Contents
1.0
Introduction
This Module establishes the requirements for Projects that use a Book and Claim chain of custody to issue Environmental Attribute Certificates (EACs) under Isometric Protocols.
Book and Claim is a chain of custody model in which the environmental attributes of a product, fuel, or service are decoupled from the physical good and transferred independently, with each transfer recorded on a registry . This enables buyers without physical access to a low-carbon product, or operating in supply chains where physical traceability is not possible, to claim its environmental benefits.
An EAC represents the environmental attributes of one functional unit of a certified product, fuel, or service. EACs are Verified and Issued by Isometric, and tracked on the Isometric Registry. Retirement of an EAC confers the unique right to claim the represented environmental attributes, in accordance with the rules of the Isometric Standard and the relevant Protocol. EACs, as defined by Isometric, are the equivalent of transferrable instruments with entitlement to claim (TIECs) as defined by ISO 22095-3, and of Energy and Commodity Certificates as defined by V2 of the SBTi Corporate Net Zero Standard.
This Module specifies the cross-cutting requirements that apply across all Book and Claim pathways, to ensure each EAC is issued in line with internationally recognized best practice. Pathway-specific requirements for each product type are set in the respective Protocols.
2.0
Sources, Reference Standards and Methodologies
Specific standards which are utilized as the foundation of this Module and for which this Module is fully compliant with are as follows:
- Isometric Standard[^1]
- ISO (International Organization for Standardization) 22095-3:2026. Chain of custody – Part 3: Requirements and guidelines for book and claim
The Module also draws on best practices outlined in existing book and claim guidance, including:
- Book and Claim for Cement and Concrete - Centre for Green Market Activation
- Criteria for High-Quality Environmental Attribute Certificates in the Concrete and Steel Sectors - Microsoft and Carbon Direct
- Principles and Best Practice for Book and Claim Systems in Heavy Transport - Book and Claim Community
- RSB Procedure for Book and Claim Chain of Custody – Roundtable on Sustainable Biomaterials
The Module also reflects the integrity principles laid out in the latest draft of the forthcoming V2 of the SBTi Corporate Net Zero Standard. It will be reviewed to ensure alignment with the final SBTi Standard once this is finalized.
3.0
Book and Claim Concepts
This Module draws on a number of key concepts that define a Book and Claim system. This section sets out the definitions of Book and Claim chains of custody, the foundational principles, and the roles that operate within an EAC value chain.
3.1
Core Principles
Book and Claim is a chain of custody model that allows environmental attributes to be decoupled from the physical products or services that would ordinarily carry them, and traded independently.
Decoupling enables Buyers without physical access to low-carbon products to financially support the decarbonization of their supply chains and claim the resulting benefits. However, once attributes and products travel separately, the integrity and credibility of such claims requires a robust system that ensures every certificate is anchored to verified physical production and genuine environmental benefits.
Best practice guidelines outline a number of key principles that define a well-functioning book and claim system. The requirements set out within this Module are designed to ensure adherence to these principles:
- Traceability. Every EAC is linkable through issuance, transfer and retirement to the underlying physical activity.
- Identification. Every EAC carries a fixed set of attributes that identify the underlying activity and the GHG attribute it represents.
- Transparency. Every retired EAC and its attribute set are published in a public record.
- Verifiability. Every issuance and retirement is independently verifiable against documented evidence.
- Additionality. Any environmental benefits claimed are truly additional and would not have occurred without the intervention.
- Conservativeness. Where attribution or quantification is ambiguous, the more conservative interpretation applies.
- "Similar in nature" matching. A claim made from a retired EAC must match the underlying activity in sector, geography and timeframe.
- No deficits. Total issuance in any period does not exceed verified production.
- No double counting. Operational controls prevent the seven categories of double counting outlined in ISO 22095-3.
- Multi-claim integrity. More than one legitimate claim per physical unit is permitted only with explicit attribute differentiation and unambiguous scope rules.
3.2
Roles in the EACs Value Chain
The role taxonomy set out in this Module is consistent with the Isometric Standard. Where Isometric terminology differs from ISO 22095-3, the equivalent term is noted. Pathway-specific Protocols may define additional roles where required by the structure of a particular value chain.
The following roles operate within the EAC value chain under this Module:
- Project Proponent: The organization that produces the low carbon commodity, fuel or service. The Project Proponent is responsible for all project documentation, regulatory compliance, and for providing the evidence required at issuance. Under ISO 22095-3, this role corresponds to the producer/supplier.
