Subsurface Biomass Carbon Removal and Storage

This Protocol provides the requirements and procedures for the calculation of net CO₂e removal from the atmosphere via the processing of biomass and storage in the shallow subsurface for long term sequestration of atmospheric CO₂. Storage of biomass in the shallow subsurface Storage is considered a subsector of Biomass Carbon Removal and Storage (BiCRS). The shallow subsurface shall include biomass placed at depths of not more than 100 meters below the ground surface. This Protocol applies to biomass storage technologies or Projects, which typically consist of activities associated with the following sub-processes: biomass growth, processing of biomass prior to storage, emplacement in the shallow subsurface and storage.

The Protocol accounts for quantification of the gross amount of CO₂ removed via storage in the shallow subsurface, as well as the accounting for all net greenhouse gas (GHG) emissions associated with the process, including emissions associated with the biomass feedstock, biomass storage processes, all transportation and embodied emissions emissions associated with the process, and emissions associated with leakage. The GHG Statement is considered as a cradle-to-grave analysis.

This Protocol is developed to adhere to the requirements of ISO 14064-2: 2019 – Greenhouse Gases – Part 2: Specification with guidance at the project level for quantification, monitoring, and reporting of greenhouse gas emission reductions or removal enhancements. The Protocol ensures:

• consistent, accurate procedures are used to measure and monitor all aspects of the process required to enable accurate accounting of net CO₂e removals
• consistent system boundaries and calculations are utilized to quantify net CO₂e removal for biomass storage in the shallow subsurface
• requirements are met to ensure the CO₂ removals are additional
• evidence is provided and verified by Validation and Verification Bodies (VVBs) to support all net CO₂e removal claims

Specific Standards and Protocols which are utilized as the foundation of this Protocol and for which this Protocol is intended to be fully compliant with are the following:

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

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

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

This Protocol was developed based on the current state of the art and current publicly available science regarding biomass processing and biomass storage. Because biomass storage is a novel Carbon Dioxide Removal (CDR) approach, with limited published literature, the Protocol incorporates requirements that may be more stringent than some current relevant regulations for underground storage or other Protocols related to biomass utilization for CDR.

This approach, notably when specifying requirements for demonstrating biomass subsurface storage durability, will likely be altered in future versions of the Protocol as the stability of biomass in the subsurface becomes well demonstrated and documented, reversal risks are proven to be limited or non-existent, and the overall body of knowledge and data regarding all processes, from feedstock supply, to processing, and to durable storage is significantly increased.

This Protocol applies to projects or processes which:

• utilize agricultural or forestry residues as eligible feedstocks in accordance with the framework set out in the Biomass Feedstock Accounting Module v1.3.
• emplace the biomass into engineered subsurface storage for long duration storage purposes

This Protocol applies to projects and associated operations that meet all of the following project conditions:

• The Project provides a net-negative CO₂e impact (net CO₂e removal), as calculated in the GHG Statement, in compliance with Section 8
• The biomass feedstock utilized is sustainably sourced
• The Project does no net harm to the environment and society
• The Project is considered additional, in accordance with the requirements of Section 6.4
• The storage site is located in an area governed by the US, Canada, United Kingdom or the European Union
• The storage site is properly permitted in accordance with all applicable regulations

Projects that are explicitly NOT eligible include the following:

• Projects that do not use sustainably sourced biomass feedstocks as detailed in Section 7.2.

The Project must consider environmental and social impacts at all Project locations, including the biomass sourcing, processing and burial sites as well as during biomass transportation.

Appropriate measures must be implemented to identify and eliminate potential risks to terrestrial and aquatic ecosystems and biodiversity.

Where risks cannot be eliminated, the Project Design Document (PDD) must identify measures to monitor ecosystem health and mitigate adverse effects through a project-specific mitigation plan. Mitigation plans must be carried out by subject matter experts, in consultation with Isometric. Refer to the relevant section of the Isometric Standard for further guidelines on environmental and social impacts.

Following the Isometric Standard, Credits issued under this Protocol are contingent on the implementation, transparent reporting and independent verification of comprehensive safeguards. These safeguards encompass a wide range of considerations, including environmental protection, social equity, community engagement and respect for cultural values. The process mandates that safeguard plans be incorporated into all major project phases, with detailed reports made accessible to stakeholders. Adherence to and verification of environmental and social safeguards is a condition for all Crediting Projects.

Project Proponents must comply with all national and local laws, regulations and policies. Where relevant, projects must comply with international conventions and standards governing human rights and uses of the environment, when conducted within or foreseeably impacting Party jurisdictions.

Project Proponents must document activities conducted under the Project that would require it to obtain environmental permits.

Environmental and social risk assessment in adherence with the relevant section of the Isometric Standard must be completed to identify potential risks, followed by the development of tailored mitigation plans. These plans must encompass specific actions to avoid, minimize or rectify identified impacts. Effective implementation of these measures must also be accompanied by a robust monitoring plan to detect negative impacts and stop projects when necessary.

