Rock and Mineral Feedstock Characterization

This Module provides the requirements and recommendations for the characterization of solid rock and mineral feedstocks that may be used in carbon dioxide removal (CDR) projects by Project Proponents. This Module is intended for use in conjunction with other Isometric pathway level Protocols and Modules. This Module can be used in any instance where physical and geochemical characterization for the use of a rock or mineral material as a feedstock is required by a Project Proponent.

The characterization requirements and recommendations outlined within this Module are based on best known scientific practices at the time of writing. Requirements may be updated in future versions of this Module in line with changes in scientific consensus. This Module outlines methodologies that may be employed to characterize feedstocks to the best of the Project Proponent’s ability, considering scientific rigor, method employment economics, best practice and feasibility. Specific analytical method standard details are outlined in Appendix 1.

Within this Module framework, the key physical and geochemical characteristics of rock feedstocks required for CDR pathways are outlined. It is a requirement that all feedstocks are characterized, prior to application, to ensure safety and suitability for CO₂ removal. We outline the core feedstock characterization requirements and recommendations in Table 1. The requirements and recommendations outlined here apply to all pathway level Protocols that utilize this Module unless otherwise specified in the Protocol. Any deviations from these requirements outlined in a Protocol will supersede the requirements listed below. These characterization parameters are outlined in more detail in Section 3.

Table 1: Feedstock Characterization Requirements and Recommendations

It is noted that the requirements outlined in Table 1 are minimum requirements for feedstock used within a Crediting Project. Where a feedstock is sourced from mining operations further characterization may be required, based on relevant regulatory requirements. A summary of such characterization methods specific to mining related feedstock is given in Section 3.4.5.

In some instances, determination methods other than those listed as required in Table 1 may be appropriate. Project Proponents may, in consultation with Isometric, conduct alternative analyses with adequate justification in the Project Design Document (PDD).

It is a requirement of all Project Proponents utilizing a rock or mineral feedstock that documentation is submitted to the project's Validation & Verification Body (VVB) that outlines the origin and nature of the utilized feedstock. This documentation should form a distinct section of the project's PDD and should contain the following information:

• The location the feedstock was recovered/collected from
• How the feedstock was recovered from the location
• A description of any pre-processing that has occurred on location or prior to characterization
• Geological maps and descriptions (if available)
• An outline of any prior geochemical or physical characterization carried out on the feedstock

If any of the information listed is not available at the time of PDD submission, Project Proponents are required to provide adequate supporting documentation to explain why. Such circumstances may occur in relation to the use of mining waste materials, where some information may be made confidential by the entity that produced or provided the feedstock to the Project Proponent.

If the rock or mineral feedstock has been recovered as a by-product of an extractive process, such as mining or quarrying, the Project Proponent is required to report on the legal status of the source material before use in a CDR Crediting Project. This requirement will apply where a feedstock may have been previously, or is currently, defined as a waste product under relevant national regulations and laws. Project Proponents are required to outline and report how such ‘waste’ products have been handled and repurposed as a CDR feedstock, providing specific evidence that its use within a Crediting Project does not breach any local or national laws and regulations. Such national regulations include the Extractive Waste Directive 2006/21/EC within the European Union.

There are a wide range of characteristics that can influence a feedstock’s weathering or dissolution rate for CO₂ removal. These include both physical properties (e.g., particle size distribution, permeability, etc.) and geochemical properties (e.g., mineralogy and elemental composition). Understanding how these characteristics interact with environmental variables to determine these rates is still an active area of scientific investigation. This Module is designed not just for material characterization, but for furthering scientific understanding of feedstock reaction rates. We envision that the data requirements outlined herein will be foundational for building scientific consensus around the underlying controls on feedstock weathering and/or dissolution, and will ultimately lead to more sophisticated model-based approaches as the field matures.

