Biochar Storage in the Built Environment

7.0 Quantification of CO₂eStorede Stored

7.1 Summary

This section details the calculation of net CO₂ storage in biochar-amended built materials. The monitoring requirements are describedset in detailout in Section 8.0 Monitoring Requirements.

Accurate quantification of net CO₂ stored requires a robust quantification of associated projectProject emissions within the project boundary. In the context of this Module, a Project refers to the point of CO₂ capture and the point of CO₂ storage. This Module defines the point of CO₂ storage as the point of incorporation of biochar into a built material. Note that thisThis Module applies only applies to biochar that is considereddurable for 200 years.

This horizon is shorter than the Isometric 1,000-year default and is specific to bebiochar durablein forbuilt materials. Over 1,000 years.

7.2 Quantification of CO₂eRemoval

The quantity of net CO2 removal for each Reporting Period,RP, can be calculated as follows:

[math: CO_2e_{Removal,\ RP} = CO_2e_{Stored,\ RP} - CO_2e_{Counterfactual,\ RP} - CO_2e_{Emissions,\ RP}]

(Equation 2)

Where:

• [math: CO_2e_{Removal,\ RP}] is the net quantity of CO2e removed as a result of Project activities during a Reporting Period, in tonnes of CO2e.
• [math: CO_2e_{Stored,\ RP}] is the total quantity of carbon stored as biochar in the built environment during a Reporting Period, in tonnes of CO2e.
• [math: CO_2e_{Counterfactual,\ RP}] is the total quantity of CO2 removed from the atmosphere and permanently stored in the baseline scenario during a Reporting Period, in tonnes of CO2e.
• [math: CO_2e_{Emissions,\ RP}] is the total quantity of greenhouse gas (GHG) emissions from Project activities for a Reporting Period, in tonnes of CO2e.

7.2.1 Calculation of CO₂eStored

[math: CO_CO_2e_{2estored,\text{Stored, RP}} = C_{\text{Biochar}biochar} \timescdot m_{\text{Biochar}biochar} \timescdot F_{\text{Durabledurable, Material}material} \timescdot \frac{44.01}{12.01}]

(Equation 32)

Where:

• [math: CO_2e_CO_2​e_{StoredRemoval,\ RP​}] is the total quantityCO₂ ofremoved carbonfrom the atmosphere and stored as biocharorganic carbon in the builtbiochar environmentfor during athe Reporting Period, [math: RP], in tonnes of CO₂e.
• [math: C_{Biocharbiochar}] is the carbon content of the biochar (empirical, in %).
• [math: m_{Biocharbiochar}] is the dry mass of biochar incorporated, in tonnesapplied.
• [math: F_{Durabledurable, Materialmaterial}] is the fraction of durable biochar that remains in the built material for the full duration of the Creditingcertification timeline (1,000200 years), and can be Creditedcertified under this Module.
• [math: \frac{44.01}{12.01}] is the mass fraction of carbon dioxide and elemental carbon.

7.2.1.1 Calculation of Organic Carbon Content

This Module only Credits forcertifies the durably stored organic carbon fraction of biochar, which is used to calculate [math: CO_2e_CO_2​e_{StoredRemoval,RP​}]. While biochar associated inorganic carbon generally makes up a small fraction of total biochar carbon. However, the fate of biochar-associated inorganic carbon is much less predictable. Thus, [math: C_{Biocharbiochar}] is calculated using the following equation:

[math: C_{\text{biochar}} = \text{Total Carbon Content} - C_{\text{inorg}}]

(Equation 43)

Where:

• [math: \text{Total Carbon Content}] is the total carbon content of the biochar as analysedanalyzed using the methods described in Table 2.
• [math: C_{inorg}] is the inorganic carbon content of the biochar as analysedanalyzed using the methods described in Table 2, in %.

Please refer to Section 8.3.1 of the Biochar Production and Storage Protocol for full guidelines on number of samples required for the measurement of biochar carbon content, [math: C_{biochar}].

7.2.1.2 Measurement of Mass of Biochar Incorporated

SeePlease refer to theSection relevant section8.4 of the Biochar Production and Storage Protocol for full guidelines on measurement of mass of biochar buriedapplied, [math: m_{Biocharbiochar}].

7.2.1.3 Calculation of FDurable[math: F_{durable, Materialmaterial}]

[math: F_{Durable, Materialdurable}]  is calculatedthe fraction of the incorporated biochar certified as durably stored over the 200-year horizon. This Module certifies the inertinite (recalcitrant) fraction of the biochar only, quantified by random reflectance and thermogravimetric analysis ([math: F_{durable}]).

[math: F_{Durabledurable, Materialmaterial} = F_{Inertinite}(1 +- [1-(3U) \timescdot F_{Reversal})] F_{Labiledurable}]

(Equation 54)

Where:

• [math: F_{Durabledurable, Materialmaterial}] is the fraction ofcertified durable biochar that remains in the built material for the full duration of the Crediting timeline (1,000 years), and can be Credited under this Modulefraction.
• [math: F_{Inertinitedurable}] is the durable fraction of the biochar thatover isthe present200-year as inertinitehorizon.
• [math: F_{Reversal}U] is the project-specific durability discount. The fraction of biocharthe certified durable carbon that is assumedphysically liberated and dispersed to degradethe open environment through wear, comminution, and recycling over athe 1,000 200-year periodhorizon. Note that a safety factor of 3It is includeddetermined by the reversal risk questionnaire in thisAppendix calculation to account for uncertainty in the amount of exposure over a 1,000 year period.
• [math: F_{Labile}] is the fraction of biochar that is not present as inertinite and may degrade if exposed to ambient atmospheric conditionsA.

