Ex Situ Mineralization in Closed Engineered Systems v1.0

1.0

Introduction

This Module details durability and monitoring requirements for storage of CO₂ removed from the atmosphere via engineered carbon removal technology (such as Direct Air Capture) and stored in the solid phase using engineered systems. Durability refers to the length of time for which carbon is removed from the Earth’s atmosphere and cannot contribute to further climate change.

CO₂ mineralization and storage in engineered systems refers to the addition of concentrated CO₂ to an engineered reactor containing crushed rock or mineral feedstock. The use of engineered systems accelerates the natural chemical reaction of mineral carbonation, which constitutes a durable (>1,000 years) CO₂ sink when storage site requirements are met. This is possible because parameters that drive the reaction rate (i.e. temperature, pressure, pCO₂) can be precisely controlled when operating in an engineered reactor. Additionally, because a reactor is a closed system, the amount of carbon stored can be precisely calculated with targeted measurements of the ingoing and outgoing CO₂ stream and feedstock. When implemented correctly, this provides high confidence in the amount of stored CO₂.

Mineralization of CO₂ as carbonate minerals, through reaction with silicate rocks, occurs naturally as part of the weathering process. The carbonation rate of silicate rock can be dramatically increased by increasing reactive surface area and/or the pressure and concentration of CO₂ in the fluid. Mineralization projects can occur at Earth’s surface (open system ex-situ mineralization), in the subsurface (in-situ mineralization), or in closed reactors (ex-situ mineralization in engineered systems). In engineered ex-situ mineralization, a concentrated CO₂ stream is introduced to rock or mineral feedstock, commonly waste materials from mining operations,¹^, ² ^,³ in a reactor to form carbonate minerals.⁴^, ⁵ Because carbonation reactions are kinetically limited in typical surface environments, reactors may be held at elevated temperature and/or pressure and may use feedstock that has been pre-treated (i.e. crushed to a fine grain size, treated with acid or base, and/or heat treated (see Section 3) to increase reactivity⁶. Laboratory and pilot studies estimate that 65-85% of the total carbonation potential of a given feedstock can be achieved in 12 hours.⁶^, ⁷ Given current global estimates of suitable feedstock, this represents a stable sink for carbon dioxide at the mega to gigatonne scale.

Reversal risks are considered to be minimal during the reaction of feedstock and concentrated CO₂. There are further reversal risks associated with storage of carbonated materials. These risks, as well as the monitoring requirements associated with them, are described in detail in the Carbonated Materials Storage and Monitoring Module 1.0.

This Module outlines the requirements for evaluating carbon storage in the solid phase via reaction of feedstock in engineered reactors for mineralization of rock or mineral feedstock, with an emphasis on in-line measurements of influent/effluent CO₂ and mineralogical change in post-reaction feedstock. Requirements for reactor design, calculation of carbon stored and CO₂ monitoring are given in Sections 2, 4 and 5 of this Module respectively. Requirements for feedstock characterization can be found in the Rock and Mineral Feedstock Characterization Module 1.0. Monitoring requirements for storage cases are detailed in the Carbonated Materials Storage and Monitoring Module 1.0.

1.1

Project Types and Applicability

This Module is applicable to any Project in which a rock or mineral feedstock is carbonated in an engineered system. This may include, but is not limited to:

Direct gaseous mineral carbonation, in which CO₂ is introduced into the reactor in gaseous form
Direct aqueous mineral carbonation, in which CO₂ is either:
- dissolved in water and introduced into the reactor
- bubbled through a reactor containing liquid
Indirect mineral carbonation, in which metals are leached from rock or mineral feedstock and precipitated as carbonate minerals in a subsequent step. Project Proponents employing indirect mineral carbonation methods, such as a pH swing method (e.g. Azdarpour et al. 2015)⁸ are required to adhere to fluid monitoring requirements at each step of the process.

Details of the carbonation method employed must be described in the Project Design Document (PDD). This description should include:

Whether the method is classified as direct gaseous mineral carbonation, direct aqueous mineral carbonation, or indirect mineral carbonation
Any pre-treatment of the feedstock, as described in Section 3
At which point CO₂ is introduced into the reactor
Details of reactor design, as described in Section 2

2.0

System Requirements

To be eligible for carbon credits using this Module, CO₂ must be reacted with feedstock in an engineered reactor. This Section details the requirements for reactor design and maintenance. These requirements are applicable to any and all reactors used in the project. For example, if a project uses an indirect carbonation method (see Section 1.1), reactors used at each step of the process must adhere to the requirements outlined in Section 1.1.

2.1

Reactor Type

Any type of engineered chemical reactor is eligible under the Module, provided that the reactor design requirements set out in Sections 2.2, 2.3, 2.4 and 2.5 below are satisfied. Acceptable reactor types include, but are not limited to, stirred tanks (batch, semi-batch or continuous) and tubular reactors (plug flow, fixed bed, fluidized bed, bubble bed or trickle bed). This list is meant to be comprehensive, but not exhaustive. A brief overview of common reactor types covered under this Module is provided in Table 1. Novel reactor designs not belonging to any of the categories listed here will be acceptable provided that the appropriate reactor design documentation according to Section 2.2 is supplied in the PDD. All reactor designs, including the reactor type, engineering design diagrams, reactor modeling calculations and materials selection must be described in the PDD.

2.2

Design Diagram Requirements

An engineering design diagram of the chemical reactor must be included in the PDD. The design diagram must include details of the dimensions of the reactor, the locations of material inflows/outflows, the positioning of sensors for the monitoring of flow rate, reactant/product chemical composition, temperature and pressure, details of any internal equipment such as agitators or heating/cooling coils and details of any external heat transfer equipment (including heat exchange fluid entry/exit points and corresponding sensors for flow rate and temperature). A sufficient number of viewpoints must be included in the engineering design diagram to show the positioning of all of the key components listed above. Any other process equipment essential to the safe and effective operation of the reactor not listed above should be included and highlighted in the engineering design diagram.

2.3

CO|2| and Feedstock Loss

CO₂ and Feedstock Loss

The reactor design must include sensors necessary to quantify any loss of CO₂ from the feedstock during operation of the reactor to leakage. This should include, at a minimum, sensors to determine the inflow/outflow of carbon dioxide from the reactor, to be used in conjunction with a suitable reactor model to determine the amount of carbon dioxide reacted and to estimate any loss of carbon dioxide to leakage. Only carbon dioxide which has been determined by this calculation to have undergone complete chemical reaction into a solid mineral product is eligible for carbon credits issued under this Module.

In addition to loss of CO₂ from the reactor, Project Proponents should consider the possibility of rock or mineral feedstock loss from the reactor in applicable systems. For example, in a packed bed or fluidized bed reactor using CO₂ dissolved in liquid, it is necessary to set flow rates such that loss of solid feedstock particles from the system is minimized. Projects using reactors in which this is a risk are required to characterize solid feedstock loss; further detail is given in Section 5.1.3.

The chemical reactor model used to characterize reactor performance and estimate CO₂ and solid feedstock losses should consider all physical and chemical mechanisms relevant to operation of the chosen reactor type. The chemical reactor model should incorporate a chemical kinetics model which is based on the latest scientific understanding for the chosen chemical reaction pathway. Where chemical kinetics are derived from in-house experimental measurements, details of the experimental procedure used to perform these measurements should be included in the PDD.

