Isometric Standard


Versionv1.0.004 Oct 2023
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SummaryThe Isometric Standard lists the requirements that ensure delivered tonnes have measurable climate impact. Tonnes must be durable, additional, and calculated using the latest scientific techniques. These tonnes must also include a scientifically robust uncertainty quantification.




The Isometric Registry records Verified Credits that represent Removals of atmospheric CO2 which satisfy the latest Version of the Isometric Standard. The Isometric Standard, detailed in this document, lists the requirements that ensure Delivered tonnes have measurable climate impact. In summary, tonnes must be Durable, Additional, and calculated using the latest scientific techniques. These tonnes must also include a scientifically robust Uncertainty quantification.

As outlined in this Isometric Standard, Isometric coordinates data curation, quantification and Verification necessary to Issue Credits on the Isometric Registry. All data, calculations and evidence associated with Credits are publicly available. The Isometric Registry is designed for voluntary Buyers focused on high durability Removals, not offsets or Emission Reductions.

This Isometric Standard sets out the duties and obligations of stakeholders in relation to the Isometric Registry. Its purpose is also to provide for a consistent and predictable experience for all parties engaging with the Isometric Registry.

This Standard and the rules contained herein were designed and developed by Isometric HQ Limited.


Purpose and Principles



The Isometric Crediting Program is guided by the Isometric Standard, and exists to:

  • provide guidance, transparent infrastructure and to set a high scientific caliber that fosters high quality climate action in the form of Durable Removals of CO₂ from the atmosphere; and

  • Issue Verified Credits that can be used as an evidentiary statement of their ownership for Removal claims and reporting purposes.



The Isometric Crediting Program adheres to the following principles:


  • Isometric engages with relevant governmental and Non-Governmental Organizations (NGOs) to facilitate equitable representation of stakeholders in a predominantly private industry and advance the creation of high quality industry standards.

  • Isometric engages the scientific community and collaborates with experts in areas such as sensor development, physical inspection, auditing, earth-system modeling and data analysis to Verify Deliveries.

  • Where appropriate and practicable, Isometric Systems may be integrated with similar tracking systems to help ensure full and accurate information for Buyers of Removals and minimize the potential for Double Counting.

Incentive Alignment

  • Isometric does not sell or broker the sale of credits.

  • Isometric charges Buyers – not Project Proponents – a single flat fee per Offtake or purchase, no matter the number of Credits issued. This mechanism reduces any incentives for overcrediting.

  • Isometric collects fees from Buyers on a payment schedule decoupled from the credit delivery schedule. This mechanism eliminates any incentives for early crediting.

  • Isometric does not receive payments from Project Proponents to Verify the delivery of tonnes and adherence to Certified Protocols.

  • Isometric undertakes the cost of Protocol development and third-party Verification to ensure neither Buyers nor Project Proponents can have undue influence over this process.

  • Isometric independently and impartially chooses third-party Validation and Verification Bodies (VVBs) for Projects.

Scientific Rigor

  • Isometric uses the latest science to quantify net negativity, durability, uncertainty and Additionality across a variety of heterogeneous Removal Pathways.

  • Isometric will review and update Protocols without a penalty on previously Issued Credits in order to incentivize continued investigation of underlying scientific questions – through which Removal estimates can be further constrained.

  • Isometric quantifies all Carbon Fluxes related to the Removal activity taken by the Project Proponent in a Conservative manner that incorporates uncertainty – including second order effects on leakage.


  • Isometric provides Buyers and Beneficiaries with access to full traceability of Carbon Fluxes involved in the quantification of Removals, alongside the evidence gathered for the Validation and Verification Process.

  • Protocols and quantification Models are transparently versioned, allowing for public tracking of changes, and public consultation after major updates

  • Each Credit Issued by Isometric is publicly accessible – allowing for inspection of the information used to quantify Removals.




Project Type

Isometric works with Projects conforming to a Protocol which has undergone or will undergo the Isometric Certification Process.


Geographic Scope

Isometric works with Projects worldwide. Isometric works in English. Additional languages may be considered given translation by a trusted source.

In some instances, Modules within Protocols may be tailored for Projects which have geographical specificities. In this circumstance, geography-specific alterations to utilized Modules will be made clear in order to maintain transparency amongst Project Proponents.


Greenhouse Gas (GHG) Eligibility

Isometric Issues Credits for the net Removal of atmospheric CO₂ only. In evaluating the comprehensive greenhouse gas (GHG) emissions of a Project, all GHGs are considered. Isometric uses the United States Environmental Protection Agency definition of GHGs1, which includes: carbon dioxide (CO₂), methane (CH4), nitrous oxide (N2O), and fluorinated gases such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3).


Notable Exclusions

Projects partaking solely in any of the following will not meet Isometric Protocol Requirements.

  • Carbon Removal Projects with <1,000 year durability that have not been otherwise approved by Isometric on a case-by-case basis

  • Ecosystem restoration, maintenance and management

  • Emissions reduction and offsetting

  • Point source carbon capture and storage

  • Reducing Emissions from Deforestation and Degradation (REDD+)2

Projects partaking in activities leading to Enhanced Oil Recovery (EOR) will also not meet Isometric Protocol Requirements.



This is version 1.0.0 of the Isometric Standard, first published 4th October 2023.

The document will be updated on an ongoing basis to reflect changes in the operation, governance and/or rules that apply to either Projects on, or activity described by, the Registry.

Any proposed material changes to the Standard will be put forward for review by the independent Science Network. Following any amendments resulting from that process, the draft changes will be put out for public comment. After having incorporated any further amendments, the final changes will be published in an updated version of the Standard, alongside a clear explanation of the stakeholder input received and how this informed the final changes that were made.

Version numbers are updated according to standard Semantic Versioning3 practice, where three positive integers A.B.C denote the version of the Protocol.

  • Major (Integer A) - Updated when the Standard has undergone a significant change that may have impacts on Project eligibility, Verification practices or Credit issuance

  • Minor (Integer B) - Updated when non-critical information has been added to, or removed from, the Standard – for example optional guidance

  • Patch (Integer C) - Updated when minor changes have been made – for example phrasing or reference changes

A full change-log, along with all previously published versions and their dates of publication, is publicly available on Isometric’s website.

The latest version is always the current version.



The appropriate citation for the document is the Isometric Standard (2023), version 1.0.0.


