# Biochar application to soils | **Module name** | Biochar application to soils | | -------------------- | ------------------------------------------ | | **Module category** | Carbon storage | | **Methodology name** | Biomass carbon removal and storage (BiCRS) | | **Version** | 2.2 | | **Methodology ID** | RBW-BICRS-CS-BCSOIL-V2.2 | | **Release date** | July 11th, 2025 | | **Status** | In use | This is a **Carbon Storage Module** and covers the biochar application to soils. This module is part of the Rainbow BiCRS methodology, which allows Project Developers to choose the relevant modules for their project, and shall be used with the necessary accompanying modules. {% content-ref url="../../../glossary" %} [glossary](https://docs.rainbowstandard.io/~/changes/113/glossary) {% endcontent-ref %} This is a **Carbon Storage Module** and covers the biochar application to soils. This module is part of the Riverse BiCRS methodology, which allows Project Developers to choose the relevant modules for their project, and shall be used with the necessary accompanying modules. See more details on how modules are organized in the [BiCRS home page](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/..#efpqng3v3ute).


How to use this module			#efpqng3v3ute	pexels-eberhardgross-1612461.jpg
BiCRS Methodology			..	BiCRS methodology.png

## Scope of the module


Feedstock	Use waste and residual biomass as feedstock, according to the Biomass feedstock module.
	Processing	Heat biomass to at least 350°C during production. Capture or cleanly burn pyrolysis gasses, as outlined in the Processing and Energy Use module Report methane emissions from pyrolysis, using the Processing and Energy Use module
	Biochar Quality and Use	Produce high-quality biochar with a molar H/C_{\text{org}} below 0.7. Apply biochar to agricultural, forest, or urban soils, ensuring permanent sequestration of its organic carbon content.

Projects may be designed to prioritize bio-oil or bioenergy production, where biochar is the co-product. Such projects may still be eligible for removal Rainbow Carbon Credits under this module, if they meet all criteria outlined herein. This module **issues removal RCCs on the basis of biochar end use/delivery**, i.e. application to soils and permanent storage, not on the basis of biochar production. This module covers industrial biochar projects that meet all of the following criteria:


Feedstock Use waste and residual biomass as feedstock, according to the Biomass feedstock module.
Processing Heat biomass to at least 350°C during production. Capture or cleanly burn pyrolysis gasses, as outlined in the Processing and Energy Use module
Biochar Quality and Use Produce high-quality biochar with a molar H/C_{org} below 0.7. Apply biochar to agricultural, forest, or urban soils, ensuring permanent sequestration of its organic carbon content.

Feedstock

Use waste and residual biomass as feedstock, according to the Biomass feedstock module.

Processing

Heat biomass to at least 350°C during production.
Capture or cleanly burn pyrolysis gasses, as outlined in the Processing and Energy Use module

Biochar Quality and Use

Produce high-quality biochar with a molar H/C_{org} below 0.7.
Apply biochar to agricultural, forest, or urban soils, ensuring permanent sequestration of its organic carbon content.

Biochar may be applied directly to soils or incorporated into soil-related products, such as soil additives, horticultural substrates, potting soils, fertilizer mixes, or compost. Projects may be designed to prioritize bio-oil or bioenergy production, where biochar is the co-product. Such projects may still be eligible for removal Riverse Carbon Credits under this module, if they meet all criteria outlined herein. This module also covers any potential avoided horticultural products from the use of biochar. This module **issues removal RCCs on the basis of biochar use/delivery**, i.e. application to soils and permanent storage, not on the basis of biochar production. ## Eligible Project Developers The Project Developer and entity eligible for receiving carbon finance may be either: * the operator of the biochar production site, or * land owners or managers who purchase biochar and apply it to their soil. Pyrolyzer and gasification equipment manufacturers are not eligible Project Developers. ## Production batches A production batch is the **biochar produced under the same conditions regarding production temperature and feedstock mix**. It is assumed that all biochar from the same production batch has similar characteristics (i.e. $$H/C\_{\text{org}}$$, moisture content…). Specifically, the definition of a production batch follows the [European Biochar Certificate Guidelines](#user-content-fn-1)[^1] definition, where pyrolysis temperature and biomass feedstock composition must not change by more than 20%. Measurements and reporting are performed at the **production batch level**. Verification and credit issuance may be done per production batch, or annually on the cumulative production batches from that year. {% hint style="info" %} For example, if the declared pyrolysis temperature is 600 °C, temporary fluctuations between 480 °C and 720 °C are acceptable. If a mixture of 50% tree clippings and 50% nut shells is pyrolyzed, the proportions can vary between 40% and 60% (±10% of the original 50%) {% endhint %} A production batch has a **maximum validity of 365 days**, after which biochar shall be considered part of a different production batch even if conditions are unchanged. In other words, the production batch ID number resets and a new production batch is created, and new monitoring requirements applied, after 365 days, regardless of if feedstock or pyrolysis conditions change or not. ## Eligibility criteria The eligibility criteria requirements specific to this module are detailed in the sections below. Other eligibility criteria requirements shall be taken from the accompanying modules and methodologies:


BiCRS methodology	Additionality No double counting Targets alignment ESDNH	..	BiCRS methodology.png
Other modules	Substitution Co-benefits No double counting ESDNH Leakage		energy co products module.jpg
Rainbow Standard Rules	Measurability Real TRL Minimum impact	rainbow-standard-rules	rainbow logo.jpg