2.4

Construction Considerations

Suitable mass/volume flow meters must be placed on all material inlets/outlets from the reactor to allow for characterization of reactor performance and to monitor any material losses to the environment. These sensors should be positioned immediately upstream/downstream of the reactor, as appropriate. Suitable sensors to measure pressure, temperature and pH (if applicable) should be implemented to allow for accurate characterisation of the reactor performance through a combination of measurements and modeling. For stirred tank reactor types, these sensors should be placed so that they accurately characterize the measured property in the bulk phase of the reactor. For tubular reactors, two (or more) measurements of each property at different locations may be necessary to accurately characterize the reactor performance. In this case, several sensors should be placed along the length of the reactor. Justification for the positioning of such sensors for characterization of reactor performance should be provided in the PDD.

It is anticipated that operation of the chemical reactor may occur at high temperature and pressure, and that the pH inside the reactor may be acidic. Appropriate considerations need to be made in the design of the reactor to mitigate these operational conditions to ensure operational loss prevention. Details must be provided in the PDD to describe the selection of materials for each component of the reactor, including suitable justification for these choices from the perspectives of heat and corrosion resistance. For reactors operating at high pressures, considerations should be made relating to the operating pressure, vessel shape/size, positioning of material inlets/outlets, and positioning of sensors to ensure mechanical integrity of the reaction vessel. Such considerations should be made in compliance with a suitable local standard which provides regulations for the design and fabrication of pressure vessels, such as 2014/68/EU (the “Pressure Equipment Directive”) or an appropriate regional equivalent standard in the region of operation. If no such regional standard exists in the area of operation, Project Proponents are required to use the 2014/68/EU standard.

2.5

Reactor maintenance

Project Proponents are required to implement an appropriate reactor maintenance plan should be in place, and must be detailed in the PDD. The maintenance plan should outline how the Project Proponent will ensure the structural integrity of the reactor vessel to mitigate against potential material loss events. This includes suitable monitoring and mitigation for mechanical, thermal and corrosive events which may lead to failure of the vessel and subsequent release of reaction materials into the environment. All maintenance plans should be in compliance with a suitable local standard which provides regulations for the maintenance of pressure vessels, such as 2014/68/EU or an appropriate regional equivalent standard in the region of operation.

Table 1. Reactor type overview

Reactor Category	Reactor Type	Description
Stirred tank	Batch	A closed well-mixed batch system where reactants are added to the vessel at the start of the batch, and products are removed from the vessel at the end of the batch. Mixing is provided by stirring with an agitator.
	Semi-batch	A well-mixed batch system where reactants are added to the vessel at the beginning of the batch, and products are removed at the end of the batch. Reactants and/or products may be added/removed from the vessel over time throughout the batch. Mixing is provided by stirring with an agitator.
	Continuous	An open well-mixed system where reactants and products are both added/removed from the vessel continuously. Mixing is provided by stirring with an agitator.
Tubular	Plug flow	A simple open tubular reactor where reactants flow through the vessel and chemical reaction occurs along the length of the vessel.
	Fixed bed	An open tubular multiphase reactor where reactants flow over a fixed packed bed of solid reactive material. Chemical reaction occurs along the length of the vessel.
	Fluidized bed	An open tubular multiphase reactor where reactants fluidize a bed of solid reactive material. Fluid reactants and solid material flow co-currently within the vessel. Chemical reaction occurs along the length of the vessel.
	Bubble bed	An open tubular multiphase reactor where gaseous reactants flow in a vessel saturated with liquid. The gaseous species migrate through the column as bubbles of gas. Chemical reaction occurs along the length of the vessel.
	Trickle bed	An open tubular multiphase reactor where liquid reactants flow downwards over a packed bed of reactive solids, while gaseous species flow upwards. Chemical reaction occurs along the length of the vessel.

3.0

Feedstock Characterization and Pre-Treatment

All feedstocks must be characterized according to the Rock and Mineral Feedstock Characterization Module 1.0 prior to commencement of project activities. Note that Project Proponents are required to perform a full suite of geotechnical characterization measurements for all feedstocks used in ex-situ mineralization projects. Ex-situ mineralization projects are additionally required to characterize carbonated feedstocks according to the Rock and Mineral Feedstock Characterization Module 1.0 prior to storage in accordance with the Carbonated Materials Storage and Monitoring Module 1.0.

Some Project Proponents may choose to pre-treat their feedstock to increase reactivity.

Methods of pre-treatment may include, but are not limited to:

Additional crushing or grinding after obtaining feedstock material but prior to the onset of project activities
Thermal activation, particularly if using serpentinite minerals⁹
Chemical activation using reagents, which may include (but is not limited to):
- NaOH⁹
- H₂SO₄⁹
- Oxalate¹⁰
- HCl¹¹
- Citrate¹²

Any pre-treatment must be fully described in the PDD, including:

Rationale for pre-treatment
Method used
Physical and chemical characteristics of the feedstock after pre-treatment, if employing thermal or chemical activation methods
- Particle Size Distribution (PSD)
- Surface area
- Total Inorganic Carbon (TIC)

Project Proponents using a thermal activation method for feedstock pre-treatment must demonstrate that there were no carbonate minerals in the feedstock prior to heating. If carbonate minerals are present in the feedstock prior to pre-treating, Project Proponents are required to characterize the mass of carbon lost during heating and include this in calculations of Greenhouse Gas Emissions (GHG) emissions related to project activities.

4.0

Calculation of CO|2| Storage via Ex-situ Mineralization in Engineered Systems

Calculation of CO₂ Storage via Ex-situ Mineralization in Engineered Systems

4.1

Summary

This section details the calculation of net CO₂ storage for ex-situ mineralization projects. The monitoring requirements are described in detail in Section 5. Ex-situ mineralization projects are subject to some additional monitoring requirements associated with pre-treated and carbonated feedstocks, including the geochemical and physical characteristics of carbonated feedstocks (see Section 3, Section 5.3 and the Rock and Mineral Feedstock Characterization Module 1.0) and reversal risk monitoring associated with the storage conditions of carbonate materials (see Carbonated Materials Storage and Monitoring Module 1.0).

4.2

Calculation of CO|2|e|Stored

Calculation of CO₂e_Stored

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

 $CO_2e_{Stored, RP} = CO_2e_{Mineralized, RP} - CO_2e_{Counterfactual, RP} - CO_2e_{Emissions, RP}$

Equation 1

Where:

$CO_2e_{Stored, RP}$ is the net quantity of CO₂ stored as a result of project activities during a reporting period, in tonnes of CO₂e.
$CO_2e_{Mineralized, RP}$ is the total quantity of inorganic carbon stored in the solid form during a reporting period, in tonnes of CO₂e.
$CO_2e_{Counterfactual, RP}$ is the amount of inorganic carbon that would be stored in a given feedstock across the lifetime of a carbon credit, in tonnes of CO₂e
$CO_2e_{Emissions, RP}$ is the total quantity of GHG emissions from project activities for a reporting period, in tonnes of CO₂e.