The Project Proponent must conduct an environmental risk assessment which adheres to the relevant section of the Isometric Standard. Potential additional environmental risks associated with biomass storage in the shallow subsurface are listed below. The severity of these risks vary based on site specifics and the intensity and duration of activities. Environmental and social risk identification, assessment, avoidance, and mitigation planning will be unique to each Project’s technical, environmental, and social contexts. This list contains minimum considerations; Isometric and the Project Proponent may add risks on a case by case basis in the PDD.

Projects may utilize synthetic material, such as storage liners or biomass wrappers, to increase the durability of biomass stored in the shallow subsurface. These synthetic materials may be required by Isometric in relevant storage Modules and/or utilized under the discretion of the Project Proponent.

The composition of any synthetic material used in a Project must be reported in the PDD. This must include:

• durability certificates of expected material lifetime
• details of any byproducts that may form as the synthetic material degrades

The environmental risk assessment must also consider these synthetic liners and wrappers.

The Project Proponent must conduct a social risk assessment which adheres to the relevant section of the Isometric Standard on Social Impacts.

Per the Isometric Standard, Project Proponents must demonstrate active stakeholder engagement throughout Project planning and operation, ensuring that all risk mitigation strategies contribute to sustainable project outcomes. Local stakeholders situated in the vicinity of the project site may contribute an in-depth understanding of the local system and provide invaluable insights and recommendations on the potential risks, necessary safeguards and specific monitoring needs. The Stakeholder input process must adhere to requirements outlined in the relevant section of the Isometric Standard, and evidence of these meetings must be submitted in the PDD.

Project Proponents must include in the PDD a plan for information sharing, emergency response and conditions for stopping or pausing a deployment. Plans for pausing or stopping a deployment must be in place in instances where:

• instrument malfunctions lead to data-gaps in required monitoring
• regulatory non-compliance, e.g. danger to ecosystem health detected (such as by the local community or government agency)
• compromised health and/or safety of workers and/or local stakeholders

The following topics are covered briefly in this Protocol due to their inclusion in the Isometric Standard, which governs all Isometric Protocols. See in-text references to the Isometric Standard for further guidance.

For each specific Project to be evaluated under this Protocol, the Project Proponent must document Project characteristics in a Project Design Document (PDD) as outlined in the relevant section of the Isometric Standard. The PDD will form the basis for Project validation and evaluation in accordance with this Protocol, and must include consideration of processes unique to biomass such as:

• location information for biomass production and the storage location and area
• conditions of biomass use prior to project initiation
• details on technologies, products, and services relevant to biomass processing, including production rates and volumes

Projects must be validated and project net CO₂e removals verified by an independent third party, consistent with the requirements described in this Protocol, as well as in the Isometric Standard.

The Validation and Verification Body (VVB) must consider following requisite components:

1. Validate that feedstock adheres to the requirements listed in the Biomass Feedstock Accounting Module v1.3.
2. Verify that storage sites adhere to the requirements listed in the relevant storage Module.
3. Verify that the quantification approach and monitoring plan adheres to requirements of Section 8, including demonstration of required records.
4. Verify that the Environmental & Social Safeguards are met.
5. Verify that the Project is compliant with requirements outlined in the Isometric Standard.

The threshold for Materiality, considering the totality of all omissions, errors and mis-statements, is 5%, in accordance with the Isometric Standard.

Verifiers should also verify the documentation of uncertainty of the GHG Statement as required by the Isometric Standard. Qualitative Materiality issues may also be identified and documented, such as ¹:

• 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

Project validation and verification must incorporate site visits to project facilities in accordance with the requirements of ISO 14064-3, 6.1.4.2, including, at a minimum, site visits during validation and initial verification to the biomass processing site and the biomass storage site. Validators should, whenever possible, observe operation of the biomass processing and burial to ensure full documentation of process inputs and outputs through visual observation.

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

Verifiers and validators must comply with the requirements defined in the Isometric Standard. In addition, teams must maintain and demonstrate expertise associated with the specific technologies of interest, including biomass growth or production, biomass processing, biomass production and terrestrial storage.

Competency must be demonstrated in accordance with Isometric's VVB policy, for example based on the relevant sectoral scope accreditations in IAF MD 14, or another demonstration of relevant expertise for this protocol and the selected storage module(s).

CDR via biomass storage is often a result of a multi-step process (such as biomass growth, harvesting, transport, processing, burial, and storage), with activities in each step managed and operated by a different operator, company, or owner. When there are multiple parties involved in the process (e.g., forestry owner or burial site operator), and to avoid double counting of net CO₂e removals, a single Project Proponent must be specified contractually as the sole owner of the Credits in order to avoid double counting of net CO₂e removals. Contracts must comply with all requirements defined in the relevant section of the Isometric Standard.

The Project Proponent must be able to demonstrate additionality through compliance with the Isometric Standard. The baseline scenario and counterfactual utilized to assess additionality must be project-specific, and are described in Section 7.2 of this Protocol.

