Biochar Storage in Low Oxygen Burial Environments

1.0 Introduction

This Module (Independent components of Isometric Certified Protocols which are transferable between and applicable to different Protocols.) details the durability (The 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.), reversal (The 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 Project Proponent has influence or control over it and it likely could have been averted through application of reasonable risk mitigation measures. Any other Reversals will be classified as unavoidable.) risks and requirements for storage (Describes the addition of carbon dioxide removed from the atmosphere to a reservoir, which serves as its ultimate destination. This is also referred to as “sequestration”.) of carbon as biochar in buried, low oxygen conditions. This Module is intended for use in conjunction with other Isometric Protocols (A 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.) and Modules, and assumes the following:

• The full quantification of the net tonnes of CO₂e (The amount of CO₂ emissions that would cause the same integrated radiative forcing or temperature change, over a given time horizon, as an emitted amount of GHG or a mixture of GHGs. One common metric of CO₂e is the 100-year Global Warming Potential.)removal (The term used to represent the CO₂ taken out of the atmosphere as a result of a CDR process.) for Crediting (A publicly visible uniquely identifiable Credit Certificate Issued by a Registry that gives the owner of the Credit the right to account for one net metric tonne of Verified CO₂e Removal or Reduction. In the case of this Standard, the net tonne of CO₂e Removal or Reduction comes from a Project Validated against a Certified Protocol.) occurs following the Isometric Biochar Production and Storage Protocol
• All environmental and social safeguards have been followed according to Section 5 in the Biochar Production and Storage Protocol

This Module was developed based on the current state of the art and publicly available science regarding biochar storage under low oxygen conditions. Biochar storage in low oxygen environments is a novel CDR approach, so this Module incorporates requirements that may be more stringent than some current relevant regulations or other protocols related to biochar for CDR. This Module will be reviewed when there is an update to scientific published literature which would affect net CO₂e removal (The term used to represent the CO₂ taken out of the atmosphere as a result of a CDR process.) quantification, durability claims or the monitoring guidelines outlined in this Module. Future versions of this Module may be altered, particularly regarding requirements for demonstrating durability of biochar, as the stability of CO₂ captured by biochar is better demonstrated and documented; quantification of biochar degradation is further improved and refined; and the overall body of knowledge and data regarding all processes, from feedstock (Raw material which is used for CO₂ Removal or GHG Reduction.) supply to conversion and to permanent storage, is significantly increased.

1.1 Applicability

1. The Project must bury biochar in waste management lined landfill sites under a local authority jurisdiction, where a permit has been issued by the local authority to allow such activity to take place. This permit must:

• be for solid waste disposal (i.e. residential and commercial waste, industrial waste, and/or construction and demolition debris)
  • incorporate findings of an environmental impact statement (EIS) or equivalent, if required by the local jurisdiction (which would also be consistent with the relevant Standard section)
  • require a post-closure care plan to be in place for at least 20 years after the date of site closure, with an adaptive management approach to respond to gas, leachate or ground and surface water monitoring results required under the permit during the post-closure period that may indicate risk to the environment
  • have safeguards in place to prevent disturbance after closure of the site (defined in Section 11), such as ensuring the integrity of final covers, liners, or any other components of any containment system, or the function of the facility's monitoring system

2. If the biochar is applied to the landfill site as part of Daily Cover (DC):

• The DC must not be removed from the landfill site once it has been applied. Daily scraping practices are permitted as long as the daily cover does not leave the active waste disposal area and is re-applied for burial
  • The DC must be permanently buried within 1 week of application to ensure functional low oxygen conditions are achieved for storage of biochar (see Section 1.2)

3. The Project must result in biochar being stored in a low oxygen environment such that biochar degradation pathways are limited in scope (defined as functionally anoxic, see Section 1.2)
4. The Project must be located in areas governed by the US, Canada, United Kingdom and European Union. Projects in other locations may be eligible for crediting if the Project Proponent (The organization that develops and/or has overall legal ownership or control of a Removal or Reduction Project.) can demonstrate adherence to an equally rigorous set of requirements for permitting and environmental protection as would be required for a similar project in one of the above jurisdictions. Such exceptions must be approved by Isometric

Future versions of this Module may expand applicability to include more categories of eligible project sites, such as specifically designed burial storage pits.