- Account Holder: Any organization with an active account on the Isometric Registry. Account Holders may hold, transfer, or retire EACs in accordance with the rules set out in this Module and the Isometric Standard. Account Holders may include Project Proponents, corporate end-users, and other value chain participants. Pathway-specific Protocols may define named sub-types of Account Holder to reflect the structure of a particular value chain.
- Beneficiary: The organization on whose behalf an EAC is retired. Only the Beneficiary can claim the environmental benefits. Under ISO 22095-3, this role corresponds to the End-User.
- Validation and Verification Bodies (VVBs): 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. Under ISO 22095-3, this role corresponds to the Verification Body.
Isometric’s role as a certifier of EACs encompasses operating the Isometric Registry and developing certification-level Protocols. Under the ISO 22095-3 definitions, Isometric operates as the Requirements Setter and Recordkeeper. Isometric satisfies the three independence tests set out in ISO 22095-3 for the Recordkeeper: no conflict of interest, no undue influence, and impartiality.
4.0
Eligibility of the Underlying Activity and Attributes
Before an EAC can be issued, the underlying product and the claimed environmental attributes must satisfy certain eligibility criteria. This section outlines the key characteristics required.
4.1
Eligibility of the Underlying Material or Activity
The underlying material or activity must be certified under a relevant Isometric Protocol or a recognized external scheme as accepted by the relevant Isometric Protocol (for example, certified by a relevant body as a low-carbon material, sustainable fuel, or renewable electricity source).
Certification must be carried out by a body independent of the producer, in accordance with ISO/IEC 17029, and the volume of EACs issued must not exceed the quantity of material or activity verified under the scheme.
4.2
Sector / Product Scope
Each EAC is issued within a defined sector and product scope, as defined by the relevant Protocol. The scope sets the nature of material, product or activity eligible to generate EACs in the system, such as low-carbon cement of a defined functional unit, or sustainable aviation fuel meeting a defined specification.
4.3
"Similar in Nature" Rule
A claim made from a retired EAC must apply to a material, product or activity "similar in nature" to the one from which the EAC was issued. Section 3.21 of ISO 22095-3 defines "similar in nature" as sharing common characteristics, such as the functional use, technical specification, or composition, making the two alike in fundamental aspects.
The eligible categories of physical product, the specification of "similar in nature", and any pathway-specific considerations are set in the relevant Protocols.
The temporal application of “similar in nature” is addressed in Section 6.3.1 (Expiry).
4.4
Book and Claim System Boundaries
Each EAC is issued within a defined system boundary. In accordance with ISO 22095-3 Section 5.2, the system boundary must be a physical region, delineated network, or market, for example a national or regional electricity grid, or a fuel market.
A claim made from a retired EAC must apply to an activity within the EAC's system boundary.
The system boundary, any matching tolerances, and any cross-border or cross-system transfer rules for each pathway are set in the relevant Protocol.
4.5
Additionality
The Isometric Standard[^1] sets out four pillars by which Additionality is assessed: Financial, Common Practice, Environmental and Regulatory. These four pillars provide the framework for assessing EAC Additionality, but the way in which each is demonstrated, and whether active demonstration is required or may be presumed, will vary by pathway.
- Financial additionality: The environmental attribute represented by the EAC reflects production that would not have occurred at the same scale without the revenue enabled by EAC issuance. For pathways where the low-carbon production method is inherently and significantly more costly than the conventional alternative (such as sustainable aviation fuel relative to conventional jet fuel), the relevant Protocol may determine that financial additionality is presumed and does not require case-by-case demonstration.
- Common Practice Additionality: The low-carbon production method is not yet common practice in the relevant sector and geography.
- Environmental additionality: The environmental attribute represented by the EAC delivers a net reduction in emissions, calculated against a baseline using the methodology outlined in the relevant Protocol (for further details on calculation methodologies and baselines, see Section 5.3).
- Regulatory Additionality: The environmental attribute represented by a unit must not be claimed toward any regulatory or compliance obligation if the same attribute is, or will be, the basis of any voluntary claim retired against that unit, and vice versa. Each attribute may be claimed once. For further information, refer to Section 4.5.1.
Each EAC pathway has distinct commercial, regulatory and technical considerations to consider when determining Additionality and the appropriate mechanisms to demonstrate it. For more detailed guidance on Additionality for a given pathway, refer to the relevant Protocol.
