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Rock and Mineral Feedstock Characterization
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This Module (Independent components of Isometric Certified Protocols which are transferable between and applicable to different Protocols.) 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 (The organization that develops and/or has overall legal ownership or control of a Removal or Reduction Project.). This moduleModule is intended for use in conjunction with other Isometric pathway level protocolsProtocols and modulesModules. This moduleModule 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 moduleModule are based on best known scientific practices at the time of writing. Requirements may be updated in future versions of this moduleModule in line with changes in scientific consensus. This moduleModule outlines methodologies that may be employed to characterize feedstocks to the best of the projectProject proponentProponent’s ability, considering scientific rigor, method employment economics, best practice and feasibility. Specific analytical method standard details are outlined in Appendix 1.
Within this moduleModule 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
| Measurement Rationale | Determination Methods |
|---|---|---|
Grain size | Assessment of weathering potential Assessment of safety | Required: Gravimetric Sieving Recommended:Particle size analyzer (e.g. laser granulometry) |
Geotechnical Properties | Assessment of weathering potential Determine feedstock characteristics | Recommended: Various. See Section 3.3.1 |
Surface area | Assessment of weathering potential | Required: BET (An analytical method for determining the surface area of a solid or porous material.) surface area |
| Assessment of weathering potential Assessment of safety (e.g. presence of asbestiform minerals) | Required: XRD (X-ray Diffraction: An analytical technique that uses X-rays to study the structure of materials, particularly crystalline materials.) qualitative and/or quantitative Mineral mapping with SEM-EDS (Scanning Electron Microscopy with Energy Dispersive Spectroscopy.)/EDX (e.g., QEMSCAN) Geological maps and information on rock source location Recommended:Light-microscopy Raman spectroscopy Wavelength-dispersive XRF |
Total Carbon and Sulfur | Assessment of baseline carbon content Assessment of acidity production potential | Required: Dry combustion analysis |
Trace and major elemental composition | Assessment of weathering potential Assessment of safety and fertilization potential | Required: ED-XRF (A non-destructive analytical technique that determines the composition of a sample using X-rays.) WD-XRF (A non-destructive analytical technique that determines the elemental composition of a sample by measuring the wavelengths of characteristic X-rays emitted from the sample.) Total digestion of rock (e.g., fusion or multi-acid (HF+HNO3+HCl) digestion) coupled with ICP-MS (Inductively Coupled Plasma Mass Spectrometry: An analytical technique used to measure elements at trace levels within a sample.)/OES (Inductively Coupled Plasma Optical Emission Spectroscopy: An analytical technique used to measure elements at trace levels within a sample.) |
Radiation levels | Assessment of safety | Required: Measurement of gross alpha and beta radioactivity |
It is noted that the requirements outlined in Table 1 are minimum requirements for feedstock used within a creditingCrediting projectProject. 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 proponentsProponents may, in consultation with Isometric, conduct alternative analyses with adequate justification in the Project Design Document (PDD) (The document that clearly outlines how a Project will generate rigorously quantifiable Additional high-quality Removals or Reductions.).
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) (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.) 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:
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 projectProject proponentProponent.
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 creditingCrediting programProject. 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 proponentsProponents 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 creditingCrediting programProject 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 moduleModule 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 moduleModule, projectProject proponentsProponents 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 (X-ray Diffraction: An analytical technique that uses X-rays to study the structure of materials, particularly crystalline materials.) 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 creditingCrediting programProject. Physical characteristics are required to be assessed in line with the methods and standards outlined within this moduleModule. Within this moduleModule, 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 proponentsProponents 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:
Recommended for all pathways, unless otherwise specified asin a required measurement in pathway protocolProtocol:
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 (Particle size distribution.)) and specific surface area analysis for all rock and mineral feedstocks used within creditingCrediting projectsProjects. Within this moduleModule, gravimetric sieving and Brunauer-Emmett-Teller (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 projectProject proponentsProponents 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 projectProject proponentProponent 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 (Particle size distribution.) 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 (A non-destructive X-Ray technique used to investigate the size, shape and distribution of nanoscale particles and other structural features in materials.)) that may be used to estimate mean particle sizes between 1 nm and 100 nm. Where such techniques are utilized by a projectProject proponentProponent 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 Energy dispersive X-ray fluorescence (ED-XRF), wavelength dispersive x-ray fluorescence (WD-XRF) or fusion / acid digestion coupled with inductively coupled plasma mass spectrometry (ICP-MS (Inductively Coupled Plasma Mass Spectrometry: An analytical technique used to measure elements at trace levels within a sample.)) or inductively coupled plasma optical emission spectroscopy (ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy: An analytical technique used to measure elements at trace levels within a sample.)) 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 projectProject proponentProponent can refine elemental analysis to reduce the total number of elements measured. Project proponentsProponents 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.