1.2 Background

Biochar is a carbon rich material with a significant fraction of the carbon being stable and durable over a time horizon of 200 years and beyond (see Isometric Biochar Production and Storage Protocol). Differences in production processes and feedstocks directly impact biochar quality and stability as they may result in variations in the labile (carbon that decomposes at rapid turnover times) and recalcitrant (stable carbon) fractions within the biochar.

The labile fraction of biochar is subject to degradation over a longer period of time due to different degradation pathways that are applicable to the physical storage location. These pathways can include:

1. Physical (dust loss, particle size reduction due to plowing or tillage)
2. Abiotic degradation Chemical reactions related to environmental factors including but not limited to: natural mineralization, photodegradation, leaching due to water flows or freeze thaw cycles¹
3. Microbial degradation can be either aerobic (presence of mycelial and fungal microbes)² or anaerobic (e.g., methanogenic microorganisms and consortia) ^3,1

Each of these pathways is directly influenced by the storage environment, with the relevant site characteristics influencing which degradation pathways may be most prevalent in that storage environment. The durability of biochar is dependent not only on the storage site conditions but on biochar physical and chemical properties (see Section 3 for more information). Several storage options are available for biochar removal, including burial of biochar in low oxygen environments. In the case of burial storage where low oxygen conditions are achieved and maintained with engineered controls and specific site characteristics, abiotic degradation will become negligible allowing only biotic degradation to take place³.

"Low oxygen" as used in this Module is defined as functional anoxia, where there is a functional absence of oxygen in soil, which occurs when the supply of oxygen is slower than the demand and oxic respiration and other oxygen-consuming biological reactions are severely limited⁴. The requirements of this Module are written to ensure that landfill conditions facilitate a sufficiently rapid transition to functional anoxia such that oxic degradation is negligible. The supply of oxygen below-surface soils and burial environments can be influenced by water content/flow and soil characteristics. To ensure water ingression is not an issue, the requirements outlined in the Section 6 (Site Characterization) of this Module must be met. In a waste management landfill for solid waste, each day, biochar can be mixed with the Daily Cover (DC), where DC is applied on top of the daily deposited waste to ensure that waste is undisturbed and mitigate odour and dust control issues in the landfill. New fresh waste cover is introduced to the site each day, and within 1 week, as per the Applicability conditions outlined in Section 1.1, the buried biochar as part of daily cover (DC) will be permanently buried. Once the DC can be judged to be buried at a sufficient depth to ensure a functionally anoxic environment, anaerobic decomposition pathways present the primary biochar degradation pathway under low oxygen storage conditions, as outlined in Section 4.2. Most soils, mud and lower permeability saturated soil environments become functionally anoxic at depths of 10s of cm ^5,6. Additionally, landfill environments contain significant labile organic carbon that will lead to rapid oxygen drawdown⁷.

Quantification of the durability of biochar according to the current best available science must focus on the use of rigorous characterization of the biochar to calculate the fraction of biochar that is stable beyond the desired crediting time horizon. This should be coupled with conservative (Purposefully erring on the side of caution under conditions of Uncertainty by choosing input parameter values that will result in a lower net CO₂ Removal or GHG Reduction than if using the median input values. This is done to increase the likelihood that a given Removal or Reduction calculation is an underestimation rather than an overestimation.) treatment of the uncertainty (A lack of knowledge of the exact amount of CO₂ removed by a particular process, Uncertainty may be quantified using probability distributions, confidence intervals, or variance estimates.) associated with that calculation (see Section 6.5 of the Biochar Production and Storage Protocol).

This Module sets requirements on the storage of biochar buried in permitted waste management sites (see Section 1.1, Applicability) for the purpose of carbon dioxide removal and describes how characterization of biochar should be used to quantify the number of Credits that are issued for a Project storing biochar in those sites. It also includes details of the environmental conditions that must be met and documented in the Project Design Document (PDD) (The document that clearly outlines how a Project will generate rigorously quantifiable Additional high-quality Removals or Reductions.) to ensure that biochar-C is stably sequestered in these burial conditions for at least 1,000 years. This Module addresses storage site conditions and quantification of CO₂e_stored for biochar burial for storage in waste management sites. For more information on biomass feedstock eligibility and accounting and pyrolysis conditions please refer to the Biomass Feedstock Accounting Module which must be followed as outlined in the Biochar Production and Storage Protocol and Section 9.0 of the Biochar Production and Storage Protocol.