Additionality determinations should be reviewed and completed every two years, at a minimum, or whenever project operating conditions change significantly, such as the following:

• regulatory requirements or other legal obligations for project implementation change or new requirements are implemented;
• project financials indicate carbon finance is no longer required, potentially due to, for example:
  • increased tipping fees for waste feedstocks;
  • sale of co-products that make the business viable without carbon finance;
  • reduced rates for capital access.

Any review and change in the determination of additionality shall not affect the availability of carbon finance and carbon Credits for the current or past Crediting Periods, but, if the review indicates the Project has become non-additional, this shall make the Project ineligible for future Credits².

The uncertainty in the overall estimate of the net CO₂e removal as a result of the Project must be accounted for. The total net CO₂e removed, ($CO_2e_{Removal}$), for a specific batch ($n$) must be conservatively determined based on the requirements outlined in the Isometric Standard.

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

• emission factors utilized, as published in public and other databases used;
• values of measured parameters from process instrumentation, such as truck weights from weigh scales, flow rates from flow meters, electricity usage from utility power meters, and other similar equipment;
• laboratory analyses, including analysis of carbon content of biomass.

The uncertainty information should at least include the minimum and maximum values of a variable. More detailed uncertainty information should be provided if available, as outlined in the Isometric Standard.

In addition, a sensitivity analysis that demonstrates the impact of each input parameter’s uncertainty on the final net CO₂e uncertainty must be provided. Details of the sensitivity analysis method must be provided such that a third party can reproduce the results. Input variables may be omitted from an uncertanty analysis if they contribute to a < 1% change in the net CO₂e removal. For all other parameters, information about uncertainty must be specified.

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

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

The Project Proponent can request certain information to be restricted (only available to authorized buyers, the Registry and VVB) where it is subject to confidentiality. This includes emissions factors from licensed databases. However, all other numerical data produced or used as part of the quantification of net CO₂e removal will be made available.

The scope of this Protocol includes GHG sources, sinks, and reservoirs (SSRs) associated with a biomass burial CDR project.

A cradle-to-grave GHG Statement must be prepared encompassing the GHG emissions relating to the activities outlined within the system boundary (Figure 1).

GHG emissions and removals associated with The Project may be direct emissions from a process, or indirect emissions from combustion of fuels, electricity generation, or other sources. Emissions must include all GHG SSRs within the system boundary, from the construction or manufacturing of each physical site and associated equipment, closure and disposal of each site and associated equipment, and operation of each process, including embodied emissions of equipment and consumables used in the project. The Project Proponent is responsible for identifying all sources of emissions directly or indirectly related to project activities.

Any emissions from sub-processes or process changes that would not have taken place without the CDR Project must be fully considered in the system boundary. Any activity that ultimately leads to the issuance of Credits should be included in the system boundary.

The system boundary must include all relevant GHG SSRs controlled and related to The Project, including but not limited to the SSRs set out in Table 1 and Figure 1. If any GHG SSRs within Table 1 are deemed not appropriate to include in the system boundary, they may be excluded provided that robust justification and appropriate evidence is provided in the PDD.

Figure 1. Process flow diagram showing system boundary for biomass burial projects

Table 1 GHG SSRs for Biomass Carbon Removal and Storage

Miscellaneous GHG emissions are those that cannot be categorized by the GHG SSR categories provided in Table 1. The Project Proponent is responsible for identifying all sources of emissions directly or indirectly related to project activities and must report any outside of the SSR categories identified as miscellaneous emissions.

Emissions associated with The Project's impact on activities that fall outside of the system boundary of The Project must also be considered. This is covered under Leakage in Section 8.5.4.

In line with the GHG Accounting Module v1.1, the Project must:

• Consider all GHGs associated with SSRs, in alignment with the United States Environmental Protection Agency’s definition of GHGs which includes: carbon dioxide (CO₂), methane (CH4), nitrous oxide (N20) and fluorinated gasses such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3). For CO2 stored, only CO2 shall be included as part of the quantification. For all other activities all GHGs must be considered. For example, the release of CO2, CH4, and N2O is expected during diesel consumption;
• Quantify emissions in tonnes CO₂ equivalent (t CO₂e) using the 100-year Global Warming Potential (GWP) for the GHG of interest, based on the most recent volume of the IPCC Assessment Report (currently the Sixth Assessment Report); and
• Consider materiality of SSRs in line with Isometric requirements.

In some instances, biomass burial CDR project activities may be integrated into existing activities. Activities or portions of activities that were already occurring in the baseline and would have continued to occur without the biomass burial CDR project may be omitted from the system boundary, subject to the conditions set below.

For the purpose of this provision, an "activity" may refer to an operational sub-unit, such as an individual trip leg, a single pass of field equipment, or a discrete processing step, where such sub-units can be cleanly delineated by equipment, timing, and physical scope. Where a pre-existing activity is partially modified by the project (for example, a transport trip whose route is extended to include project-specific stops, or a field operation whose pass is lengthened to include project inputs), the activity must be partitioned into:

• portions that are materially unchanged by the project, which may be excluded from the system boundary under this provision; and
• portions that are new, extended, or altered as a result of the project, which must remain within the system boundary and be quantified in the relevant sub-section of Section 8.5.