All projects are required to demonstrate that solid materials utilized as feedstock in CDR projects have been characterized in line with the relevant national standards of the country that the project is located within. If there is a lack of distinct relevant standards to meet the minimum requirements of this Module, Project Proponents are required to utilize methods outlined by the International Organization for Standardization (ISO). All projects are required to clearly report the standards that are utilized to characterize feedstock materials, with any amendments to standard operating procedures (SOP) or deviations from the relevant ISO or national standard outlined within the PDD upon submission to the relevant VVB (see Appendix 1).

Where specific standards do not exist for analytical techniques, the Project Proponent is required to provide an SOP for the analysis undertaken that can be reviewed by the VVB. Such situations may occur for specific analysis, such as XRD based mineralogical analysis, where methods and SOPs may be defined by the instrument manufacturer. In such cases these SOPs must be clearly defined, with reference to specific manufacturer documentation.

Similarly, there may be instances in which the most accessible analytical testing facilities do not conform to ISO or other standard, and instead utilizes their own in-house methodologies. Such deviations may be permissible and require explicit approval by Isometric.

Sample preparation, identification, sub-sampling and storage should be undertaken in accordance with national standards related to extractive waste, such as those outlined in the CEN/TR 16365:2012 standard. A Project Proponent is responsible for ensuring standards are followed by partner laboratory facilities. Project Proponents must outline the standard used in the PDD.

Project Proponents are required to provide detailed information on the preparation and handling of rock and mineral feedstocks within the project PDD. A chain of custody is required to be submitted with the results obtained through material characterization. Chain of custody documents must outline detailed information on the handling of rock and mineral feedstock materials, from their source location to the production of characterization results.

The physical properties of rock and mineral feedstocks are required to be characterized before use in a Crediting Project. Physical characteristics are required to be assessed in line with the methods and standards outlined within this Module. Within this Module, physical characterization covers a material's geotechnical and physical characteristics.

It is required that all materials are characterized for their geotechnical properties. These properties are key to understanding the physical nature of utilized rock feedstocks at the time of analysis. Key parameters may include water content, specific gravity, particle density, bulk density and permeability.

Project Proponents are required to undertake geotechnical investigation and testing. The exact set of tests required will vary on a project basis, but should generally be in line with the ISO standards group ISO 17892. This standard set is listed below, with feedstock-specific requirements highlighted.

Required for all pathways, unless otherwise specified in a pathway Protocol:

• Determination of water content - e.g., ISO 17892-1:2014
• Determination of particle size distribution - e.g., ISO 17892-4:2016

Recommended for all pathways, unless otherwise specified in a pathway Protocol:

• Determination of bulk density - e.g., ISO 17892-2:2014
• Determination of particle density - e.g., ISO 17892-3:2015
• Incremental loading oedometer test - e.g., ISO 17892-5:2017
• Fall cone test - e.g., ISO 17892-6:2017
• Unconfined compression test - e.g., ISO 17892-7:2017
• Unconsolidated undrained triaxial test - e.g., ISO 17892-8:2018
• Consolidated triaxial compression tests on water saturated soils - e.g., ISO 17892-9:2018
• Direct shear tests - e.g., ISO 17892-10:2018
• Permeability tests - e.g., ISO 17892-11:2019

A Project Proponent is responsible for ensuring that all geotechnical laboratory testing undertaken on rock and mineral feedstock materials meet standards in accordance with national regulations in a project's location. If a Project Proponent or partner facility undertakes testing in line with a national alternative to the aforementioned ISO standards, this must be reported within the project PDD.

Projects are required to carry out particle size distribution (PSD) and specific surface area analysis for all rock and mineral feedstocks used within Crediting Projects. Within this Module, gravimetric sieving and BET analysis are required to determine these parameters.

Gravimetric Sieving

It is required that all proposed rock and mineral feedstock materials are analyzed for particle size distribution through gravimetric sieving. It is required that all Project Proponents carry out this analysis in line with the ISO 11277:2020 or ISO 17892-4:2016 standardized procedures, or an equivalent national or regional standard. If a Project Proponent chooses to utilize a specific national variation of the ISO standard, such as BS ISO 11277:2020, any variations from the ISO procedures must be clearly reported.