Calculation of CO₂e_{Mineralized^.}

4.2.1

| can be calculated as:

$CO_2e_{Mineralized}$ can be calculated as:

 $CO_2e_{Mineralized, RP} =\sum \Delta CO_2e_{Mineralized, T2 - T1, MP} - \sum CO_2e_{Losses, MP}$

Equation 2

Where:

$CO_2e_{Mineralized, T2 - T1, MP}$ is the difference in total inorganic carbon (TIC) present as carbonate minerals in the feedstock before and after reaction, summed across a measurement period. Measurement periods can either be equal to a reporting period, or divided into small time intervals which are then summed across the length of the reporting period.
$CO_2e_{Losses, MP}$ is the sum of CO₂ reversals across a measurement period. Measurement periods can either be equal to a reporting period, or divided into small time intervals which are then summed across the length of the reporting period. Details on calculation of $CO_2e_{Losses, MP}$ are given in the Carbonated Materials Storage and Monitoring Module 1.0.

$CO_2e_{Mineralized, T2 - T1, MP}$ must be calculated from direct measurements of feedstock prior to and following the carbonation reaction. Feedstock characterization is required to include quantification of pre-existing carbonate minerals; these analyses must be conducted for every batch of feedstock, as defined in the Rock and Mineral Feedstock Characterization Module 1.0.

4.2.2

Calculation of CO|2|e|Counterfactual

Calculation of CO₂e_{Counterfactual}

$CO_2e_{Counterfactual, RP}$ is defined as the amount of inorganic carbon that would have been stored in the aqueous or solid phase as a result of passive weathering of the feedstock used, without project intervention, across a credit lifetime (in this case, 1,000 years). In calculating $CO_2e_{Counterfactual}$ , this is the default assumption if no additional information regarding the storage conditions and duration of the feedstock at the mine/quarry site can be provided. If additional information on the conditions and duration of feedstock storage at the feedstock supplier are available, Project Proponents may justify calculating the counterfactual across a time period relevant to the specific mine or quarry from which the feedstock is sourced in the PDD. For example, projects operating in conjunction with active mines may find it appropriate to use the time of mine closure and provide details of the closure plan in the PDD; alternatively, if sufficient documentation exists suggesting that piles of waste materials generated by the feedstock will not be exposed to ambient environmental conditions for a period exceeding a set number of years, the counterfactual may be considered across that time span.

Additionally, it is important to note that studies have shown that the vast majority of weathering in tailings piles occurs in the surface layer that is exposed to the atmosphere, provided that there is no mechanical overturn¹³^,¹⁴^,¹⁵. For this reason, counterfactual weathering needs to be accounted for in the top meter of the tailings pile.

$CO_2e_{Counterfactual, RP}$ must be calculated by a combination of direct measurements and modeling of the expected weathering rate of feedstock under storage conditions relevant to the source site for either 1,000 years or a time period justified in the PDD as described above. Models must be justified by empirical data from subsamples of the feedstock; guidelines for sampling procedures that adequately capture feedstock heterogeneity are described in the Rock and Mineral Feedstock Characterization Module 1.0. Models must take into account:

Feedstock mineralogy (direct measurement)
Feedstock surface area (direct measurement)
Baseline carbonation of the tailings pile (direct measurement)
Carbon Dioxide Removal (CDR) potential of the tailings pile in the top meter (calculated from direct measurements)
Environmental conditions of the source site (direct measurement or publicly available data), including:
- Temperature
- Average yearly precipitation
- Rainwater pH
- Groundwater pH
- Carbonate saturation
Permeability (direct measurement or calculated from direct measurement)
Water saturation (direct measurement or calculated from direct measurement)
Microbial activity (direct measurement)

The measurements and model used to calculate $CO_2e_{Counterfactual}$ must be provided to Isometric and the VVB. Project Proponents may choose to either assume the total counterfactual as a one-time deduction or to spread the counterfactual deduction across a project lifetime.

4.2.3

Calculation of CO|2|e|Emissions

Calculation of CO₂e_Emissions

$CO_2e_{Emissions}$ is the total greenhouse gas emissions associated with a given Reporting Period, RP.

Equations and emissions calculation requirements for $CO_2e_{Emissions}$ , including emissions associated with reactor operations and reaction monitoring, are set out in the relevant Protocol and are not included in this Module.

5.0

Monitoring Requirements

5.1

Fluid measurements

This Module requires that fluids are characterized at the point of fluid introduction (influent) and at the point of fluid exit from the system (effluent). Where applicable, analytical methods must be cross-referenced with an appropriate standard (e.g. ISO, EN, BSI, ASTM, EPA) or standard 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 project design document (PDD) submitted to the Validation and Verification Bodies (VVB). Note that this Module does not prescribe specific measurement methods, though suggested methods are included. Novel measurement methods may be considered on a case-by-case basis. Further detail is given in Section 5.4.

5.1.1

Baseline Characterization

Project Proponents are required to characterize the amount of non-carbonic acid present in the water source used prior to commencement of project activities. This is to determine the potential risk of non-carbonic acid for dissolution of precipitated carbonates in ex-situ mineralization projects. This must be measured as major anions in the water source, including NO_3^-, Cl^-, PO_4^3-, SO_4^2-, and any other anions relevant to the specific fluid and feedstock used. Measurement methods should comply with ISO 10304-1:2007 or an equivalent national standard. If anion measurements are made on the influent by a partner facility (e.g. wastewater treatment plant, industrial facility), these values may be substituted for direct measurements. To conservatively calculate weathering that occurs as a result of non-carbonic acid, Project Proponents choosing to substitute this data for measurements must assume that all non-carbonic acid present in the fluid will react with feedstock:

 $CO_2e_{Non-carbonic acid} = \sum_i c_i n_i$

Equation 3

Where:

$c_i$ is the charge of the anion
$n_i$ is the concentration of the anion in solution in ppm

The concentration of non-carbonic acid in the source fluid must be reported in the PDD. Project Proponents are strongly encouraged to calculate the expected losses related to non-carbonic acid and compare this value to expected CO₂ storage based on feedstock characteristics to ensure that the water source is suitable for the project.

Depending on the source of the fluid, the concentration of anions may be highly temporally variable. Project Proponents using direct measurements must provide details of their baseline sampling plan and describe how the chosen sampling frequency is appropriate for capturing any significant variation in concentration in the water source.

5.1.2

Carbonic acid system

This Module requires direct monitoring of the carbonic acid system to verify storage via ex-situ mineralization. To adequately constrain the carbonic acid system within the engineered reactor, Project Proponents are required to measure at least two of the following parameters in both the influent and effluent fluids:

pH (via direct measurement -- [ISO 10523:2008])
Alkalinity (via titration -- [ISO 9963-1:1994])
Dissolved Inorganic Carbon (DIC; via acid titration or infrared detection)
pCO2 (via in-line sensor or headspace equilibration and gas chromatography)

To reduce uncertainty in carbonic acid system calculations, it is highly recommended to measure all four of these parameters where possible. Bicarbonate (HCO3^-) and carbonate (CO3^2-) can then be calculated using the two-for-six method¹⁶, which is commonly accomplished using PHREEQC (typically used for freshwater) software. Project proponents are required to submit data for all parameters of the carbonic acid system, both measured and calculated; where calculations were performed using methods other than PHREEQC, Project Proponents are required to submit the script or spreadsheet where the calculations were made.

