# Feedstock characterization

Project Developers shall submit a **Feedstock Characterization Report** **for each spreading event**, that includes the applicable information outlined in the following sections: a qualitative [description of feedstock](#feedstock-description), [measurement results](#feedstock-measurements), [CDR estimates](#cdr-estimates), and the [feedstock sampling protocol](#feedstock-sampling-protocol).&#x20;

## Feedstock description

Project Developers shall provide a comprehensive qualitative description of the feedstock **once for each** [**feedstock source**](#user-content-fn-1)[^1] (in addition to the quantitative [Feedstock measurements ](#measurements)described below). This description shall include: &#x20;

* location of the source (GPS coordinates, name of the quarry/mine/site)
* partner companies extracting the feedstock
* additional processing steps undertaken by the project
* **general** mineralogic composition and heterogeneity (specific mineralogic composition will be measured more frequently for each feedstock batch)
* any jurisdictional regulations around rock spreading frequency, amount and mineral content (e.g. fertilizer guidelines)
* waste status
  * if it is waste, describe its alternative use. This informs the creation of the [baseline scenario](https://docs.rainbowstandard.io/~/changes/215/methodologies/ghg-quantification#baseline-scenario), to determine whether to include baseline CDR from feedstock counterfactual use.

## Feedstock measurements

Project Developers shall measure the following characteristics of feedstock described in Tables 1 and 2 on a composite representative sample **at least once for each feedstock batch**. A feedstock batch is all feedstock that comes from the same feedstock source, in the same mining/extraction period (within [72 hours](#user-content-fn-2)[^2]). Project Developers may justify **alternative definitions for a feedstock batch** if the feedstock source is highly homogeneous, and if aggregating feedstock does not increase variability in the overall batch composition.

It is assumed that all feedstock in the same batch has the same characteristics, and samples and measurements only need to be taken once per feedstock batch. The exception is moisture content, which must be measured just before each spreading event.

Equivalent measurement results already performed by the mine operator, for the same feedstock batch, can be used instead of performing the same measurements again.

Measurements shall be performed by third-party independent labs, and follow a recognized and standardized measurement technique (e.g. ISO 12677:2011 for XRD mineralogical analysis).

{% hint style="info" %}
For example, if a Project Developer receives one feedstock batch of 1,000 tonnes of waste mine tailing rock from a single feedstock source, and spreads 400 tonnes at at Farm A and 400 tonnes at Farm B in Year 1, they shall submit one Feedstock Characterization Report with:

* one comprehensive qualitative description
* one set of feedstock measurements
* one calculation of CDR estimates
* one description of the feedstock sampling protocol

If they receive another 500 tonnes of rock from the same source 2 months later, it is considered a **new feedstock batch**. If it is spread at Farm A, then all components listed above must be updated and a separate Feedstock Characterization Report submitted.&#x20;

If they store the remaining 200 tonnes of rock from the first delivery for one year, in a covered protected area,  and in Year 2 spread the additional 200 tonnes at Farm A, then they only need to update the CDR estimate calculations. The other components remain valid for the new spreading event. See the [Monitoring requirements for successive spreading event with new feedstock batch](https://docs.rainbowstandard.io/~/changes/215/methodologies/monitoring-plan#monitoring-requirements-for-successive-spreading-event-with-new-feedstock-batch) section.
{% endhint %}

{% hint style="info" %}
Feedstock within one feedstock batch does not need to be sampled for each spreading event, as long as feedstock is stored in covered areas protected from moisture.&#x20;

If exposed to moisture, weathering may occur, altering its previously measured characteristics. In this case, the feedstock stored uncovered shall be considered a new feedstock batch.&#x20;
{% endhint %}

{% tabs %}
{% tab title="CDR potential" %}
The following measurements shall be taken of feedstock before spreading for the purpose of estimating the maximum potential CDR for a given feedstock, and for modeling the potential CDR and weathering rate over the project lifetime (both detailed in the [CDR Estimates](#cdr-estimates) section below).

Characteristics with two asterisks (\*\*) **do not need to be measured for every feedstock batch**, if Project Developers measure them at least once and justify that they are not expected to vary across batches from the same feedstock source.

*Table 1 List of measurements to perform on feedstock to determine CDR **potential**, via calculations and models described below. Provide average and distribution of results.*&#x20;

<table><thead><tr><th width="147">Characteristic</th><th width="506">Description</th></tr></thead><tbody><tr><td>Chemical composition</td><td>Concentration of calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), sulfur (S), phosphorus (P), aluminum (Al), silicon (Si), and iron (Fe), measured via XRF or similar</td></tr><tr><td>Mineralogical composition**</td><td>proportion of the different crystalline minerals and (assumed) amorphous phases, measured via XRD or similar</td></tr><tr><td>Mineralogical composition**</td><td>amount of carbonate minerals, measured via XRD or similar</td></tr><tr><td>Particle size distribution and morphology</td><td>measure particles with a diameter of greater than 2.0 mm to those with a diameter of 2.5 µm or less</td></tr><tr><td>Moisture content</td><td>gravimetric water content*</td></tr></tbody></table>

\*to be measured from samples taken immediately prior to spreading feedstock
{% endtab %}

{% tab title="ESDNH" %}
The following measurements shall be taken before feedstock spreading for the purpose of demonstrating that the project meets [Environmental and Social Do No Harm](https://docs.rainbowstandard.io/~/changes/215/methodologies/eligibility-criteria#environmental-and-social-do-no-harm) requirements. **Project Developers shall compare all measurement results to the thresholds set in the relevant jurisdictional regulations.** It shall be transparently stated when no regulation covers the given measurement, and which thresholds are used instead.