BET Analysis

To quantify the specific surface area of a rock and mineral feedstock materials, it is required that projects undertake BET analysis. This analysis will aid in quantifying the potential reactive surface area of rock feedstock and will aid in estimating the relative reaction kinetics of a feedstock for CDR. It is required that the BET method undertaken is in line with ISO 9277:2022.

Other PSD and surface area techniques

The Project Proponent may, in consultation with Isometric, perform alternate techniques to measure or validate a rock feedstock's PSD or relative surface area. Such techniques, for example, may include small angle X-ray scattering (SAXS) that may be used to estimate mean particle sizes between 1 nm and 100 nm. Where such techniques are utilized by a Project Proponent the procedures undertaken must be clearly and adequately reported, with reference to SOP’s or standards, such as ISO 17867:2020.

Geochemical characterization is required for all proposed rock and mineral feedstock materials. Project Proponents are required to determine the abundance of major and minor elements within a feedstock, the mineralogy of the feedstock, the total elemental carbon and sulfur and feedstock radioactivity using the methods described in the following section.

Elemental characterization is required to establish baseline metal cation and anion contents of a rock feedstock material. Elemental composition evaluation can be carried out using a range of methods, dependent on the exact composition of the feedstock rock. Projects are required to undertake ED-XRF, WD-XRF or fusion / acid digestion coupled with ICP-MS or ICP-OES on utilized rock feedstocks.

Projects are required to initially characterize rock feedstocks for the following elements at a minimum:

Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Ba, W, Hg, Tl, Pb and Zr

Initial characterization must also include any elements, isotopes, and/or isotope ratios not listed above that will be used to quantify weathering rates in the field. Following initial assessment of elemental composition, a Project Proponent can refine elemental analysis to reduce the total number of elements measured. Project Proponents are required to demonstrate that eliminated target elements do not represent a measurable portion of the assessed feedstock material. This can be quantified through elemental mass balance calculations.

ED-XRF

Major and minor elemental compositions are required to be analyzed via ED-XRF. This analysis is required as it will allow Project Proponents to identify the proportions of key elements Mg and Ca (often reported as oxides MgO and CaO) within a proposed feedstock material. Major and minor elemental analysis is also required to assess the suitability of a material for use in CDR projects, taking into consideration the concentrations of potentially environmentally harmful elements within a feedstock source. Data collected by a portable XRF is not eligible for crediting within this Module.

Acid Digestion and/or Fusion coupled with ICP-MS/OES

It is required that Project Proponents undertake detailed elemental analysis of rock feedstocks. Although it is acknowledged that digestion, fusion, and fluorescence based analysis methods are not directly comparable, a more detailed level of analysis will potentially reduce analytical uncertainties when characterizing a rock feedstock. At least one of the following analyses are required for elemental characterization:

• Fusion + Two-Acid Digest / Aqua Regia Digest (with ICP-OES/MS)
• Fusion + Multi-Acid (4-Acid) Digest (with ICP-OES/MS)
• Fusion + Nitric Acid Digest Digest (with ICP-OES/MS)

Other elemental measurement techniques

If a Project Proponent chooses to utilize additional elemental measurement techniques, such as Atomic Absorption Spectroscopy (AAS) or WD-XRF, it is a requirement that details of the analyses are outlined within the PDD.

It is strongly recommended that Project Proponents consider the analytical uncertainty associated with various measurement techniques when developing an analytical framework for feedstock characterization. For example, XRF techniques may have sufficient precision to determine major elemental composition, but higher analytical resolution may be required for a full characterization of trace elements. Project Proponents must provide justification for their chosen methods in the PDD, including evidence that there is sufficient analytical resolution to determine the concentrations of trace elements relevant to calculation of weathering rates or to environmental safeguards.