7.2.1.3.1 Calculation of [math: F_{Inertinitedurable}]

The quantificationdurable frameworkfraction is quantified by the random-reflectance inertinite method, following Sanei et al. (2024)¹ for determining the [math: CO_2e_{Stored}R_0]inertinite forbenchmark, 1000-year durability is based on the quantification approach set outrefined by Sanei et al,. (20242025)⁸¹¹² Thistto approachaccount quantifiesfor biochar ononly the randomrecalcitrant reflectancefraction, value ofwith the biochar,reactive comparedfraction todiscounted inertinitevia asthermogravimetric aanalysis. proxyThe only difference from that Module is the horizon label (200 years for geologicallybuilt stable carbon. Using petrographic analysis, Sanei et al., (2024materials)8 identified that biochars with a mean random reflectance (R₀ ≥ 2%) exhibit structural characteristics equivalent to inertinite macerals in fossil coals and chars,the whichdownstream arereversal knowndiscount to[math: persistU] over(Equation geological timescales4).

To ensure a conservative  approach when Creditingissuing certificates against biochar durability, we account for uncertainty in both [math:the R_0]fraction measurement,of biochar passing the 2% R₀ benchmark and the proportion of carbon that is non-reactive. Specifically, for each replicate sample we determine the credited durable fraction ([math:of F_{Durable}])R₀ measurements that meet or exceed the 2% benchmark. The certified inertinite fraction is calculated using the mean valuesof forthese eachfractions parameteracross all samples analyzed, reduced by one standard deviation of the fractions (Equation 5). This methodis applied to the non-reactive carbon fraction, itself reduced by one standard deviation (Equation 6), to give the durable fraction of the biochar (Equation 7). This ensures that the durability estimate reflects a lower-bound confidence level, mitigating the risk of overestimating long-term carbon storage.

As such, [math: F_{Durabledurable}] is calculated through:

Calculating the sample standard deviation of [math: R_0] quantifying the typical deviation of individual [math: R_0] measurements from their mean, which is used to account for uncertainty and conservatively adjust the estimated durable fraction of biochar carbon, as:

[math: F_{\text{inertinite}} =
\left(
\overlines_{R_0} -
= \sqrt{
\frac{1}{n_{R_0}-1}
 \sum_{i=1}^{n_{R_0}}
\left ( R_{0,i} - \overlinebar{R_0} \right)^2
}
]

(Equation 5)

Where:

• [math: s_{R_0}] is the standard deviation of the fractions passing the 2% benchmark.
• [math: {n_{R_0}}] is the number of samples analyzed (i.e. ≥ 3).
• [math: R_{0,i}] is the fraction of R₀ measurements ≥ 2% in the [math: i]-th sample.
• [math: \rightbar{R_0}] is the mean of the fractions (≥ 2%) \times \left( \overline across all samples.

Calculating the sample standard deviation of [math: C_{non-reactive}] quantifying the typical deviation of individual [math: C_{non-reactive}] measurements from their mean, which is used to account for uncertainty and conservatively adjust the estimated durable fraction of biochar carbon, as:

[math: s_{C_{\text{non-reactive}}} -
= \sqrt{
\frac{1}{n_C n_{C_{non- reactive}}-1}
 \sum_{i=1}^{n_Cn_{C_{non-reactive}
}} \left( C_{\text{non-reactive},i} - \overlinebar{C_C}_{\text{non-reactive}}} \right)^2
}
\right)]

(Equation 6)

Where:

• [math: F_{inertinite}] is the fraction of inert carboniferous material in a sample after 1000 years.
• [math: \overline{R_0}] is the mean of R₀ measurements, in %.
• [math: R_{0,i}] is the individual measurements of [math: R_{0}], in %.
• [math: nR_0] is the number of measurements for [math: R_{0}].
• [math: \overlines_{C_{non-reactive}}] is the meanstandard deviation of [math: C_{non-reactive}] measurements,
• [math: inn_{C_{non-reactive}}] %is the number of samples analyzed (i.e. ≥ 3).
• [math: {C_{non-reactive,i}}] is the individual measurementsmeasurement for the [math: i]-th sample.
• [math: \bar{C}_{\text{non-reactive}}] is the mean of all [math: C_{non-reactive}], in %.
• [math: nC] is the number of measurements for [math: C_{non-reactive}].

Quantification of biochar storage for Crediting in the built environment will be updated in future versions of this Module in line with the best available science as more research in peer-reviewed literature is published.

7.2.1.3.2 Calculation of [math: F_{Reversal}]

This Module distinguishes between [math: F_{Reversal}] for biochar stored in concrete and biochar stored in asphalt. Note that [math: F_{Reversal}] for biochar stored in asphalt is assumed to be 100%, and thus the labile fraction is not included in calculation of [math: F_{Durable, Material}].

[math: F_{Reversal}] in concrete is determined through a geochemical model that assesses the weathering of a given built material over 1,000 years. An overview of the geochemical model used for this assessment and key assumptions underlying this model are given in Section 10.0.

The default value, based on a worst-case assessment (described in Section 10.0), is 2%. Project Proponents may choose to submit additional documentation to conduct a project-specific reversal assessment. As shown in Equation 5, a safety factor of 3 is applied to [math: F_{Reversal}] to ensure a conservative estimate. This approach, and the safety factor applied, will be reassessed as scientific consensus evolves.

7.2.1.3.3 Calculation of [math: F_{Labile}]

[math: F_{Labile}] is defined as the portion of biochar that is not considered inertinite (e.g. does not pass the 2% [math: R_0] threshold). It is calculated asThen:

[math: F_{Labiledurable} = \frac{m_{Biocharmin(0.95 , totalmax( 0 , (\bar{R_0} - m_s_{Biochar,R_0}) inertinite(\bar{C}_{\text{non-reactive}} − s_{m_C_{Biochar, totalnon-reactive}}) ) ) )]

(Equation 7)

Where:

• [math: F_{Labiledurable}] is the fraction of durable (inert) carbon in the biochar thatafter is200 notyears, presentadjusted asconservatively inertinitefor and may degrade if exposed to ambient atmospheric conditionsuncertainty.
• [math: m_\bar{Biochar, totalR_0}] is the total massmean of biochar mixed into the concretefractions (≥ 2%) across all samples.
• [math: m_s_{Biochar, inertiniteR_0}] is the totalstandard massdeviation of the [math: R_0] passing the 2% benchmark.
• [math: \bar{C}_{\text{non-reactive}}] is the mean of all non-reactive carbon measurements.
• [math: s_{C_{non-reactive}}] is the standard deviation of [math: C_{non-reactive}].