An activity, or portion of an activity, may only be excluded where the Project Proponent can demonstrate all of the following:

• it was occurring as part of routine operations prior to project activities;
• it would have continued to occur in the absence of the biomass burial CDR project; and
• its scope, frequency, equipment, route, payload, and intensity are not materially altered as a result of project activities.

Evidence supporting these conditions must be provided in the PDD. This must include either:

• Historic records documenting the activity prior to project start. Acceptable records include management logs, operational records, applicator invoices, or equivalent documentation; or
• A signed affidavit from the relevant operator (e.g., farmer, land manager, applicator, or equivalent party) confirming the activity was part of routine operations prior to the project.

And the following:

• A signed affidavit from the relevant operator (e.g., farmer, land manager, applicator, or equivalent party) confirming:
  • the equipment, route, timing, cadence, and intensity of the activity are not materially changed as a result of the biomass burial CDR project; and
  • the activity would have continued at a comparable level absent the project.

Where these conditions are met, only the emissions associated with the activity as it would have occurred in the baseline may be excluded. Any incremental emissions attributable to the project must remain within the system boundary and be accounted for in the relevant emissions sub-section.

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

The counterfactual is the CO₂ stored in the biomass feedstock that would have remained durably stored in the biomass in the absence of the Project. This is known as ineligible biomass, given that the CO₂ stored would have remained stored in the biomass in the absence of the CDR project and is therefore not eligible to count towards Crediting. The Biomass Feedstock Accounting Module v1.3 sets out requirements for establishing ineligible biomass as part of the Counterfactual Storage Eligibility criteria. The Biomass Feedstock Accounting Module v1.3 includes details for quantification of $CO_2e_{Counterfactual}$.

The biomass storage process typically involves a processing step followed by a burial step. The processing step may operate on a continual or batch basis and may involve single or mixed forms of biomass. Irrespective of whether the processing step is operated continually or batch wise or whether it involves single or mixed forms of biomass, the processing step yields a known amount of biomass containing a known amount of carbon. A 'Production Batch', $p$, is then a an amount of processed biomass, produced over a specific time period to be mutually agreed between Isometric and Project Proponent (e.g., a day, week, or month).

An ‘Burial Batch’, $n$, is a single burial activity where a quantity of biomass is buried at an approved storage site. The Burial Batch consists of the biomass from the processing step which is buried for durable storage.

The approach for emissions calculations here is based on Burial Batches and the specific calculation of net CO₂e removal for each Burial Batch. The following sections outline the process for calculating the net CO₂e removed for each specific Burial Batch of biomass processed and associated biomass burial, defined as a Removal.

The Reporting Period for shallow subsurface biomass storage projects represents an interval of time over which removals are calculated and reported for verification. When total net CO₂e removals must be calculated for a Reporting Period, for example during submission of Claimed Removals in a GHG statement, it is calculated as the sum of removals during the Reporting Period:

$$CO_2e_{Removal,\ RP} = \sum_{n=1}^{k} CO_2e_{Removal,\ n}$$

(Equation 1)

Where

• $k$ = number of Burial Batches $n$
• $CO_2e_{Removal,\ RP}$ = the total net CO₂e removal for Reporting Period $RP$, in tonnes of CO₂e
• $CO_2e_{Removal,\ n}$ = the total net CO₂e removal for Burial Batch $n$ occurring in Reporting Period $RP$, in tonnes of CO₂e, see Section 8.2, Equation 2

Note: Reversals occur after Credits have been issued so are not included in this equation. See the relevant section of the Isometric Standard for further information.

Net CO₂e removal for a process biomass storage Project can be calculated as follows. Note that the calculation is completed for a discrete batch, $n$, of biomass that is buried (‘Burial Batch’). The final net CO₂e quantification must be conservatively determined, giving high confidence that at least the estimated amount of carbon dioxide was removed.

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

(Equation 2)

Where

• $CO_2e_{Stored,\ n}$ is the total CO₂ removed from the atmosphere and durably stored as organic carbon for batch n, in tonnes of CO₂e, see Section 8.3
• $CO_2e_{Counterfactual,\ n}$ is the total counterfactual CO₂ removed from the atmosphere and durably stored as biogenic carbon in the absence of the Project, for batch n, in tonnes of CO₂e, see Section 8.4
• $CO_2e_{Emissions,\ n}$ is the total GHG emissions for batch $n$, in tonnes of CO₂e, see Section 8.5

$CO_2e_{Stored}$ represents the amount of CO₂ (stored as organic carbon, C) that is buried and stored in the shallow subsurface. This is the gross amount stored for each batch burial and does not account for reversals of storage from the storage formation.

The total amount of CO₂ contained in the buried biomass can be calculated as follows.