### Permanence #### Estimating permanent carbon fraction Projects issuing removal RCCs from biochar application to soil may claim one of two different permanence horizons, depending on their [GHG reduction quantification](#ghg-reduction-quantification) method: a permanence horizon **of 100 years or 1000 years.** Permanence is ensured by measuring one of the following characteristics of biochar that are known indicators of carbon stability: * 100 year pathway: **Hydrogen and organic carbon content** ($$H/C\_{\text{org}}$$). $$H/C\_{\text{org}}$$ must be less than 0.7 to be considered eligible for 100-year permanent removals. * 1000 year pathway: **Random reflectance**. The fraction of the biochar residual organic carbon that has a random reflectance of 2% or higher can be considered inertinite, which is an extremely stable, permanent storage of mineral-like[^2] organic carbon. The distinction between the two permanence horizons is **supplementary, qualitative information that does not affect the inherent attributes of the removal RCC**. These indicators are **suitable proof that a substantial fraction** of the carbon present in biochar is permanently stable. The **specific amount** of permanently stored carbon is determined using the models and equations detailed in the [GHG reduction quantification](#ghg-quantification) section. These indicators shall be monitored for each production batch according to the Rainbow [Sampling Requirements](#sampling-requirements). Project Developers shall fill in the [Rainbow Biochar application to soils risk evaluation](#risk-evaluation-template) to **evaluate the risk of carbon storage reversal**, based on social, economic, natural, and delivery risks. Project Developers shall assign a likelihood and severity score to each risk, and provide an explanation of their choices. The Rainbow Certification Team shall evaluate the assessment and may recommend changes to the assigned scores. The Project Developer, Rainbow Certification Team, or the third-party auditor may suggest additional risks to be considered for a specific project. Each reversal risk with a **high or very risk score** is subject to: * **risk mitigation plan**, developed by the Project Developer, that details the long-term strategies and investments for preventing, monitoring, reporting and compensating carbon removal reversal, or * **additional contributions to the buffer pool**, at a rate of 3% of verified removal Rainbow Carbon Credits for each high or very high risk Project Developers shall assign a likelihood and severity score to each risk, and provide an explanation of their choices. The Rainbow Certification team shall evaluate the assessment and may recommend changes to the assigned scores. The Project Developer, Rainbow Certification team, or the third-party auditor may suggest additional risks to be considered for a specific project. Each reversal risk with a **high or very risk score** is subject to: * **risk mitigation plan**, developed by the Project Developer, that details the long-term strategies and investments for preventing, monitoring, reporting and compensating carbon removal reversal, or * **additional contributions to the buffer pool**, at a rate of 3% of verified removal Rainbow Carbon Credits for each high or very high risk #### Risk of reversal Project Developers shall fill in the Methodology Risk evaluation template at the link below to **evaluate the risk of carbon storage reversal**, based on social, economic, natural, and delivery risks. Project Developers shall assign a likelihood and severity score to each risk, and provide an explanation of their choices. The Rainbow Certification team shall evaluate the assessment and may recommend changes to the assigned scores. The Project Developer, Rainbow Certification team, or the third-party auditor may suggest additional risks to be considered for a specific project. Each reversal risk with a **high or very risk score** is subject to: * **risk mitigation plan**, developed by the Project Developer, that details the long-term strategies and investments for preventing, monitoring, reporting and compensating carbon removal reversal, OR * **additional contributions to the buffer pool**, at a rate of 3% of verified removal Rainbow Carbon Credits for each high or very high risk


	Riverse Biochar application to soils risk evaluation

### No double counting See the [BiCRS methodology No double counting](https://docs.rainbowstandard.io/~/changes/113/methodologies/carbon-capture/biomass-feedstock#eligibility-criteria) section for general requirements on this topic. Since both **biochar producers and users** are eligible for removal RCCs under this methodology, additional details are provided here. If **both the biochar producer and the farmer intend to issue carbon credits**, they must agree on how to divide the annual biochar production for credit issuance. The credited biochar amount must be tracked and reported separately, governed by agreements outlining which party receives credits. {% hint style="info" %} For example, they might decide that the farmer will issue credits for the biochar produced from January through April (Production Batch #1), while the producer will issue credits for biochar produced from May through December (Production Batch #2). {% endhint %} Since both **biochar producers and users** are eligible for removal RCCs under this methodology, additional details are provided here. If **only one party seeks to issue carbon credits**, this must be proven through signed agreements, minimizing the risk of double counting. {% hint style="info" %} For example, if only the biochar producer seeks to issue carbon credits, they must obtain a signed agreement from the farmer whose land biochar will be spread on, stating that the farmer will not also try to issue carbon credits for their use of biochar. {% endhint %} If **both the biochar producer and the farmer intend to issue carbon credits**, they must agree on how to divide the annual biochar production for credit issuance. The credited biochar amount must be tracked and reported separately, governed by agreements outlining which party receives credits. {% hint style="info" %} For example, they might decide that the farmer will issue credits for the biochar produced from January through April (Production Batch #1), while the producer will issue credits for biochar produced from May through December (Production Batch #2). {% endhint %} ### Co-benefits Project Developers shall prove that their project provides **at least 2 co-benefits** from the [UN Sustainable Development Goals](https://unstats.un.org/sdgs/indicators/Global-Indicator-Framework-after-2024-refinement-English.pdf) (SDGs) framework (and no more than 4). Common co-benefits of projects certified under this methodology, and their sources of proof, are detailed in Table 1. Project Developers may suggest and prove other co-benefits not mentioned here. SDG 13 on Climate Action by default is not considered a co-benefit here, since it is implicitly accounted for in the issuance of carbon credits. If the project delivers climate benefits that are not accounted for in the GHG reduction quantifications, then they may be considered as co-benefits. *Table 1 Summary of common co-benefits provided by projects certified under this methodology. Co-benefits are organized under the United Nation Sustainable Development Goals (UN SDGs) framework.* Project developers shall prove that their project provides **at least 2 co-benefits** from the [UN Sustainable Development Goals](https://unstats.un.org/sdgs/indicators/Global-Indicator-Framework-after-2024-refinement-English.pdf) (SDGs) framework (and no more than 4). Common co-benefits under this methodology are detailed in the table below. Project Developers may suggest and prove other co-benefits not mentioned here. SDG 13 on Climate Action by default is not considered a co-benefit here, since it is implicitly accounted for in the issuance of carbon credits. If the project delivers climate benefits that are not accounted for in the GHG reduction quantifications, then they may be considered as co-benefits. *Table 1 Common co-benefits that projects under this methodology may provide are detailed, including types of proof that can be used to justify each co-benefit.*