To assess the theoretical maximum carbon removal potential of an alkaline rock or mineral feedstock, an adjusted version of the Steinour equation is recommended¹. The equation uses bulk elemental oxide composition to estimate the maximum CO₂ removal potential of a feedstock material:

$${E_{pot}} = 
(\frac{1000}{100}) \times (\frac{CaO}{M_{W, CaO}} + \frac{MgO}{M_{W, MgO}} + \frac{Na_2O}{M_{W, Na_2O}} + \frac{K_2O}{M_{W, K_2O}} - \frac{SO_4}{M_{W, SO_4}} - \frac{P_2O_5}{M_{W, P_2O_5}}) \times M_{W, CO_2} \times \eta  - C_{feedstock}$$

(Equation 1)

Where:

• $E_{pot}$ is the CO₂ capture potential of an alkaline rock and mineral feedstock used in enhanced weathering, in kg of $CO_2$ per ton of feedstock
• The factor $(\frac{1000}{100})$ is a unit conversion that adjusts oxide weight percentages to kilograms per ton of feedstock
• $M_W$ is the molecular mass of the specific oxide
• All oxides are in the unit of weight percent of the bulk feedstock (i.e., 5 wt% is input as 5)
• $\eta$ is the molar ratio of CO₂ to divalent alkalinity released from feedstock. This term has a maximum value of 2
• $C_{feedstock}$ is the carbon content (organic and inorganic) of the feedstock

The adjusted equation utilizes elemental composition to identify maximum CO₂ capture potential of an enhanced mineralization project ($E_{pot}$) based solely on bulk elemental analysis. The calculation output is in the form of kg of CO₂ per tonne of feedstock and represents the quantitative hypothetical potential of the material to capture CO₂ as bicarbonate or carbonate. It must be noted that this equation does not take into consideration variables that effect carbonation and carbonation rates such as temperature, known reaction rates, pressure, moisture content and PSD. The equation considers the presence of elemental sulfur and phosphorus as having a reducing effect on overall theoretical potential. This is due to two distinct rationales: (1) their dissolution has no implicit reaction with CO₂ directly and (2) they may become acid compounds, producing acidity which has implications on the carbonate system as CO₂ may be produced².

Elemental abundance data should be produced according to methods prescribed in this Module. The CDR potential calculated in Equation 1 represents the upper limit of creditable removals for a single batch of feedstock as defined in Section 4.1.1. Project Proponents are required to report the CDR potential of each batch of feedstock used pursuant to project activities in the PDD.

It is recommended that the Project Proponent determines the impact of previous chemical alteration and weathering on rock and mineral feedstocks as part of a suitability assessment prior to application. One tool that may be used for aluminosilicate rocks and minerals that are not Mg²⁺ or Fe³⁺ rich, such as plagioclase and other feldspars, is the chemical index of alteration (CIA)³. This geochemical tool was introduced by Nesbitt and Young (1982) and is commonly used in sedimentary geology, geochemistry, and paleoclimatology to infer the intensity of weathering processes and climatic conditions. The CIA is calculated from the molar proportions of major oxides in a sample, focusing on the loss of mobile cations (like Ca²⁺, Na⁺, and K⁺) relative to immobile aluminum. The CIA has been historically used in the weathering literature³⁴⁵⁶⁷⁸ including mafic terrains, and provides the most straightforward interpretation of incipient alteration. The maximum CDR potential of the feedstock will be inherently limited by the initial degree of alteration. Additionally, the CIA value can be used in concert with the mineralogical assessment of the feedstock to evaluate the input of clay minerals from weathered feedstock and/or a source of contamination to the feedstock (e.g., atmospheric dust). The equations uses molar proportions of elements as follows:

$$CIA= \frac{Al_2O_3}{Al_2O_3 + CaO^*+ Na_2O + K_2O} \times 100$$

(Equation 2)

Where CaO* is traditionally the amount of CaO incorporated into only the silicate fraction, i.e., a correction for any calcium in carbonate or apatite in the feedstock. Pairing the CIA calculation with the mineralogy of the feedstock, this CaO* correction can be ignored if these phases are absent. Lower values (less than 50) tend to indicate very limited weathering and high CDR potential. Values approaching 100 indicate significant weathering and very low CDR potential. Project Proponents may also consider applying alternative weathering indicies that are more appropriate for a given feedstock chemistry (e.g., Mafic Index of Alteration and/or Weathering Intensity Scale).