Where all biomass production batches are composited prior to burial:

$$CO_2e_{Stored,\ n} = \frac{C_{Biomass,\ n}\cdot m_{Bur,\ n}}{C_{CO_{2}}}$$

(Equation 3)

Where biomass production batches are not blended prior to burial:

$$CO_2e_{Stored,\ n} = \sum_{p=1}^{j} \bigg(\frac{C_{Biomass,\ p}\cdot m_{Bur,\ p}}{C_{CO_{2}}} \bigg)$$

(Equation 4)

Where:

• $n$ = Burial Batch
• $p$ = Production Batch
• $j$ = total number of Production Batches in Burial Batch ($n$)
• $CO_2e_{Stored,\ n}$= the total CO₂ removed for batch $n$, in tonnes of CO₂e
• $C_{Biomass,\ n (p)}$ = the concentration as weight percent (%wt) of carbon in the biomass buried for Burial Batch $n$ OR for each production batch $p$ included in Burial Batch $n$
• $m_{Bur,\ n (p)}$= the total mass of biomass emplaced via burial (tonne) for Burial Batch $n$ OR for each production batch $p$ included in Burial Batch $n$
• $C_{CO_{2}}$ = the content of C in CO₂ (as a mass percent)

Calculation of $CO_2e_{Stored}$ requires two primary measurements:

• $C_{Biomass}$ - %wt of C in the biomass and
• $m_{Bur}$ - total mass of the biomass

In order to determine $C_{Biomass}$, the %wt of C in the processed biomass for either a blended biomass in a Burial Batch $n$, or for individual Production Batches $p$, is determined via the analysis of samples of processed biomass for total carbon content. This must be assessed via test method ASTM D5373: Standard Test Methods for Instrumental Determination of Carbon and Hydrogen in Analysis Samples of Coal and Carbon in Analysis Samples of Coal and Coke or similar procedure.

Analysis must be completed directly by the Project Proponent or by a qualified laboratory, as evidenced by accreditation to ISO 17025 or equivalent standards for laboratory quality management for the specific test method (ASTM D5291).

Laboratories must complete standard quality assurance procedures on a schedule in accordance with their quality management plans and accreditation requirements to include:

• analysis of blanks
• analysis of duplicates
• instrumentation calibrations and analysis of calibration standards

This Protocol provides two alternative methods for how often carbon content must be measured and quantified. The first method (A) involves measuring every batch, the second method (B) involves only sampling some batches, and conservatively estimating the carbon content of unsampled batches.

Method A: Measure every Batch

Using this method, the carbon content of every Burial Batch must be ascertained through direct measurement, either by:

1. Sampling the Burial Batch (which may be blended, or non-blended)
2. Sampling all constituent Production Batches which comprise the Burial Batch, and calculating the carbon content of the Burial Batch through a linear weighted combination of the carbon contents of these Production Batches, as given in Equation 3.

• Note that in the case of an unblended Burial Batch, the Burial Batch originates from only a single Production Batch, by definition, and no calculation is required

For the acceptable minimum number of samples to take per sampled Batch, see Minimum number of samples per Batch below. If multiple samples are taken per Batch, the average carbon content of these samples must be used.

Method B: Sampling a Production Process

For a given Production Process of a feedstock, samples must be taken directly for at least 30 Production Batches, to ensure there is enough data to estimate carbon content for future Production Batches with appropriate statistical significance. Until this threshold is reached, Method A must be used.

Subsequently, samples must be taken at least every 10 Production Batches.

For the acceptable minimum number of samples to take per Batch, see Minimum number of samples per Batch below.

For batches which are not sampled, carbon content must be conservatively estimated, as follows:

$$C_{Biomass} = \mu_{CC} - \sigma_{\overline{CC}}$$

(Equation 5)

$$\sigma_{\overline{CC}} = \frac{\sigma_{CC}}{\sqrt{n_{samples}}}$$

(Equation 6)

where:

• $\sigma_{\overline{CC}}$ is the standard error of the mean of carbon content, across all eligible samples for this Production Process
• $\sigma_{CC}$ is the standard deviation of carbon content, across all eligible samples for this Production Process
• $n_{samples}$ is the number of eligible samples for this Production Process
• $\mu_{CC}$ is the mean carbon content of all eligible samples for this Production Process

Eligible samples are those taken in the previous 6 months before a specific Production Batch was produced. Older samples may not be used.

Additionally, batches must be subject to random sampling, to alleviate the risk of any given batch containing a substance with a substantially different carbon content.

A random sampling approach must be agreed and documented in the Project Design Document, whereby Isometric will contact the Project Proponent on randomly selected days, at an agreed cadence, which must be no less frequent than once per month, on average. Once contacted, the Project Proponent must sample the carbon content of the subsequent batches processed.

If the Project Proponent is unable to carry this random sampling out on 3 occasions within a 6 month period, or within a 6 month period more than 3 measurements are below 3 SD from the mean, this will trigger a Project review by Isometric.

If there is a significant change to a Production Process for a feedstock, which is likely to alter the average carbon content of the feedstock, or if significant deviations in carbon content are detected, the feedstock should be considered as a new Production Process. This means that sampling must be restarted, with all prior samples no longer able to be used for estimating carbon content.