UN SDG	Example	Proof
SDG 2.4: Ensure sustainable food production systems, increase productivity, help maintain resilient ecosystems, improve land and soil quality.	Biochar application to agricultural soils can increase crop yields, therefore reducing the amount of land, pesticides, fertilizer, and other environmentally impactful resources needed to grow food	Proof of biochar use in agriculture as opposed to other applications: contract, invoices, receipts of sale of biochar to farmers.
SDG 12.2: Achieve the sustainable management and efficient use of natural resources	The project’s circularity will be measured by the Material Circularity Indicator (MCI), according to the Ellen MacArthur Foundation's methodology. The indicator is expected to be 100% circularity for all biochar projects, since they use biomass feedstock and do not landfill or incinerate their product.	Type of feedstocks used, verification of end use of biochar

### Substitution If Project Developers can prove that their biochar product replaces a **specific and known amount of a specific product**, (e.g. a known fraction of a horticultural substrate mix), then the product may be considered as replaced and avoided. The Project Developer shall justify the amount of material actually replaced by biochar, and may not simply use a 1:1 mass replacement ratio. A non-exhaustive list of possible replaced products include: * Horticultural peat/peat moss * Lime * Perlite and vermiculite * Synthetic mineral fertilizers (only when biochar is used as an ingredient in fertilizer mixes, not when it is directly applied to soils) {% hint style="warning" %} Project Developers must prove that: * the biochar is an appropriate and realistic substitute for the avoided product, and * that the user of the biochar **actually uses less of the horticultural product than they did previously** In other words, it is not sufficient to prove that biochar could technically substitute products, because there is high uncertainty in which products biochar would actually substitute. It must be shown using operations tracking or invoices from the biochar user that they actually use less of the replaced product, thanks to the addition of biochar. {% endhint %} By default, it shall be **assumed that biochar application to soils does not replace any measurable, verifiable product**. If only removal RCCs are issued, then this eligibility criteria is not applicable. Note that avoidance from [energy co-products](https://docs.rainbowstandard.io/~/changes/113/modules/energy-co-products) is covered in a a separate module. ### Environmental and social do no harm Project Developers shall prove that the **project does not contribute to substantial environmental and social harms.** Projects must follow all national, local, and European (if located in Europe) environmental regulations related to, for example, pyrolysis, gasification, waste feedstock management, and biochar spreading on soils. **Feedstock sustainability risks** shall be taken from the [Biomass feedstock module](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/carbon-capture/biomass-feedstock). Biochar applied to soils must be below the pollutant concentration thresholds outlined in Table 2, defined by the [World Biochar Certificate Guidelines](#user-content-fn-6)[^6] (for WBC-Agro). This shall be measured for each production batch. *Table 2 The thresholds for pollutant concentrations allowed in biochar, as detailed in the* [*World Biochar Certificate Guidelines*](#user-content-fn-6)[^6]*.*

Substance	Limit amount (g/tonne dry matter)
Pb	300
Cd	5
Cu	200
Ni	100
Hg	2
Zn	1000
Cr	200
As	20
8 EFSA PAH	1

#### ESDNH risk evaluation Project Developers shall fill in the [Rainbow Biochar application to soils risk evaluation](#risk-evaluation-template), to evaluate the identified environmental and social risks of projects. The identified risks include: * Heavy metal or other pollutants in biochar applied to agricultural soils Project Developers shall assign a likelihood and severity score of each risk, and provide an explanation of their choices. The VVB and Rainbow’s Certification team shall evaluate the assessment and may recommend changes to the assigned scores. All risks with a high or very high risk score are subject to a [Risk Mitigation Plan](https://docs.rainbowstandard.io/~/changes/113/rainbow-standard-documents/rainbow-standard-rules/general-eligibility-criteria#risk-mitigation-plan), which outlines how Project Developers will mitigate, monitor, report, and if necessary, compensate for any environmental and/or social harms. Additional proof may be required for certain high risk environmental and social problems. The Project Developer, the Rainbow Certification Team, or the VVB may suggest additional risks to be considered for a specific project. {% hint style="info" %} Note that the **life-cycle GHG reduction calculations account for the climate change impacts of most environmental risks**. Nonetheless, Project Developers shall transparently describe any identified GHG emission risks in the risk evaluation template. {% endhint %} {% hint style="info" %} All risk assessments must also address the [Minimum ESDNH risks ](https://docs.rainbowstandard.io/~/changes/113/rainbow-standard-documents/rainbow-standard-rules/general-eligibility-criteria#minimum-esdnh-risks-to-assess)defined in the Rainbow Standard Rules. {% endhint %} ## GHG quantification The GHG quantification instructions from all other BiCRS modules used by the project must be used in conjunction with the present module in order to obtain full life-cycle GHG quantifications. The system boundary of this quantification section starts at the arrival of biochar at the site of permanent incorporation/application (i.e. field for spreading, mixing into potting soil...) and ends at the biochar end of life, after accounting for decay and re-emission in its end use application. The system boundary of this quantification section starts at the arrival of biochar at the site of permanent incorporation/application (i.e. field for spreading, mixing into potting soil...) and ends at the biochar end of life, after accounting for decay and re-emission in its end use application. **Quantification shall be done at a minimum for each biochar production batch**, and may be done more frequently for continuous issuance. GHG emissions covered in this module include: * Permanent carbon storage modeling * Production of avoided baseline scenario materials ### Data sources The required **primary data** for GHG reduction calculations from projects are presented in Table 2. These data shall be provided for each production batch and made publicly available. *Table 2 Summary of primary data needed from projects and their source for initial project certification and validation. All primary data sources listed here are required to be monitored and updated during verification (see Monitoring Plan section).* {% tabs %} {% tab title="Option 1: 100-year removals with H/C" %} | Parameter | Unit | Source | | ---------------------------------------------------------------------- | ---------------------- | -------------------------------------------------------------------------- | | Amount of biochar produced\* | Tonnes of fresh matter | Internal tracking documents, invoices, contracts | | Biochar $$H/C\_{\text{org}}$$\* | Ratio | Laboratory chemical analyses | | Organic carbon content | Percent | Laboratory chemical analyses | | Biochar moisture content ($$M\_{\text{%}}$$) \* | Percent | Laboratory chemical analyses | | [GPS coordinates ](#user-content-fn-7)[^7]of biochar spreading sites\* | coordinates | Internal tracking documents, invoices, mapping software (e.g. Google Maps) | | Amount and type of avoided horticultural product (optional) | kg, tonnes, m3 | Operations tracking and invoices from the product user | | {% endtab %} | | | {% tab title="Option 2: 1000-year removals random reflectance" %}