The maximum and minimum functions are applied to ensure that the fractions are bounded.

7.2.1.3.2 Calculation of Uncertainty Discount, [math: U]

[math: U] is the project-specific durability discount for physical liberation and dispersal of the certified durable carbon through wear, comminution, and recycling over the 200-year horizon. It does not re-discount the labile fraction (which is not certified), the one-standard-deviation conservatism already contained within [math: F_{durable}], or acid and matrix dissolution: acid dissolves the host matrix and can expose biochar, but does not mineralize the inertinite fraction, which is the same basis on which the inertinite fraction is treated as permanent in the Biochar Storage in Low Oxygen Burial Environments Module.

[math: U] is determined per Project, and per distinct placement or mix design where a Project spans several, by the reversal risk questionnaire in Appendix A. The questionnaire scores placement and incorporation, physical exposure, and end-of-life and recycling factors, applies gating exclusions, and maps the net score to a durability discount band.

7.2.2 Calculation of CO2eCounterfactualCO2e Counterfactual, RP

For biochar production, the calculation of [math: CO_2e_{Counterfactual,\ RP}] is determined by the requirements laid out in the Counterfactuals sectionSection of the Biomass Feedstock Accounting Module.

7.2.3 Calculation of CO2eEmissionsCO2e Emissions, RP

[math: CO_2e_{Emissions,\ RP}] is the total greenhouse gas emissions associated with a given Reporting Period, RP.

Equations and emissions calculation requirements for [math: CO_2e_{Emissions,\ RP}] including emissions associated with reactor operations and reaction monitoring, are set out in the relevant Protocol and are not included in this Module. Specific considerations for CO₂ stored as biochar in built materials are set out here.

CO₂ removals must not be double counted, regardless of the production of product Environmental Product Declarations.. The product must still comply with all relevant emission accounting regulations and requirements, which may mean emissions are double counted,; however, removals must not be double counted. This is the most conservative approach to take. CreditingCertificate issuance claims must be transparently reported and must not form part of marketing for a separate product.

Allocation procedures may be undertaken to separate emissions associated with the concrete production and the emissions associated with the CO₂ storage process. Allocation procedures must follow the following emissions allocation procedure:

• Procedure 1: Allocate all emissions to CDR.
   Projects may opt to allocate all emissions to CDR.
• Procedure 2: Divide the process into sub-processes.
   Where possible, the process may be divided into sub-processes. For example it may be possible to isolate processes relating to processing and storing CO₂ only. Only sub-processes and relevant inputs that are physically separable may undergo division, for example electricity usage for equipment with separate electricity meters. Sub-processes that are physically separable and do not contribute to CDR may be excluded from the CDR system boundary.

Transport emissions must be considered if the average transport distance for biochar-amended built materials is more than the average transport distance of normal products produced by the production facility. All other downstream emissions may be excluded from the system boundary if these activities were already occurring and would continue to occur in the absence of theThe Project. This can be evidenced by providing documentation that the biochar-amended product meets the same performance requirements of a conventional product for the intended use case, as is described under 'the Section 2.0 Applicability'.

7.3 Buffer Pool

As outlined in the Risk of Reversal section of the Isometric Standard, the Buffer Pool 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 will not be directly observable with measurements and attributable to a particular project. Projects Crediting againstusing this Storage Module are Creditedtypically conservativelydeemed to accounthave forNo degradationObservable Risk of labile pools of biochar within the relevant Crediting time horizon. Projects applicable to this Module are categorized as having a Very Low Risk Level of Reversalreversal, according to the Isometric Standard Risk Assessment Questionnaire (also found in the relevant Protocol), as all reversal risk is accounted for using the reversal risk modelling and Uncertainty Discount approach. TheThis Bufferresults Poolin correspondinga to0% buffer pool for Projects using this lowestStorage Module. This reversal risk scorewill isbe 2%reassessed at the renewal of the Crediting Period, or when new scientific research and isknowledge intendedare as an additional precaution against unknownsproduced.

8.0 Monitoring Requirements

ThisThe requirements in this section outlinesapply to the monitoringprocess requirementssteps and equipment within the Project system boundary. Where the exclusion of downstream manufacturing emissions set out in the System Boundaries section is relied upon, the boundary terminates at the point at which biochar or a biochar-containing material transfers to the downstream manufacturer, and process data for Projectsthe incorporatingmanufacturer's own operations is not required. Requirements relating to the mass of biochar incorporated, the mix into which it was incorporated, and the pavement layer in buildingwhich materialsit eitherwas aslaid aapply filler,irrespective aggregate,of modifierthat or other formexclusion.

8.1 Process Requirements

Process specific details, including energy consumption, curing steps and processing temperatures, are required only where the exclusion of downstream manufacturing emissions set out in the System Boundaries section is not relied upon. Where the biochar-amended product meets the same performance requirements as a conventional product for the intended use case and requires no additional products or activities related to product manufacturing, installation, maintenance and end-of-life, those emissions are omitted from the system boundary and the underlying process data is not required.

8.1.1 Incorporation and Placement Evidence

IfProduction batch records must identify the biochar-basedissuing productfacility, isthe soldbatching system from which they are extracted and the date of extraction, must cover the full Reporting Period, and must reconcile to multiplethe downstreamProject manufacturersProponent's records of biochar dispatched to that facility. For asphalt, the documentation provided must identify the mix designation (e.g., concreteEN producers13108 withor differentSuperpave) mixfor designs)each batch, Projectso Proponentsthat maythe providepavement layer can be established as required under the Asphalt Layer Eligibility section.

Where biochar is added to an asphalt mixture as a separate component rather than through the binder, the Project Proponent must state the point at which it is added in the plant (for example, directly to a batch-plant mixer, or through an additive or filler feed on a drum plant).