Due to the high CO₂ concentrations in reactor streams, it is critical that samples are stored properly and analyzed as soon after collection as possible to mitigate any potential re-equilibration of the carbonic acid system. Samples must be stored in refrigerated conditions without headspace in sealed vials. Sample collection procedures and sample storage conditions must be described in the PDD. Where possible, measurement via in-line sensors is highly recommended. Where in-line sensors are installed, Project Proponents are required to report calibration data and frequency, fluid flow paths through the sensor and measurement error (as determined by measurement of standards).

As part of reporting carbonic acid system measurements, Project Proponents must describe in detail the point at which concentrated CO₂ is introduced to the system, whether it is dissolved in water prior to introduction into the reactor or if it is introduced into the reactor directly via bubbling or similar. Where possible, the CO₂ concentration of the influent must be measured directly. Where this is not possible (e.g. in instances where CO₂ is introduced to the reactor directly), Project Proponents must calculate a conservative estimate of CO₂ concentration using the concentration of the CO₂ stream, the reactor volume, and the partial pressure of CO₂ in the reactor. All calculations must be described and reported in the PDD.

5.1.3

Turbidity/Total Suspended Solids

In engineered systems where feedstock may be lost, such as fluidized bed reactors, Project Proponents are required to monitor feedstock loss from the system. This should be monitored using turbidity/total suspended solids sensors installed at the influent and effluent points. Alternate methods of quantifying feedstock loss may be appropriate and must be described and justified in the PDD.

5.1.4

Major and Trace Elements

This Module requires a full suite of elemental analyses in influent and effluent samples. Fluid samples must be analyzed by either inductively coupled plasma mass spectrometry (ICP-MS; [ISO 17294-1:2004]) or inductively coupled plasma optical emission spectroscopy (ICP-OES; [ISO 11885:2007]) as the primary determination method. Project proponents should take analytical precision and detection limits into account when determining their measurement method. Project proponents are required to describe their measurement methods in the PDD. When reporting data from ICP-MS/OES, project proponents must include information on calibration standards, blanks, and geostandards; requirements for data reports are described in the Rock and Mineral Feedstock Characterization Module 1.0).

5.1.5

Requirements for Direct Carbonation Processes

For Projects employing a direct carbonation method, in which concentrated CO₂ is introduced directly into the reactor without being dissolved in water, Project Proponents are exempt from liquid-phase measurements; instead, influent CO₂ concentration must be reported. Reactors must be closely monitored for any potential leakage of CO₂ and this monitoring plan must be provided in the PDD.

5.2

System Measurements

As outlined in Section 2.4, measurements of temperature, pressure, flow rate and/or pH inside the reactor at one or more locations (depending on the reactor type) may be required for (i) characterization of loss of CO₂ due to leakage from the reactor, and/or (ii) as part of a maintenance plan to ensure reactor integrity in terms of thermal, mechanical, or corrosive containment failures. Measurement methods to determine temperature should comply with the ASTM Temperature Measurement Standards, or an equivalent standard in the region of operation. Measurement methods to determine pressure should comply with ASME 19.2-2010, or an equivalent standard in the region of operation. Measurement methods to determine pH should comply with ASTM E70-19, or an equivalent standard in the region of operation. Reactor modeling conducted for quantification of CO₂ loss due to leakage from the reactor should follow best practice reactor modeling principles. Owing to the variety of valid approaches which could be used to accurately model the performance of a given chemical reactor, justification of the chosen reactor model formulation should be supplied in the PDD.

5.3

Characterization of Carbonated Materials

In addition to feedstock characterization prior to introduction to the reactor, ex-situ mineralization projects are required to characterize their materials post-carbonation, following the requirements in the Rock and Mineral Feedstock Characterization Module 1.0. This is required for all ex-situ mineralization projects, including those choosing to quantify carbon removal based on aqueous phase measurements, as the physical and geochemical characteristics of carbonated materials are critical for determining appropriate storage conditions and reversal risk monitoring (detailed further in the Carbonated Materials Storage and Monitoring Module 1.0).

Project Proponents must describe their sampling plan in detail in the PDD, paying particular attention to how it addresses heterogeneity in the carbonated feedstock. This includes variation associated with the degree of carbonation, grain sorting based on particle size, geochemical variability inherent to the source material, or any other feedstock characteristics that may introduce bias into the quantification scheme.

5.4

Verification of Novel Measurement Methods

Novel measurement methods may be permissible for quantification of any parameter and will be examined on a case-by-case basis. To be eligible, Project Proponents must demonstrate that the novel measurement technique performs within error of conventional methods for all system variation that can be expected under normal operational conditions. Where system variability is well-characterized, Project Proponents may choose to perform this comparison at intervals that reflect the full variability of the system. If this is not possible, due to high variability or lack of system characterization, this comparison must be performed across a full reporting cycle. System variability characterization must include the following parameters:

The parameter targeted by the novel measurement method
Operational temperature
Operational pressure
Flow rate
pH

6.0

Storage

The final storage reservoir for ex-situ mineralization projects is in the carbonated materials removed from the reactor. Modeling and monitoring requirements associated with storage of carbonated materials are given in the Carbonated Materials Storage and Monitoring Module. Carbonated Materials Storage and Monitoring Module 1.0.

Monitoring requirements for storage in carbonated materials

8.0

Definitions and Acronyms

ActivityThe steps of a Project Proponent’s Removal or Reduction process that result in carbon fluxes. The carbon flux associated with an activity is a component of the Project Proponent’s Protocol.
BaselineA set of data describing pre-intervention or control conditions to be used as a reference scenario for comparison.
Carbon Dioxide Removal (CDR)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.
ConservativePurposefully 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.
CounterfactualAn assessment of what would have happened in the absence of a particular intervention – i.e., assuming the Baseline scenario.
DurabilityThe 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.
LeakageThe increase in GHG emissions outside the geographic or temporal boundary of a project that results from that project's activities.
ModuleIndependent components of Isometric Certified Protocols which are transferable between and applicable to different Protocols.
ProjectAn activity or process or group of activities or processes that alter the condition of a Baseline and leads to Removals or Reductions.
Project Design Document (PDD)The document that clearly outlines how a Project will generate rigorously quantifiable Additional high-quality Removals or Reductions.
Project ProponentThe organization that develops and/or has overall legal ownership or control of a Removal or Reduction Project.
ProtocolA 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.
ReversalThe 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.
SinkAny process, activity, or mechanism that removes a greenhouse gas, a precursor to a greenhouse gas, or an aerosol from the atmosphere.
StorageDescribes 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”.
UncertaintyA lack of knowledge of the exact amount of CO₂ removed by a particular process, Uncertainty may be quantified using probability distributions, confidence intervals, or variance estimates.