Parameter	Unit	Source
Amount of biochar produced*	Tonnes of fresh matter	Internal tracking documents, invoices, contracts
Organic carbon content	Percent	Laboratory chemical analyses
Average random reflectance R_o	Percent	Laboratory chemical analyses
Fraction of R_o distribution measurements above 2%	Fraction	Laboratory chemical analyses
Residual organic carbon (C_{org,\ \%residual})	Fraction	Laboratory analyses
Biochar moisture content (M_{\text{%}})*	percent	Laboratory chemical analyses
Amount and type of avoided horticultural product (optional)	kg, tonne, m3	Operations tracking and invoices from the product user

{% endtab %} {% endtabs %} The [ecoinvent database](#user-content-fn-8)[^8] version 3.11 (hereafter referred to as ecoinvent) shall be the main source of emission factors unless otherwise specified. Ecoinvent is preferred because it is traceable, reliable, and well-recognized. The ecoinvent processes selected are detailed in [Appendix 1](#appendix). No other secondary data sources are used in this module. ### Co-product allocation The rules outlined at the methodology-level in the [BiCRS methodology document](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs) shall be applied for allocating GHG emissions between co-products. ### Assumptions 1. By default, biochar application to soils does not replace any product. 2. The fraction of biochar with an $$R\_o$$ below 2% does not contribute to any permanent carbon storage. This fraction, classified as semi-inertinite rather than inertinite, likely plays a role in long-term carbon storage. However, due to limited research on its quantification, it is conservatively excluded from this analysis. 3. All biochar from the same production batch has the same characteristics (e.g. $$M\_{\text{%}}$$, $$H/C\_{\text{org}}$$, $$R\_o$$). ### Baseline scenario The baseline scenario for the purpose of Removal vs Avoidance RCCs issuance is detailed below. {% tabs %} {% tab title="Removal RCCs" %} For removal RCCs, there is no baseline from this module because it is assumed that there is no significant share of the project activity already occurring in business-as-usual. Therefore, the baseline for removal credits is zero and is omitted from calculations. According to the Rainbow Procedures Manual, this assumption shall be re-assessed at a [minimum every 3 years](https://docs.rainbowstandard.io/~/changes/113/rainbow-standard-documents/procedures-manual/documentation-and-methodologies-management#revising-a-methodology) during the mandatory methodology revision process, and any changes to this assumption would be [applied to existing projects](https://docs.rainbowstandard.io/~/changes/113/rainbow-standard-documents/procedures-manual/project-certification-procedure#compliance-and-project-updates). Note that baseline scenario carbon sequestration may be included for the project from the [biomass feedstock module](https://docs.rainbowstandard.io/~/changes/113/methodologies/carbon-capture/biomass-feedstock#ghg-quantification). {% endtab %} {% tab title="Avoidance RCCs" %} For avoidance RCCs, a baseline scenario shall only be considered if the project meets the [Substitution criteria](#id-82n4j72vjt9v) and is eligible to claim avoidance RCCs. By default, it shall be **assumed that biochar application to soils does not replace any measurable, verifiable product**. If Project Developers can prove that their biochar product replaces a **specific and known amount of a specific product**, then the product may be considered as replaced and avoided. Examples of ecoinvent processes for these products are presented in [Appendix 1](#appendix). Note that avoidance from energy co-products is covered in a[ separate module](https://docs.rainbowstandard.io/~/changes/113/modules/energy-co-products). The equations for calculating avoidance are presented in the [BiCRS methodology document](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/carbon-storage/broken-reference) and shall be applied here. {% endtab %} {% endtabs %} The baseline scenario for the purpose of Removal vs Avoidance RCCs issuance is detailed below. {% tabs %} {% tab title="Removal RCCs" %} For removal RCCs, there is no baseline from this module because it is assumed that there is no significant share of the project activity already occurring in business-as-usual. Therefore, the baseline for removal credits is zero and is omitted from calculations. According to the Riverse Procedures Manual, this assumption shall be re-assessed at a [minimum every 3 years](https://docs.rainbowstandard.io/~/changes/113/rainbow-standard-documents/procedures-manual/documentation-and-methodologies-management#revising-a-methodology) during the mandatory methodology revision process, and any changes to this assumption would be [applied to existing projects](https://docs.rainbowstandard.io/~/changes/113/rainbow-standard-documents/procedures-manual/project-certification-procedure#compliance-and-project-updates). Note that baseline scenario carbon sequestration may be included for the project from the [biomass feedstock module](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/carbon-capture/biomass-feedstock). {% endtab %} {% tab title="Avoidance RCCs" %} A baseline scenario shall only be considered if the project meets the [Substitution criteria](#id-82n4j72vjt9v) and seeks to claim avoidance RCCs. By default, it shall be **assumed that biochar application to soils does not replace any measurable, verifiable product**. If Project Developers can prove that their biochar product replaces a **specific and known amount of a specific product**, then the product may be considered as replaced and avoided. Examples of ecoinvent processes for these products are presented in [Appendix 1](#appendix). Note that avoidance from energy co-products will be covered in a separate module. The equations for calculating avoidance are presented in the [BiCRS methodology document](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/carbon-storage/broken-reference) and shall be applied here. {% endtab %} {% endtabs %} ### Project scenario Project Developers must choose between one of two approaches to quantify the total carbon removals from their biochar product, as described in the [Permanence section](#lc9eewbyvlyk). A single approach must be used consistently throughout each reporting period, though a different approach may be chosen for subsequent reporting periods. 1. [Modeling 100-year removals using bulk measurements of $$H/C\_{\text{org}}$$](#unteq8ror26g), or 2. [Estimating 1000-year removals using random reflectance measurements as proxies for inertinite](#id-2rhx2av7of74). #### Approach 1: Modeling 100-year removals with $$H/C\_{\text{org}}$$ This approach is based on research from [Woolf et al., 2021](#user-content-fn-9)[^9], and the [IPCC modeling method](#user-content-fn-10)[^10]. It is rooted in soil ecology and soil biochemistry disciplines. The **permanent fraction** of biochar carbon remaining after 100 years ( $$F\_{\text{perm 100}}$$) is modeled according to the local average annual soil temperature. Soil temperature shall be obtained for the location of each biochar spreading/end use event, using the GPS coordinates provided in the [Verification of end use report](#id-1vij2jfikmk5) and the global soil temperature dataset from [Lembrechts et al., 2021](#user-content-fn-11)[^11]. The Rainbow Certification Team can provide soil temperature values for Project Developers based on the provided GPS coordinates. The **permanent fraction** of biochar carbon remaining after 100 years ( [Azzi et al., 2024](#user-content-fn-12)[^12], and is least likely to overestimate carbon removals. For verification, Project Developers shall provide primary project data in the form of laboratory measurements for $$H/C\_{\text{org}}$$ and $$M\_{\text{%}}$$ following the [Sampling requirements](#sampling-requirements). *Table 3 Soil temperature ranges are categorized and their corresponding c and m regression coefficients are presented, which are used in Eq. 1 below to calculate* $$F\_{perm}$$. Values are taken from [Woolf et al., 2021](#user-content-fn-9)[^9]. | Soil temperature (°C) | c | m | | --------------------- | ---- | ---- | | <7.49 | 1.13 | 0.46 | | 7.5-12.49 | 1.10 | 0.59 | | 12.5-17.49 | 1.04 | 0.64 | | 17.5-22.49 | 1.01 | 0.65 | | >22.5 | 0.98 | 0.66 |