4.5.1
Regulatory Additionality
EACs issued using this Module are eligible for either voluntary or compliance market trading. EACs issued under this Module are explicitly ineligible for use in both a voluntary and compliance market.
4.5.1.1
Market Designation at Issuance
At the point of issuance, each EAC must be assigned a market designation (voluntary or compliance) that determines how it may be transacted, retired and claimed. Once designated, an EAC cannot be reclassified. The designation must be recorded as a non-editable attribute on the certificate. A voluntary-designated EAC must not subsequently be used to satisfy a regulatory obligation. A compliance-designated EAC cannot be retired for voluntary corporate claims, including substantiating corporate climate targets, ongoing emissions responsibility contributions, or scope 1, 2 or 3 performance claims under voluntary standards including but not limited to the SBTi Corporate Net-Zero Standard.
Projects must satisfy the following conditions before an EAC may be designated as “compliance”:
- The relevant regulatory authority administering the compliance obligation must explicitly permit the use of book-and-claim instruments by third-party registries. Projects must provide documentation as evidence of this, including reference to the specific legislative or regulatory provision.
- The compliance designation must be specific to a named regulatory scheme and jurisdiction. An EAC designated for compliance under one scheme is not automatically eligible for use under another.
- Where the compliance scheme imposes additional data or verification requirements beyond those specified in this Module, the Project must satisfy those additional requirements independently.
4.5.1.2
Demonstrating Regulatory Additionality
Projects must demonstrate Regulatory Additionality for all EACs designated as “voluntary”, to ensure that the environmental attribute represented by the EAC is not already required by, credited under, or counted toward any mandatory regulatory obligation.
The following evidence is required to demonstrate Regulatory Additionality:
- A description of all mandatory GHG reduction, blending, or carbon intensity obligations applicable to the production activity in the jurisdiction(s) where production occurs.
- Evidence that the environmental attribute represented by the EAC is surplus to any applicable regulatory obligation. This means it must exceed or is not accounted towards that regulatory obligation. Where a compliance scheme uses a threshold-based crediting mechanism, only the portion of the environmental performance that exceeds the compliance threshold is eligible for voluntary EAC issuance.
- A signed affidavit from the producer confirming that the environmental attributes represented by voluntary-designated EACs have not been, and will not be, submitted for credit, recognition or accounting under any compliance scheme.
5.0
Calculation Methodology
This section sets out the requirements for the carbon accounting methodology associated with an EAC. This Module sets the framing principles and minimum requirements for quantification of carbon intensity, the Emission Reduction Value, baselines, leakage and reversal and buffer pools. Detailed pathway-specific quantification rules are defined in the relevant Protocol.
5.1
Carbon Intensity
Each EAC must carry a carbon intensity value representing the GHG emissions per functional unit of the underlying product, fuel, or service. This must be reflected in tonnes of carbon dioxide equivalent (tCO2e) per functional unit and derived from a methodology that has been independently verified under a recognized certification scheme, as specified by the relevant Protocol.
The Isometric Standard[^1] details the overarching principles relating to system boundaries, default emission factors, proxies and models, common calculator factors and uncertainty accounting. Protocols provide the detailed requirements applicable to each pathway.
5.2
Emission Reduction Value
EACs include an Emission Reduction Value, unless otherwise specified by the Protocol. An Emission Reduction Value is the quantified GHG emissions reduction as a result of a lower-carbon product or process, relative to a defined baseline.
The Emission Reduction Value is expressed in tCO2e and is informed by the determination of the carbon intensity (See Section 5.1) and the Baseline (See Section 5.3).
5.3
Baselines
Baselines are defined for EACs to determine the Emission Reduction Value, including thresholds for minimum Emission Reduction Values, where relevant. The Baseline represents the carbon intensity of the conventional product, fuel, or service that the low-carbon alternative displaces.
The methodology for quantifying the Baseline is set by the relevant Pathway Protocol.
5.4
Leakage
Leakage is the increase in GHG emissions outside the geographic or temporal boundary of a project that results from that project's activities. For example, the diversion of a feedstock from an existing use to a low-carbon production pathway may cause that existing use to be served by a higher-emitting alternative, generating displacement emissions outside the Project boundary.
The Emission Reduction Value carried by an EAC is quantified as the difference between the carbon intensity of the underlying product and the Baseline. Where leakage occurs as a consequence of the Project's activities, the Emission Reduction Value overstates the GHG benefit delivered. The leakage assessment is therefore an integrity requirement, particularly for EACs that carry an Emission Reduction Value. Pathway Protocols set out how leakage risk is identified, quantified and managed.