2.0 Environmental and Social Safeguards

2.1 Safeguarding of low oxygen burial storage sites

Guidelines on appropriate site closure, leachate management, use of liners and covers, and odor control are provided in Section 9, Section 10 and Section 11 to minimize adverse impacts on soil, air, water and human health.

2.2 Required measurements

As outlined in the Biochar Production and Storage Protocol, there are some potential risks to environmental and human health associated with biochar composition, for example:

• Heavy metals, potassium and phosphorus that may impact soil health and soil amendment properties (reduced fertilizer needs)
• Soil contamination by heavy metals or Persistent Organic Pollutants

Project Proponents should outline in the PDD what legal and regulatory requirements their Project adheres to in terms of environmental risks. In the absence of regulation, Projects should adhere to safe limits associated with the upper bounds set for the following by the World Biochar Certificate (WBC)⁸ for storage of biochar in agricultural soils:

1. Heavy metals; including Pb, Cd, Cu, Ni, Hg, Zn, Cr, As, Sb, Co, V
2. Organic contaminants; including PAHs, Benzo(a)pyrene, PCBs, PCDD/F⁹

Methods of measurement for these parameters should be outlined in full in the PDD and must adhere to the sampling guidance and monitoring frequency requirements set out in this Storage Module. Heavy metals, PBCs and PCDD/F measurements should adhere to the same sampling guidance and monitoring frequency included in Table 2 for PAHs ¹⁰.

2.3 Co-benefits and soil remediation

Certain characteristics of biochar have demonstrated a potential positive impact on soil remediation and contaminant removal particularly in soils that are heavily impacted by elevated contaminant levels^11,12. There is evidence that biochar applied to locations with high concentrations of contaminants/hazards¹³ to human health could potentially lead to a decrease in the bioavailability of these contaminants^14,15by means of adsorption, therefore serving as a land remediation medium ^16,17,18.

Potential co-benefits of biochar burial in waste management landfill sites with elevated contaminant levels may include:

• Remediation of environmental pollutants ^19,10
• Decreased bioavailability of heavy metals ²⁰
• Reduced soil acidity ²¹
• Potential reduction of Persistent Organic Pollutants, including, but not limited to, PAHs, PCBs, Dioxins and Furans ^17,22
• Gas pollutant adsorption ²³

Section 3 outlines key parameters that influence biochar contaminant remediation potential, including properties that impact sorption capacity²⁴. Project Proponents may choose to report in the PDD any specific wider co-benefits related to remediation.

3.0 Biochar Characterization

3.1 Physical Characteristics

The analyses described in this section include measurements of physical properties that can influence a biochar's durability and capacity to absorb contaminants (PAHs, heavy metals) and landfill gas.

Table 1 Requirements for physical characterization of biochar

3.2 Chemical Characteristics

The following chemical analyses will be used to assess the reactivity and durability of biochar-C in different storage environments. Some of these measurements will be used in the quantification of CO₂e_stored, as outlined in Quantification of biochar durability Section 4.1 . The required and recommended measurements listed below investigate multiple mechanisms of reactivity (or prevention of), including aromaticity and aromatic condensation, functional groups, and volatility.

Specific analysis, including Heavy metals and PAHs are related to the impact the biochar can have as a soil remediating agent and are included to monitor long- term effect on heavy metal retention or PAHs impact.

Table 2 Requirements for physical characterization of biochar

4.0 Quantification of biochar durability in low oxygen environments

There are multiple methods³¹ available to estimate biochar stability over long timeframes. These methods include: 1 upfront biochar characterization² and estimating the long term durability of the stable fractions and 2 using incubation studies and field³⁶ trials. Field trials and incubation studies are able to more accurately measure carbon and its impacts, capturing the unique interaction between biochar, soil and the surrounding environment³⁷. However, incubation studies or field trials are time consuming and location specific, making this option difficult for wide adoption³⁸.