Calculations: 100-year removal credits with H/C_{org}

$$\textbf{(Eq.1)}\ F\_{perm\ 100} = c - m\*H/C\_{org}$$ where, * $$F\_{perm\ 100}$$ represents the fraction of biochar carbon remaining after 100 years * $$c$$ and $$m$$ represent regression coefficients, taken from [Woolf et al., 2021](#user-content-fn-9)[^9], and summarized in Table 3 for the corresponding project's soil temperature. * $$H/C\_{org}$$ represents the ratio of molar hydrogen to organic carbon in biochar, measured by laboratory analysis for each project. $$\textbf{(Eq.2)}\ R\_{P,\ Storage\ 100}= F\_{perm\ 100}\*{C\_{org}*A}\_{biochar}*(1 - M\_{%})\*C\ to\ {CO}\_{2}$$ where, * $$R\_{P,\ Storage\ 100}$$ represents the total carbon removals from biochar during the verification period, in tonnes of CO$$\_2$$eq. This value shall be applied to Equation 1 from the [General BiCRS methodology](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/carbon-storage/broken-reference) document to calculate total project removals. * $$F\_{perm\ 100}$$ is calculated in Equation 1 * $$C\_{org}$$ represents the concentration of organic carbon in biochar, on a weight basis. * $$A\_{biochar}$$ represents the amount of biochar delivered during the verification period, in tonnes of fresh biochar. * $$M\_{%}$$ represents the moisture content of biochar, on a weight basis (%w/w), so $$1-M\_{%}$$converts to dry mass of biochar * $$C\ to\ {CO}\_{2}$$ is 44/12 = 3.67, and represents the molar masses of CO$$\_2$$ and C respectively, and is used to convert tonnes C to tonnes of CO$$\_2$$eq.

