maintained by the Project Proponent and provided for verification purposes for a period of five years.

$CO_2e_{Leakage,\ n}$ includes emissions associated with a Project's impact on activities outside the system boundary of The Project. This includes instances where The Project causes an increase in GHG emissions by diverting material from other uses or incentivizing increased production activity.

It is the Project Proponent's responsibility to identify potential sources of leakage emissions. For a DAC Project, market leakage emissions associated with the replacement of consumables used must be considered as a minimum. Project Proponents may also consider the impact of project operations on potential increased use of rare-earth materials for the production of sorbents, land use change, and increased strain on existing CO₂ transportation and storage infrastructure.

This Protocol provides multiple options for conversion and durable storage of CO₂. The Project Proponent can choose from available options when submitting their Project for verification:

Isometric would like to thank following contributors to this Protocol and relevant Modules:

• Tim Hansen (350 Solutions); Direct Air Capture Protocol and Energy Use Accounting, Transportation Emissions Accounting and Embodied Emissions Accounting Modules.
• Chris Holdsworth, Ph.D. (University of Edinburgh); CO₂ Storage in Saline Aquifers and CO₂ Storage via In-Situ Mineralization in Mafic and Ultramafic Formations Modules.
• Wilson Ricks (Princeton University); Energy Use Accounting Module.
• Grant Faber (Carbon Based Consulting); Transportation Emissions Accounting Module.

Isometric would like to thank following reviewers of this Protocol and relevant Modules:

• James Campbell, Ph.D. (Herriot Watt University); Direct Air Capture Protocol and CO₂ Storage via In-Situ Mineralization in Mafic and Ultramafic Formations Module.
• Grant Faber (Carbon Based Consulting); Energy Use Accounting and Embodied Emissions Accounting Modules.

This appendix details how the Project Proponent must monitor, document and report all metrics identified within this Protocol. Following this guidance will ensure the Project Proponent measures and confirms carbon removed and long-term storage compliance, and will enable quantification of the emissions removal resulting from the Project activity during The Project Crediting Period, prior to each verification.

This methodology utilizes a comprehensive monitoring and documentation framework that captures the GHG impact in each stage of a Project. Monitoring and detailed accounting practices must be conducted throughout to ensure the continuous integrity of Crediting.

The Project Proponent must develop and apply a monitoring plan according to ISO 14064-2 principles of transparency and accuracy that allows the quantification and evidencing of GHG emissions and CO₂ removals.

The conversion and durable storage modules associated with this Protocol have their own set of required parameters that need to be monitored. Please refer to the following requirements Sections of the relevant Modules to see a complete list of all requirements:

These parameters must be monitored for the purpose of Carbon Emissions Calculation and Embodied Carbon Emissions Calculation.

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:

Risk Score Categories

• 0: Very Low Risk Level (2% buffer)
• 1-2: Low Risk Level (5% buffer)
• 3-4: Medium Risk Level (7% buffer)
• 5+: High Risk Level (10-20% buffer)

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:

• Acidic fluid
• Alkaline fluid (if stored as dissolved inorganic carbon)
• Temperatures in excess of 800 degrees celsius

For projects with any form of subsurface carbon storage, the presence of the following risk factors must be reflected in the risk score corresponding to question 10:

• Seismicity
• Subsurface migration

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3. Fujikawa, S., and Selyanchyn, R. (2022). Direct air capture by membranes. MRS Bulletin, 47, 416–423. https://doi.org/10.1557/s43577-022-00313-6 ↩

4. Renfrew, S. E., Starr, D. E., and Strasser, P. (2020). Electrochemical Approaches toward CO2 Capture and Concentration. ACS Catalysis, 10, 13058–13074. https://doi.org/10.1021/acscatal.0c03639 ↩

5. Al Hameli, F., Belhaj, H., and Al Dhuhoori, M. (2022). CO2 Sequestration Overview in Geological Formations: Trapping Mechanisms Matrix Assessment. Energies, 15, Article 20. https://doi.org/10.3390/en15207805 ↩

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8. Goeppert, A., Czaun, M., Prakash, G. K. S., and Olah, G. A. (2012). Air as the renewable carbon source of the future: An overview of CO2 capture from the atmosphere. Energy & Environmental Science, 5, 7833–7853. https://doi.org/10.1039/C2EE21586A ↩

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12. For example, 49 CFR §195.402 - Transportation of Hazardous Liquids via Pipeline: Procedural manual for operations, maintenance, and emergencies, and 40 CFR §146.94 - Class VI Wells: Emergency and remedial response. ↩ ↩²

13. Water neutrality is defined as: the total demand for water should be the same after new development is built, as it was before. That is, the new demand for water should be offset in the existing community by making existing infrastructure and homes in the area more water efficient. ↩

14. ISO 14064-3:2019, Section 5.1.7 ↩

15. Carbon Credit Quality Initiative. Methodology for assessing the quality of carbon credits, Version 3.0 (May 2022). https://carboncreditquality.org/methodology.html ↩

16. Lyons, L., Kavvadias, K. and Carlsson, J., (2021). Defining and accounting for waste heat and cold. EUR 30869 EN, Publications Office of the European Union, Luxembourg. doi:10.2760/73253. https://publications.jrc.ec.europa.eu/repository/handle/JRC126383 ↩

17. Flow meters must be calibrated to national traceable standards by an ISO 17025 accredited metrology laboratory. Flow meters may include critical nozzle flow meters (i.e. ISO 9300:2022 compliant meters), coriolis mass flow meters, and other applicable meters for mixed gas flows, as long as properly calibrated and maintained. ↩

18. Dinh, T.-V., Choi, I.-Y., Son, Y.-S., and Kim, J.-C. (2016). A review on non-dispersive infrared gas sensors: Improvement of sensor detection limit and interference correction. Sensors and Actuators B: Chemical, 231, 529–538. https://doi.org/10.1016/j.snb.2016.03.040 ↩

19. Sandoval-Bohorquez, V. S., Rozo, E. A. V., and Baldovino-Medrano, V. G. (2020). A method for the highly accurate quantification of gas streams by on-line chromatography. Journal of Chromatography A, 1626, 461355. https://doi.org/10.1016/j.chroma.2020.461355 ↩