Incubation experiments and field trials examining the durability of biochar application to soil have shown that a significant volume of the labile carbon (up to 50%)² can be lost within the first year under aerobic conditions. These reported carbon loss values span from 2.2% after two years of controlled incubation tests³⁸ to >27% after two years of field experiments ^1,37 and have been conducted to study degradation of biochar under aerobic conditions. The wide range in reported carbon loss can be attributed not only to variations in labile carbon and biochar quality but also to site conditions and whether the tests or trials were conducted in a controlled or open field experiments. In open field aerobic experiments other factors such as abiotic degradation will also take place.

Incubation tests conducted in a representative inoculum environment^39,40can simulate site storage conditions, and are therefore a valuable approach to quantifying carbon loss in biochar^41,42,43. Maintaining controlled storage conditions under an anaerobic environment significantly lowers abiotic degradation (which can be greater than 10% of the total carbon ³), making microbial degradation the primary factor in carbon loss (which accounts for 5% 10% of the total carbon loss). At present there is insuffient data for anaerobic degradation of biochar in field trials or smaller scale incubation studies.

4.1 Quantification of CO₂eStored

This Module presents two quantification frameworks for calculating the fraction of biochar ([math: F_{durable}]) that is stable for 1,000+ years.

Both quantification frameworks calculate the carbon stored, or [math: CO_2e_{stored}], as follows:

[math: CO_2e_{stored} = C_{biochar} \times m_{biochar} \times F_{durable} \times \frac{44}{12}]

Equation 1

Where

• [math: C_{biochar}] is the carbon content of the biochar (empirical), expressed as a fraction
• [math: m_{biochar}] is the dry mass of biochar applied, in tonnes
• [math: F_{durable}] is the fraction of durable biochar that remains in the soil for the full duration of the crediting timeline (1,000 years), and can be credited under this Module
• [math: \frac{44}{12}] is the mass fraction of carbon dioxide and elemental carbon

Measurement of Carbon Content

See Section 8.3.1 of the Biochar Production and Storage Protocol for full guidelines on measurement of biochar carbon content, [math: C_{biochar}].

Measurement of Mass of biochar buried

See Section 8.3.1.1 of the Biochar Production and Storage Protocol for full guidelines on measurement of mass of biochar buried, [math: m_{biochar}].

**Calculation of [math: F_{durable}]

4.1.1 Option 1: Random Reflectance to quantify the stable or inertinite fraction plus Incubation Experiments to quantify the likelihood of degradation of the labile biochar fraction

At this early stage in understanding of degradation of biochar under functionally anoxic conditions, the true degradation risk over a Project's durability horizon has some uncertainty and reversals via GHG emissions cannot be directly observed given that they are co-mingled with organic waste baseline (A set of data describing pre-intervention or control conditions to be used as a reference scenario for comparison.) GHG emissions. The presence of alternative electron acceptors (e.g., nitrates, oxides) or site conditions not included in incubations studies may present some risk of microbial degradation. While there is a reasonable likelihood that accelerated degradation experiments will capture a significant fraction of biochar degradation in functional anoxia, this Module requires that the fraction of biochar degradation observed be multiplied by a safety factor of 3 for the purpose of crediting. As such, the deduction associated with the degradation of the labile fraction is meant to be conservative based on available data from incubation, giving a high confidence in the credited outcome.

If the corresponding deduction is greater than the non-inertinite fraction, the Project Proponent must use option 2 instead.

This approach, and the safety factor used, will be reassessed and revised as new evidence from scientific research and commercial deployment are surfaced.

[math: F_{durable}= F_{inertinite} + F_{labile}]

Equation 2

Where

• [math: F_{durable}] is the fraction of durable biochar that remains in the soil for the full duration of the crediting timeline (1,000 years), and can be credited under this Module
• [math: F_{inertinite}] is the fraction of biochar carbon that is stable for the durability period as determined by random reflectance
• [math: F_{labile}] is fraction of biochar carbon that is not inertinite but determined to be observationally stable from incubation studies

In any case, the evidence used to support a durability claim and conservative reversal estimate must be specific to a feedstock and processing method. All evidence supporting implementations of B and C above must be reviewed and approved by Isometric and provided in the PDD. Evidence of durability and conservative reversal estimates using option A must be conducted as described above. Indicative reference values for the calculation of a conservative discount factor (reported as maximum reported carbon loss or a suitable decay rate) are included in Appendix A (data used are based on aerobic degradation which is considerably higher than anaerobic) for guidance. Project Proponents can refer to reference values or choose an appropriate alternative, which must be pre-approved by Isometric prior to verification, provided sufficient justification is provided in the PDD. Alternative approaches to conservatively estimating long-term biochar degradation must be approved by the Isometric science team.