Analysis of baseline carbon and sulfur contents are required for all rock feedstocks utilized within Crediting Projects. It is recommended that carbon and sulfur analysis is carried out via combustion analysis in line with the following standards:

• Determination of organic and total carbon after dry combustion (elementary analysis) - e.g., ISO 10694:1995
• Determination of total sulfur by dry combustion - e.g., ISO 15178:2000

Total carbon and sulfur content are required as baseline measurements before a rock feedstock can be utilized within a Crediting Project by Project Proponents.

Consideration of feedstock radiation levels is required prior to rock application. At a minimum, the Project Proponent must either determine gross alpha and beta activities or provide adequate, geologically and geographically specific justification demonstrating low radiation levels. The following standard is recommended:

• Measurement of radioactivity in the environment - Soil - e.g., ISO 18589:2019

Where an alternative standard is used, documentation of such standard must be provided to the VVB. The Project Proponent is required to ensure adherence to all applicable local, national and international laws regarding acceptable levels of radiation within the context of the project.

In some cases, there may be sufficient pre-existing data demonstrating that radioactivity of a certain feedstock is negligible. Project Proponents may, in consultation with Isometric, choose to submit this pre-existing data with sufficient justification in the PDD.

Mineralogical characterization is required for all rock feedstock materials used within Crediting Projects. Mineralogical characterization can be performed through multiple analytical methods, depending on the feedstock source, target mineral phases and the ability of a Project Proponent to access analytical facilities. Bulk mineral abundance is required for all rock feedstocks, including analysis by XRD and mineral mapping via scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS/EDX).

Mineralogical Analytical Requirements and Recommendations

A combination of XRD, light microscopy and/or SEM-EDS mineral mapping are required to determine a rock feedstock's mineral type and abundance. As XRD can be used for either qualitative analysis, which identifies mineral phases present, or quantitative analysis, which measures the relative abundances of those minerals, quantitative XRD (qXRD) is required when examining mineral type and abundance in feedstock materials. Project Proponents are required to report bulk mineral abundances for all rock and mineral feedstocks used in CDR Crediting Projects. Project Proponents are required to outline the specific methodology used, with reference to source laboratory SOPs or the utilized equipment’s manufacturer methodologies. Project Proponents choosing to utilize light microscopy for mineralogical characterization are required to send rock samples to an accredited external laboratory for analysis and must cross-check results with qXRD, SEM-EDS and/or geologic information.

Rock Feedstock Mineral Abundance Risk Descriptions and Assessments

When assessing the use of potential rock feedstock within Crediting Projects, we require Project Proponents to outline key target mineral groups that may pose a project risk. Project risks may include, but are not limited to, the following:

1. Human/health Risk
2. Environmental Risk
3. CO₂ Removal Inefficiency

Mineral groups, including carbonates, sulfides and asbestos group minerals, should be assessed in the context of these risk factors on a project by project basis. A Project Proponent is required to provide detailed quantitative and qualitative descriptions of its feedstock with direct reference to key target mineral groups.

Where a rock feedstock material contains sulfide and asbestos group minerals, a Project Proponent is required to assess the viability of utilizing such feedstocks within a Crediting Project. Such assessments should consider the potential for reversals (for example where the oxidation of sulfide minerals leads to the production of acidity), and environmental harm (e.g., potential for release of fibrous asbestos particles into the environment). A Project Proponent is required to report the findings of these assessments within the PDD upon submission to the VVB and relevant regulatory bodies.

The specific risks related to use of a rock feedstock material will depend on the application of the material within an individual project. Therefore, risk assessments are required on a project by project basis in consultation with the project registry, VVB and relevant regulatory bodies.

Rock and mineral feedstock sourced from mining operations, both active and closed, may require further geochemical characterization in line with relevant local regulatory requirements. The terms mine wastes/by-products within this Module refers specifically to tailings and waste rock (overburden) materials. Specific geochemical characterization for mining wastes beyond the requirements listed above is not specifically required within this Module, although Project Proponents must demonstrate that any further characterization required by relevant regulatory bodies has been undertaken.