Where production batch records are not available, mix-level evidence may be usedprovided instead to establish placement: for asphalt, a job mix formula that identifies the biochar and its dosage and restricts it to a mix designated for a Sub-Surface Layer; for concrete, an element and mix specification that ties the biochar-amended mix to its placement. The mass of biochar incorporated must still be established by one of the forms listed above. Placement evidenced in this way is scored under the mix-level response to question A3 of the reversal risk questionnaire (Appendix A).

8.1.12 Reactor and Equipment Description

The process flow diagram must be prepared to ISO 10628 or an equivalent convention, and must show:

• Details of theEach processing steps.
• Dimensionsstep andas footprintsa ofdiscrete theunit equipment and/or reactoroperation.
• The locationmaterial inflows and outflows of materialseach inflows/outflowsstep, including waste and loss streams.
• PositioningThe ofenergy sensorsinputs to each step and anytheir monitoringsource.
• The devicesmeasurement point and instrument for each metered stream (e.g., flow meters, temperature sensors, weighbridges).

Project Proponents must also provide an equipment list stating, for each item of equipment within the boundary, its function, make and model or asset identifier, and rated throughput capacity.

Process detailssteps should include acceptable processes including, but not limited to:

• Particle size reduction grinding or milling.
• Mixing, stirring or blending.
• Calcination.
• Drying and heating (mainly applicable for asphalt production).

8.1.2 Biochar Characterization

8.1.3 Storage Site

9.0 Compliance withWith Product Standards

10.0 Contributors

• Konstantina Stamouli, Ph.D.
• Ella Holme, Ph.D.
• Xueya Lu, Ph.D.
• Rob Brown, Ph.D.

11.0 Definitions and Acronyms

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

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”.

The escape of CO₂ to the atmosphere after it has been stored, and after a Certificate has been Issued. A Reversal is classified as avoidable if a Project Proponent has influence or control over it and it likely could have been averted through application of reasonable risk mitigation measures. Any other Reversals will be classified as unavoidable.

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.

A material used in the construction of an asset.

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

A composite material composed of aggregate, cement, sand and water that cures to a solid over time.

A chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Ordinary Portland Cement (PC) is the most common cement used in modern concrete. Other types of cement include Ground Granulated Blast-furnace Slag (GGBS), Pulverised Fly Ash (PFA) and natural pozzolans.

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.

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.

TheA amountpublicly visible, uniquely identifiable, Verified instrument Issued on the Isometric Registry. Isometric Issues three Certificate Types: Carbon Dioxide Removal Certificates, Emission Reduction Certificates and Environmental Attribute Certificates.

A lack of CO₂knowledge emissions that would causeof the sameexact integratedgreenhouse radiativegas forcingimpact (removal, reduction, or temperatureavoidance) change,associated overwith a givenparticular time horizon, as an emitted amount of GHGprocess or aEnvironmental mixture of GHGsAttribute. OneUncertainty commonmay metricbe ofquantified CO₂eusing isprobability thedistributions, 100-yearconfidence Globalintervals, Warmingor Potentialvariance estimates.

Activities that remove carbon dioxide (CO₂) from the atmosphere and store it in products or geological, terrestrial, and oceanic Reservoirs. CDR includes the enhancement of biological or geochemical sinks and direct air capture (DAC) and storage, but excludes natural CO₂ uptake not directly caused by human intervention.

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

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

A publiclyretirement visiblepathway uniquelyin identifiablewhich Creditan Certificateexisting IssuedEAC byis retired to enable the issuance of a Registrynew thatEAC giveswith thedifferent ownerspecified 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 Protocolcharacteristics.

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

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.

The document, written by a Project Proponent, which records key characteristics of a Project and which forms the basis for Project Validation and evaluation in accordance with the relevant Certified Protocol. (Also known as “PDD”).

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

TheA termprocess usedfor toevaluating describeand greenhouse gas emissions toconfirming the atmospherenet asRemovals aand resultReductions of Project activities.

The steps offor a Project, Proponent’susing Removaldata orand Reductioninformation processcollected that result in carbon fluxes. The carbon flux associated with an activity is a component offrom the Project Proponent’sand 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 measurement which correlates with but is not a direct measurement of the variable of interest.

A collection of Removal or Reduction processes that have mechanisms in common.

for open systems, biogeochemical and/or physical interactions which occur during the removal process that decrease the CO₂ removal .

A lack of knowledge of the exact greenhouse gas impact (removal, reduction, or avoidance) associated with a particular process or Environmental Attribute. Uncertainty may be quantified using probability distributions, confidence intervals, or variance estimates.

Emissions that are produced by a specific CDR process and are directly controllable.

A mixture of water, organic acids, aldehydes, ketones, sugars, phenols, and other organic compounds derived from the thermal breakdown of biomass. Thermal breakdown of biomass is achieved via thermochemical processes, such as pyrolysis, which heat biomass in low- or no-oxygen environments to high temperatures (~e.g. 350-650°C). Bio-oil is often also referred to as pyrolysis oil or bio-crude.

Any tangible or intangible property that has value and can be owned, controlled or utilized by an individual or organization. In the context of this module, an asset refers to a physical structure.

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.

An output of a process that has no intended value to the producer.

The document, written by a Project Proponent, which records key characteristics of a Project and which forms the basis for Project Validation and evaluation in accordance with the relevant Certified Protocol. (Also known as “PDD”).

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

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

A United States Government agency that protects human health and the environment.

GHG sources, sinks and reservoirs (SSRs) associated with the project boundary and included in the GHG Statement.

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).

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).

The defined temporal and geographical boundary of a Project.

Reporting Period

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

A conservative adjustment applied to estimated greenhouse gas (GHG) emission reductions or carbon removals to account for uncertainties, risks, or variability in measurement, permanence, or effectiveness of the credited activity. It reduces the amount of carbon Certificates issued to ensure environmental integrity and avoid over-crediting.

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).