Definitions and Acronyms

  • RegistryA database that holds information on Verified Removals based on Protocols. Registries Issue Credits, and track their ownership and Retirement.
  • CreditA 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 CO₂ Removal. In the case of this Standard, the net tonne of CO₂ Removal comes from a Project Validated against a Certified Protocol.
  • RemovalThe term used in this Standard to represent the CO2 taken out of the atmosphere as a result of a CDR process.
  • DeliveryThe outcome of a Project Proponent providing Credits to fulfill Buyers' purchases.
  • 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.
  • 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.
  • 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.
  • VerificationA process for evaluating and confirming the net Removals for a Project, using data and information collected from the Project and assessing conformity with the criteria set forth in the Isometric Standard and the Protocol by which it is governed. Verification must be completed by an Isometric approved third-party (VVB).
  • Issuance (of a Credit)Credits are issued to the Credit Account of a Project Proponent with whom Isometric has a Validated Protocol after an Order for Verification and Credit Issuance services from a Buyer and once a Verified Removal has taken place.
  • BuyerAn entity that purchases Removals, often with the purpose of Retiring Credits to make a Removal claim.
  • Emission ReductionsLowering or avoiding future GHG releases from a specific entity.
  • Isometric Crediting ProgramThe scope of Isometric which involves all of the processes relevant to the entire life cycle of a Credit.
  • Non-Governmental Organization (NGO)A nonprofit, usually with a societal, scientific, or political purpose; by definition an NGO is not associated with a governmental entity.
  • Isometric SystemsIsometric's proprietary code and processes that create/contain intellectual property (IP) and enable the Registry to function smoothly.
  • Double CountingImproperly allocating the same Removal from a Project Proponent more than once to multiple Buyers.
  • Project ProponentThe organization that develops and/or has overall legal ownership or control of a Removal Project.
  • OfftakeA contract in which a Buyer agrees to purchase a set Removal at a set price.
  • Certification (of a Protocol)The Isometric process which involves expert review and Public Consultation in order to arrive at an approved version of a Protocol, against which Projects will be Validated and Removals will be Verified.
  • ProtocolA document that describes how to quantitatively assess the net amount of CO₂ removed by a process. To Isometric, a Protocol is specific to a Project Proponent's process and comprised of Modules representing the Carbon Fluxes involved in the CDR process. A Protocol measures the full carbon impact of a process against the Baseline of it not occurring.
  • 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.
  • ProjectAn activity or process or group of activities or processes that alter the condition of a Baseline and leads to Removals.
  • Carbon FluxThe amount of carbon exchanged between two or more Reservoirs over a period of time.
  • ConservativePurposefully erring on the side of caution under conditions of Uncertainty by choosing input parameter values that will result in a lower net CO2 Removal than if using the median input values. This is done to increase the likelihood that a given Removal calculation is an underestimation rather than an overestimation.
  • LeakageThe increase or decrease in GHG emissions outside the geographic or temporal boundary of a project that results from that project's activities.
  • BeneficiaryThe organization benefiting from the Removal claim afforded by a Credit. This may be the current holder of the Credit at the time of Retirement, or an organization specified by the Credit account holder during the Retirement procedure.
  • ModelA calculation, series of calculations or simulations that use input variables in order to generate values for variables of interest that are not directly measured.
  • ModuleIndependent components of Isometric Certified Protocols which are transferable between and applicable to different Protocols.
  • 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).
  • Isometric Science NetworkThe Isometric group aimed at bringing together scientists working in industry, academia, NGOs and more to promote more efficient collaboration across the CDR ecosystem.
  • Public ConsultationThe process by which a Protocol or Module is made available to the public for comment on the Isometric Science Platform.
  • Isometric Science PlatformA community resource where Project Proponents publish and visualize their early processes, Removal data and Protocols – enabling the scientific community to share feedback and advice.
  • Embodied EmissionsLife cycle GHG emissions associated with production of materials, transportation, and construction or other processes for goods or buildings.
  • Cradle-to-Grave​​Considering impacts at each stage of a product's life cycle, from the time natural resources are extracted from the ground and processed through each subsequent stage of manufacturing, transportation, product use, and ultimately, disposal.
  • BaselineA set of data describing pre-intervention or control conditions to be used as a reference scenario for comparison.
  • CounterfactualA quantification of what would have happened in the absence of a particular intervention – i.e., assuming the Baseline conditions.
  • Crediting PeriodThe period of time over which a Project Design Document is valid, and over which Removals may be Verified, resulting in Issued Credits.
  • FeedstockRaw material which is used for CO₂ Removal.
  • Standards (scientific)Standard physical constants as well as standard values set forth by bodies such as the National Institute of Standards and Technology (NIST) or others.
  • ProxyA measurement which correlates with but is not a direct measurement of the variable of interest.
  • Reputable SourceA source that would be widely considered trustworthy based on the process undertaken (e.g., peer review) or origin of the information (e.g., government body).
  • Sensitivity AnalysisAn analysis of how much different components in a Model contribute to the overall Uncertainty.
  • Monte Carlo SimulationsA mathematical approach for estimating the possible outcomes of an uncertain event through repeated random sampling. It can also be referred to as a "multiple probability simulation".
  • ReversalThe escape of CO₂ to the atmosphere after it has been stored, and after a Credit has been Issued. A Reversal is classified as _'avoidable'_ if a Credit Accounts 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.'_
  • Consequential AnalysisThe analysis of specific Uncertainties, hazards and scenarios inherent in complex systems such as the natural and engineered environment, aiming to describe how systems-level environmentally relevant flows will change in response to possible decisions.
  • Attributional AnalysisAnalysis aiming to describe the environmentally relevant physical flows to and from a life cycle and its subsystems
  • Ex-ante CreditsDelivery of Credits prior to full physical Removal from the atmosphere. Isometric does not Deliver Credits in this manner.
  • International Standards Organization (ISO)A worldwide federation (NGO) of national standards bodies from more than 160 countries, one from each member country[^8].
  • MaterialityAn acceptable difference between reported Removals/emissions and what an auditor determines is the actual Removal/emissions.
  • Retirement (of a Credit)The act of confirming the final ownership of a given Credit and permanent withdrawal from circulation. The Counterfactual of this act is the ultimate owner of the tonne of Removal and the sole claimant as to its attributes for the purpose of carbon accounting.
  • Ex-post CreditsDelivery of Credits after the carbon has been reasonably determined to have been physically removed from the atmosphere. This is the manner in which Isometric Delivers Credits.
  • Credit AccountsA function of the Isometric Registry that allows either Buyers or Project Proponents to receive Issued Credits, either by way of direct Credit Issuance in the case of Project Proponents, or by way of a Credit Transfer in the case of a Buyer.

Protocol Requirements

This section outlines the requirements for all Isometric Certified Protocols including Isometric Certified Modules.


Protocol Certification Process

All Projects must be Validated against, and Removals Verified against, an Isometric Certified Protocol.

An Isometric Certified Protocol is either:

  • a Protocol developed by Isometric that has undergone Public Consultation; or

  • a Protocol developed by external authors that has been reviewed by Isometric and undergone Public Consultation and which finally has been approved by Isometric for use on the Isometric Registry.

Externally-assembled protocols, once authorized by Isometric, may utilize the Isometric Modular Framework – in which Isometric Certified Modules are incorporated into a Project Proponent's Protocol where Isometric is represented as an author. All Modules will undergo rigorous Isometric review, with external Consultation deemed necessary on externally-assembled protocols which substantially modify Isometric Certified Modules. Upon completion of the protocol development and/or assembly process and final approval by Isometric, the Protocol will be listed as Certified and can be used by Projects.


Consultation Requirements

The external Consultation process will be as follows:

  1. Expert review through the Isometric Science Network

  2. Public Consultation

Expert review will be conducted through the Isometric Science Network. Expert review is the process in which the internal Isometric Science Team invites individuals with deep subject matter expertise to submit feedback on a Protocol. Isometric generously compensates experts for their detailed review with a flat hourly fee paid upon feedback submission.

Public Consultation will be announced on the Isometric Science Platform and to the Isometric Science Network. Protocols are open for public commenting for a minimum of 30 days. All relevant stakeholder comments are considered and responded to by the internal Isometric Science Team via the Science Platform, and the results of the Consultation will be published on the Science Platform. All anonymized comments and reviews will be made available upon request.

Typically, at least 5-10 scientific experts are engaged for a given Module or Protocol via the combination of the above processes.

The Consultation process will be conducted in compliance with the Isometric Stakeholder Input Process for Projects.


Modular Framework

A Protocol can reference or incorporate an existing Isometric Certified Module. Protocols which incorporate these Modules are subject to the same Protocol requirements as entirely externally-developed Protocols. Modules are developed by Isometric and will be Certified either through an Isometric-developed Protocol or individually as stand-alone items through the same Certification process.