Minimum number of samples per Batch

For all measurements taken, samples must be from a well mixed and representative aliquot of the biomass. To account for the possibility of variation within a single Production Batch (for example within a large container of liquid biomass), either of the following approaches must be adopted:

1. A minimum of 3 samples must be taken for each measured Production Batch.
2. Justification and evidence must be provided to demonstrate that the “within batch” variation is likely to be minimal. For example, this could be justified due to the physical details of the Production Process used, or alternatively by providing data examining the “within batch” carbon content variation.

Process for handling carbon content measurement outliers

This process applies only if method B is used to calculate carbon content and should be used whether the a batch was sampled or not. For a given Production Process, an Outlier is defined as any individual sample which lies more than 3 standard deviations, $\sigma_{CC}$, above or below the mean. To minimize the potential overall impact of outlier measurements, all carbon content measurement outliers must be handled via the applying the technique of "winsorization”, as follows.

For a given measurement, $m$, the winsorized measurement $m_w$ is defined as follows:

• For a measurement $m$ where $m > \mu + 3\sigma_{CC}$, $m_w = \mu + 3\sigma_{CC}$
• For a measurement $m$ where $m < \mu - 3\sigma_{CC}$, $m_w = \mu - 3\sigma_{CC}$

Where $\mu$ and $\sigma_{CC}$ are calculated from all carbon content samples from the same Production Process taken within 6 months of the removal for which we are calculating the carbon content. For estimating the carbon content from sampled batches, only historical samples should be used to calculate $\mu$ and $\sigma_{CC}$ and not samples from the batch being calculated. The standard deviation, $\sigma_{CC}$, should be calculated with the formula for sample standard deviation.

The winsorized measurement, $m_w$, must be used for the determination of carbon content.

This winsorization process must only be applied once a minimum number of 30 measurements have been taken, to ensure statistical significance.

The Project Proponent must monitor occurrences of outliers, and investigate if significantly more than the statistically expected number occurs, as it may be indicative of a systematic issue. This may be checked at verification, at the discretion of the verifying VVB.

The mass of buried biomass, $m_{Bur}$, is measured via determination of weight of delivered processed biomass to the burial site using a calibrated scale. The total mass buried may be determined by the difference in biomass delivery truck weight measured upon arrival at the burial facility and at departure, after offloading of biomass, either into storage or directly to burial.

Any scale used must have a current certification in accordance with applicable local, state, or federal regulations for legal-for-trade weights and measures. Testing and calibration of scales must utilize certified weights in accordance with local, state, or other regulations, calibration weights must meet NIST Handbook 44 specifications², and scale testing and calibration must be performed by a state certified entity.

The total mass buried may also be determined by other methods, such as use of a calibrated flow meter and density measurement, or use of calibrated on site weigh scales for smaller containers, where such methods are viable and justified. Note that, due to the typical viscosity of biomass, the use of flow meters is not often viable and can result in poor data quality.

The Project Proponent must maintain the following records as evidence of gross CO₂e stored in buried biomass:

• weigh scale tickets for each delivery of biomass (arrival and departure weights) or other equivalent records
• analytical results for each ASTM D5291, or equivalent, analysis for carbon content of biomass from each batch as required
• Documentation of any biomass losses during burial operations and estimates of quantity lost

Records of all carbon analyses and burial masses (e.g. weigh scale tickets) must be maintained by the burial facility and provided for verification purposes for a period of five years after the end of the monitoring period.

Although limited and of small quantity, burial processes should be monitored to ensure that any process upsets or equipment failures and resulting spills of biomass are monitored, documented, quantified, and accounted for in the GHG Statement of the project batch. For each batch, where a process upset results in loss of biomass, that amount must be deducted from the delivered amount of biomass based on delivery weigh tickets. Such amounts must be allocated directly to the specific burial batch of biomass.

The calculation of $CO_2e_{Counterfactual,\ n}$, is determined by the requirements of the Biomass Feedstock Accounting Module 1.3.

${CO}_{2}^{}e_{Emissions,\ RP}^{}$ is the total quantity of GHG emissions associated with a Reporting Period $RP$. This can be calculated as:

$${CO}_{2}^{}e_{Emissions,\ RP}^{}\ = \ {CO}_{2}^{}e_{Establishment,\ RP}^{}\ + \ {CO}_{2}^{}e_{Operations,\ RP}^{} + \ {CO}_{2}^{}e_{End-of-life,\ RP}^{}+ \ {CO}_{2}^{}e_{Leakage,\ RP}^{}$$

(Equation 7)

Where:

• ${CO}_{2}^{}e_{Emissions,\ RP}^{}$ - the total GHG emissions for a Reporting Period, RP, in tonnes of CO₂e.
• ${CO}_{2}^{}e_{Establishment,\ RP}^{}$ - the total GHG emissions associated with project establishment for a RP, in tonnes of CO₂e, see Section 8.5.1
• ${CO}_{2}^{}e_{Operations,\ RP}^{}$ - the total GHG emissions associated with operational processes for a RP, in tonnes of CO₂e, see Section 8.5.2
• ${CO}_{2}^{}e_{End-of-life,\ RP}^{}$ - the total GHG emissions that occur after the RP and are allocated to the RP, in tonnes of CO₂e, see see Section 8.5.3
• ${CO}_{2}^{}e_{Leakage,\ RP}^{}$ - represents GHG emissions associated with the Project’s impact on activities that fall outside of the system boundary of a project, over a given Reporting Period, in tonnes of CO₂e, see Section 8.5.4.