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 public document that transparently reports objective, comparable and third-party verified data about products and services' environmental performances from a lifecycle perspective. The EPD is supported by an underlying Life Cycle Assessment (LCA) report, a systematic and comprehensive summary of the LCA project to support the third-party verifier when verifying the EPD.

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

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

Certificates are issued to the Certificate Account of a Project Proponent with whom Isometric has a Validated Protocol after an Order for Verification and Certificate Issuance services from a Buyer and once a Verified Removal or Reduction has taken place.

A worldwide federation (NGO) of national standards bodies from more than 160 countries, one from each member country.

TotalA Inorganiccalculation, Carbon.

An analysisseries of howcalculations muchor differentsimulations componentsthat use input variables in a Model contributeorder to thegenerate overallvalues Uncertaintyfor variables of interest that are not directly measured.

1211.0 Appendix A: Reversal riskRisk

1211.1 Biochar Durability Horizon and Storage Uncertainty in the Built Environment

1211.1.1 Definition of Storage Uncertainty

AThis keyModule certifies biochar in built materials over a 200-year durability horizon, rather than the Isometric 1,000-year default. The grounds are set out in full in Section 1.0 and summarized here. They are specific to biochar rather than general to built materials. Containment over 1,000 years is neither guaranteed nor observable for this pathway, because the fate of the material through demolition, recycling, and end-of-life reprocessing across that span is extrapolated rather than documented. For cementitious materials, a further consideration forapplies. Biochar is exposed to the durabilitypore solution of CO2a storedcementitious inmatrix during encapsulation, typically at pH 12.5 to 13.5³, which alters its structure, including pore enlargement and matrix defectiveness⁴. While the builtmaterial environmentremains intact this is not onlyitself a carbon-loss pathway, because there is no oxygen, no export route, and the condensed inertinite core is chemically resistant¹. Altered and aged carbon is, however, more susceptible to oxidation⁵, so the exposure may leave the biochar more vulnerable to conditionsdegradation once the material is broken up and the carbon is exposed to the open environment. This consideration does not apply to asphalt, in which biocharthe durabilitybinder is likelya hydrophobic bituminous matrix rather than an alkaline aqueous environment; for asphalt, the horizon rests solely on the extent to which the fate of the material can be negativelydocumented. impactedThe 200-year horizon corresponds approximately to the design life of a built asset, butindicatively also50 years for common buildings and 100 years for monumental structures and bridges under EN 1990:2023, plus first reuse.
A second consideration is the uncertainty in the location of the productmaterial at any given time. As described inwith the relevant section of the CO₂ Storage via Carbonation in the Built Environment Module, a built material may gopass through many different use cases inacross its life cycle, depending on the initial use case, local regulatory requirements, and economic incentives. In the traditional construction industry, there has not been ano need to track built materials past the life cycle of an asset, particularly where elements are designed to perform with minimal maintenance or intervention. Thus, biocharBiochar-amended built materials are therefore likely to transition through several construction-demolition-reuse cycles with minimal ability to track these changes. Over longthe time200-year periods (e.g. 1,000 years),horizon this leads to a high degree of uncertainty in both the storage location of the productmaterial and, consequently, whether or not the productit is exposed to conditions that lead to degradationloss of the biocharcertified carbon. This treats built-environment storage as an open system and necessitates athe conservative, project-specific approach to reversal risk,set describedout in the following sectionbelow.

1211.1.2 Biochar Reversal

TheThis labileModule certifies inertinite (recalcitrant) fraction of the biochar only (Equation 7). That fraction is subjectdurable over geological timescales once formed¹ and is refined to degradationthe overthermally anon-reactive longerresidual periodby thermogravimetric analysis². It is chemically resistant while it remains encapsulated in the host matrix, and while it remains in contained chunks after the matrix is broken up. The reversal concern is therefore not chemical mineralization of timeencapsulated duecarbon, but physical liberation of the certified inertinite to differentmobile degradationfines that are dispersed into the open environment. Once dispersed, the location and fate of the fines cannot be verified, and they are exposed to pathways that arecan applicablereturn the carbon to the physicalatmosphere, including oxidation of fine, high-surface-area and aged material⁵ and thermal destruction where sewage sludge, road runoff solids, or sweepings are incinerated. Consistent with the conservative approach this Module takes to a novel storage locationpathway, carbon is certified only where its retention can be quantified and verified, and certified carbon liberated to mobile fines is therefore treated as not retained. TheseThis treatment is adopted because the retention of dispersed fines cannot be demonstrated; it is not a finding that dispersed inertinite degrades in every receiving environment. Isometric will revisit it if evidence on the fate of dispersed biochar fines becomes available. Liberation happens through wear, comminution, and recycling. The pathways canthat act on liberated, dispersed material include:

• Physical loss -: abrasion or erosion of the material surface, or delamination or spalling, fireand orcomminution highduring temperaturedemolition, eventscrushing, and recycling ⁴³.
• Abiotic degradation -: chemical reactions related towith environmental factors, including but not limited to: natural mineralization, photodegradation, and leaching due toby water flows orand freeze - thaw cycles, acid rain, reaction with aggressive chemicals⁴¹¹⁷.
• Microbial degradation -: through the actionsaction of aerobic or anaerobic microorganisms orand lichen colonisation colonization^4244,43,4445.

EachTwo related mechanisms are handled outside this dispersal term. Acid and matrix dissolution can expose biochar as the host matrix is lost, but does not mineralize the inertinite fraction, so it is treated as an exposure driver in the questionnaire (Section B), not a carbon-loss term. Thermal exposure during hot asphalt recycling (approximately 150 to 190°C) is highly unlikey to reverse the certified fraction, because that fraction is by construction the thermally non-reactive residual determined by thermogravimetric analysis (Equation 7), which is stable well above that range: road-grade biochar loses only about 1% of theseits pathwaysmass to 150°C and about 5% to 400°C⁴⁶, and oxidation onset rises with pyrolysis temperature, well above the hot-mix range⁴⁷. High-temperature reprocessing of concrete to clinker (approximately 1,400°C, the calcination temperature described in the Concrete background) destroys even the inertinite, and is directlyhandled influencedas bya thegating 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's physical and chemical propertiesexclusion (see Section 6.0 for more informationbelow).