Individual Isometric Certified Modules which are incorporated into a Protocol will not be subject to individual Consultation unless changes are made in accordance with Isometric's Updates to Protocols policy. Protocols which incorporate Modules will still require Consultation, with input and revisions only occurring to additional (non-Modular) parts of the Protocol and to assess the suitability of the incorporation of appropriate Modules.

All Protocols will include the same Modules for accounting for transport emissions, energy emissions and Embodied Emissions, in order to create a consistent accounting framework across all Projects.

Isometric will review individual Modules annually and be responsible for version changes in accordance with our Updates to Protocols policy.


Updates to Protocols

The internal Isometric Science Team will review a Protocol or Module if Isometric deems it necessary due to material changes in realms such as scientific knowledge, technology and/or regulatory frameworks. This review must be completed within a period of 6 months from the date an issue is raised. If the review results in substantial changes to a Protocol or Module such that a new version is required, these changes must adhere to the full Certification process.

In addition to the triggers for review outlined above, each Protocol will be reviewed at the sooner of the following criteria:

  • after 2 years have passed since the original Certification; or

  • whenever the number of Credits Issued under a Protocol passes the following milestones: 100,000 Credits Issued; 500,000 Credits Issued; 1,000,000 Credits Issued; 5,000,000 Credits Issued.

All changes will be documented on the Isometric Science Platform and published with the results of any Consultations. All versions of Protocols and Modules will be documented, archived and made publicly available. Revisions and updates to Protocols will be done in accordance with our standard Versioning Policy.

If a Module is updated, all existing Protocols which make use of this Module will be automatically updated. Existing Projects Validated against the previous Protocol version will remain unchanged until Project re-Validation unless otherwise specified with justification in the updated Protocol.


Protocol Contents



All Projects must have a defined temporal and geographical boundary as specified by the relevant Protocol. This must include at a minimum all GHG sources, sinks, and Reservoirs from:

  • the construction or manufacturing of each physical site and associated equipment;

  • the closure and disposal of each site and associated equipment; and

  • the operation of each process.

Protocols use a Cradle-to-Grave life cycle assessment (LCA) of all emissions associated with a Project's Removal process. The GHG emissions that result from the Project's activities within the defined boundary combined with any Leakages should together encompass the entire impact of a Project on GHG emissions.



All Projects must be assessed against a Baseline of their activities not having taken place. The method for Baseline assessment will differ between Project types and will be specified in the Protocols specific to certain processes. Baselines will be calculated using Conservative assumptions as outlined in relevant Protocols. Any Removals accounted for will need to include quantification of CO2e released as a diversion from the Baseline in the Project activities.

Projects will only be Credited for Removals above and beyond what Isometric has assessed to have likely occurred in a Counterfactual scenario. Projects will not be Credited for Emissions Reductions or avoidance.

If Projects cause additional temporary (<1,000 years) CO2 storage through their processes, this is not able to count positively towards the end number of Credits, but this carbon can be used to offset losses in Counterfactual storage.

Projects must reassess Baselines whenever a Crediting Period extension is requested, unless otherwise specified in the relevant Certified Protocol, and must be validated as part of Project Validation.



The Project Proponent must be able to demonstrate three pillars of Additionality (Financial, Environmental and Regulatory), in order to show that the claimed environmental impact would not have otherwise occurred in the Counterfactual Scenario.

A Project can be considered Additional when all of the following criteria are met.

  • Financial:
    • The Project can be considered to demonstrate Financial Additionality if Removals are the main purpose and only source of revenue of the Project.
    • Otherwise, the Project must demonstrate that economic barriers would prevent Project implementation in the absence of Carbon Finance, as outlined in the Financial Additionality Considerations section below.
  • Environmental:
    • The Project can be considered to demonstrate Environmental Additionality if the climate impact of the Project is net negative when compared to the Counterfactual scenario, using a Cradle-to-Grave LCA, in accordance with the LCA framework defined in the relevant Protocol.
  • Regulatory:
    • The Project can be considered to demonstrate Regulatory Additionality if the Project is not required by any regulatory, policy or other legal requirement.
    • Otherwise, the Project must be able to demonstrate that it exceeds the minimum regulatory requirements, as outlined in the Regulatory Additionality Considerations section below.
Financial Additionality Considerations

Evidence of Financial Additionality must be provided via full Project financials and comparison of financials to a Baseline analysis. The Baseline utilized must be Project-specific.

Proof of financial Additionality requires, at minimum, the calculation of the return on investment via calculation of the Internal Rate of Return (IRR) for the Project, as well as the IRR for the Baseline. The IRR determination may be completed in accordance with generally-accepted accounting practices. The analysis should be completed for a 10-year period, with non-depreciated residual values of any equipment or assets included as positive cash flows in year 10.

The Project Proponent must determine the IRR for the Project without Carbon Finance revenues and the IRR for the Project with Carbon Finance revenues.

For new Projects, The Project must ultimately demonstrate:

  • For a Project IRR without Carbon Finance revenues:

    • a zero or negative IRR; or
    • an IRR of less than the cost of capital (required rate of return) or return on equity for the Project.
  • For a Project IRR with Carbon Finance revenues:

    • a positive IRR; or
    • an IRR greater than the cost of capital (required rate of return) or return on equity for the Project.

A Project may justify a higher IRR as additional if the Project Proponents can demonstrate that the Project requires such an IRR to enable financing for higher risk Projects, which may require higher interest rate loans, high interest rate venture or equity investment, or similar.

The IRR analysis should also include a scenario analysis that demonstrates the ability to meet the above Additionality criteria for cases where values in the analysis change. Scenario analyses should include:

  • variation of initial investment costs, if greater than 20% of total Project costs;
  • variation of projected revenues to consider market changes for products or fees charged;
  • variation of the Removal Credit revenue value, based on current and historic Credit pricing for the specific type of Removal Credit being produced by the Project; and
  • evaluation of any assumption, value, or projection that accounts for greater than 20% of Project costs or Project revenues, or any value that impacts less than 20% of costs or revenues but which the Project Proponent determines can have significant impact (>10%) on IRR.

At a minimum, the IRR analysis should include variation of the factors above by ±20% or by a more appropriate value based on historical data or literature.

For pre-existing Projects:

  • Projects must provide a historical Counterfactual Baseline in the absence of Carbon Finance.
  • Removals only in excess of this Counterfactual Baseline may be considered Financially Additional.
Regulatory and Policy Additionality Considerations

Project Proponents must demonstrate that the Project is not required by existing laws, regulations, policies, or other binding obligations. If the activity is required by such legal requirements, the Project is not considered Additional. Legal requirements that should be considered include, but are not limited to:

  • any national, state, municipality or other local law or regulation; and
  • any policy, such as a procurement practice that requires the specific Project activity.

If the Project is legally required as described above, but the Project provides Removals that exceed the legal requirement, the Removals in excess of the legal requirement may be considered additional if the other Additionality requirements are also met.



Projects should demonstrate a robust assessment of potential increases in GHG emissions outside the defined project boundary that occurs as a result of the Project activity. Where the potential for such Leakage is identified, it must be quantified and deducted from the CO2 Removals in accordance with the relevant Protocol.

Where appropriate, Leakage includes, but is not limited to:

  • upstream considerations (such as Feedstock sourcing or energy procurement) as laid out in the relevant Protocol; and

  • downstream storage considerations beyond a Project's direct activities.


Default Emission Factors, Proxies and Models

Protocols can use Default Emission Factors, Standards, Proxies and Models to quantify Removals, demonstrate Additionality and/or establish Baselines. In metered systems, the preference is for direct measurement of required variables where possible.