9.0

Appendix 1: Monitoring Requirements

	Parameter	Rationale	Possible Measurement Technique/Standards	Requirements	Acceptable Data Sources	Public on registry/Private
Fluid Measurements	pH	One component of the carbonic acid system, used to calculate the concentration of dissolved CO₂ in a fluid. Note that at least 2 components of the carbonic acid system must be directly measured.	In-line pH sensor Discrete pH measurements	Required for influent and effluent samples	Direct measurement or calculation using a 2 for 6 model	Public
	Dissolved Inorganic Carbon (DIC)	One component of the carbonic acid system, used to calculate the concentration of dissolved CO₂ in a fluid. Note that at least 2 components of the carbonic acid system must be directly measured.	Total carbon analyzer	Required for influent and effluent samples	Direct measurement or calculation using a 2 for 6 model	Public
	Total Alkalinity	One component of the carbonic acid system, used to calculate the concentration of dissolved CO₂ in a fluid. Note that at least 2 components of the carbonic acid system must be directly measured.	Titration	Required for influent and effluent samples	Direct measurement or calculation using a 2 for 6 model	Public
	pCO₂	One component of the carbonic acid system, used to calculate the concentration of dissolved CO₂ in a fluid. Note that at least 2 components of the carbonic acid system must be directly measured.	In-line pCO₂ sensor Headspace equilibration + gas chromatography	Required for influent and effluent samples	Direct measurement or calculation using a 2 for 6 model	Public
	Turbidity	Determination of rock or mineral feedstock loss	Turbidity sensor	Required for influent and effluent samples for projects in which rock or mineral feedstock may be lost from the system due to fluid flow	Direct measurement	Private
	Total Suspended Solids	Determination of rock or mineral feedstock loss	Total suspended solids sensor Filtration test	Required for influent and effluent samples for projects in which rock or mineral feedstock may be lost from the system due to fluid flow	Direct measurement	Private
	Major and trace elements	Determination of weathering by mass balance Determination of trace metal concentrations for regulatory compliance	ICP-MS ICP-OES	Required for influent and effluent samples	Direct measurement	Public
	Anions	Determination of strong acid concentration	Ion chromatography	Required for baseline samples	Direct measurements Regulatory data may be substituted if available	Private
	Electrical conductivity	Can serve as an additional parameter in 2 for 6 calculations to reduce uncertainty	In-line conductivity sensor	Recommended for baseline, influent and effluent samples	Direct measurement	Private
System Measurements	Pressure	Reactor performance monitoring	Pressure gauge	Required in reactors; variable based on reactor type	Direct measurement	Private
	Temperature	Reactor performance monitoring Calculation of reaction kinetics	In-line thermometer	Required in reactors; variable based on reactor type	Direct measurement	Private
	Flow rate	Reactor performance monitoring Chemical reactor model input	Flow meter	Required in reactors; variable based on reactor type	Direct measurement	Private
Feedstock Measurements	Mineralogy	Assessment of CDR potential and environmental risk	X-ray diffraction (XRD) Scanning electron microscopy (SEM)	Required prior to and following carbonation	Direct measurement	Public
	Major and trace elements	Assessment of CDR potential and environmental risk	Acid digestion coupled with ICP-MS Acid digestion coupled with ICP-OES X-ray fluorescence (XRF)	Required prior to and following carbonation	Direct measurement	Private
	Particle Size Distribution	Reaction rate and chemical reactor modeling	Gravimetric sieving Laser diffraction X-ray scattering	Required prior to and following carbonation	Direct measurement	Private
	Surface Area	Reaction rate modeling	Brunauer Emmett Teller (BET) analysis	Required prior to and following carbonation	Direct measurement	Private
	Total Inorganic Carbon (TIC)	Determination of carbonation	Thermogravimetric analysis (TGA)	Required prior to and following carbonation	Direct measurement	Public

10.0

Appendix 2: Project Design Document Requirements

Reactor Design	Parameter	Documentation Required	Requires justification	Other Requirements
	Reactor Type	Engineering Design Diagram	Yes
	Materials Selection	Engineering Design Diagram	Yes
	Sensor Positioning	Engineering Design Diagram	Yes
	CO₂ Introduction Point	Engineering Design Diagram	Yes
	Reactor modeling calculations	Chemical reactor model	Yes	If in-house experimental measurements are used to derive chemical kinetics, experimental procedures and measurements must be provided
	Reactor maintenance plan	Documentation detailing the maintenance plan	Yes
Feedstock	Requirements detailed in the Rock and Mineral Feedstock Characterization Module 1.0
Feedstock Pre-treatment, if used	Pre-treatment Method	Pre-treatment plan	Yes	Standard method or laboratory SOP must be provided
Feedstock Pre-treatment, if used	Physical and chemical characteristics of feedstock after pre-treatment	Data report, including particle size distribution, surface area, and total inorganic carbon	No	Methods used for feedstock characterization must be provided
Counterfactual	Model timescale	Counterfactual weathering model	Yes	If using a timescale other than the default of 1,000 years, documentation must be provided to support the timescale claimed.
	Source site temperature	Data report	No
	Source site average yearly precipitation	Data report, generated either by rain gauges installed by the Project Proponent or sourced from a weather station	Yes – justification of data source
	Source site average rainwater pH	Data report, generated either by direct measurements by the Project Proponent or sourced from a weather station	Yes – justification of data source
	Source site average groundwater pH	Data report, generated either from direct measurements by the Project Proponent or sourced from a groundwater database	Yes – justification of data source
Measurements	All measurements listed in Appendix 1 must be reported in the PDD	Data report	Yes, where alternate methods than those listed are used	Standard and calibration data must be provided alongside measurements. All standards or SOPs used for measurements must be provided.
Measurements	Carbonic acid system calculations	Data report and calculations used (spreadsheet, script)	No
Sampling	Feedstock sampling plan and procedure	See guidance in the Rock and Mineral Feedstock Characterization Module 1.0	Yes	Sampling plans should be provided for raw feedstock, carbonated feedstock, and pre-treated feedstock (if applicable)
	Fluid sampling plan and procedure	Detailed description of fluid sampling, both temporally and spatially, and the sampling procedure	Yes
	Aqueous sample storage	Detailed description of storage conditions for aqueous samples	Yes
Miscellaneous	Any significant but allowable deviation from the requirements outlined in this Module, as approved in consultation with Isometric	Detailed documentation appropriate to the deviation	Yes