5.5
Reversal and Buffer Pool Interaction
The concept of a reversal is not universally applicable to EACs as a physical reversal cannot occur in many projects. For example, the climate impact of generating energy from a solar panel or the avoidance of calcination emissions for low-carbon cement cannot be undone. Thus for many EACs, there is no need for a buffer pool.
However, some emissions claims may have a risk of reversal after an EAC has been issued, for example, if the production of a low-carbon material relies on CCS and durable storage of CO2. If there was a release of CO2 from the storage site, then the emissions claims associated with the low-carbon material would no longer be valid. For these projects that rely on the durable storage of carbon, the reversal risk must be accounted for using the framework outlined in the Isometric Standard[^1] and the relevant Pathway Protocol.
6.0
EAC Lifecycle
To ensure each EAC is traceable, verifiable, and transparent, every EAC issued under this Module must be listed on the Isometric Registry.
A typical lifecycle that an EAC follows on the registry is: (1) A physical product is created, and an EAC is issued upon successful verification, (2) the EAC may be transferred between users on the Registry, (3) the EAC reaches its end-of-life, which is expected to be retirement to support a public claim. EACs may alternatively reach end-of-life through Expiry, Retirement, or Cancellation. Each lifecycle event must be recorded and traceable on the Registry. This section sets out the requirements applicable at each life stage.
Further detail on requirements for documentation and Crediting are outlined in the Isometric Standard[^1].
6.1
Issuance
Issuance is the point at which an EAC is created on the Registry, representing when a defined quantity of underlying physical product with specified characteristics is verified and has entered into the Book and Claim system.
The following requirements must be met in order for an EAC to be issued:
- The EAC must be issued from an active Project that has been validated by a VVB against the relevant Protocol. The Project must be compliant with the required re-validation frequency (see Section 8 on Validation and Verification).
- The time period between the production of the physical product and the EAC issuance must follow the requirements set forth in the relevant Protocol. The Protocol-specific limit reflects the principle that this period should be as short as possible, so that claims remain temporally relevant to when the product was created.
- The quantity of EACs issued and the specified characteristics of the EACs must be based on measured or modeled data that has been reported and independently verified. See Pathway Protocols for details on the data requirements.
- Evidence that the underlying physical product has entered the supply chain must be provided and verified. Production of a material alone is insufficient for EAC issuance, to safeguard against the creation of waste products. See Pathway Protocols for the acceptable forms of evidence for a particular EAC.
- Evidence that the environmental attribute represented by the EAC has been severed from the underlying physical product must be provided and verified. This is to ensure that the physical product cannot carry the same attribute claim and to prevent double counting. See Pathway Protocols for more details.
Upon issuance on the Registry, each EAC must, as a minimum, include the metadata outlined in the Credit Attributes section of the Isometric Standard[^1], as well as any pathway-specific attributes defined in the respective Protocols.
6.2
Storage
There may be instances where the underlying product is held in a storage system for a period of time before being released into the supply chain.
In these scenarios, the issuance of EACs for product released from storage is only allowed if one of the following conditions outlined under ISO-22095-3 apply:
- Scenario 1: The product was produced at the site of the storage system and no EAC has been issued prior to its release from storage.
- Scenario 2: The EACs corresponding to the product that entered the storage system have been retired. In this scenario, a new EAC can be issued upon release from storage.
Storage losses must be accounted for in determining the quantity of EACs that are issued upon exit from the storage system. This occurs automatically in scenario 1, and storage losses must be reflected in the reissued EAC for scenario 2.
Protocols will set out the requirements for when storage provisions apply. Where applicable, Projects utilizing a storage site must report the following information for verification and documentation:
- Location of storage site
- Time of input to a storage system
- Time of release from the storage system
- Description of the quantification of storage losses, see Pathway Protocols for further details.
6.3
End of Life
Each EAC will reach a permanent end of life stage through one of the following events: Expiry, Retirement, or Cancellation. Reaching an end of life stage is an irreversible event, and EACs at this stage can no longer be transferred.
6.3.1
Expiry
Expiration of unused EACs is important for ensuring there is temporal alignment between when the physical product was produced and when the claims are made. Every EAC must have an expiration date specified upon issuance. Upon expiry, an EAC can no longer be transferred or retired for claims.
Requirements for the maximum period of time between issuance and expiration are set in the relevant Pathway Protocol. The default expiry period is 24 months, unless otherwise specified by the Protocol.