4.1.2 Option 2: Use of Random Reflectance to quantify stable fraction of biochar

Additional evidence and data, supporting the durability of the stored carbon can be submitted from Project Proponents for review. Type of additional data can include experimental site data or biochar sampling post application in the storage site and can be used to review the durability calculations for both Option 1 and Option 2.

4.2 Long-term carbon degradation under low oxygen conditions

In the 1,000 year durability timeline, evidence indicates that biotic degradation (fungi and anaerobic methanogenic bacteria) ⁴⁴ of complex organics under low oxygen conditions is exceedingly slow. However, some studies have shown degradation of very small fractions of the fused aromatic hydrocarbons in coal and potentially in biochar^45,46.

Data from previous studies were mainly reported on coal and hydrocarbons and involved some form of pre-treatment to increase the biodegradability of the hydrocarbons and are therefore not representative of the storage environments described in this Module. In addition, all relevant studies were conducted on coals and hydrocarbons and reported decreasing anaerobic degradation efficiency with decreasing number of hydrolytic bonds⁴⁷. Certain bacterial strains have been shown to be able to degrade low grade coals especially, those with higher H/C and O/C ratios⁴⁸. The impact and applicability on biochar samples is expected to be limited^44,49.

4.3 Emissions reductions or removal potential

Certain physical and chemical characteristics of biochar, such as the active surface area, functional groups and cation exchange capacity have been shown to have a positive impact on soil remediation and contaminant removal. This impact is significant especially in cases with existing issues of soil contamination which affects 33% of global soils ^11,12.

Recent research has explored the potential of biochar for additional CO₂ capture by selective adsorption in gas streams ^24,50, which has the potential to serve as an additional carbon dioxide removal pathway. Some research^51,52,23 indicates that biochar (dependent on biochar properties), may be an effective sorbent of some greenhouse gasses (Those gaseous constituents of the atmosphere, both natural and anthropogenic (human-caused), that absorb and emit radiation at specific wavelengths within the spectrum of terrestrial radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. This property causes the greenhouse effect, whereby heat is trapped in Earth’s atmosphere (CDR Primer, 2022).) including methane and carbon dioxide ⁵¹. Biochar sorption capacity can potentially have a significant impact in storage locations where large volumes of gasses are emitted (landfill sites) as it could result in selectively absorbing gasses. When the latter is combined with an effective site closure and appropriately maintained storage conditions, carbon may be absorbed by biochar and stored durably. If the additional absorbed carbon was biogenic in origin, then this could be classified as additional CO₂ removal. If the additional carbon absorbed was fossil fuel in origin, then this would represent an emissions reduction.

At the time of writing, there is not sufficient evidence to include this in the quantification framework for net CDR achieved by biochar storage in low oxygen environments. This will be revisited in future editions of the Module as new evidence is published and/or presented to Isometric by Project Proponents as proof of quantification.

5.0 Maintenance of low oxygen conditions

5.1 Landfill site best practice guidelines

As outlined in Background (Section 1.2), "low oxygen" storage conditions can be reasonably assumed in landfills in a matter of days after Daily Cover (DC) has been applied. This is because the depth of burial and high rate of organic matter degradation in landfills is sufficient to ensure functional anoxia (see Section 1.2). The thickness of Daily Cover (DC) applied to landfills should be at an average depth of 15 cm, so that biochar applied as DC reaches depths of meters within a few weeks depending on the landfill size and operations ⁷. Daily cover material can include materials such as foundry sand, recycling fluff, soil, quarry minerals, green waste, compost based materials, bottom ash or synthetic materials like foam, so long that the materials comply with the site's permit requirements ⁵³. Additional landfill practices including compaction of the waste and daily cover once applied ensure that relatively consistent density of the waste mass is achieved which can help avoid differential settlement, slope stability issues and oxygen intrusion. The Project Proponent should clearly outline in the PDD the daily cover practices that apply to the Project boundary.