The following sections set out specific quantification requirements for each variable.

GHG emissions associated with project establishment should include all historic emissions incurred as a result of project establishment, including but not limited to the SSRs set out in Table 1.

Project establishment emissions occur from the point of project inception to the moment before the first removal activity takes place. GHG emissions associated with project establishment may be amortized over the anticipated project lifetime, or per output of product. Requirements for amortization are outlined in Section 7 of the GHG Accounting Module v1.1.

GHG emissions associated with $CO_2e_{Operations, RP}$ should include all emissions associated with operational activities including but not limited to the SSRs set out in Table 1.

$CO_2e_{Operations, RP}$ emissions occur over the Reporting Period for the period being credited and are applicable to that Reporting Period only. $CO_2e_{Operations, RP}$ emissions must be attributed to the Reporting Period in which they occur. Allocation may be permitted in certain instances, on a case by case basis in agreement with Isometric.

$CO_2e_{End-of-Life, RP}$ includes all emissions associated with activities that are anticipated to occur after the Crediting Period until the end of the Project Commitment Period. This includes activities related to ongoing monitoring for Reversals.

$CO_2e_{End-of-Life, RP}$ must be estimated upfront and allocated in the same way as set out for calculation of $CO_2e_{Establishment, RP}$.

Given the uncertain nature of $CO_2e_{End-of-Life, RP}$ emissions, assumptions must be revisited at each Reporting Period and any necessary adjustments made.

$CO_2e_{Leakage, RP}$ includes emissions associated with a project's impact on activities that fall outside of the system boundary of a project.

It includes increases in GHG emissions as a result of the Project displacing emissions or causing a knock on effect that increases emissions elsewhere. This includes emissions associated with activity-shifting, market leakage and ecological leakage.

It is the Project Proponent's responsibility to identify potential sources of leakage emissions.

$CO_2e_{Leakage, RP}$ emissions must be attributed to the Reporting Period in which they occur. Allocation may be permitted in certain instances, on a case by case basis in agreement with Isometric.

GHG emissions accounting must be undertaken in alignment with the GHG Accounting Module v1.1, which ensures a consistently rigorous standard in how GHG emissions are quantified and reported between different CDR Projects and approaches. This includes:

• Requirements for data quality, including a detailed data quality hierarchy for activity data and emission factors;
• Consideration of materiality in emissions accounting;
• Emissions amortization requirements;
• Co-product allocation requirements;
• By-product accounting relating to inputs to the process that are by-products, for example [list of by-products]; and
• Waste input accounting relating to inputs to the process that are wastes, for example [list of waste inputs].

The Energy Use Accounting Module v1.3 provides requirements on how energy-related emissions must be calculated for The Project so that they can be subtracted in the net CO₂e removal calculation. It sets out the calculation approach to be followed for intensive facilities and non-intensive facilities and acceptable emission factors.

Energy emissions are those related to electricity or fuel usage. Examples of electricity usage may include, but are not limited to:

• processing equipment, motors, drives, instrumentation
• facility operation
• burial activities
• monitoring equipment operation, including analyzers, instrumentation, on-site laboratories specifically for monitoring activities
• off site analytical laboratory operation and sample analysis
• electricity for building operation & management for monitoring facility buildings

Examples of fuel consumption may include, but are not limited to:

• Handling equipment, such as fork trucks or loaders
• Fuel consumption of agricultural machinery for spreading, tilling, and sampling

The ++GHG Accounting Module v1.1++ provides requirements on how transportation and embodied emissions must be calculated for The Project so that they can be subtracted in the net CO₂e removal calculation.

Embodied emissions are those related to the life cycle impact of equipment and consumables. They may include, but are not limited to:

• Biomass feedstock production, processing, treatment and transportation equipment
• consumables used in the process
• feedstock conveyors, augers, feed bins, and related equipment
• all support structures, facilities, and infrastructure, including steel platforms, framing, supports, concrete footings and building structures
• Sampling equipment and consumable materials such as augers and storage containers
• buildings and associated equipment utilized for monitoring purposes (e.g. on-site laboratories)

Transportation emissions are those related to transportation of products and equipment. They may include, but are not limited to:

• Transportation of biomass feedstock to processing site
• Transportation of biomass to the storage site
• Transportation and shipping related to collecting samples for environmental monitoring

This Protocol may provide the following options for durable storage of biomass. The Project Proponent can choose from available options when submitting their Project for verification.