Major and minor elemental compositions are required to be analyzed via ED-XRF. This analysis is required as it will allow projectProject proponentsProponents 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 moduleModule.
Acid Digestion and/or Fusion coupled with ICP-MS (Inductively Coupled Plasma Mass Spectrometry: An analytical technique used to measure elements at trace levels within a sample.)/OES
It is required that projectProject proponentsProponents 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:
Other elemental measurement techniques
If a Project Proponent chooses to utilize additional elemental measurement techniques, such as Atomic Absorption Spectroscopy (AAS (A technique used in analytical chemistry that measures element concentrations through the application of characteristic wavelengths of electromagnetic radiation from a light source.)) or wavelength dispersive x-ray fluorescence (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 enhancedcarbon weatheringremoval potential of an alkaline rock andor 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:
[math: {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:
The adjusted equation utilizes elemental composition to identify maximum CO2 capture potential of an enhanced weatheringmineralization project ([math: 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 moduleModule. 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 proponentsProponents 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:
[math: 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 creditingCrediting projectsProjects. It is recommended that carbon and sulfur analysis is carried out via combustion analysis in line with the following standards:
Total carbon and sulfur content are required as baseline measurements before a rock feedstock can be utilized within a creditingCrediting programProject by projectProject proponentsProponents.
Consideration of feedstock radiation levels is required prior to rock application. At a minimum, the projectProject proponentProponent 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:
Where an alternative standard is used, documentation of such standard must be provided to the VVB. The projectProject proponentProponent is required to ensure adheranceadherence to all applicalapplicable 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 proponentsProponents 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 creditingCrediting projectsProjects. Mineralogical characterization can be performed through multiple analytical methods, depending on the feedstock source, target mineral phases and the ability of a projectProject proponentProponent to access analytical facilities. Bulk mineral abundance is required for all rock feedstocks, including analysis by X-ray diffraction analysis (XRD (X-ray Diffraction: An analytical technique that uses X-rays to study the structure of materials, particularly crystalline materials.)) 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 X-ray diffraction analysis (XRD (X-ray Diffraction: An analytical technique that uses X-rays to study the structure of materials, particularly crystalline materials.)), light microscopy and/or SEM-EDS (Scanning Electron Microscopy with Energy Dispersive Spectroscopy.) mineral mapping are required to determine a rock feedstock's mineral compositiontype 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 proponentsProponents are required to report bulk mineral abundances for all rock and mineral feedstocks used in CDR creditingCrediting projectsProjects. Project proponentsProponents 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 XRDqXRD, SEM-EDS and/or geologic information.
Rock Feedstock Mineral Abundance Risk Descriptions and Assessments
When assessing the use of potential rock feedstock within creditingCrediting projectsProjects, we require projectProject proponentsProponents to outline key target mineral groups that may pose a project risk. Project risks may include, but are not limited to, the following:
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 creditingCrediting programProject. 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 locationallocal regulatory requirements. The terms mine wastes/by-products within this moduleModule 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 moduleModule, although projectProject proponentsProponents 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 a programprograms should include consideration of the potential environmental implication of utilizing such feedstocks within the creditingCrediting projectsProjects. 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 creditingCrediting projectProject, we recommend that the projectProject proponentsProponents 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:
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:
This moduleModule 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 projectProject proponentsProponents 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 moduleModule, 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 thisthe feedstock to Isometric, itensuring isthat data are spatially representative of the responsibility ofentire project proponentsarea toand undertakethat thesesampling routinecaptures batchboth characterizationshorizontal onand rockvertical variability within the feedstock utilizedused withinin a creditingCrediting projectProject.
A Project Proponent is required to report the analytical laboratory/laboratories that have been utilized for feedstock characterization. It is the responsibility of the projectProject proponentProponent to ensure that the chosen analytical facilities are reputable and conduct characterization techniques to the required standards indicated within this moduleModule and Appendix 1.