It is recommended that projects that utilize rock feedstocks produced by mining operations undertake a detailed geochemical characterization program. Such programs should include consideration of the potential environmental implication of utilizing such feedstocks within the Crediting Projects. Multiple international guides and standards exist specifically for characterizing extractive wastes such as tailings and waste rock. Project Proponents are responsible for ensuring such wastes are characterized in accordance with local regulatory requirements.

Where specific regulatory guidance on the characterization of mining wastes and by-products does not exist within the locality of a Crediting Project, we recommend that the Project Proponents revert to the mandated characterization standards outlined by the European Commission. These standards provide a detailed baseline for the characterization of rock feedstocks sourced from mining operations. The following standards are recommended:

• EN 15875:2011 Characterization of waste - Static test for determination of acid potential and neutralization potential of sulfidic waste
• CEN/TR 16363:2012 Characterization of waste - Kinetic testing for assessing acid generation potential of sulfidic waste from extractive industries
• CEN/TR 16376:2012 Characterization of waste - Overall guidance document for characterization of waste from extractive industries
• CEN/TS 16229:2011 Characterization of waste - Sampling and analysis of weak acid dissociable cyanide discharged into tailings ponds
• CEN/TR 16365:2012 Characterization of waste - Sampling of waste from extractive industries

Regionally specific mining waste characterization programs may be undertaken dependent on the national regulatory requirements of the project's host country. Project Proponents are required to report utilized mining waste characterization procedures and methods within the project's PDD. Project Proponents are required to demonstrate that wastes recovered from extractive processes meet national environmental regulations within the project's location.

Where a mining operation's waste characterization program follows specific guidance based on best practices, rather than ISO or CEN standards, the Project Proponent is required, and responsible for, outlining the specific methods and procedures that have been utilized to characterize the mining waste materials. Such alternative guides or handbooks may include the following:

• The predictive manual for drainage chemistry from sulfidic geological materials (MEND Report 1.20.1)
• The Global Acid Rock Drainage Guide (GARD Guide)
• EPA 530-R-94-036 (Technical Document - Acid Mine Drainage Prediction)

This Module does not currently prescribe a specific number of samples or replicates that need to be collected for any one batch of feedstock. This is due to the fact that a batch associated with any one project may have a unique history or characteristics that could require individual consideration. Instead, it is required that the Project Proponent conduct characterization of every batch and justify the sampling procedure and number of analyses based on project-specific considerations. The Project Proponent must consider a broad range of feedstock characteristics and relevant context that may influence rock homogeneity when determining a sampling plan. These considerations include, but are not limited to, grain size distribution, particle sorting that may occur during processing and transport, the amount of feedstock being spread and the geological/geochemical setting from which the feedstock was extracted. All relevant details of the sampling plan, number of analyses, and adequate justification for these choices must be included in the PDD. It is recommended that projects utilizing relatively homogenous feedstock sourced from a single location should conduct a full suite of geochemical analyses a minimum of once for every 5000 tonnes of rock⁹¹⁰.

While the number of samples needed for feedstock characterization will depend on the particular feedstock being used, we expect and encourage Project Proponents to utilize high-throughput, non-destructive and less expensive analyses such as XRD and XRF with high frequency to characterize the level of batch heterogeneity. Conversely, it is acceptable for Project Proponents to use the results of such high-throughput methods to identify a more limited number of representative samples for lower-throughput analyses (e.g., mineral mapping with SEM-EDS).

It is a requirement that all projects demonstrate the degree of homogeneity within a single feedstock batch. For the purpose of this Module, we define a batch as a unit of feedstock sourced from a particular location at a particular time that is processed and transported as a single unit. All projects are required to include in the PDD a detailed description of how the chosen sampling plan addresses any heterogeneity that might be present within the batch. This may include sampling across horizontal and vertical dimensions of a feedstock batch as a consideration of particle sorting that may happen during processing and transportation. Recommended methods for assessing feedstock homogeneity include compositional variance analysis, such as ANOVA (Analysis of Variance), performed on major element or mineralogical characterization data; field screening techniques using handheld XRF or near-infrared spectroscopy; and approaches such as the ITRC Incremental Sampling Methodology⁹, which suggests collecting a large number of small increments—typically 30–100—systematically and randomly distributed throughout the bulk feedstock pile. It is acknowledged that rock feedstocks are likely to vary in composition as an extractive material, depending on the source location. As a result, Project Proponents are responsible for reporting the homogeneity of the feedstock to Isometric, ensuring that data are spatially representative of the entire project area and that sampling captures both horizontal and vertical variability within the feedstock used in a Crediting Project.