Proxies and Models will only be permitted for use under circumstances which are justifiable, such as for reasons of practicality, reliability, and for gap filling in variable un-metered systems. This justification must be outlined in the Protocol. Proxy measurements are secondarily preferred, and models may be used when neither Proxy or direct measurements are viable. When used, Models and Proxy measurements must apply Conservative Uncertainty factors and make Conservative assumptions. When Models and Proxy measurements are used, Uncertainty must be assessed and clearly outlined in the Protocol.

Further requirements and guidance for the use of Default Emission Factors, Standards, Proxies and Models in Protocols are outlined below.
Default Emission Factors

The Protocol must appropriately cite and describe the source of any third-party Default Emission Factor, Standard, Model or Proxy. Third-party Default Emission Factors and Standards must be either internationally recognized or derived from a Reputable Source.

Where a newly established Default Emission Factor is used in a Protocol, the reasoning behind this choice and documentation of Default Emission Factor calculations must be clearly outlined and will be subject to review in accordance with the Consultation Requirements.

Protocols must identify Default Emission Factors that are likely subject to future changes. Default Emission Factors can be subject to updates and revisions given the Isometric Updates to Protocols policy.

Proxies must be shown to be well-correlated with the variable of interest, preferably through established calibration studies from Reputable Sources. The Proxy data, empirical fits, correlation data, and sources must be provided to Isometric.

Models must be from a Reputable Source and/or shown to be reliable via peer-review, testing or correlation with empirical data. The source of models, any modifications, input parameters, data used and validation results must be clearly outlined to Isometric.


Common Calculation Factors

All calculations should use consistent, standardized factors, including the following:

Global Warming Potential (GWP): Calculations shall use the 100-yr GWP for the greenhouse gas of interest, based on the current volume of the IPCC Assessment Report, currently the Sixth Assessment Report4. Current 100-yr GWPs are: CO2 = 1; CH4= 27.9, N2O = 273.


Uncertainty in Removals

Uncertainty is due to factors such as inability to precisely measure certain physical phenomena and/or simplified assumptions in Models or LCAs. Protocols must set up frameworks that allow for the reduction of uncertainties with time as measurements, models, and scientific understanding improves.

Protocols must report a list of all parameters that are used in Removal calculations (see Table 1). 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 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. Uncertainty information will vary depending on the data, but may include the type of distribution and parameters needed to describe uncertainty and/or shape of the data when plotted. Appendix A provides additional guidelines for assessing different types of uncertainties.

Furthermore, the source for information relevant to Uncertainty calculation and/or justification is required for each input parameter. The Uncertainty information may be obtained from instrument calibrations, measurement variability, published literature, Proxies, expert judgment, and/or other Reputable Sources.
Conservative Estimate of Removals

Protocols must include a procedure for incorporating Uncertainties into a Conservative estimate of Removal. The following approaches are acceptable, and other methods may be considered after an internal Isometric review.

A. Conservative estimate of input parameters

B. Variance propagation

C. Monte Carlo Simulations

Option A will lead to a more Conservative Removal estimate. This approach is suitable for Projects where it is difficult to obtain detailed information on input parameter distributions.

Option B can be used when parameters follow normal distributions and errors are linear (i.e., errors increase linearly as parameter values increase) and independent (i.e., changing one variable has no effect on another variable).

Option C provides a more comprehensive representation of Uncertainties and may result in more Credits Issued. This approach is suitable for Projects where sufficient information is available for all input variables so that Monte Carlo Simulations can be conducted.

As Removal quantifications become better-constrained and more data is gathered, Protocols may progress from using Option A to Option B to Option C.
Conservative Estimate of Input Parameters

For Option A, a uniform distribution is assumed for all parameters, unless it can be demonstrated otherwise. The value used in the Removal calculation should be either ≤16th or ≥84th percentile, depending on which one yields a more Conservative estimate of Removal. See Table 1 below for examples.

ParameterMinimumMaximumConservative estimateSource/Justification
Air-sea equilibration efficiency0.510.58 (16th percentile)

Modeling studies from a peer-review paper. A lower efficiency leads to less CO2 Removal, so the Conservative estimate should be ≤ 0.58

Truck transportation carbon intensity0.2 kg/km/t1.2 kg/km/t1.04 (84th percentile)

Range from published emissions factor database for different vehicle types. In this case, a higher carbon intensity leads to less net CO 2 Removal, so the Conservative estimate should be ≥ 1.04

Table 1
Example of Conservative estimation of input parameters.
Variance Propagation

For Option B, the variance must be defined for all input parameters. Variance propagation should be conducted following uncertainty propagation rules5, where the outcome is the variance in the Removal. The Conservative Removal estimate should be at least 1 standard deviation (square-root of the variance) below the mean, equivalent to ≤16th percentile.
Monte Carlo Simulations

For Option C, the input distributions must be specified for all input parameters. The final distribution for the Removal is determined by randomly sampling from input distributions many times (e.g., n = 1,000).6 The Conservative estimate of Removal will be ≤16th percentile for consistency between Option B and C in the case of normal distributions.
Expert Reviews and Updates

Parameter Uncertainties that are based on expert judgment and which contribute the most significantly to the final Removal calculation (based on a Sensitivity Analysis) will be subject to expert review by Isometric and/or selected Science Network experts.

Uncertainty assessment should initially be revisited as part of every Verification, with updates incorporated as appropriate. The frequency of assessments may be amended on a Protocol-by-Protocol basis as Uncertainties reduce over time.


Durability and Monitoring

Project Proponents must demonstrate a Durability of at least 1,000 years to ensure meaningful long-term climate action. Projects with <1,000 year durability will need to be reviewed on a case-by-case basis.
Proof of Durability

Proof of Durability can be established in two possible ways:

  • via containment mechanisms, where the Conservatively-estimated engineering and/or scientific methods for containment exceed 1,000 years – possibly supported by secondary containment; or

  • via scientifically falsifiable hypotheses that can be used to show there is no alternative destination for carbon storage other than the Reservoir in question.

A full risk assessment must be undertaken to identify all possible mechanisms that will lead to Reversals and subsequent decreases in Durability. There must be a monitoring plan in place to quantify the amount of potential Reversal that may occur via each identified Reversal mechanism.

Monitoring requirements must include:

  • adherence to the monitoring program of the Protocol that the individual Project is following;

  • the frequency of measurement and reporting, which should be specified in the relevant Protocol, reflect the relative Uncertainties of a technology at the start of a program and be reviewed on an annual basis;

  • consideration of Baselines and incorporating provisions for reevaluation at the end of a Project's Crediting Period or at set timescales as defined within the Protocol;

  • the methodology for assessing Removal Durability and detecting and calculating Reversals;

  • provisions for reporting Reversals to the VVB and Isometric, as adequate deductions to net Removals may be required;

  • identification and remediation of emissions of CO2e to best possible practices during a Project's operational and post-cessation life cycle; and

  • monitoring reports that are made publicly available to the Registry.


Risk of Reversal

Protocols must categorize the Risk of Reversal for determining the appropriate Buffer Pool Size in the event of a Reversal. Isometric has provided a risk questionnaire (see Appendix B) that can serve as guidance on how Risk of Reversal is determined. The answers to the risk questionnaire are used to support the Risk of Reversal and Buffer Pool Size.

The Risk of Reversal and the corresponding Buffer Pool Size are meant to insure against Reversals that may be observed as a result of monitoring. The Buffer Pool is not meant to insure against risks in cases in which carbon is stored in an open system (e.g., the ocean) and direct observation would not be possible. In open systems, storage risks should be assessed as part of the Uncertainty assessment and accounted for in the Conservative estimate of Removal.