5.2 Oxygen monitoring

6.0 Site Characterization

6.1 Hydrology Surface water

6.2 Hydrology groundwater

6.3 Local Geology and Soil Properties

6.4 Seismicity

6.5 Target values

Table 3 Target values for site characterization

7.0 Legal Framework to Ensure Permanence

There is no single credible mechanism that can ensure, without uncertainty, that biochar buried in waste management sites will remain undisturbed in perpetuity given the relative nascency of such legal mechanisms relative to the time horizons required in the Isometric Standard. Land durability claims are subject to social and political factors and are thus different in nature from claims regarding physical or geologic durability. Isometric has developed a set of land security eligibility criteria that align with current best practices for legal strategies to restrict future uses of land.

Table 4 Land durability requirements

8.0 Counterfactual Land Use

9.0 Base Liner Construction and Leachate Management

10.0 Landfill Gas Management and Odor Control

11.0 Site Closure

Direct monitoring of stored biochar will be difficult due to:

1. the challenges in exhuming stored solid wastes from landfill sites, and
2. the impossibility of attributing landfill gas emissions to biochar degradation, rather than from baseline waste degradation at the waste management site.

• A description of how final closure of the facility will be achieved
• An estimate of the maximum amount of possible hazardous additives (if used) kept on site during the facility's operating life, with a description of each hazardous additive (if applicable) and management to be performed
• A detailed description of closure methods
• A description of any other required steps, such as groundwater monitoring and leachate management that will continue post-closure
• A schedule of closure activities, including closure dates for each unit and the entire facility
• A description of procedures, structures and equipment to prevent surface water run - on and control run - off
• As outlined in Section 2.1, landfill sites should have a landfill gas and methane emissions monitoring and management system in place with appropriate emissions control to minimize methane emissions such as an installed flare system

• At least 20 years of post-closure care after the date of closure
• A monitoring plan (described below)
• A description of planned maintenance activities for carbon storage (e.g., liners, final covers, leachate management systems)
• Contact information during the required post-closure care period

Projects should not, for any reason, encourage or incentivize the creation or expansion of industrial wastelands due to Project activities. The reclamation of Project sites and their surroundings, while potentially required by the legal mechanism for land preservation (e.g. conservation easement), will be supportive of positive stewardship of lands and demonstrating respect for local stakeholders.

12.0 Risk of Reversal and Buffer Pool

AsProjects outlinedusing this Storage Module are typically deemed to have No Observable Risk of reversal, according to the ++Isometric Standard Risk Assessment Questionnaire++ (also found in the relevant sectionProtocol), as all Projects Crediting against this Protocol are credited conservatively to account for degradation of labile pools of biochar within the relevant crediting time horizon. Based on present understanding, reversals in biochar storage in low oxygen burial environments will not be directly observable with measurements, nor attributable to a particular project. Following the Risk of Reversal Section of the Isometric Standard, storage uncertainty for open systems is primarily accounted for within the removal quantification framework. This results in a 0% ++Bufferbuffer Poolpool (A common and recognized insurance mechanism among Registries allowing Credits to be set aside (in this case by Isometric) to compensate for Reversals which may occur in the future.) is a mechanism used to insure against Reversal risks that may be observable and attributable to a particular project through monitoring. Based on present understanding, reversals in Biochar storage in low oxygen burial environments will not be directly observable with measurements and attributable to a particular project.++ for Projects Crediting againstusing this Storage Module are credited conservatively to account for degradation of labile pools of biochar within the relevant crediting time horizon. ProjectsFor thatmore meetdetails, the applicability criteria of this Module are categorized as having a Very Low Risk Level of Reversal accordingrefer to the IsometricReversals Standard Risk Assessment Questionnaire. Theand Buffer PoolPools corresponding to this lowest risk score is 2% and is intended as an additional precaution against unknowns.

Following the relevant sectionSection of the Isometric Standard,. storageThis uncertaintyreversal forrisk openwill systemsbe isreassessed primarily accounted for withinat the removal quantification framework. For more details on Reversals, refer to the relevant sectionsrenewal of the ++Crediting IsometricPeriod Standard(The period of time over which a Project Design Document is valid, and over which Removals or Reductions may be Verified, resulting in Issued Credits.)++, or when new scientific research and knowledge are produced.