1211.1.2.1 Biochar in Concrete

Quantifying the risk of reversal associated with biochar-amended concrete is inherently complex, given the high degree of uncertainty and variability in possible end-states of the concrete over 1,000 years. Degradation of the labile fractionLiberation of biochar withinfrom concrete can occur when biochar particles become exposed, which may occuroccurs when the concretematerial is inlost aor 'broken up, either during use case'or (e.g.at as partend of alife. building)During use, or when the concreterelevant goesdrivers throughare an end-of-life transition (e.g. recycled). This is the result of processes such as concretesurface loss by physical or chemical weathering, demolition of a built asset or other processes that expose additional surface area of the concrete. In most scenarios, physical loss of concrete is likely to be the most prevalent loss pathway, leading toincluding exposure of embedded biochar. This may occur under the following scenarios:

During use:

• Exposure to acid rain
• Contact and contact with acidic groundwater or soils (most relevant for foundation uses)
• Exposure. to high temperatures, such as those from house or forest fires

DuringThe end-of-life processespathways and their reversal treatment are set out in the Section 3.2.3.2.1 End-State Use Cases (Concrete) background and summarized here:

• Demolition or detonation, which breaks apart concreteIn-situ and exposesex-situ internalreuse: the material remains in its original form, so no additional carbon is liberated.
• ExposureDowncycling (the dominant pathway in most regions): crushing liberates a fraction of the biochar to highfines, temperaturesbut duringthe majority remains bound in coarse, re-encapsulated aggregate. Downcycling is treated as a terminal state, though the alkaline pre-conditioning⁴ applies to the exposed material.
• Mechanical closed-loop recycling: the biochar is liberated and re-encapsulated in new concrete, whereand is not exposed to conditions that destroy the stable fraction.
• [G-B0T4-0, Conditional: Where concrete iscould credibly be reprocessed intoto clinker
• Contact, withprojects acidicmust groundwaterprovide evidence of a binding design or leachatecontractual inrestriction landfill

Noteagainst thatthermal theclosed-loop likelihood ofrecycling.]Thermal closed-loop recycling occurring,to whileclinker: potentiallyreprocessing resultingat incalcination sometemperatures degradation ofdestroys the labilecertified fractioninertinite. ofThis biochar,pathway is currentlya extremelygating lowexclusion due to the nascency of the technology. At the time of drafting, there are(G3): a limitedProject numberwith a credible, unconstrained likelihood of pilot projects operating at small scale, including in the United Kingdom, France and Canada. As closed-loop recycling is not currently operating at scale, it has been excluded from the calculation of reversal risk at this time. However, it is importantineligible tounless notea that closed-loop recyclingbinding, ifevidenced includedrestriction against it is in place. [/G-B0T4-0]

1211.1.2.2 Biochar in Asphalt

AsOnly discussedbiochar in a Sub-Surface Layer is eligible for certification under this Module; biochar in the surface course, and in bituminous surface treatments, is an ineligible practice, as set out in the Section 3.2.30.2.2 Surface-course material abrades directly under tire contact, generating tire and road pavement wear particles at a size (peaking at 63 to 106 μm)¹⁵ asphaltthat is abraded over time due to friction between tire treads and the pavement surface. Abraded particles fall within a dust-sized particle size distribution, and thus these particles can be easilyreadily transported away from the road surface by wind orand water. ThisThe leadsabraded fraction cannot be quantified or verified for an individual pavement, and its subsequent location and fate cannot be determined (see Asphalt Layer Eligibility). For eligible Sub-Surface placements, the reversal concern is the biochar comminuted to uncertaintymobile infines during milling and recycling over the finalhorizon, locationwhich ofis quantified through the abradedquestionnaire particles, as well asand the interactionsUncertainty betweenDiscount the([math: environmentU]) andderivation co-abraded biocharbelow. Equally, exposureExposure to chemicals such as chlorides (from road salt) and sulphatessulfates (from surface water) may leadincrease tothe destabilisationreactivity of thedispersed biochar structure and increased reactivity. Conservatively constraining the amount of biochar that is abraded and subject to degradation is a critical step in reliably determining the amount of carbon that is durably stored in biochar-amended asphaltmaterial.

1211.2 Reversal Risk Approach and Calculation of Uncertainty Discounts

12.2.1

Reversal Concrete

Dueis toassessed limitedfor dataeach onProject the incidence of high-temperature structure fires, the reversal risk presented in this section focuses on reversal through contact with low-pH fluids. Numerical Modelling was adopted asusing a method for evaluating the associated reversal risksquestionnaire. The modelnet willscore be revisited as more data becomes available.

To refine the assumption of reversal duemaps to acidic exposure, a geochemicalbanded modeldurability that simulates CO2 loss from concrete due to long-term acid exposure was developed using PHREEQC (version 3)discount, an open-source program for simulating chemical reactions and transport processes. This model quantifies the extent of degradation in biochar-based concrete over a 1,000-year period due to dissolution of concrete in acidic environments, both naturally occurring (e.g., acid rain, acidic groundwater) and industrially impacted (e.g., acid mine drainage)—across a pH range from 7 to 0.1, and subsequent exposure of the labile biochar fraction to atmospheric conditions.

The geochemical model incorporates equilibrium and kinetic interactions between aqueous solutions and cement phases using the Cemdata18 database: a chemical thermodynamic database for hydrated Portland cement and alkali-activated materials. Key model parameters, data input are sourced from literature studies include: cement composition44^,45, reactive surface area (grain size)46^,47, reaction constant of specific mineral phases48^,49,50,51 and acid concentration52^,53.