Characteristics with two asterisks (\*\*) **do not need to be measured for every feedstock batch**, if Project Developers measure them at least once and justify that they are not expected to vary across batches from the same feedstock source.

*Table 2 List of measurements to perform on feedstock to determine ESDNH compliance.*&#x20;

<table><thead><tr><th width="143">Characteristic</th><th width="530">Description</th></tr></thead><tbody><tr><td>Chemical composition</td><td>Concentration of antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), selenium (Se), silver (Ag), thallium (Tl), uranium (U), vanadium (V) and zinc (Zn), measured via XRF or similar</td></tr><tr><td>Mineralogical composition**</td><td><ul><li>Concentration of asbestos, asbestiform minerals</li><li>respirable crystalline silica (RCS) (quartz, cristobalite, and tridymite)*</li><li>measured via XRD or similar</li></ul></td></tr><tr><td>Radioactivity**</td><td><ul><li>measurement of radioactivity</li><li>Proof of adherence to jurisdictional regulations regarding radioactivity, such as BSSD (2013/59/Euratom) in the EU or OSHA 1910 Subpart Z in the US. </li></ul></td></tr><tr><td>Particle size distribution</td><td>Concentration of particles with a diameter of 2.5 µm or less</td></tr></tbody></table>

\*optional measurement. If not measured, safety precautions must be implemented and described to protect workers from RCS
{% endtab %}
{% endtabs %}

## CDR Estimates

Using the CDR measurements described above, and site-specific considerations, Project Developers shall provide the following **for ex-ante project validation** and **for each spreading event**:

{% tabs %}
{% tab title="Maximum potential CDR" %}
**Maximum potential CDR** of applied feedstock shall be calculated based on the modified Steinor equation, shown below ([Renforth, 2019](#user-content-fn-3)[^3]). Project Developers should use the average, minimum and maximum results from feedstock measurements and report the range of results.

$$\textbf{(Eq.1)}\ E\_{pot} = \frac{M\_{CO\_2}}{100} \times \left( \alpha \frac{CaO}{M\_{CaO}} + \beta \frac{MgO}{M\_{MgO}} + \varepsilon \frac{Na\_2O}{M\_{Na\_2O}} + \theta \frac{K\_2O}{M\_{K\_2O}} + \gamma \frac{SO\_3}{M\_{SO\_3}} + \delta \frac{P\_2O\_5}{M\_{P\_2O\_5}} \right) \times 10^3 \times \eta$$

* $$E\_{pot}$$ represents the maximum CDR potential of a feedstock
* $$CaO, MgO, SO\_3, P\_2O\_5, Na\_2O$$ and $$K\_2O$$ represent the elemental concentrations in the form of oxides
* $$M\_x$$ denotes the molecular mass of each respective oxide $$x$$
* $$\alpha, \beta, \gamma, \delta, \varepsilon, \text{ and } \theta$$ represent the relative contributions of each oxide. According to [Renforth, 2019](#user-content-fn-3)[^3], $$\alpha, \beta, \varepsilon, \text{ and } \theta$$ are equal to -1; $$\gamma$$ equals -1; and $$\delta$$ equals -2.
* $$\eta$$ represents the molar ratio of CO$$\_2$$ sequestered per divalent cation present in the feedstock. As a default, this may be assumed to be 0.85. See the [Measurements ](https://docs.rainbowstandard.io/~/changes/215/methodologies/ghg-quantification#surface-ocean-ffz)section for more details.&#x20;
  {% endtab %}

{% tab title="Potential CDR over the project lifetime" %}
**Potential CDR over the project lifetime** should be modeled, specifying CDR across any expected crediting period renewals.&#x20;

The model should include a curve of expected weathering completion (e.g. 10 years after application, it is estimated that 70% of the material has weathered). The results of this modeling are used for informing allocation of upstream impacts in the [GHG quantification](https://docs.rainbowstandard.io/~/changes/215/methodologies/ghg-quantification#project-emissions). The models used shall:

* include at least a consideration of moisture, temperature, and pH in the project region.
* link biogeochemical and hydrological processes.
* have already been calibrated and validated with appropriate independent datasets of CDR measurements.
* transparently assess initialization assumptions and model uncertainty, and the resulting effect on CDR estimates.
* include an estimate of CDR loss in the FFZ (i.e. in rivers, surface water, and the ocean).
* use direct measurements of multiple variables to ground-truth models wherever possible.
* provide all technical details needed to assess the validity of the approach to the VVB and/or peer reviewers

Alternatively, Project Developers may opt to count all upstream impacts in the first reporting period and credit issuance.
{% endtab %}
{% endtabs %}

## Feedstock sampling protocol

In the Feedstock Characterization Report, Project Developers shall describe and justify the following, considering feedstock heterogeneity and site-specific factors:

* sampling frequency
* how to ensure representative sampling
* number of subsamples to combine into a composite sample
* total amount of sampled material needed to conduct all [measurements](#measurements) and obtain precise results&#x20;
* sample collection and handling methods

[^1]: A given site where feedstock is sourced from, with one set of GPS coordinates, name of the mine/quarry/area, and feedstock waste status.

[^2]: Feedstock used in a project must be sourced from the same area of a mine **within a defined timeframe**. This is because rock mined on **Day 1** may differ substantially in composition from rock extracted even **one week later**, as different areas of a mine can yield material with varying mineralogical and chemical properties.

[^3]: Renforth, P., 2019. The negative emission potential of alkaline materials. Nat. Commun. 10, 1401. <https://doi.org/10.1038/s41467-019-09475-5>. [URL](https://doi.org/10.1038/s41467-019-09475-5).&#x20;