It is recommended that Project Proponents should utilize UKAS, MCERTS, DWTS and ISO accredited analytical services whenever feasible. Where a projectProject proponentProponent 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 creditingCrediting programsProjects. All projects are required to report their QA/QC processes within the PDD, in accordance with the requirements of this moduleModule. As part of QA/QC projectProject proponentsProponents 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 projectProject proponentProponent 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 protocolModule 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:
Isometric would like to thank following reviewers of this moduleModule:
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 protocolsProtocols 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 validation and verification body (VVB).
| Analysis | Parameters | Purpose | Example Standard |
|---|---|---|---|
| X-ray diffraction (XRD | Mineralogy | Assessment of weathering potential Assessment of feedstock safety | ASTM D 934-52 |
| X-ray fluorescence (XRF) | Mineralogy Elemental composition reported as oxides | Assessment of weathering potential Assessment of feedstock safety | ISO 12677:2011 |
| Scanning | Mineralogy | Assessment of weathering potential Assessment of feedstock safety | ISO/TS 21383:2021ISO 16700:2016 |
| Electron microprobe (EMP or EPMA) | Mineralogy | Assessment of weathering potential Assessment of feedstock safety | ISO 11938:2012ISO 14595:2023 |
| Light microscopy | Mineralogy | Assessment of weathering potential | No ISO |
| Acid digestion, paired with inductively coupled plasma mass spectrometry (ICP-MS | Major and trace elements | Assessment of weathering potential Assessment of feedstock safety | EPA Method 3050B
ISO 17294-1: |
| Radiation levels | Gross alpha and beta activity | Assessment of feedstock safety | ISO 18589-6:2019 |
| Particle size analysis via gravimetric sieve, laser diffraction, or | Particle size distribution | Assessment of weathering potential | Gravimetric sieving: ISO 11277:2020ISO 17892-4:2016 BS ISO 11277:2020 Laser diffraction:ISO 13320:2020X-ray scattering:ISO 17867:2020 |
| Brunauer Emmett-Teller (BET) | Surface area | Assessment of weathering potential | ISO 9277:2022 |
| Dry combustion | Total carbon, nitrogen, and sulfur | Assessment of weathering potential | ISO 10694:1995ISO 13878:1998ISO 15178:2000 |
| Thermogravimetric analysis (TGA) | Total inorganic carbon (TIC (Total Inorganic Carbon.))Water content | Assessment of carbonation | Water content:ISO 17892-1:2014ASTM D8474-22 |
| Carbon isotopes | δ13C | Geochemical characterization | No ISO |
| Fluid displacement test | Bulk density | Geotechnical characterization | ISO 17892-2:2014 |
| Pycnometer test (fluid or gas displacement) | Particle density | Geotechnical characterization | ISO 17892-3:2015 |
| Incremental loading odometer test | Compressibility | Geotechnical characterization | ISO 17892-5:2017 |
| Fall cone test | Shear strength | Geotechnical characterization | ISO 17892-6:2017 |
| Unconfined compression test | Shear strength | Geotechnical characterization | ISO 17892-7:2017 |
| Unconsolidated undrained triaxial test | Shear strength | Geotechnical characterization | ISO 17892-8:2018 |
| Direct shear test | Shear strength | Geotechnical characterization | ISO 17892-10:2018 |
| Consolidated triaxial compression test on water saturated soils | Shear strength | Geotechnical characterization | ISO 17892-9:2018 |
| Permeability test | Permeability | Geotechnical characterization | ISO 17892-11:2019 |
| Fall cone | Liquid and plastic limits | Geotechnical characterization | ISO 17892-12:2018 |
| Analysis | Parameters | Purpose | Example Standard |
|---|---|---|---|
| Cation extraction | Cation exchange capacity (CEC) | Assessment of soil quality Determination of exchangeable cations | ISO 23470:2018ISO 11260:2018 |
Total soil digest coupled with ICP-MS | Major and trace elements | Assessment of soil quality Determination of weathering by cation mass balance | ISO 17294-1: |
| Calcimetry | Soil inorganic carbon | Determination of secondary carbonate formation | ISO 23400:2021 |
| Ramped combustion coupled with infrared gas analysis | Soil inorganic carbon | Determination of secondary carbonate formation | No ISO |
| Thermo-gravimetric analysis (TGA) | Soil inorganic carbon | Determination of secondary carbonate formation | ASTM D8474-22 |