Environmental and Socioeconomic Impacts

Projects at minimum should do no net environmental, social or economic harm and should avoid circumstances with the potential for unintended Leakage. Protocols must specify the relevant permitting a Project should receive to demonstrate this, in addition to the Isometric Standard Project Requirements. Crediting is subject to cessation and cancellation if no tangible effort is made to remediate harm that occurs as part of a project.


Life Cycle Assessment (LCA) Policies

All Projects must follow LCA guidelines as set out by the relevant Protocol. This includes guidelines for conducting transport emission accounting, energy use accounting and embodied emission accounting as well as specific Protocol requirements such as Default Emission Factors.

Protocols Certified by Isometric should use Consequential Analysis to determine carbon emissions. Protocols must address:

  • byproduct accounting;

  • accounting regime (consequential); and

  • considerations relating to the temporal aspects of emissions and possible effects on quantification.

Attributional Analysis may be permitted on a case by case basis by Isometric, if appropriately justified (e.g. on grounds of accuracy and feasibility).


Project Requirements

Removals are conducted and Verified as part of specific Projects. This section describes the requirements for Projects to be compliant with the Isometric Standard.



Projects must demonstrate that they have legal ownership over the rights to all Removals that will be claimed from the Project, including at minimum making a representation to Isometric to this effect.

When there are multiple parties involved in the Removal process, and to avoid Double Counting, a single Project Proponent must be specified as the sole owner of the Removals.

Ownership must be defined in contracts between the Project Proponent and other Project participants, which may include, for example, suppliers of Feedstocks, transportation and logistics companies, and/or storage site owners and operators.

Contracts must:

  • relinquish ownership of all Removals to the Project Proponent;

  • clearly indicate that other companies or operators participating in the Project cannot claim Credits, Emissions Reductions or offsets as a result of participation in the Project;

  • provide mechanisms for the Project Proponent to obtain required information to fully calculate the Removals from aspects of the Project relevant to the company; and

  • stipulate that unless these third parties are the end owners of the generated Credits that they will not advertise that they are producing a “low emission product or practice,” in connection with or benefitting from the Removals carried out by the Project.



For a Project to be evaluated for the Isometric Registry, the Project Proponent must document Project characteristics in a Project Design Document (PDD). The plan will form the basis for Project Validation and evaluation in accordance with the relevant Certified Protocol. This Project Plan should be consistent with ISO 14064-2:20197, and should include:

  • Project title, purpose(s) and objective(s);

  • type of Project, including descriptions of how the Project will achieve Removal based on the emission calculation requirements laid out in the relevant Protocol;

  • Project location, including organizational, geographic and physical location information, allowing for the unique identification and delineation of the specific extent of the Project;

  • conditions prior to Project initiation to support identification of the Counterfactual emissions;

  • Project technologies, products and services;

  • anticipated aggregated net Removals in tonnes of CO2 likely to occur from the Project;

  • anticipated Uncertainty determination approach;

  • identification of risks that could substantially affect the Project's Removals and, if applicable, any measures to manage those risks;

  • roles and responsibilities, including contact information of the Project Proponent and other Project participants;

  • a summary environmental impact assessment;

  • description of stakeholder, community, or other interested party Consultations and mechanisms for ongoing communication, and outcomes of any such discussions;

  • a chronological plan or actual dates and justification for the following:

    • Project Start Date;

    • GHG Baseline time period;

    • Project Crediting Period; and

    • frequency of monitoring and reporting and the Project period, including relevant Project activities in each step of the Project cycle, as applicable; and

  • Project Risk of Reversal.

    • Note that project Risk of Reversal must be greater than or equal to the Risk of Reversal outlined in the relevant Protocol. The Risk of Reversal can be increased to account for site-specific considerations that may make a Reversal more likely (e.g., increased risk of a natural disaster). Any increase in Risk of Reversal must be documented, along with its justification, in the PDD.

Isometric will not publicly disclose sensitive business information inherent to data included in the PDD or otherwise provided by the Project Proponent.



Projects are only eligible to claim Credits for activities that are exclusively registered with the Isometric Registry. Projects are only eligible to receive Credits on the Isometric Registry using an Isometric Certified Protocol.

At time of Project application and Validation, Projects must use the latest available version of a Certified Protocol, unless a grace period has been explicitly specified by Isometric, whereby a former version of a Protocol may continue to be used for a defined time period.

Projects which have already been Validated may continue to apply the version of the protocol they were Validated under, until the next Crediting Period renewal, unless otherwise specified in the updated Certified Protocol.

Projects shall conform to all relevant laws and regulations in the jurisdiction in which they operate.

Projects must be Additional, according to the guidance described in the Isometric Standard Additionality approach.

Projects must use the Isometric approved Default Emission Factors as laid out in relevant Protocols. If Projects believe there is reason for them to deviate from these values they may contact Isometric with supporting information.

The Project Proponent is responsible for notifying Isometric of any changes to operations that could change the eligibility of their process.


Project Crediting

Projects are eligible to begin submitting Claimed Removals to Isometric following Project Validation which, once Verified, may be used to issue Credits. See Section 6 for more information on Crediting.

Projects are eligible to Issue Credits for the duration of the Crediting Period specified in the Project's PDD. If a Project Proponent wishes to renew the Crediting Period of a Project, an updated PDD must be provided and the Project must be re-Validated. In general, the maximum Crediting Period is 5 years, unless otherwise specified by the relevant Certified Protocol.

Isometric does not Issue Ex-ante Credits.


Stakeholder Input Process

Relevant stakeholders must be informed of the Project's proposed and current activities by the Project Proponent. All stakeholders should be equitably represented, involved and able to contribute freely. This includes but is not limited to Indigenous Peoples and Local Communities (IPLCs), stakeholders with land-tenure rights, local policymakers, national government officials and local NGOs.

The Project Proponent must respect and not infringe upon IPLCs. If the potential for negative socioeconomic impacts are identified, the Project must not proceed without the free, prior and informed consent (FPIC)8 of the relevant IPLCs.

Consultation with stakeholders and rights-holders should be conducted. Consultations should meet the requirements below.

  • Iterative:

    • The first consultation meeting should occur prior to Project development, such that any input and concerns can be incorporated into the Project's design, and meeting and correspondence should be operational throughout the Project's life cycle.
  • Accessible:

    • Stakeholders and rights-holders should be invited to consultation meetings with a minimum notice of 14 days.

    • Stakeholders and rights-holders should be invited to consultation meetings via methods including but not limited to the post, email, or notices in newspapers and public places.

    • Consultation meetings should be scheduled to maximize attendance, taking note of cultural or religious holidays and heritage.

    • Meetings, documentation and correspondence should be:

      • in the local language(s), or have a translator where necessary to facilitate communication;

      • respectful of local knowledge; and

      • accessible to a non-technical audience.

  • Transparent:

    • The intention of each consultation meeting should be communicated to all stakeholders prior to the meeting.

    • All stakeholder or Project Proponent conflicts of interests should be declared.

  • Free from external manipulation

  • Include a system for stakeholders to voice, process, and resolve grievances:

    • Project Proponent contact information must be made available to all stakeholders.

    • Grievances must be acknowledged no later than 14 days after receipt by the Project Proponent.

    • Grievances must be resolved or escalated no later than 60 days after receipt.

  • Systematically documented and made public or accessible upon reasonable request


Regulatory Compliance

Projects must assert with the PDD the method(s) for compliance with regulations for all jurisdictions to which the Project is beholden.