6.3.2
Retirement
An EAC may only be retired once. Retirement can be for one of the following use cases:
- Retirement for making claims: See the Retirement Rules of the Isometric Standard for more details.
- Retirement for Conversion of EACs: This scenario occurs when an EAC with one set of characteristics is retired to enable the issuance of a new EAC with a different set of characteristics. Note that retirement must take place before the issuance of the new EAC. In the case of Retirement for Conversion of EACs, the linkage between the Retired EAC and the newly Issued EAC, and associated conversion factors, must be documented. Detailed requirements on the conversion routes within a given pathway are provided in the relevant Protocol.
6.3.3
Cancellation
In the case of material error, fraud, or non-compliance that is discovered after issuance, Isometric may cancel EACs at which point their status on the Registry becomes “Canceled”. Canceled EACs may not be transferred or Retired.
6.4
Claims and External Communication
The act of retiring an EAC under this Module unlocks a defined claim. ISO 22095-3 sets the requirements for how such claims must be made, including the underlying attribute, the qualifiers that must accompany the claim, and the obligation that claims be supported, accurately qualified, and non-misleading.
Isometric does not audit downstream communication of claims. Responsibility for the accuracy, completeness and lawfulness of any external claim rests with the entity making the claim.
7.0
Integrity Safeguards
The integrity of the Book and Claim system depends on safeguards that operate across the full EAC lifecycle. This section sets out those cross-cutting safeguards: double counting prevention, multi-claim integrity, no deficits, residual mix calculation, and inter-registry coordination. Stage-specific controls within the lifecycle are addressed within the relevant subsections of Section 6.
Isometric acts as Recordkeeper and does not verify claims made on the basis of retired EACs. Upon retirement, Isometric will record the details necessary for a claim on its public registry, including the retiring Account Holder, the quantity retired, and the full attributes of the retired EAC. The beneficiary is responsible for ensuring that any environmental attribute claim made on the basis of a retired EAC is consistent with its recorded characteristics in accordance with ISO 22095-3.
7.1
Double Counting Prevention
Double counting occurs when the environmental attributes represented by an EAC are counted more than once toward climate targets or regulatory obligations. A Book and Claim system decouples the environmental attribute from the physical product. Therefore the opportunities for duplication are in some cases greater than those in physical chain of custody models.
This section establishes the double-counting prevention framework for this Module. The Isometric Standard[^1] aligns with all categories of double counting outlined in ISO 22095-3:2026, which provides the most comprehensive taxonomy currently available and is one of the primary reference standards for this Module. Where additional safeguards are required for some of those categories, these are outlined in the subsections below.
7.1.1
Multiple EAC Claims per Unit
To prevent double counting, by default, only one EAC can be issued for a quantity of physical product with a given set of characteristics. However, there may be scenarios where it is legitimate for multiple parties in the same value chain to make claims about the same underlying product, for example an airline burning sustainable aviation fuel as a direct (Scope 1) emission and a corporate customer claiming that same fuel use as an indirect (Scope 3) emission.
Issuing multiple EACs for the same underlying physical product may be allowed under certain Protocols, provided that the claims are made by organizations representing distinct and non-overlapping roles in the same value chain. If the issuance of multiple EACs is justified, additional requirements surrounding the transfer and retirement of claims must be adhered to for the prevention of double counting. See Pathway Protocols for details and justification on scenarios where multiple claims are allowed, including additional relevant requirements and guardrails.
7.1.2
Residual Mix Calculation
The residual mix is what remains after all EACs have been allocated, i.e. the production within the Book and Claim system whose environmental attributes are not represented by an EAC.
The calculation of residual mix can serve several important functions, for example:
- Supporting accurate accounting by non-Buyers: participants who have not purchased EACs use the residual mix as their default emission factor, preventing sold attributes from being implicitly counted elsewhere.
- Separating voluntary and compliance claims: where EACs interact with a compliance market, a residual mix calculation prevents the same attributes being counted in both.
ISO 22095-3 recommends that a residual mix be calculated and maintained, but permits the Requirements Setter to opt out where appropriate.
The definition and relevance of residual mix will depend on the pathway and use case. For pathway-specific guidance, refer to the relevant Protocol.