A Project Proponent is required to report the analytical laboratory/laboratories that have been utilized for feedstock characterization. It is the responsibility of the Project Proponent to ensure that the chosen analytical facilities are reputable and conduct characterization techniques to the required standards indicated within this Module and Appendix 1.

It is recommended that Project Proponents should utilize UKAS, MCERTS, DWTS and ISO accredited analytical services whenever feasible. Where a Project Proponent utilizes laboratory facilities within an academic institution, or a non-accredited commercial laboratory, periodic external validation must be undertaken with an accredited facility. The frequency of these external checks will vary by project and analytical procedure chosen within an individual project. Project Proponents are required to report the frequency of external validation checks within their PDD prior to use of a rock material as a feedstock in a CDR project.

Project Proponents are required to report calibration records (where available) from analytical facilities to the relevant VVB when submitting feedstock characterization data. Projects are also required to outline specific analytical checks that have been carried out to maintain data quality, with specific reference to the relevant certified reference materials (CRM) used by the utilized laboratory facility.

Characterization data should be validated through set quality assurance and quality control (QA/QC) criteria within all Crediting Projects. All projects are required to report their QA/QC processes within the PDD, in accordance with the requirements of this Module. As part of QA/QC Project Proponents are required to clearly describe analytical checks (including duplicate, blanks and analytical standards checks) and calibration procedures.

Project Proponents are required and are responsible for the delivery of rock feedstock characterization data to a project’s VVB. Although a Project Proponent is expected to carry out characterization data externally at an accredited facility, it is the responsibility of the Project Proponent to deliver data that is accurate and externally verifiable. Submitted data reports are required to include results of all standards to verify data quality. Project Proponents are required to maintain data records for a minimum of 5 years following the date of data collection.

Project Proponents are required to report data such that the data analysis methods used are easily identified, verified and replicated. This Module requires that any data reports include the raw data from which any data analysis/reduction was performed, including standards and replicate measurements. A summary containing information on analytical uncertainty, number of samples taken, standards used and number of standard runs, standard deviation and percentage error on the standards must also be included. This may, for example, take the form of a spreadsheet containing four sheets:

• Summary sheet detailing metadata:
  • Number of samples run
  • Analytical uncertainty
  • Standards used
  • Number of standards run
  • Standard deviation
  • Percentage error on standards
• Reduced data sheet (data summary)
• Data reduction sheet (if applicable; e.g. processing of ICP-MS data)
• Raw data

Isometric would like to thank following reviewers of this Module:

• Amanda Stubbs (University of Glasgow)
• James Campbell, Ph.D. (Heriot-Watt University)
• Alison Marklein, Ph.D. (Terradot)
• Christina Larkin, Ph.D. (InPlanet)

This appendix outlines required and recommended analytical techniques and measurements, the parameters they provide, and their purpose in calculation of CO₂ removal and material characterization. Required analyses will be pathway and project-specific. Project Proponents are required to refer to specific Isometric Protocols for pathway-specific requirements. This appendix is intended to provide a comprehensive, but not exhaustive, overview of analytical methods relevant to carbon dioxide removal calculations and feedstock characterization. Any analytical methods not listed here should be submitted for approval and, where applicable, cross-referenced with an appropriate standard (e.g. ISO, EN, BSI, ASTM and EPA) or standardized operating procedure. Where a project utilizes a non-standardized methodology or SOP for the determination of a listed parameter, the Project Proponent is required to outline the relevant method within the PDD submitted to the VVB.

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