Isometric would like to thank following contributors to this Protocol:

• National Renewable Energy Laboratory (NREL)
• Lawrence Livermore National Lab (LLNL)
• EcoEngineers
• Ning Zeng, Ph.D., University of Maryland

Isometric would like to thank following reviewers of this Protocol:

• EcoEngineers

NREL and LLNL were supported by the DOE Office of Technology Transitions in collaboration with the Office of Clean Energy Demonstrations (OCED), Office of Fossil Energy and Carbon Management (FECM), Office of Energy Efficiency and Renewable Energy (EERE), and the Bioenergy Technology Office (BETO).

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

• Biomass Feedstock Accounting Module 1.3
• Subsurface Biomass Storage Module v1.0
• Biomass Storage in Subsurface Mines v1.0

This risk assessment identifies the pathway specific risk factors relevant to a carbon removal project. The relevant risk factors identified as part of a risk assessment are included in the monitoring plan requirements for the project, with details included in the Project Design Document. Project specific risk factors inform the required duration of monitoring along with the monitoring requirements set out in the Protocol and the requirements set out in the Monitoring Section of the Isometric Standard.

The risk score, as determined by the Risk of Reversal Questionnaire, will determine a project’s buffer pool contribution. Projects must re-assess their reversal risk at the renewal of each crediting period, or if monitoring identifies a reversal-related risk, or if an actual reversal event takes place.

Projects using this Protocol and associated Storage Modules are typically deemed to have a Medium Risk of Reversal. This results in a 7% buffer pool for Projects using this Storage Module. This reversal risk will be reassessed at the renewal of the Crediting Period, or when new scientific research and knowledge are produced.

The Risk of Reversal Questionnaire questions that pertain to this protocol, drawn from the programme-level Risk of Reversal Questionnaire in the Isometric Standard, include the following:

Note the Risk Score at any step cannot be negative.

Risk Score Categories:

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

Project specific risk factors will depend on the form of carbon being stored (i.e., organic vs. inorganic), the method of storage (e.g., mineralization, encapsulation), the location of carbon storage (e.g., subsurface, ocean), and the proximity of that carbon to potential agents of reversal.

For projects with carbon storage as organic carbon, the presence the following risk factors must be reflected in the risk score corresponding to question 10:

• High-potential oxidants
• Temperatures in excess of thermal stability
• Fires
• Microbial degradation

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

• Seismicity
• Subsurface migration

ASTM D5291-21 Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants. (2021, November). https://www.astm.org/standards/d5291

Carbon Direct & EcoEngineers. (2022). Bio-oil Sequestration Prototype Protocol for Measurement, Reporting, & Verification. https://insights.carbon-direct.com/hubfs/Bio-oil-proto-protocol.pdf

International Organization for Standardization. (2006). ISO 14040:2006 Environmental management — Life cycle assessment — Principles and framework. https://www.iso.org/standard/37456.html

International Organization for Standardization. (2008). Evaluation of measurement data — Guide to the expression of uncertainty in measurement (ISO JGCM GUM). https://www.iso.org/sites/JCGM/GUM/JCGM100/C045315e-html/C045315e.html?csnumber=50461

International Organization for Standardization. (2011). ISO 14066:2011 Greenhouse gases — Competence requirements for greenhouse gas validation teams and verification teams. https://www.iso.org/standard/43277.html

International Organization for Standardization. (2017). ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories. https://www.iso.org/standard/66912.html

Isometric. (n.d.). Isometric — Glossary: Defining the terms that appear regularly in our work. Isometric. https://isometric.com/glossary

NIST. (2023). Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices - 2023 Edition. NIST. https://www.nist.gov/pml/owm/publications/nist-handbooks/handbook-44-current-edition

Sandalow, D., Aines, R., Friedman, J., McCormick, C., & Sanchez, D. (2020, October 2). Biomass Carbon Removal and Storage (BiRCS) Roadmap. https://www.osti.gov/servlets/purl/1763937

Schmidt, H., Anca-Couce, A., Hagemann, N., Werner, C., Gerten, D., Lucht, W., & Kammann, C. (20118, August 17). Pyrogenic carbon capture and storage. GCB Bioenergy, 11(4), 573-591. https://onlinelibrary.wiley.com/doi/full/10.1111/gcbb.12553

Society of Petroleum Engineers. (2020, April 13). Enhanced oil recovery (EOR) - PetroWiki. PetroWiki. Retrieved June 14, 2023, from https://petrowiki.spe.org/Enhanced_oil_recovery_(EOR)

U.S. Environmental Protection Agency. (2014). Test Methods for Evaluating Solid Waste: Physical/Chemical Methods Compendium (SW-846). https://www.epa.gov/hw-sw846/sw-846-compendium

U.S. Environmental Protection Agency. (2023, April 18). Understanding Global Warming Potentials | US EPA. Environmental Protection Agency. Retrieved June 14, 2023, from https://www.epa.gov/ghgemissions/understanding-global-warming-potentials

1. ISO 14064-3: 2019, Section 5.1.7 ↩

2. https://www.nist.gov/pml/owm/publications/nist-handbooks/handbook-44-current-edition ↩ ↩²