7.1.3
Double Disclosure
Double disclosure occurs when the environmental attributes represented by a retired EAC are claimed by means other than EAC retirement, for example through a producer’s own GHG inventory, product environmental declaration, or compliance reporting submission. The Isometric Standard outlines requirements for ensuring this does not occur[^1]. The following additional safeguards must be followed specifically for EACs in order to mitigate this risk:
- At the point of EAC issuance, the Project must attest that the environmental attributes represented by the EAC have not been and will not be claimed through any method other than EAC retirement.
- As outlined in Section 7.1.2, Projects must follow the residual mix guidance in the relevant Protocol to determine whether a residual mix calculation is appropriate, and provide evidence accordingly to demonstrate that no claims have been made outside of EACs.
- Where EACs interact with a compliance market, the environmental attributes represented by a compliance-designated EAC must not also be claimed through voluntary retirement, and vice versa. For the full framework governing voluntary and compliance market separation, see Section 4.5.
- Organizations that retire EACs must disclose the retirement in the relevant reporting context for the claim made against the EAC e.g. GHG inventory or sustainability report.
7.2
Deficits and Negative Balances
EACs may only be issued after the underlying physical production has occurred and been verified. The creation of EACs against production that has not yet taken place (forward issuance) is not permitted.
Account Holders may only transfer or retire EACs already held in their registry account. No account may hold a negative balance at any point.
7.3
Inter-Registry Operability
The Isometric Registry operates alongside other registries that may issue EACs against the same or similar underlying activities and certification schemes. Without coordination, this creates a risk of cross-registry double counting.
The Isometric Registry does not currently provide formal interoperability mechanisms with other Book and Claim registries. Isometric will assess adoption or alignment with inter-registry coordination frameworks that meet the following minimum integrity expectations:
- Operated or governed by a body independent of any participating registry, with a published conflict-of-interest policy
- Defined membership and assurance requirements for participating registries
- Data-sharing architecture that protects commercially sensitive supplier data while enabling detection of double issuance
- Clear rules for dispute resolution where suspected double issuance is identified
In the meantime, Isometric will cooperate with other registries on a case-by-case basis to prevent the same underlying attribute from being issued, transferred or retired in more than one registry. Cooperation may include information-sharing on issued and retired EACs, mutual verification of certification chains, and joint response to suspected cases of double counting. Pathway Protocols may specify additional inter-registry coordination requirements where sector-specific frameworks exist.
8.0
Assurance
EACs are subject to independent oversight through ongoing checks by Isometric and periodic reviews by an external Validation and Verification Body (VVB).
8.1
Validation and Surveillance Audits
Each Project must undergo initial Validation to confirm conformity with the Isometric Standard[^1] and the relevant Protocol, and must subsequently be re-Validated at the end of each Crediting Period. For details on the maximum Crediting Period for each EACs pathway, refer to the relevant Protocol.
Each Project will then be subject to a periodic Surveillance Audit to ensure ongoing conformity. These audits will occur on an annual basis, unless otherwise specified in the Protocol.
All Validations and Surveillance Audits will be carried out by a third-party Validation and Verification Body (VVB).
8.2
Verification
Following Validation, each ongoing EAC issuance request will be verified by Isometric in its role as a Registry operator.
At each Surveillance Audit and at re-Validation, the VVB shall review a representative sample of issuance requests made since the previous audit and confirm their conformity with the validated scope and the Protocol. Non-conformities identified in sampling may result in corrective action, suspension, or cancellation of EACs.
More detail on these processes, including the role and qualifications of VVBs, are set out in the Isometric Standard[^1].
9.0
Definitions and Acronyms
- AdditionalityAn evaluation of the likelihood that an intervention—for example, a CDR Project—causes a climate benefit above and beyond what would have happened in a no-intervention Baseline scenario.
- BaselineA set of data describing pre-intervention or control conditions to be used as a reference scenario for comparison.
- Book and ClaimA chain of custody model in which environmental attributes are unbundled from the physical good to which they relate and transacted independently via a registry.
- Buffer PoolA common and recognized insurance mechanism among Registries allowing Certificates to be set aside (in this case by Isometric) to compensate for Reversals which may occur in the future.
- Cancellation (of a Certificate)The permanent annulling of a Certificate to compensate for erroneous over-issuance or a Reversal. Once Canceled, the certificate will no longer be available for Delivery or Retirement.
- ConversionA retirement pathway in which an existing EAC is retired to enable the issuance of a new EAC with different specified characteristics.
- Crediting PeriodThe period of time over which a Project Design Document is valid, and over which Removals, Reductions or Environmental Attributes may be Verified, resulting in Issued Certificates.