11.0

Appendix 3: Measurement Frequency

	Parameter	Measurement Frequency	Rationale
Fluid Measurements	pH	Continuous or pre-defined time steps	pH can be continuously monitored through in-line pH sensors. Discrete pH measurements should be taken at regular intervals to confirm the functionality of in-line sensors. The sampling cadence will be determined by reactor type and flow rate.
	Dissolved Inorganic Carbon	Pre-defined time steps	Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with other measurements of the carbonic acid system (e.g. tied to a time on continuous sensor output or taken from a volume of fluid collected at the same sampling interval).
	Total Alkalinity	Pre-defined time steps	Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with other measurements of the carbonic acid system (e.g. tied to a time on continuous sensor output or taken from a volume of fluid collected at the same sampling interval).
	pCO₂	Continuous or pre-defined time steps	pCO₂ can be monitored continuously through in-line pCO₂ sensors. Where in-line pCO₂ sensors cannot be installed, discrete measurements may be substituted. Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with other measurements of the carbonic acid system (e.g. tied to a time on continuous sensor output or taken from a volume of fluid collected at the same sampling interval).
	Turbidity	Continuous	Turbidity can be monitored continuously through in-line turbidity sensors.
	Total Suspended Solids	Continuous or pre-defined time intervals	Total suspended solids can be monitored continuously through in-line suspended solids sensors. Discrete measurements can be substituted for in-line measurements. Project Proponents choosing to monitor TSS through discrete measurements must justify the time intervals of measurement based on reactor type, flow rate through the reactor and particle size distribution of the feedstock.
	Major and trace elements	Pre-defined time intervals	Measurement of major and trace elements requires discrete sampling. Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with sampling for other geochemical measurements.
	Anions	Baseline and pre-defined time intervals	Anion measurements are required for baseline fluids and at regular intervals if a strong risk of non-carbonic acid weathering is identified. Measurement of anions requires discrete sampling. Sampling cadence for applicable projects will be determined by the reactor type and flow rate. This must be temporally consistent with sampling for other geochemical measurements.
	Electrical Conductivity	Continuous or pre-defined time intervals	Electrical conductivity can be measured continuously using in-line conductivity sensors. Project Proponents choosing to measure electrical conductivity may also use discrete measurements. Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with sampling for other geochemical measurements.
System Measurements	Pressure	Continuous	Pressure should be measured continuously by an in-line pressure gauge.
	Temperature	Continuous	Temperature should be measured continuously by an in-line thermometer.
	Flow Rate	Continuous	Flow rate should be measured continuously by an in-line flow meter.
Feedstock Measurements	Mineralogy	Prior to and following carbonation, as well as following any feedstock pre-treatment	Mineralogy of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.
	Major and Trace Elements	Prior to and following carbonation	Geochemical composition of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.
	Particle Size Distribution	Prior to and following carbonation, as well as following any feedstock pre-treatment	Particle size distribution of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.
	Surface Area	Prior to and following carbonation, as well as following any feedstock pre-treatment	Surface area of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.
	Total Inorganic Carbon (TIC)	Prior to and following carbonation, as well as following any feedstock pre-treatment	TIC of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions, as well as to ensure accurate accounting of carbon storage.

12.0

Relevant Works

Bodénan, Françoise, et al. "Ex situ mineral carbonation for CO2 mitigation: Evaluation of mining waste resources, aqueous carbonation processability and life cycle assessment (Carmex project)." Minerals Engineering 59 (2014): 52-63. ↩
Pan, Shu-Yuan, et al. "An innovative approach to integrated carbon mineralization and waste utilization: A review." Aerosol and Air Quality Research 15.3 (2015): 1072-1091. ↩
Hills, Colin D., Nimisha Tripathi, and Paula J. Carey. "Mineralization technology for carbon capture, utilization, and storage." Frontiers in Energy Research 8 (2020): 142. ↩
Power, Ian M., et al. "Carbon mineralization: from natural analogues to engineered systems." Reviews in Mineralogy and Geochemistry 77.1 (2013): 305-360. ↩
Romanov, Vyacheslav, et al. "Mineralization of carbon dioxide: a literature review." ChemBioEng Reviews 2.4 (2015): 231-256. ↩
Gerdemann, Stephen J., et al. "Ex situ aqueous mineral carbonation." Environmental science & technology 41.7 (2007): 2587-2593. ↩ ↩²
Huijgen, Wouter JJ, Geert-Jan Witkamp, and Rob NJ Comans. "Mechanisms of aqueous wollastonite carbonation as a possible CO2 sequestration process." Chemical engineering science 61.13 (2006): 4242-4251. ↩
Azdarpour, Amin, et al. "A review on carbon dioxide mineral carbonation through pH-swing process." Chemical Engineering Journal 279 (2015): 615-630. ↩
Maroto-Valer, M. Mercedes, et al. "Activation of magnesium rich minerals as carbonation feedstock materials for CO2 sequestration." Fuel Processing Technology 86.14-15 (2005): 1627-1645. ↩ ↩² ↩³
Olsen, Amanda Albright, and J. Donald Rimstidt. "Oxalate-promoted forsterite dissolution at low pH." Geochimica et Cosmochimica Acta 72.7 (2008): 1758-1766. ↩
House, Kurt Zenz, et al. "Electrochemical acceleration of chemical weathering as an energetically feasible approach to mitigating anthropogenic climate change." Environmental Science & Technology 41.24 (2007): 8464-8470. ↩
Krevor, S., and K. S. Lackner. "Enhancing the reaction kinetics of the dissolution of serpentine for mineral carbon sequestration." Second International Conference on Accelerated Carbonation For Environmental and Materials Engineering (ACEME 08) October. 2008. ↩
Lechat, Karl, et al. "Field evidence of CO2 sequestration by mineral carbonation in ultramafic milling wastes, Thetford Mines, Canada." International Journal of Greenhouse Gas Control 47 (2016): 110-121. ↩
Gras, A., et al. "Isotopic evidence of passive mineral carbonation in mine wastes from the Dumont Nickel Project (Abitibi, Quebec)." International Journal of Greenhouse Gas Control 60 (2017): 10-23. ↩
Plante, Benoît, et al. "Kinetic testing to evaluate the mineral carbonation and metal leaching potential of ultramafic tailings: Case study of the Dumont Nickel Project, Amos, Québec." Applied geochemistry 84 (2017): 262-276. ↩
CO2 in Seawater: Equilibrium, Kinetics, Isotopes, Volume 65—1st Edition. (2001) https://shop.elsevier.com/books/co2-in-seawater-equilibrium-kinetics-isotopes/zeebe/978-0-444-50946-8 ↩

Contributors

Ella Holme, Ph.D.

Rhys Savage, Ph.D.

Rebecca Tyne, Ph.D.

Isometric

Reactor Category

Reactor Type

Description

Stirred tank

Batch

A closed well-mixed batch system where reactants are added to the vessel at the start of the batch, and products are removed from the vessel at the end of the batch. Mixing is provided by stirring with an agitator.

Semi-batch

A well-mixed batch system where reactants are added to the vessel at the beginning of the batch, and products are removed at the end of the batch. Reactants and/or products may be added/removed from the vessel over time throughout the batch. Mixing is provided by stirring with an agitator.

Continuous

An open well-mixed system where reactants and products are both added/removed from the vessel continuously. Mixing is provided by stirring with an agitator.

Tubular

Plug flow

A simple open tubular reactor where reactants flow through the vessel and chemical reaction occurs along the length of the vessel.

Fixed bed

An open tubular multiphase reactor where reactants flow over a fixed packed bed of solid reactive material. Chemical reaction occurs along the length of the vessel.

Fluidized bed

An open tubular multiphase reactor where reactants fluidize a bed of solid reactive material. Fluid reactants and solid material flow co-currently within the vessel. Chemical reaction occurs along the length of the vessel.

Bubble bed

An open tubular multiphase reactor where gaseous reactants flow in a vessel saturated with liquid. The gaseous species migrate through the column as bubbles of gas. Chemical reaction occurs along the length of the vessel.