The geochemical model assumes no carbonation happened within concrete in advance. The Total Inorganic Carbon (TIC[math: U]) content before acid weathering is recorded and used as baseline comparison with remaining TIC after interaction with various acidic fluids. This model considers acid rain, acidic groundwater, acid mine drainage, and an extreme pH scenario, represented by varying the amount of sulfuric acid in the model conditions. Sensitivity analysis was performed on scenarios where reactive surface area and temperature varied from low to high. The remaining TIC reported for different scenarios is based on consumption of the initial material, with the reaction reaching equilibrium at the last step of the model. This allows for the computation and comparison of the worst case scenario (pH 0.1, high reactive surface area, room temperature). ThisEach scenarioband's resulted in approximately 2% lossvalue of the initial concrete material. In some less aggressive conditions (e.g., groundwater at pH 7), the loss was as low as less than 0.001%.

Taking the result of this reversal risk model, some simplifying assumptions can be used to conservatively estimate the portion of biochar that will degrade over 1000 years. These assumptions include:

• Biochar is evenly distributed in the concrete, and the labile fraction is evenly distributed among the biochar particles.
• The labile fraction of exposed biochar will degrade.

Using this framework, it can be assumed that 2% of concrete loss by mass over 1000 years correlates with 2% of biochar by mass that will be exposed to conditions that may lead to degradation of the labile fraction. Thus, to account for this uncertainty, the percentage of the labile fraction that is associated with the 2% of the exposed biochar surfaces will be discounted from [math: CO_{2e_{Stored}}U] is derived from a comminution and dispersal model of how the certified inertinite is physically liberated over the horizon, set out under Derivation of the Durability Discount below.

Reversal risk is assessed on a project-by-project basis. The Project Proponent must complete the questionnaire for each Project, for each distinct placement or mix design where a Project spans several, and for each new storage site added to the Project after validation (see Calculation of Uncertainty Discount,[math: U]). Because built-environment storage is largely unobservable over the horizon, the output is a durability uncertainty discount on the certified durable fraction ([math: U] applied in Equation 4), instead of a buffer-pool contribution. This assessment is alsoconservative givenby adefault: safetyany factor of 3, as described in Section 7.2.1.3, to account for concrete degradation pathways that arevariable not consideredcharacterized withinwith verifiable evidence is scored at its worst option, and gating answers override the geochemicaltotal modeland but maycan result in biocharineligibility exposure,of suchthe as crushing during demolitionProject.

Note that Projects may choose to provide documentationdocumentations specific to the region of operations to calculate a Project-specific reversal risk. This documentation may include, but is not limited to:

• Geologic maps of bedrock lithology (from USGS or national equivalent) and groundwater pH.
• Climatic data, including average yearly temperature, precipitation volume and precipitation pH.
• Estimated transport radius of produced materials.
  • If this is unknown for a given Project, Project Proponents may use either the maximum possible transport distance or a conservative average distance.
• Types of assets that materials may be used in and a breakdown by percentage.
• Proof of material suitability for the range of applications (e.g. certificates of compliance with concrete quality and performance standards).
• Risk of external acid attack, based on:
  • Regional groundwater and precipitation pH.
  • Likely exposure risk of the concrete containing stored carbon.
    • This can be determined through analysis of possible asset types and well-justified assumptions about the location of the concrete within the asset.
• ProbabilityChain-of-custody evidence for placement, or, where unavailable, a probability analysis of the concrete or asphalt end-state based on regional trends.

1211.2.21 AsphaltThe Reversal Risk Questionnaire

ToTable conservativelyA1: estimateGating Criteria.

Table A2: Section A (placement and incorporation).

Table A3: Section B (physical exposure over the horizon).

Table A4: Section C (end-of-life and recycling).

For asphalt, C1 and C2 are answered for the biochar-bearing layer. C1 is the expected time until that layer is first milled, removed, or reprocessed. C2 is the number of asphaltsuch is abradedevents within 90the yearshorizon, and thusmust webe assumeconsistent thatwith 100%[math: N] as determined under Derivation of the labileDurability fractionDiscount degradesU. withinWhere a layer-specific interval is not evidenced, C1 and C2 are answered on the resurfacing interval.

For C3, engineered landfill means disposal at a landfill operated under a permit issued under the applicable waste regulation for the class of waste concerned (for example, Council Directive 1999/31/EC on the landfill of waste, or equivalent national regulation), with the basal barrier, leachate controls, and capping required for that timelandfill frameclass, and with records of the waste accepted. TheDisposal calculationsat shownunpermitted insites Figureor A2open assumedumps, or use as unregulated fill, is not engineered landfill and is scored as Unknown. To score C3 as contained on the basis of landfill, the Project Proponent must evidence, from national or regional waste statistics, that thelandfill labileat fractionsuch facilities is 5%the perdominant massend-of-life ofpathway biochar;for importantly,the because a key assumption is that biochar particles are evenly distributedmaterial in the pavementregion, and must identify the lossregulatory percentagesregime under which those facilities operate.

Table A5: Section D (containment safeguards and mitigants). Subtract from the Section A to C total.

Completion of the questionnaire for each new storage site added to the Project, and its re-completion at each Crediting Period renewal or on material change, are required of all Projects (Calculation of Uncertainty Discount,[math: U]) and do not changescore withunder Section D. Where D3 is claimed, the biocharregister concentrationentry or withand the labileasset fraction.

[Image:owner's Figureagreement A2must biocharbe loss]

Figureprovided A2in Percentagethe of biochar lost over time from a 1 m3 block of asphaltPDD, assumingworks annotified abrasionunder ratethe ofagreement 0.5must mm/yearbe reported at the next Verification, and anotified biocharworks contenttrigger of 5% by mass.

Because these calculations demonstrate complete lossre-completion of the labilequestionnaire.

Scoring. fractionSum ofSections biochar-amendedA asphaltto within 100 yearsC, 100%then subtract Section D to give the net score. Map the net score to the risk rating and durability discount [math: U] in the banded discount schedule below (Derivation of the labileDurability fractionDiscount U). A Project that does not complete the questionnaire, or that leaves variables uncharacterized, receives the worst-case discount.