#### Approach 2: Estimating 1000-year removals based on inertinite fraction This approach is based on the research from [Sanei et al., 2024](#user-content-fn-13)[^13], and is rooted in the organic petrology and geochemistry disciplines. This approach is built upon research showing that fractions of inertinite in biochar samples are: * [inert and permanent](#user-content-fn-14)[^14] and will not re-release their carbon for at least 1000 years. * represented by the fraction of residual (i.e. not reactive, not labile) organic carbon in the sample with a Random Reflectance ($$R\_o$$) of [2% or higher](#user-content-fn-13)[^13]. For verification, Project Developers shall provide primary project data in the form of laboratory measurements for $$R\_o$$ distribution, [labile organic carbon content](#user-content-fn-15)[^15], and moisture content for each production batch, following the [Sampling requirements](#sampling-requirements). To determine the inertinite fraction of the biochar's organic carbon, first the labile carbon fraction is measured and subtracted from total organic carbon content, and only the residual organic carbon content is considered. Next, random reflectance measurements are used to determine the fraction of residual organic carbon that is classified as inertinite: * The fraction of the distribution with an $$R\_o$$ **above 2%** represents the fraction of the biochar carbon that is stored permanently for 1000 years. * The fraction of the distribution with an $$R\_o$$ **below 2%** represents the fraction of biochar carbon that is not permanently stored, and for which no removal RCCs are issued. * $$R\_o$$ distribution shall be based on at least 500 measurements, yielding a frequency distribution diagram similar to the examples in Figure 1a and 1b. ![Figure 1a An example of a random reflectance frequency distribution diagram, with an analysis described below.](https://1461901304-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FE1FUJsBoIj20nqp3CtMf%2Fuploads%2F3FHPC6iokBLUMTixdIuU%2F1.png?alt=media) {% hint style="info" %} Example 1: This biochar sample has heterogenous quality and a wide distribution of $$R\_o$$ measurements. The biochar sample has: * labile organic carbon content of 5%, * residual organic carbon content of 95%, * mean $$R\_o$$ of 2.12, and * 72% of the $$R\_o$$ measurements are above the 2% inertinite threshold. Therefore, this biochar sample has an $$F\_{\text{perm\ 1000}}$$ of $$0.72 \times 0.95=0.684$$ , so 68.4% of the organic carbon in the sample will be converted to CO$$\_2$$eq and considered as 1000-year carbon removals. The remaining 31.6% of carbon is assumed to decompose within the 1000-year permanence horizon, and is not considered for any removal RCCs. {% endhint %} ![Figure 1b An example of a random reflectance frequency distribution diagram, with an analysis described below.](https://1461901304-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FE1FUJsBoIj20nqp3CtMf%2Fuploads%2FXSzIluGV4b126OQCggHx%2F2.png?alt=media) {% hint style="info" %} Example 2: This biochar sample has rather homogenous quality and a narrow distribution of $$R\_o$$ measurements. The biochar sample has: * labile organic carbon content of 1% * residual organic carbon content of 99% * mean $$R\_o$$ of 2.32, and * 95% of the $$R\_o$$ measurements are above the 2% inertinite threshold. Therefore, this biochar sample has an $$F\_{\text{perm\ 1000}}$$ of $$0.99\*0.95=0.94$$, so 94% of the organic carbon in the sample will be converted to CO$$\_2$$eq and considered as 1000-year carbon removals. The remaining 6% of carbon is assumed to decompose within the 1000-year permanence horizon, and is not considered for any removal RCCs. {% endhint %}

Calculations: 1000-year removal credits with random reflectance

$$\textbf{(Eq.3)}\ F\_{perm\ 1000} = {Sample\ fraction}*{> 2%\ Ro} \times C*{org,\ f\ residual}$$ where, * $$F\_{perm\ 1000}$$ represents the fraction of biochar carbon remaining after 1000 years. * $${Sample\ fraction}\_{> 2%\ Ro}$$ represents the fraction of the distribution sample that has a random reflectance ($$R\_O$$) of 2% or higher. * $$C\_{org,\ f\ residual}$$ represents the fraction of the biochar organic carbon that is residual carbon, as opposed to reactive/labile organic carbon. It may be measured and reported directly, or obtained by subtracting measured *reactive* carbon from 100. $$\textbf{(Eq.4)}\ R\_{P,\ removal\ 1000}=F\_{perm\ 1000}\*{C\_{org}*A}\_{biochar}*{(1 - M}*{%})\*C\ to\ {CO}*{2}$$ where, * $$R\_{P,\ removal\ 1000}$$ represents the total carbon removals from biochar during the verification period, in tonnes of CO$$\_2$$eq. This value shall be applied to Equation 1 from the [General BiCRS methodology](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/carbon-storage/broken-reference) document to calculate overall project removals. * $$F\_{perm\ 1000}$$ is calculated in Equation 3 * $$C\_{org}$$, $$A\_{biochar}$$, $$M\_{%}$$, and $$C\ to\ {CO}\_{2}$$ are described in Equation 1.

Rainbow is actively monitoring ongoing research and seeking expert advice on the potential development of a third approach that uses $$H/C\_{\text{org}}$$ measurements as proxies for inertinite content. For example, if the $$H/C\_{\text{org}}$$ value is less than 0.2, it could be interpreted as indicating that 95% of the biochar is inertinite. While this simplification has been suggested by experts and holds promise, it is currently considered insufficiently rigorous due to a lack of supporting evidence and clear guidance. #### Future Approach 3: Using H/C as a proxy for inertinite Riverse is actively monitoring ongoing research and seeking expert advice on the potential development of a third approach that uses $$H/C\_{org}$$ measurements as proxies for inertinite content. For example, if the $$H/C\_{org}$$ value is less than 0.2, it could be interpreted as indicating that 95% of the biochar is inertinite. While this simplification has been suggested by experts and holds promise, it is currently considered insufficiently rigorous due to a lack of supporting evidence and clear guidance. ### Uncertainty assessment See general instructions for uncertainty assessment in the [Rainbow Standard Rules](https://docs.rainbowstandard.io/~/changes/113/rainbow-standard-documents/rainbow-standard-rules/ghg-reduction-quantification#uncertainty-assessment). The outcome of the assessment shall be used to determine the percent of RCCs to eliminate with the [**discount factor**](#user-content-fn-16)[^16]. The three assumptions presented in the [Assumptions ](#assumptions)section have moderate uncertainty, but the most conservative approach is taken in the quantifications. The baseline scenario selection (if applicable) has low uncertainty, because the specific circumstances, amount and type of baseline material must be proven by the Project Developer. The equations and models have low uncertainty. The model for 100-year permanence from [Woolf et al., 2021](#user-content-fn-9)[^9] has moderate uncertainty because it is a model fitted to experimental data, which always introduces variability. The equations for 1000-year permanence from [Sanei et al., 2024](#user-content-fn-13)[^13] have low uncertainty because they are basic conversion equations. The uncertainty at the methodology level is estimated to be low. This translates to an **expected discount factor of at least 3%** for projects under this methodology. ## Sampling requirements The following indicators shall be measured for each production batch: * $$H/C\_{\text{org}}$$ * Carbon content (organic and/or total) * moisture content * random reflectance and residual organic carbon (only if applying for 1000-year permanence) Measurements shall be performed by laboratories with at least one quality assurance accreditation, such as: * ISO/IEC 17025 * CEN/TS 17225-1 * ISO 10694 Unaccredited laboratories from academic settings shall be evaluated on a case by case basis by the VVB and the Rainbow Certification Team. The sampling procedure detailed in sections below and summarized in Figure 1 is the **recommended approach** for representative sampling. However, Project Developers may implement their own approach if it is detailed in the PDD and in [Sampling Records](#sampling-records); ensures one representative sample per production batch; addresses samples and composite samples amount and frequency; and ensures homogenization. The VVB and the Riverse Certification team must validate the rigor and representativeness of the proposed sampling approach. The recommended approach sampling requirements are based on the following sources: * [EU Fertilising Products Regulation (EU) 2019/1009](#user-content-fn-17)[^17] * [European Biochar Certificate Guidelines Annex 4 Representative Sampling](#user-content-fn-18)[^18]