Environmental and Socioeconomic Impacts

Projects must comply with national and local laws and regulations and, where relevant, international conventions.

Projects must consider the material environmental and socioeconomic impacts that could potentially arise as a result of their activities, both within and beyond its boundary, and at minimum must do no net environmental or socioeconomic harm and remediate any unintentional harm done (or be subject to Credit cessation and cancellation). The consideration of these impacts should be ongoing throughout a Project's lifespan, and should include provisions for post Project closure.

A Project must report potential impacts identified by an Environmental Impact Assessment (EIA) to Isometric and environmental regulators where applicable.


Impact Assessments

A Project must demonstrate that it creates no net social or environmental harm (as assessed by an independent third party) by undertaking all of items below.

  • An EIA, including social impact assessment, is suggested for all Projects, but at a minimum EIA’s should be carried out as required by local regulations prior to the Project start date. It is the responsibility of the Project to ensure that an undertaken EIA meets all local, regional and national environmental regulations and laws.
  • Ongoing environmental assessments should be completed both during Project operation and post cessation of Project activities. This should include environmental monitoring, maintenance, and remediation strategies where necessary.
  • A closure plan that outlines post-cessation actions that are needed by the Project Proponent. A closure plan should be designed at the beginning of a Project and periodically updated throughout the Project life cycle.

These assessments and mitigation strategies should consider, where applicable, the Project’s impact upon risks of negative environmental and social impacts. This should include, but not be limited to, the following, as outlined in the ICVCM Core Carbon Principles9:

  • labor rights and working conditions;
  • resource efficiency and pollution prevention, including:
    • pollutant emissions to air,
    • pollutant discharges to water, noise and vibration; and,
    • generation of waste and release of hazardous materials, chemical pesticides and fertilizers;
  • land acquisition and involuntary resettlement, including:
  • biodiversity conservation and sustainable management of living natural resources,
    • avoid, or where this is not feasible, minimize negative impacts on terrestrial and marine biodiversity and ecosystems,
    • protect the habitats of rare, threatened, and endangered species, including areas needed for habitat connectivity,
    • do not convert natural forests, grasslands, wetlands, or high conservation value habitats,
    • minimize soil degradation and soil erosion,
    • minimize water consumption and stress in the mitigation activity;
  • impacts on IPLC, and cultural heritage;
  • respect for human rights, stakeholder engagement;
  • gender equality.

Validation and Verification Requirements

This section defines the requirements for Validation and Verification of Projects on the Isometric Registry. Accredited VVBs Validate Projects and Verify Removals in line with this Isometric Standard and a Certified Protocol.


Validation and Verification Body Qualification Requirements

All VVBs are approved by Isometric independently and impartially based on alignment with Conflict of Interest policies, rotation of VVB policies, oversight on quality, and the following requirements:

  • VVBs must be able to demonstrate accreditation from:

    • an International Accreditation Forum10 member against ISO 14065 or other relevant ISO standard, including but not limited to ISO 14034, ISO 17020, ISO 17029; or

    • a relevant governmental or intergovernmental regulatory body.

  • Alternatively, on a case-by-case basis, if VVBs are able to demonstrate to Isometric that they satisfy all required Verification needs and competencies required for the relevant Protocol and follow the guidelines of ISO 19011 or other relevant standards, they may be approved.


Validation and Verification Process

All Projects must undergo an initial Project Validation, carried out by an independent VVB, to assess conformity with the Isometric Standard, and with the applied Certified Protocol. Once a Project has been Validated, the Project is subsequently able to submit Claimed Removals to Isometric. Isometric requires Verification of any Claimed Removal in order to Issue Credits. Validation and Verification will be carried out in line with ISO 14064-3 and ISO 14065. Additional requirements are listed below.

  • Removals may be Verified annually, or more or less frequently, according to the requirements of the relevant Certified Protocol, or at the Project Proponent's request.

  • Project Validation may occur at the same time as the first Verification, or before the first Verification.

  • If a Project Proponent wishes to renew the Crediting Period of a Project, an updated PDD must be provided and the Project must be re-Validated.

  • Unless otherwise specified in the relevant Certified Protocol, a site visit is required for Validation and the first Verification of a Project. For subsequent Verifications, the VVB must identify whether a site visit is needed, based on an independent risk assessment.

  • The level of assurance for Verifications must be reasonable.

Prior to Validation/Verification, the third party shall prepare a Validation/Verification plan that details the activities and schedules. The plan may be revised as necessary during the process. The plan shall be communicated with the Project Proponent and shall include, at minimum:

  • the scope and objectives;

  • identification of the Validation/Verification team and their roles;

  • client/responsible party contact;

  • schedule of activities;

  • level of assurance;

  • Verification criteria;

  • Materiality; and

  • schedule for site visits.

The Verifier shall produce a report that documents the activities, results, findings, and conclusion of the Verification. The Verification report shall contain, at a minimum11:

  • a statement that the Project Proponent is responsible for the fair presentation of the PDD in accordance with the criteria;

  • a statement that the Verifier is responsible for expressing an opinion on the PDD based on the Verification;

  • a description of the Verification evidence-gathering procedures used to assess the PDD;

  • the Verification opinion, which will will state the net Removal during the covered period to a reasonable Level of Assurance;

  • the date of the report;

  • the Verifier’s location;

  • the Verifier’s signature;

  • a summary of the Claimed Removals;

  • reference to the Verification criteria; and

  • Verification scope.

Following this process, Isometric will review the Project documents used for Validation and Verification, and either accept them, request corrections or clarifications for the Project Proponent or VVB to address, or reject them. Once Isometric has accepted a Verification Report, the corresponding Removals will be deemed Verified, and eligible for issuance of Credits. The results of the Validation and Verification process, including the Verification Report and Opinion, will be made available for each Project.


Materiality Threshold

The threshold for Materiality, considering the totality of all omissions, errors and mis-statements, is 5% for all Projects. To accept a Verification Opinion, Isometric requires that discrepancies between the Removal Claimed by the Project Proponent and that estimated by the VVB for a given statement be less than the Materiality threshold.

Qualitative materiality issues may also be identified and documented, such as12:

  • control issues that erode the verifier’s confidence in the reported data;
  • poorly managed documented information;
  • difficulty in locating requested information;
  • noncompliance with regulations indirectly related to GHG emissions, removals or storage

If an overstated Project (one which claims more Credits than it has produced) is discovered after Credits have been Issued, please see the Isometric policy on Changes to Issued Credits.


Conflicts of Interest

Any organization which has been involved in the development of a particular Project Proponent may not act as a VVB for Validation and/or Verification purposes for that Project. Any organization which has been paid by a particular Project to assist in developing any part of a Certified Protocol for their process may not act as a VVB for Validation and/or Verification purposes for that Project.

To minimize the risk of conflicts of interest occurring between the Project Proponent and the VVB, Isometric will select and engage VVBs for Project Validation and Verification, and VVBs must complete a conflict of interest disclosure.


Rotation of Validation and Verification Bodies

Isometric requires that Projects must work with a single VVB for no longer than five consecutive years. A given VVB may conduct Verification for a Project during no more than five out of seven consecutive years.


Validation and Verification Body Oversight

In addition to the qualification requirements, Isometric may oversee VVB activity during the Validation and/or Verification process, and may suspend approval of a previously approved VVB. Oversight can include review of VVB documentation, including Verification and sampling plans, reports, opinions and conflict of interest disclosures, as well as review of Project Proponent documentation.

Isometric will report significant and/or repeated VVB performance concerns to the relevant accreditation body.