- DurabilityThe amount of time carbon removed from the atmosphere by an intervention – for example, a CDR project – is expected to reside in a given Reservoir, taking into account both physical risks and socioeconomic constructs (such as contracts) to protect the Reservoir in question.
- Emission FactorAn estimate of the emissions intensity per unit of an activity.
- Emission Reduction ValueThe net greenhouse gas reduction attributable to one Functional Unit of a low-carbon product relative to a defined Baseline, calculated as the difference between the Baseline Carbon Intensity and the certified product Carbon Intensity. Expressed in kg CO₂e per Functional Unit; the quantity one EAC represents is expressed in tCO₂e. It is a simplification of the intervention outcome, being the impact of the intervention, referenced in the AIM Platform Standard V1.0.
- EmissionsThe term used to describe greenhouse gas emissions to the atmosphere as a result of Project activities.
- Environmental AdditionalityAn evaluation of the likelihood that an intervention causes a climate benefit above and beyond what would have happened in a no-intervention Baseline scenario.
- Environmental Attribute Certificate (EAC)A Certificate representing the Environmental Attribute of one Functional Unit of a certified product, fuel, or service, Issued where that attribute has been severed from the physical product under a Book and Claim chain of custody. An EAC is equivalent to a transferable instrument with entitlement to claim (TIEC) as defined in ISO 22095-3:2026, and to an Energy and Commodity Certificate as defined in V2 of the SBTi Corporate Net-Zero Standard.
- Financial AdditionalityAn evaluation of the likelihood that an intervention that causes a climate benefit above and beyond what would have happened in a no-intervention Baseline scenario was the result of revenues from carbon finance.
- Functional UnitThe defined quantity of a product or service against which an EAC is Issued, and in which EAC quantities are recorded, transferred and Retired on the Registry. The Functional Units available for a pathway are set in the relevant Certified Protocol.
- Greenhouse Gas (GHG)Those gaseous constituents of the atmosphere, both natural and anthropogenic (human-caused), that absorb and emit radiation at specific wavelengths within the spectrum of terrestrial radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. This property causes the greenhouse effect, whereby heat is trapped in Earth’s atmosphere (CDR Primer, 2022).
- LeakageThe increase in GHG emissions outside the geographic or temporal boundary of a project that results from that project's activities.
- ModuleIndependent components of Isometric Certified Protocols which are transferable between and applicable to different Protocols.
- ProxyA measurement which correlates with but is not a direct measurement of the variable of interest.
- Residual mixThe emissions profile of production volume within a Book and Claim system whose environmental attributes are not represented by any issued EAC. Participants who have not purchased EACs use this as their default emissions factor, ensuring sold attributes cannot be implicitly counted elsewhere. Whether a residual mix calculation applies to a given pathway is specified in the relevant Protocol.
- ReversalThe escape of CO₂ to the atmosphere after it has been stored, and after a Certificate has been Issued. A Reversal is classified as avoidable if a Project Proponent has influence or control over it and it likely could have been averted through application of reasonable risk mitigation measures. Any other Reversals will be classified as unavoidable.
- SeveringThe decoupling of an Environmental Attribute from the physical product, fuel, or service that carries it, so that it may be Issued as an EAC and transferred independently.
- Similar in natureA condition for EAC retirement, per ISO 22095-3 Section 3.21. The activity against which a claim is made must share common characteristics with the underlying activity from which the EAC was issued, such as functional use, technical specification or composition.
- StorageDescribes the addition of carbon dioxide removed from the atmosphere to a reservoir, which serves as its ultimate destination. This is also referred to as “sequestration”.
- Surveillance AuditA periodic audit carried out by a VVB of a Project issuing EACs, reviewing a representative sample of the issuance requests made since the previous audit.
- System BoundaryGHG sources, sinks and reservoirs (SSRs) associated with the project boundary and included in the GHG Statement.
- UncertaintyA 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.
- ValidationA systematic and independent process for evaluating the reasonableness of the assumptions, limitations and methods that support a Project and assessing whether the Project conforms to the criteria set forth in the Isometric Standard and the Protocol by which the Project is governed. Validation must be completed by an Isometric approved third-party (VVB).
- Validation and Verification Bodies (VVBs)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.
- Waste productAn output of a process that has no intended value to the producer.
[^1]: For details of planned updates to the Isometric Standard, refer to Appendix A.
10.0
Appendix A - Updates to the Isometric Standard
The Isometric Standard sets the overarching framework for all credits and certificates issued by Isometric, including common requirements, and high-level principles.