13.0 Record Keeping

14.0 Acknowledgements

Isometric would like to thank following contributors to this Module:

• Konstantina Stamouli, Ph.D.
• Sophie Gill, Ph.D.
• Kevin Sutherland, Ph. D.

Isometric would like to thank following reviewers of this Module:

• Christian Wurzer, Ph.D. (UK Biochar Research Centre)
• Anne Ware, Ph.D. (National Renewable Energy Laboratory)
• Isaac Fuhr (Carlson McCain)
• Nick Bonow (Carlson McCain)

15.0 Definitions and Acronyms

Independent components of Isometric Certified Protocols which are transferable between and applicable to different Protocols.

The 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.

The 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 Project Proponent has influence or control over it and it likely could have been averted through application of reasonable risk mitigation measures. Any other Reversals will be classified as unavoidable.

Describes the addition of carbon dioxide removed from the atmosphere to a reservoir, which serves as its ultimate destination. This is also referred to as “sequestration”.

A 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.

The amount of CO₂ emissions that would cause the same integrated radiative forcing or temperature change, over a given time horizon, as an emitted amount of GHG or a mixture of GHGs. One common metric of CO₂e is the 100-year Global Warming Potential.

The term used to represent the CO₂ taken out of the atmosphere as a result of a CDR process.

A publicly visible uniquely identifiable Credit Certificate Issued by a Registry that gives the owner of the Credit the right to account for one net metric tonne of Verified CO₂e Removal or Reduction. In the case of this Standard, the net tonne of CO₂e Removal or Reduction comes from a Project Validated against a Certified Protocol.

Raw material which is used for CO₂ Removal or GHG Reduction.

An activity or process or group of activities or processes that alter the condition of a Baseline and leads to Removals or Reductions.

The organization that develops and/or has overall legal ownership or control of a Removal or Reduction Project.

Purposefully erring on the side of caution under conditions of Uncertainty by choosing input parameter values that will result in a lower net CO₂ Removal or GHG Reduction than if using the median input values. This is done to increase the likelihood that a given Removal or Reduction calculation is an underestimation rather than an overestimation.

A lack of knowledge of the exact amount of CO₂ removed by a particular process, Uncertainty may be quantified using probability distributions, confidence intervals, or variance estimates.

The document that clearly outlines how a Project will generate rigorously quantifiable Additional high-quality Removals or Reductions.

Any person or entity who can potentially affect or be affected by Isometric or an individual Project activity.

A 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).

A process for evaluating and confirming the net Removals and Reductions 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).

A set of data describing pre-intervention or control conditions to be used as a reference scenario for comparison.

Those gaseous constituents of the atmosphere, both natural and anthropogenic (human-caused), that absorb and emit radiation at specific wavelengths within the spectrum of terrestrial radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. This property causes the greenhouse effect, whereby heat is trapped in Earth’s atmosphere (CDR Primer, 2022).

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 or Reduction has taken place.

A calculation, series of calculations or simulations that use input variables in order to generate values for variables of interest that are not directly measured.

Any emissions that occur to compensate for biomass that was previously serving another purpose and is now being used for carbon removal or GHG reduction. For example, if agricultural waste was previously left on a field to decompose - fertilizer production to replace those nutrients need to be accounted for.

An assessment of what would have happened in the absence of a particular intervention – i.e., assuming the Baseline scenario.

Standard physical constants as well as standard values set forth by bodies such as the National Institute of Standards and Technology (NIST) or others.

A common and recognized insurance mechanism among Registries allowing Credits to be set aside (in this case by Isometric) to compensate for Reversals which may occur in the future.

The period of time over which a Project Design Document is valid, and over which Removals or Reductions may be Verified, resulting in Issued Credits.

16.0 Appendix A

This appendix contains indicative reference values for the selection of a discount factor as according to the quantification framework set out in Section 4.1.1. Please see Section 4.1.1 for full details on how these values will be pre-approved prior to verification by Isometric.

Data on the table were extracted from different sources and studies and only the upper values of reported carbon loss have been included for the longest reported experiment duration⁵⁸. Selection of a value should be based on feedstock and if available on process conditions for the longest duration included.

Table A1. Cumulative Carbon Loss reference values. All material types are biochar.

Table A2. Residual Decay Rates reference values. All material types are biochar.

17.0 Relevant Works