Isometric Credits are Issued, Transferred and Retired on the Isometric Registry according to the rules and requirements set out in this section.

Isometric is the sole Credit issuing body on the Isometric Registry.


Credit Attributes

Credits have only one owner at any time. A full ownership history is tracked and is publicly visible for each Credit. Each Credit is Issued Ex-post against a net Verified Removal, thereby ensuring every tonne of CO2 removed is Credited and accounted for only once, and that any Credit can be traced back to an individual Removal.

Each Credit has a publicly available history of ownership that indicates when the Credit was first Issued, who it was first Issued to, if and when it was subsequently Delivered or Transfered, if and when it was Retired and by whom, on behalf of whom.

When first Issued, a Credit's status is Active. Upon Retirement of the Credit, its status becomes Retired.

Credit metadata include:

  • Unique Serial Number;

  • Issuance Date;

  • Issuing Project;

  • Issuing Project Proponent;

  • Country of Removal;

  • Ownership history, including the current Owner (the Owner who is retiring the Credit) and all previous Owners and Transfer Dates;

  • Retirement Date;

  • Retirement Beneficiary; and

  • Credit Status.


Issuance Process

Credits are Issued against a specific Removal. This process is undertaken once a Removal has been Verified. Credits are always Issued to the Project Proponent of the Removal. The Project Proponent is then able to Deliver Credits to Buyer Credit Accounts on the Registry, and can do so at a time and in an order of their own discretion.


Transfer and Delivery Rules and Ownership History

Deliveries can be made by Project Proponents to Buyer Credit Accounts, resulting in transfer of ownership of one or more newly Issued Credits. Further Transfers can be made by Credit Account holders to other Credit Accounts, resulting in transfer of ownership of one or more Credits. For each Credit, the initial Delivery and all Transfers are logged on the Credit and made publicly available in the Credit's history.

Project Proponent Deliveries are subject to the following rules:

  • Project Proponents can only Deliver Credits that have been Issued;

  • Project Proponents can only Deliver Credits that they own; and

  • Project Proponents can only Deliver Credits to Buyers who have an active Isometric Registry Credit Account.

Buyer Transfers are subject to the following rules:

  • Buyers can only transfer Credits that they own; and

  • Buyers can only transfer Credits to another organization that has a Credit Account on the Isometric Registry.


Retirement Rules

Retirement is the mechanism by which a Credit's ownership state is finalized. This ensures that once the tonne of CO2 represented by the retired Credit is used towards an accounting activity, it can never be used again by the owner, the Beneficiary of the retirement, or any other actor.

The Beneficiary of a Retirement is the organization on behalf of whom the Credit was retired, and must be publicly identified. Beneficiaries can be the current holder of a Credit at the time of retirement, or an organization that is specified by the Credit Account holder during the Retirement procedure. The Credit Account holder can retire Credits by following the Retirement process through their Credit Account on the Registry.

The owner of an unretired Credit may publicly market its ownership of said Credit, as well as the potential for the Credit to be retired by any current or future owners, but only the Beneficiary of a Retired Credit may claim the environmental benefits associated with that Credit.

Retirement is subject to the following rules:

  • a Credit Account holder can only retire Credits they own, which are in their Credit Account;

  • a Credit can only be Retired once; and

  • any number of Credits can be retired at any given time, provided that number of Credits does not exceed the number of Credits held by the Credit Account.


Retirement Certificates

Retirement Certificates serve as proof of the Retirement of one or more Credits, and are produced only on completion of a Retirement. Every Retirement Certificate relates to one or more Retired Credits. If more than one Credit is Retired at a time, the Certificate will list all Retired Credits. Retirement Certificates show the relationship between retired Credits and the Removals they derive from.


Reversals and Buffer Pools

This section outlines how Reversals are handled on the Isometric Registry, through the use of Buffer Pools.

All Reversals will be reviewed by the Isometric Science Team.

Note that changes to calculations as a result of updates to Protocols are not considered Reversals, and will generally not affect previously issued Credits. However, Isometric will monitor for significant impacts due to Protocol updates to ensure overall quality and to address system level impacts (e.g. considerable evolution of scientific consensus).



Project Proponents must monitor for Reversals as prescribed by a Project's Monitoring Plan, and promptly report Reversals to Isometric if identified. At the verification following a Reversal, the Project Proponent must report relevant monitoring data for any Reversal which has occurred, to be assessed by the verifier as part of that verification. Reversal data from Projects will be made public.

When a Reversal is identified, Credits will be Retired from the Project Proponent's Buffer Pool to compensate for the Reversal. The number of Credits to be Retired must equal the size of the Reversal.

In the event that a Project Proponent is not able to comply with monitoring, closing or Embodied Emission amortization requirements as outlined in the relevant Protocol, the treatment of possible Reversals will be assessed on a case by case basis.


Buffer Pools (Uncertainty in Storage)

Isometric will maintain a Buffer Pool of Credits in accounts specific to each Project Proponent from which Credits will be Retired in the case of a Reversal.

Whenever Credits are Issued following a Verified Removal, a percentage of these Credits will be Issued to the Project Proponent's Buffer Pool account, according to the Buffer Pool Size below.

Credits in a Buffer Pool can not be Transferred, or used to make Deliveries.

In the case that there are insufficient Credits in a Project Proponent's Buffer Pool to compensate for any triggered Reversals, all further Credits Issued from Removals conducted by the Project Proponent (whether from the same Project, or other Projects run by the same Project Proponent) will be assigned to their Buffer Pool and Retired, until all such Reversals have been fully compensated.

The Buffer Pool Size is determined by the Risk of Reversal of a given approach, as outlined below. The Risk of Reversal is defined in the relevant Certified Protocol. Projects with a higher Risk of Reversal have a correspondingly larger Buffer Pool. Note that the Buffer Pool is applied in addition to the Conservative approach taken in the quantification of net CO2 Removal, whereby uncertainty is factored into the Credited Removal. The following Buffer Pool sizes may be subject to change in future Standard versions based on empirical data.

Risk of ReversalBuffer Pool Size
Very low2%

Furthermore, Reversals are classed as either avoidable or unavoidable, as judged by Isometric, in consultation with selected VVB(s) and/or Science Network representatives.

Where an Avoidable Reversal has occurred, a Project Proponent must reimburse their Buffer Pool account by transferring a number of Credits equal to the size of the Reversal to the Buffer Account. While there are any outstanding Avoidable Reversals to be remedied in this way, all further Credits Issued from Removals conducted by the Project Proponent (whether from the same Project, or other Projects run by the same Project Proponent) will be assigned to their Buffer Pool, until all such Reversals have been fully remedied.

Where an Unavoidable Reversal has occurred, the Project Proponent is not required to reimburse their Buffer Pool account.


No Double Counting

Isometric has rules and procedures in place to mitigate the risk of occurrence of Double Counting, which can occur in different ways, including double issuance, double use and double claiming.

Double issuance (occurring when more than one unique unit is Issued for the same Removal activity) is not permissible, and Isometric has checks in place to mitigate the possibility of double issuance. Any Removal activity listed on the Isometric registry must not be listed on another program, and may not be used to make a separate carbon Removal claim elsewhere.

Double use (occurring when an Issued credit is further transferred, used or retired after already having been retired) is mitigated through a transparent, public record of all Credits and Retirements, ensuring all Retirements used as claims towards mitigation targets can be uniquely identified, and can be traced back to the specific Removal activity the Credit was Issued against. Once a Credit has been Retired, it cannot be used further, and a unique, public Retirement Certificate is produced.