Responses to Section C are forecasts over the 200-year horizon, based on the evidence available at the time of theassessment, biocharand producedare not commitments by the Project Proponent. A response other than the worst option must be supported by documented evidence, such as the design working life of the asset under the applicable design standard, the maintenance, rehabilitation, and reconstruction policy of the asset owner or road authority, and national or regional data on end-of-life and recycling practice, and the highest-risk response consistent with that evidence must be selected. The questionnaire is deductedcompleted fromfor each new storage site added to the CreditsProject and re-completed at each Crediting Period renewal or on material change, and a revised discount applies to Certificates issued after the re-assessment.

11.2.2 Derivation of the Durability Discount U

[math: U] is the project-specific durability discount as specified in Equation 4, Section 7. The term also represents the fraction of the certified inertinite that may be physically liberated to mobile fines and dispersed into oxic surface environments over the 200-year horizon. The calculation for [math: U]does not re-discount the labile fraction, which is not certified under this Module.

Note; thatthe thisone-standard-deviation frameworkconservatism is already accounted for in [math: F_{durable}]; or acid and matrix dissolution, which exposes but does not takemineralize intoinertinite¹. accountThermal commondestruction maintenance(clinker practicesreprocessing) and surface abrasion are handled as gating exclusions, so they are also excluded from the graded discounts here.

[math: U] is derived from the comminuted-inertinite retention model as shown by the equation below:

[math: U = 1 - (1 - f_{disp})^{N}]

(Equation 8)

Where:

• [math: f_{disp}] is the fraction of biochar comminuted to mobile fines (sub-0.075 mm) per comminution or recycling round.
• [math: N] is the number of comminution rounds over the 200-year horizon for the placement band.

[math: N] follows from the service life of the element or, for asphalt pavements, suchof the biochar-bearing layer. The basis is the design standards and documented maintenance and replacement-interval data. Design working lives under EN 1990:2023 are 50 years for common buildings, 100 years for monumental structures and bridges, and 25 years for agricultural buildings; foundations are frequently left in situ.

For asphalt, [math: N] is the number of events within the 200-year horizon at which the biochar-bearing layer is milled, removed, or reprocessed, because the biochar is comminuted only when its own layer is disturbed. A resurfacing event counts for a layer where the milling or removal depth reaches any part of that layer. Rehabilitation, reconstruction, full-depth reclamation, and in-place recycling count where they reach that layer.

By default, every resurfacing event is treated as sealcoatingdisturbing the biochar-bearing layer. [math: N] is then set by the resurfacing interval, roughly 15 to 25 years¹⁴, rather than the 40-year pavement design-life label in Table 1. A longer interval may be used only where the Project Proponent evidences, for the application type and region:

• the depth of routine resurfacing relative to the depth of the biochar-bearing layer; and
• the interval at which that layer is milled, removed, or reconstructed.

This must be set out as theserequired practicesunder varyStorage by region and specific applicationSite. ThusThe basis may be the applicable pavement design standard or the published maintenance policy of the road authority or asset owner, together with the layer thicknesses in the absencepavement design. Where the evidence supports a range of specific information regardingintervals, the useshortest caseinterval andis regionalused.

Table practicesA6: relevantComminution rounds N over the 200-year horizon, by placement band.

The Reclaimed Asphalt Pavement (RAP) multiple-recycling literature shows the binder degrades cycle-on-cycle⁴⁸, so later asphalt cycles are downcycling rather than re-laying, but this does not reduce [math: N], because the biochar is comminuted at each event that mills or reclaims the biochar-bearing layer, whether the material is re-laid or downcycled.

Recycling of biochar-bearing reclaimed asphalt into a new bound mixture, whether by hot, warm, or cold recycling, is not treated as a reversal of the biochar it contains. The durability discount applies only to the fraction comminuted to mobile fines at each milling or processing round ([math: f_{disp}]); the remainder is treated as retained, whether it is re-bound in a new pavement or used in another construction application.

[math: f_{disp}], no study measures biochar carbon retention through actual asphalt or concrete recycling and this represents a gap in the current literature. As such, [math: f_{disp}] is inferred from the fines (sub-0.075 mm) generated per processing round in the aggregate-recycling literature:

• Asphalt (RAP milling and crushing): roughly 5 to 10% passing the 200 (0.075 mm) sieve per round⁴⁹, so [math: f_{disp}] approximately 0.05 to 0.10.
• Concrete, coarse crush: the sub-0.075 mm fraction is usually minimal, and the biochar stays bound in coarse re-encapsulated aggregate⁵⁰, so [math: f_{disp}] 0.02 to 0.05. This is the physical basis for treating concrete inertinite retention as near-complete for thick elements.
• Concrete, fine crush (thin elements, repeated crushing): fine recycled aggregate carries roughly 4.86 times the sub-0.075 mm crush dust of natural sand⁵¹, and repeated crushing produces progressively finer distributions⁵², so [math: f_{disp}] approximately 0.05 to 0.10.

The high end of each range is taken because biochar is more friable than mineral aggregate and the dispersed fraction is untraceable.

These values are a conservative scenarioproxy isfor used.the Projectliberation Proponentsof may choosebiochar to providemobile additionalfines, informationpending direct measurement. Isometric will recalibrate [math: f_{disp}] as direct measurements of biochar carbon retention through asphalt and concrete milling, crushing, and recycling become available.

Applying Equation 8 across the sourced parameter ranges of [math: f_{disp}] gives: concrete structural ([math: f_{disp}] 0.03 to conduct0.05, aN Project1 to 2) roughly 0 to 10%; concrete above-specificground (0.04 to 0.05, N 3.5 to 4) roughly 13 to 19%; asphalt base (0.05 to 0.075, N 7) roughly 30 to 42%; concrete thin (0.06 to 0.08, N 9 to 10) roughly 43 to 57%; and asphalt binder (0.075 to 0.10, N 10 to 13) roughly 63 to 65%. These model outputs cluster into four risk bands shown in Table A7. The Module adopts one durability discount calculation[math: U] per band; the Table below maps each net score and risk rating to that discount and to the representative placement and parameter basis behind it.

Table A7: Durability discount U by risk band.

1312.0 Relevant Works