Trickle bed

An open tubular multiphase reactor where liquid reactants flow downwards over a packed bed of reactive solids, while gaseous species flow upwards. Chemical reaction occurs along the length of the vessel.

CO_2e_{Stored, RP} = CO_2e_{Mineralized, RP} - CO_2e_{Counterfactual, RP} - CO_2e_{Emissions, RP}

CO_2e_{Mineralized, RP} =\sum \Delta CO_2e_{Mineralized, T2 - T1, MP} - \sum CO_2e_{Losses, MP}

Parameter

Rationale

Possible Measurement Technique/Standards

Requirements

Acceptable Data Sources

Public on registry/Private

Fluid Measurements

One component of the carbonic acid system, used to calculate the concentration of dissolved CO₂ in a fluid. Note that at least 2 components of the carbonic acid system must be directly measured.

In-line pH sensor

Discrete pH measurements

Required for influent and effluent samples

Direct measurement or calculation using a 2 for 6 model

Public

Dissolved Inorganic Carbon (DIC)

Total carbon analyzer

Required for influent and effluent samples

Direct measurement or calculation using a 2 for 6 model

Public

Total Alkalinity

Titration

Required for influent and effluent samples

Direct measurement or calculation using a 2 for 6 model

Public

pCO₂

In-line pCO₂ sensor

Headspace equilibration + gas chromatography

Required for influent and effluent samples

Direct measurement or calculation using a 2 for 6 model

Public

Turbidity

Determination of rock or mineral feedstock loss

Turbidity sensor

Required for influent and effluent samples for projects in which rock or mineral feedstock may be lost from the system due to fluid flow

Direct measurement

Private

Total Suspended Solids

Determination of rock or mineral feedstock loss

Total suspended solids sensor

Filtration test

Required for influent and effluent samples for projects in which rock or mineral feedstock may be lost from the system due to fluid flow

Direct measurement

Private

Major and trace elements

Determination of weathering by mass balance

Determination of trace metal concentrations for regulatory compliance

ICP-MS

ICP-OES

Required for influent and effluent samples

Direct measurement

Public

Anions

Determination of strong acid concentration

Ion chromatography

Required for baseline samples

Direct measurements

Regulatory data may be substituted if available

Private

Electrical conductivity

Can serve as an additional parameter in 2 for 6 calculations to reduce uncertainty

In-line conductivity sensor

Recommended for baseline, influent and effluent samples

Direct measurement

Private

System Measurements

Pressure

Reactor performance monitoring

Pressure gauge

Required in reactors; variable based on reactor type

Direct measurement

Private

Temperature

Reactor performance monitoring

Calculation of reaction kinetics

In-line thermometer

Required in reactors; variable based on reactor type

Direct measurement

Private

Flow rate

Reactor performance monitoring

Chemical reactor model input

Flow meter

Required in reactors; variable based on reactor type

Direct measurement

Private

Feedstock Measurements

Mineralogy

Assessment of CDR potential and environmental risk

X-ray diffraction (XRD)

Scanning electron microscopy (SEM)

Required prior to and following carbonation

Direct measurement

Public

Major and trace elements

Assessment of CDR potential and environmental risk

Acid digestion coupled with ICP-MS

Acid digestion coupled with ICP-OES

X-ray fluorescence (XRF)

Required prior to and following carbonation

Direct measurement

Private

Particle Size Distribution

Reaction rate and chemical reactor modeling

Gravimetric sieving

Laser diffraction

X-ray scattering

Required prior to and following carbonation

Direct measurement

Private

Surface Area

Reaction rate modeling

Brunauer Emmett Teller (BET) analysis

Required prior to and following carbonation

Direct measurement

Private

Total Inorganic Carbon (TIC)

Determination of carbonation

Thermogravimetric analysis (TGA)

Required prior to and following carbonation

Direct measurement

Public

Reactor Design	Parameter	Documentation Required	Requires justification	Other Requirements
Reactor Type	Engineering Design Diagram	Yes
Materials Selection	Engineering Design Diagram	Yes
Sensor Positioning	Engineering Design Diagram	Yes
CO₂ Introduction Point	Engineering Design Diagram	Yes
Reactor modeling calculations	Chemical reactor model	Yes	If in-house experimental measurements are used to derive chemical kinetics, experimental procedures and measurements must be provided
Reactor maintenance plan	Documentation detailing the maintenance plan	Yes
Feedstock	Requirements detailed in the Rock and Mineral Feedstock Characterization Module 1.0
Feedstock Pre-treatment, if used	Pre-treatment Method	Pre-treatment plan	Yes	Standard method or laboratory SOP must be provided
Physical and chemical characteristics of feedstock after pre-treatment	Data report, including particle size distribution, surface area, and total inorganic carbon	No	Methods used for feedstock characterization must be provided
Counterfactual	Model timescale	Counterfactual weathering model	Yes	If using a timescale other than the default of 1,000 years, documentation must be provided to support the timescale claimed.
Source site temperature	Data report	No
Source site average yearly precipitation	Data report, generated either by rain gauges installed by the Project Proponent or sourced from a weather station	Yes – justification of data source
Source site average rainwater pH	Data report, generated either by direct measurements by the Project Proponent or sourced from a weather station	Yes – justification of data source
Source site average groundwater pH	Data report, generated either from direct measurements by the Project Proponent or sourced from a groundwater database	Yes – justification of data source
Measurements	All measurements listed in Appendix 1 must be reported in the PDD	Data report	Yes, where alternate methods than those listed are used	Standard and calibration data must be provided alongside measurements. All standards or SOPs used for measurements must be provided.
Carbonic acid system calculations	Data report and calculations used (spreadsheet, script)	No
Sampling	Feedstock sampling plan and procedure	See guidance in the Rock and Mineral Feedstock Characterization Module 1.0	Yes	Sampling plans should be provided for raw feedstock, carbonated feedstock, and pre-treated feedstock (if applicable)
Fluid sampling plan and procedure	Detailed description of fluid sampling, both temporally and spatially, and the sampling procedure	Yes
Aqueous sample storage	Detailed description of storage conditions for aqueous samples	Yes
Miscellaneous	Any significant but allowable deviation from the requirements outlined in this Module, as approved in consultation with Isometric	Detailed documentation appropriate to the deviation	Yes

Reactor Design

Parameter

Documentation Required

Requires justification

Other Requirements

Reactor Type

Engineering Design Diagram

Yes

Materials Selection

Engineering Design Diagram

Yes

Sensor Positioning

Engineering Design Diagram

Yes

CO₂ Introduction Point

Engineering Design Diagram

Yes

Reactor modeling calculations

Chemical reactor model

Yes

If in-house experimental measurements are used to derive chemical kinetics, experimental procedures and measurements must be provided

Reactor maintenance plan

Documentation detailing the maintenance plan

Yes

Feedstock

Requirements detailed in the Rock and Mineral Feedstock Characterization Module 1.0

Feedstock Pre-treatment, if used

Pre-treatment Method

Pre-treatment plan

Yes

Standard method or laboratory SOP must be provided

Physical and chemical characteristics of feedstock after pre-treatment

Data report, including particle size distribution, surface area, and total inorganic carbon

Methods used for feedstock characterization must be provided

Counterfactual

Model timescale

Counterfactual weathering model

Yes

If using a timescale other than the default of 1,000 years, documentation must be provided to support the timescale claimed.