Figure 1: The Rainbow recommended sampling approach is summarized here, and detailed in the text in following sections.

#### Representative sampling One **representative sample per Production Batch** shall be created and sent for laboratory testing. This sample ensures that any within-batch variability is captured in the measurements. Table 1 details the number of composite samples that shall be taken per Production Batch to obtain one representative sample, based on the [EU Fertilising Products Regulation (EU) 2019/1009](#user-content-fn-17)[^17]. The representative sample size should be be 24 liters \* the *n* number of composite samples per Production Batch detailed in Table 1. *Table 1 Recommendations for the number of composite samples of biochar to take, based on the site's annual biochar production output.* | Annual output (tonnes) | Composite samples per Production Batch (n) | | ---------------------- | ------------------------------------------ | | ≤ 3 000 | 4 | | 3 001 – 10 000 | 8 | | 10 001 – 20 000 | 12 | | 20 001 – 40 000 | 16 | | 40 001 – 60 000 | 20 | | 60 001 – 80 000 | 24 | | 80 001 – 100 000 | 28 | The [European Biochar Certificate Guidelines Annex 4 Representative Sampling](#user-content-fn-19)[^19] should be followed for **taking composite samples**. Those requirements are summarized below. {% tabs %} {% tab title="Continuous production" %} * The first sample must be taken within 7 days of the start of the Production Batch. * To prepare **one sample**, 8 sub-samples of 3 liters each are taken at intervals of at least one hour directly at the discharge of the freshly produced material. This shall be repeated for three consecutive days. * The 24 samples are combined to form one composite sample. {% endtab %} {% tab title="Non-continuous production" %} * The first sample must be taken within 7 days of the start of the Production Batch. * Samples may be taken from a well-mixed pile of biochar produced within the last 7 days. * The amount of biochar used for one sample shall be equivalent to at least one day's production. * 24 sub-samples of 3 liters each shall be taken from different spots in the pile. * The 24 subsamples are combined to form one composite sample. {% endtab %} {% endtabs %} #### Homogenization The representative sample shall be homogenized by the Project Developer or by the laboratory that performs testing. The biochar shall be ground to a size of <3 mm. The ground sample is mixed by shoveling the pile three times from one pile to another. A sub-sample of 1.5 liters shall be taken from 15 spots in the mixed pile. The 15 sub-samples are re-combined, and then mixed by shoveling the pile three times from one pile to another. From the mixed pile of the combined sub-samples, 15 subsamples of 150 ml each should be taken at 15 different spots in the pile and combined. This combined homogenized representative cross sample is used for laboratory testing. #### Retention samples A one-liter retention sample shall be collected each day that biochar is produced. These samples should be combined for storage over the calendar month. Retention samples must be stored for a minimum of two years. #### Sampling records For **each Production Batch**, Project Developers shall submit a **Sampling Record** for verification to prove their adherence to the requirements above. Sampling Records shall include the following information for each sample taken: * Date of sampling * Amount of biochar sampled * Description of representative sampling process (either followed the recommended approach, or describe the individual approach) * Sample ID * Visual description and observation of biochar * Description of any potential anomalies * Proof of retention sampling (if performed for that Production Batch) * Photos showing the date, sample ID, and amount of biochar that is included in the present Sampling Record ## Validation and verification requirements #### Ex-ante validation data requirements Biochar projects often use carbon financing to launch new projects, and validation is done ex-ante before the project begins operations. In this case, [provisional RCCs](#user-content-fn-18) are estimated using reasonable project data estimates. These **provisional credit estimates are converted to verified issued credits upon verification** using real project data. Required project data estimates are detailed below. A project may use one quantification approach for ex-ante estimation, and use a different approach for verification. A project may use one quantification approach for ex-ante estimation, and use a different approach for verification. {% tabs %} {% tab title="Approach 1: 100-year removals with H/C" %} An estimated $$H/C\_{\text{org}}$$ ratio and $$C\_{\text{org}}$$ must be provided based on 1. measurements from samples from pilot phase or previous operations for the same site (**preferred option**), 2. equipment manufacturer data/quotes/estimates, 3. scientific literature for similar project conditions, or 4. verified measurements from other projects under similar conditions. If options 2-4 are used, the estimated $$C\_{\text{org}}$$ and $$H/C\_{\text{org}}$$ shall automatically be **discounted by 10% for the validation-stage estimates**, in order to ensure conservative estimates and avoid over-estimations. {% endtab %} {% tab title="Approach 2: 1000-year removals random reflectance" %} An estimated $$C\_{\text{org}}$$ must be provided based on the same sources described for Approach 1: 100-year removals with H/C. This estimated value shall be used for quantification. Project Developers must prove that they plan to perform pyrolysis at a temperature of at least 500°C. Project Developers shall provide either: * $$R\_o$$ distribution results for a sample of biochar produced at the project site under pilot/testing conditions. Measurements shall be used in Eq. 3 and 4 to estimate 1000 year removals. * $$H/C\_{\text{org}}$$ may be used as a proxy **only for validation stage estimates** (not during verification). $$H/C\_{\text{org}}$$ must be provided based on the same sources described for Approach 1: 100-year removals with H/C. This estimated value **must be below 0.4** to use the 1000-year approach. A conservative **default value of** $$F\_{perm}$$ **= 0.8 shall be assumed** for all projects with a $$H/C\_{\text{org}}$$ < 0.4 for the purpose of ex-ante validation estimates of 1000-year removals. The real $$R\_o$$ results shall be used for verification and the final issuance of 1000-year removal RCCs. {% endtab %} {% endtabs %} #### Ex-ante validation delivery risk When validation is conducted on non-operating projects that are in the planning stage, Project Developers shall prove during **validation** that the biochar is reasonably expected with strong certainty to end up in its intended use (application to soil). This shall be provided by either: * Option 1: Signed agreements with the end-buyers that they intend to purchase the agreed upon quantity of biochar annually (preferable). * Option 2: If the project is in planning stages and has not yet secured a buyer, a signed agreement from the Project Developer of their intended buyer/user of biochar. Note that the **delivery risk** is higher for this option, so Option 1 is preferable. An increased discount factor may be applied. #### Verification of biochar end use Upon **verification**, once the project has started operating, Project Developers shall prove that biochar has been used in the intended application for each Production Batch, (e.g. incorporated into soils, added to fertilizer mixes…). This shall be done in **Biochar Application Verification Reports** that shall contain all of the following: * Tracking records of the purchase and/or delivery of the biochar to its end use point of use, specifying the date, amount of biochar and Production Batch ID. * GPS coordinates of all end use points with according amounts of biochar, if known to the Project Developer. * Company name and individual contact information for each buyer/user of biochar, for traceability and random checking by VVBs. * Photo diary of biochar application, including photos of for example the biochar being delivered, tags/labels with information, road signs during delivery, process of biochar spreading. ## Monitoring plan Monitoring Plans for this module shall include, but are not limited to, tracking of the following information **for each Production Batch**: * Description of the pyrolysis conditions (temperature and residence time) and any variability in the process * Amount of biochar produced, in tonnes of fresh biochar * Moisture content of biochar * Organic carbon content * $$H/C\_{\text{org}}$$ (only for [Approach 1: Modeling 100-year removals with H/C org](#unteq8ror26g)) * Random reflectance ( $$R\_o$$) mean and distribution, and residual carbon content (only for [Approach 2: Estimating 1000-year removals using random reflectance](#id-2rhx2av7of74)) * [ESDNH pollutant measurements](#id-82n4j72vjt9v-1) * [Biochar Application Verification Reports](#id-1vij2jfikmk5-1), with names and GPS coordinates of spreading locations, among other information * [Sampling records](#sampling-records) Monitoring Plans for this module shall include, but are not limited to, tracking of the following information **for each calendar year**: * Number of Production Batches * Total amount of biochar produced per year, in tonnes of fresh biochar The Project Developer is the party responsible for adhering to the Monitoring Plan. ## Appendix The table below presents a non-exhaustive selection of Ecoinvent activities that may be used in the GHG reduction calculations for this module. Additional activities may be used for any project, if the following selection does not cover all relevant activities. *Table A1 List of ecoinvent 3.11 processes used in the GHG reduction quantification model, all processes are from the cutoff database*