Double claiming (occurring when an Issued credit is claimed twice towards achieving mitigation targets or goals) is not permitted on the Isometric Registry. For any Credit, no separate Removal claims may be made for the underlying Removal from which the Credit was Issued. Isometric will monitor for instances of Double claiming, and Credit Account users engaging in double claiming may have their Credit Account suspended.


Appendix A. Types of uncertainties

Calculation of uncertainty shall follow documented best practices, such as the requirements of the Joint Committee for Guides in Metrology (JCGM) JCGM100:2008 - Evaluation of measurement data — Guide to the expression of uncertainty in measurement (GUM)12._ _Uncertainty can be assessed using two different methods13:

  • Type A uncertainty, where uncertainty is assessed by making repeated observations of the parameter of interest
  • Type B uncertainty, where uncertainty is founded on a priori distributions, evaluated by scientific judgment based on all of the available information on the possible variability of the parameter of interest

Type B uncertainties may frequently be encountered, since it is not always practical to make repeated measurements for every input parameter, and many input parameters are published values or estimated through other means.


Emission factor uncertainty

Emission factors utilized should provide an uncertainty value associated with the specific factor. Some databases from which emission factors are derived include and report the uncertainty within the database14. The factor used, its source, and the value of the uncertainty reported and used, shall be documented. For emission factors for which no uncertainty information is provided, clearly document this and refer to [11.10.5 Unknown uncertainties]


Measured parameter uncertainty

See the GUM for details on calculation of parameter or measurement uncertainty. For instance, measurement parameter uncertainty estimates could be derived from manufacturers specifications or calibration records. If repeated measurements are taken, the type A uncertainty shall be reported as the standard deviation. Uncertainties should be documented and reported for each measured parameter.


Laboratory analysis uncertainty

For laboratory analyses, uncertainty may be reported based on laboratory quality assurance documentation, including laboratory calibration results and records which use a reference calibration standard that is traceable to a national standard.

For a reported value based on multiple laboratory analyses, for which the value is reported as a mean, the type A uncertainty is calculated based on the standard deviation of the value around the mean.


Unknown uncertainties

When published uncertainty information is not available and calculation via direct measurement is not feasible, estimation of uncertainty shall follow documented best practices, such as guidance from the GUM for evaluating type B uncertainty. The specific approaches taken shall be clearly documented.

Specifically regarding emission factors, the default values for basic uncertainty from Section 10.1 of Ecoinvent’s Overview and Methodology document may be used. Ecoinvent’s protocol assumes a lognormal distribution for a value and then uses a Pedigree Matrix to assign uncertainties based on data quality.


Appendix B: Risk Reversal Questionnaire

This questionnaire provides guidance on assessing Risk of Reversal, to be used by Protocols and Projects which need to make this assessment for use on the Isometric Registry. Please see the Reversals and Buffer Pools for more details on how Risk of Reversal is used.

#QuestionIf answered “Yes”If answered “No”

Is a reversal directly observable with a physical or chemical measurement as opposed to a modeled result?

Proceed to questions 2-8Proceed to questions 7-8
2Is the carbon being stored organic?Add 1 to Risk Score-

Does scientific consensus suggest that the carbon storage reservoir has a less than 10,000 year durability?

Add 1 to Risk Score 
4Is methane production a project risk?Add 1 to Risk Score 

Does this approach have a material risk of reversal due to natural disasters including, but not limited to, floods, storms, earthquakes, fires, etc.?

Add 1 to Risk Score 

Does this approach have a material risk of reversal due to human-induced events from outside actors, such as change in farming practices, change in ownership and management of project sites, or similar?

Add 1 to Risk Score 
7Does this pathway have a documented history of reversals?Add up to 2 to Risk Score 

Is there one or more project-specific factors that merit a high risk level?

Add up to 2 to Risk Score 

Risk Score Categories

  • 0: Very Low Risk Level (2% buffer)

  • 1-3: Low Risk Level (5% buffer)

  • 4-5: Medium Level (10% buffer)

  • 6+: High Risk Level (20% buffer)


Worked Examples

Isometric's Uncertainty and Buffer Pool policies represent two mostly non-overlapping approaches for how Isometric plans to be conservative in how credits are quantified and to potentially insure against future events that may result in a Reversal. Specifically, in removal pathways that utilize large, open-system reservoirs (e.g., the ocean) where direct observation of a reversal is not feasible, Isometric's Uncertainty policy will generally result in a larger uncertainty discount15, and Isometric's Buffer Pool policy will generally result in a smaller Buffer Pool Size. Conversely, in removal pathways that utilize closed-system reservoirs that are more straightforward to monitor, Isometric's Uncertainty policy will generally result in a smaller uncertainty discount, but the activity will be subject to a larger Buffer Pool Size. Below are two example scenarios that illustrate how and when these two policies are invoked.

Example 1: Ocean Alkalinity Enhancement

An OAE Project Proponent releases a known amount of alkalinity into the ocean. In accordance with the Protocol and PDD, the Project Proponent uses a model to estimate that the median CO2 uptake after a certain amount of time is 100 tonnes. In accordance with Isometric's Uncertainty policy, the Project Proponent reports that the 16th percentile of CO2 uptake outcomes is 15 tonnes below the median (resulting in a 15t uncertainty discount that is subtracted from the gross CO2e removed). The Project Proponent follows Isometric's guidance in answering the risk questionnaire and determines they have a Risk of Reversal that corresponds to Risk Level A (resulting in a 2% Buffer Pool Size).

  • Net CO2 removed = 100t - 20t - 15t = 65t

    • Gross CO2e removed: 100t

    • LCA and counterfactuals: -20t

    • Uncertainty discount: -15t

  • Credits issued to Supplier: 63.7 credits (65 - 1.3)

    • Total Credits issued: 65 credits

    • Credits deposited to Buffer Pool account: 65 credits * 2% = 1.3 credits

Example 2: Bio-oil Production and Injection

A bio-oil production and injection Project Proponent produces 100 tonnes of bio-oil with well-constrained LCAs and counterfactuals (there is no uncertainty discount for the amount of CO2 removed because conservative parameters were used in the calculation). This bio-oil is then injected into an underground reservoir that is equipped with a suite of chemical sensors that can measure CO2 and methane. The corresponding PDD has provisions to continue monitoring for fugitive gases for 40 years after injection has concluded. The Project Proponent follows Isometric's guidance in answering the risk questionnaire and determines they have a Risk of Reversal that corresponds to Risk Level B (resulting in a 5% Buffer Pool Size).

  • Net CO2e removed = 100t - 20t - 0t = 80t

    • Gross CO2e removed: 100t

    • LCA and counterfactuals: -20t

  • Credits issued to Supplier: 76 credits (80 - 4)

    • Total Credits Issued: 80 credits

    • Credits deposited to Buffer Pool account: 80 credits * 5% = 4 credits







  6. Johansen, A.M., Evers, L. and Whiteley, N., 2010. Monte Carlo methods. International Encyclopedia of Education, pp.296-303.



  9. Section 4: Assessment Framework - Core Carbon Principles 2023, The Integrity Council for the Voluntary Carbon Market


  11. ISO 14064-3:2019, 6.3.3


  13. Ibid.

  14. Databases such as Ecoinvent provide uncertainty factors, often based on a lognormal probability distribution, with a 95% confidence interval. The reported uncertainty accounts for systematic error, random error, and may also use a pedigree matrix to assign additional qualitative data quality impacts as an uncertainty value. These uncertainties are reported as a combined standard uncertainty. See details and examples for ecoinvent:

  15. "Uncertainty discount" is defined as the difference between the Conservative estimate of Removal, and the estimate of Removal in the absence of accounting for uncertainty