Source site temperature

Data report

Source site average yearly precipitation

Data report, generated either by rain gauges installed by the Project Proponent or sourced from a weather station

Yes – justification of data source

Source site average rainwater pH

Data report, generated either by direct measurements by the Project Proponent or sourced from a weather station

Yes – justification of data source

Source site average groundwater pH

Data report, generated either from direct measurements by the Project Proponent or sourced from a groundwater database

Yes – justification of data source

Measurements

All measurements listed in Appendix 1 must be reported in the PDD

Data report

Yes, where alternate methods than those listed are used

Standard and calibration data must be provided alongside measurements. All standards or SOPs used for measurements must be provided.

Carbonic acid system calculations

Data report and calculations used (spreadsheet, script)

Sampling

Feedstock sampling plan and procedure

See guidance in the Rock and Mineral Feedstock Characterization Module 1.0

Yes

Sampling plans should be provided for raw feedstock, carbonated feedstock, and pre-treated feedstock (if applicable)

Fluid sampling plan and procedure

Detailed description of fluid sampling, both temporally and spatially, and the sampling procedure

Yes

Aqueous sample storage

Detailed description of storage conditions for aqueous samples

Yes

Miscellaneous

Any significant but allowable deviation from the requirements outlined in this Module, as approved in consultation with Isometric

Detailed documentation appropriate to the deviation

Yes

Parameter

Measurement Frequency

Rationale

Fluid Measurements

Continuous or pre-defined time steps

pH can be continuously monitored through in-line pH sensors.

Discrete pH measurements should be taken at regular intervals to confirm the functionality of in-line sensors. The sampling cadence will be determined by reactor type and flow rate.

Dissolved Inorganic Carbon

Pre-defined time steps

Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with other measurements of the carbonic acid system (e.g. tied to a time on continuous sensor output or taken from a volume of fluid collected at the same sampling interval).

Total Alkalinity

Pre-defined time steps

pCO₂

Continuous or pre-defined time steps

pCO₂ can be monitored continuously through in-line pCO₂ sensors.

Where in-line pCO₂ sensors cannot be installed, discrete measurements may be substituted.

Turbidity

Continuous

Turbidity can be monitored continuously through in-line turbidity sensors.

Total Suspended Solids

Continuous or pre-defined time intervals

Total suspended solids can be monitored continuously through in-line suspended solids sensors.

Discrete measurements can be substituted for in-line measurements. Project Proponents choosing to monitor TSS through discrete measurements must justify the time intervals of measurement based on reactor type, flow rate through the reactor and particle size distribution of the feedstock.

Major and trace elements

Pre-defined time intervals

Measurement of major and trace elements requires discrete sampling. Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with sampling for other geochemical measurements.

Anions

Baseline and pre-defined time intervals

Anion measurements are required for baseline fluids and at regular intervals if a strong risk of non-carbonic acid weathering is identified.

Measurement of anions requires discrete sampling. Sampling cadence for applicable projects will be determined by the reactor type and flow rate. This must be temporally consistent with sampling for other geochemical measurements.

Electrical Conductivity

Continuous or pre-defined time intervals

Electrical conductivity can be measured continuously using in-line conductivity sensors.

Project Proponents choosing to measure electrical conductivity may also use discrete measurements. Sampling cadence will be determined by the reactor type and flow rate. This must be temporally consistent with sampling for other geochemical measurements.

System Measurements

Pressure

Continuous

Pressure should be measured continuously by an in-line pressure gauge.

Temperature

Continuous

Temperature should be measured continuously by an in-line thermometer.

Flow Rate

Continuous

Flow rate should be measured continuously by an in-line flow meter.

Feedstock Measurements

Mineralogy

Prior to and following carbonation, as well as following any feedstock pre-treatment

Mineralogy of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.

Major and Trace Elements

Prior to and following carbonation

Geochemical composition of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.

Particle Size Distribution

Prior to and following carbonation, as well as following any feedstock pre-treatment

Particle size distribution of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.

Surface Area

Prior to and following carbonation, as well as following any feedstock pre-treatment

Surface area of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions.

Total Inorganic Carbon (TIC)

Prior to and following carbonation, as well as following any feedstock pre-treatment

TIC of the feedstock must be constrained prior to and following carbonation to inform the conditions of pre-treatment (if applicable), reactor conditions and mineral storage conditions, as well as to ensure accurate accounting of carbon storage.

Contents

Introduction

Project Types and Applicability

System Requirements

Reactor Type

Design Diagram Requirements

CO2 and Feedstock Loss

Construction Considerations

Reactor maintenance

Feedstock Characterization and Pre-Treatment

Calculation of CO2 Storage via Ex-situ Mineralization in Engineered Systems

Summary

Calculation of CO2eStored

CO2eMineralizedCO_2e_{Mineralized}CO2​eMineralized​ can be calculated as:

Calculation of CO2eCounterfactual

Calculation of CO2eEmissions

Monitoring Requirements

Fluid measurements

Baseline Characterization

Carbonic acid system

Turbidity/Total Suspended Solids

Major and Trace Elements

Requirements for Direct Carbonation Processes

System Measurements

Characterization of Carbonated Materials

Verification of Novel Measurement Methods

Storage

Data Sharing and Transparency

Definitions and Acronyms

Appendix 1: Monitoring Requirements

Appendix 2: Project Design Document Requirements

Appendix 3: Measurement Frequency

Relevant Works

Footnotes

Contributors

Contents

Introduction

Project Types and Applicability

System Requirements

Reactor Type

Design Diagram Requirements

CO2 and Feedstock Loss

Construction Considerations

Reactor maintenance

Feedstock Characterization and Pre-Treatment

Calculation of CO2 Storage via Ex-situ Mineralization in Engineered Systems

Summary

Calculation of CO2eStored

CO2eMineralizedCO_2e_{Mineralized}CO2​eMineralized​ can be calculated as:

Calculation of CO2eCounterfactual

Calculation of CO2eEmissions

Monitoring Requirements

Fluid measurements

Baseline Characterization

Carbonic acid system

Turbidity/Total Suspended Solids

Major and Trace Elements

Requirements for Direct Carbonation Processes

System Measurements

Characterization of Carbonated Materials

Verification of Novel Measurement Methods

Storage

Data Sharing and Transparency

Definitions and Acronyms

Appendix 1: Monitoring Requirements

Appendix 2: Project Design Document Requirements

Appendix 3: Measurement Frequency

Relevant Works

Footnotes

Contributors

CO₂ and Feedstock Loss

Calculation of CO₂ Storage via Ex-situ Mineralization in Engineered Systems

Calculation of CO₂e_Stored

$CO_2e_{Mineralized}$ can be calculated as:

Calculation of CO₂e_{Counterfactual}

Calculation of CO₂e_Emissions

CO₂ and Feedstock Loss

Calculation of CO₂ Storage via Ex-situ Mineralization in Engineered Systems

Calculation of CO₂e_Stored

$CO_2e_{Mineralized}$ can be calculated as:

Calculation of CO₂e_{Counterfactual}

Calculation of CO₂e_Emissions