| Dry combustion | Total carbon, nitrogen, and sulfur | Assessment of soil quality | ISO 10694:1995ISO 13878:1998ISO 15178:2000 |
| Oven drying | Soil moisture | Assessment of weathering potential | ISO 17892-1:2014 |
| Soil slurry measurement | Soil pH | Assessment of weathering potential | ISO 10390:2021 |
| Carbon isotopes | δ13C Radiocarbon | Weathering/carbon dioxide removal calculation | No ISO |
| Particle size analysis via sieving or laser diffraction | Soil texture | Assessment of field heterogeneity | Laser diffraction: ISO 13320:2020 Sieving: ISO 11277:2020 |
| Analysis | Parameters | Purpose | Example Standard |
|---|---|---|---|
| pH | pH | Porewater characterization | ISO 10523:2008 |
| Titration | Alkalinity | Weathering/carbon dioxide removal calculation | ISO 9963-1:1994 |
| Electrical conductivity | Electrical conductivity | Porewater characterization | ISO 7888:1985 |
| Salinity | Salinity | Porewater characterization | No ISO |
| Inductively coupled plasma mass spectrometry | Major and trace elements | Weathering/carbon dioxide removal calculation | ISO 17294-1:2004 |
| Inductively coupled plasma optical emission spectroscopy | Major and trace elements | Weathering/carbon dioxide removal calculation | ISO 11885:2007 |
| Inductively coupled plasma atomic emission spectroscopy | Major and trace elements Soil quality | Weathering/carbon dioxide removal calculation | ISO 22036: |
| Atomic absorption spectroscopy (AAS) | Major and trace elements | Weathering/carbon dioxide removal calculation | ISO 10058-3:2008 |
| Ion chromatography (IC) | Cations Anions | Weathering/carbon dioxide removal calculation | ISO 14911:1998ISO 10304-1:2007ISO 10304-3:2007ISO 10304-4:2022 |
| Stable isotopes | δ13Cδ18OδD | Weathering/carbon dioxide removal calculation | No ISO |
| Filtration | Total suspended solids Dissolved solids | Fluid characterization | ISO 11923:1997 |
| Analysis | Parameters | Purpose | Example Standard |
|---|---|---|---|
| Gas flux chamber | CO2, CH4, N2O flux | Carbon dioxide removal calculation | ASTM WK77257 |
| Eddy covariance tower | CO2, CH4, N2O flux | Carbon dioxide removal calculation | No ISO |
Gas chromatography (coupled with fluid equilibration, if applicable) | Dissolved gasses and/or instantaneous gas concentrations | Gas flux characterization | No ISO |
| Analysis | Parameters | Purpose | Example Standard |
|---|---|---|---|
Sample digestion coupled with ICP-MS | Plant uptake | Cation mass balance calculation | ISO 17294-1: |
| Static testing | Acid generation/neutralization potential | Characterization of waste material | EN 15875:2011 |
| Kinetic testing | Acid generation potential of sulfidic waste from extractive industries | Characterization of waste material | CEN/TR 1636:2012 |
| Weak acid dissociable cyanide | Weak acid dissociable cyanide | Characterization of waste material | CEN/TS 16229:2011 |
| Waste sampling | Waste sampling from extractive industries | Characterization of waste material | CEN/TR 16365:2012 |
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Renforth, P. (2019) The negative emission potential of alkaline materials. Nature Communications 10, 1401. https://doi.org/10.1038/s41467-019-09475-5↩
Nesbitt, HW, and Young, GM. (1982). Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature, 299(5885), 715-717. DOI: https://doi.org/10.1038/299715a0↩↩2
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Babechuk, MG, and Fedo, CM. (2023). Analysis of chemical weathering trends across three compositional dimensions: applications to modern and ancient mafic-rock weathering profiles. Canadian Journal of Earth Sciences, 60(7), 839-864. DOI: https://doi.org/10.1139/cjes-2022-0053↩
Fedo, CM, and Babechuk, MG (2023). Petrogenesis of siliciclastic sediments and sedimentary rocks explored in three-dimensional Al2O3–CaO*+ Na2O–K2O–FeO+ MgO (A–CN–K–FM) compositional space. Canadian Journal of Earth Sciences, 60(7), 818-838. DOI: https://doi.org/10.1139/cjes-2022-0051↩
Thorpe, MT, Hurowitz, JA, Dehouck, E.(2019). Sediment geochemistry and mineralogy from a glacial terrain river system in southwest Iceland, Geochim. Cosmochim. Ac., 263, 140–166,DOI: https://doi.org/10.1016/j.gca.2019.08.003. ↩
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Hosseini-Dinani, H., Mokhtari, A.R., Shahrestani, S. et al. Sampling Density in Regional Exploration and Environmental Geochemical Studies: A Review. Nat Resour Res 28, 967–994 (2019). https://doi.org/10.1007/s11053-018-9431-2↩