The current version of the Isometric Standard was developed for carbon credits, including Reductions and Removals, and does not currently contain provisions to enable the issuance of EACs. In parallel with the development of this Module and Pathway Protocols for EACs, the Isometric Standard will be updated to enable EACs to be issued on the Registry. The Isometric Standard will be updated in accordance with Isometric's Protocol Update Schedule.
Some of the key changes to the Isometric Standard are summarized below.
10.1
Credit types
The Standard covers the issuance of Removals and Reductions. The Standard will be updated to also enable the issuance of EACs.
10.2
Additionality
The Standard outlines four pillars for additionality, together with commentary on their application to Reduction and Removal credits. The Standard will be updated to also address these four pillars in EAC-specific terms, in line with the additionality principles and evidence requirements set out in this Module (See Section 4.4) and the relevant Protocols.
10.3
Double counting
The existing double-counting requirements will be updated to ensure their relevance to EACs, and to reflect the related areas outlined in Section 7.1 of this Module.
10.4
Baselines
The Standard contains some prescriptive requirements on the definition of baselines, designed for Removal and Reduction projects.
To accommodate EACs, the scope or approach to baselines in the Standard will be broadened, reflecting the principles outlined in Section 5.3 of this Module.
10.5
Buffer pools and risk of reversal
As discussed in Section 5.5, the risk of reversal is not universally applicable to all EACs pathways. EACs that rely on storing CO₂ from CCS will be subject to buffer pool requirements and risk of reversal assessments. The Standard’s requirements for risk of reversal and the associated buffer pool will be updated to align with the concepts outlined in this Module.
10.6
Validation and Verification Requirements
The Standard currently outlines the Validation and Verification approach for Removals and Reductions, whereby a project is validated at the start of a Crediting Period and each GHG Statement is subsequently verified before issuing credits.
For EACs, the approach to Validation and Verification must be adapted to meet the specific needs of book and claim value chains, and the different commercial contexts within which they will operate, while still ensuring a suitable level of independent oversight.
For example, EACs will typically rely on an existing certification of the physical product, which has already been verified by an external party (such as an Environmental Product Declaration (EPD)). The role of Isometric and the VVB in this case is to verify the claims being made in the Book and Claim chain of custody, rather than to re-validate the underlying certification.
While some high-level details are provided within this Module, the core requirements for the EAC assurance process will be outlined in the Standard.
10.7
Attributes
The Isometric Standard specifies a list of credit attributes that apply to every credit in the Isometric registry. This will be updated to include a set of attributes that will be used for EACs. The attribute set will include, at a minimum: the date or time period during which the underlying material or activity was produced or made available for transfer; the site or facility, including location, where production took place; the date of EAC issuance; the applicable certification scheme and certificate reference; and the EAC pathway. These minimum attributes are required for conformance with ISO 22095-3.
10.8
Retirement Rules
The existing retirement rules will be updated to include the scenario of retiring EACs for conversion, transfer, and EAC expiry.
10.9
Uncertainty accounting
The existing Standard framework does not have a treatment for "inherited" uncertainty from an external certification, for example when a carbon intensity (CI) for an EAC is quantified via an approved certification scheme. The existing framework will be updated to include specific rules around this for EACs. The detailed requirements for uncertainty quantification and approved certification schemes will be set out in the relevant Protocols.
10.10
System boundaries
While guidelines are provided in this Module and detailed system boundary requirements will be included in Pathway Protocols, definitions for system boundaries will be harmonized at the Standard level.
10.11
For most EACs, the Standard’s requirements around durability are not relevant. However, for CCS-reliant pathways as noted in this Module, the Standard will be updated to make clear (a) the physical durability of the emission impact and (b) expiry of the EAC claim.
10.12
GHG statement policies
The Standard will be updated to accommodate the quantification approach for EACs, to include consideration of externally certified CI values and defining an Emission Reduction Value.
10.13
Record retention
The Standard will be updated to confirm compliance with the requirements for record retention within ISO 22093-3. Isometric, in its role as the party responsible for recordkeeping, shall retain all records relating to EAC issuance, transfer, retirement, expiry, and cancellation for a minimum of 3 years from the date of the relevant event. Where regulatory requirements applicable to a specific pathway require a longer retention period, the relevant Protocol shall specify the extended period.
Contributors
Isometric
Emma Marsland
Jing He, Ph.D.
Jeni Reeve, Ph.D.
Sophie Gill, Ph.D.
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