Input	Ecoinvent activity name
Peat moss	peat moss production, horticultural use, RoW
Perlite	expanded perlite production, CH
Lime	market for lime, RER
Nitrogen mineral fertilizer	market for inorganic nitrogen fertiliser, as N, country specific
Phosphorus mineral fertilizer	market for inorganic phosphorus fertiliser, as P2O5, country specific
Potassium mineral fertilizer	market for inorganic potassium fertiliser, as K2O, country specific
Mineral NPK fertilizer #1	market for NPK (26-15-15) fertiliser, RER
Mineral NPK fertilizer #2	market for NPK (15-15-15) fertiliser, RER

## Risk evaluation template :point\_right: Download the template [here](https://docs.google.com/spreadsheets/d/1UowlcXUj2W2FIiM8Qn_YFd5NDH1l5UGgm4isfy0Gk-8/edit?usp=sharing) {% embed url="" fullWidth="true" %} ## Version history This page describes the changes in the Biochar application to soils module. Because this module is considered the V2.0 of the Rainbow BECCS and Biochar V1.0 methodology, the table below also includes changes from the Rainbow BECCS and Biochar V1.0 methodology that are covered in other modules (e.g. [Biomass feedstock](https://docs.rainbowstandard.io/~/changes/113/methodologies/biomass-carbon-removal-and-storage-bicrs/carbon-capture/biomass-feedstock)).

Description of the change	Justification	Date	Version changed to
Specify residual organic carbon measurements needed for 1000-year removal claims	Provide clearer and more comprehensive instructions	July 2025	V2.2
Re-introduce 100-year carbon degradation model equations based on soil temperature	Aligning with common biochar modeling practices.	March 2025	V2.1
Changed pollutant requirements from European Biochar Certificate (EBC) thresholds to World Biochar Certificate (WBC) thresholds	Adding more projects outside Europe, more reasonable and feasible to hold them to worldwide best standards, not European	March 2025	V2.1
Added equations for calculation GHG reductions	Increased transparency.	September 2024	V2.0
Aligned terminology with ISO 14064-2:2019	Improved consistency with the voluntary carbon market. LCA principles still apply.	September 2024	V2.0
Added risk assessment template for environmental and social do no harm	Provide more detailed and prescriptive assessment framework, clearer instructions for project developers.	September 2024	V2.0
Removed text for sections that are the same for all methodologies: Measurability Real Additionality Technology readiness level Minimum impact Independently verified	Repeated text from the Standard Rules.	September 2024	V2.0
Added Monitoring Plan section	Alignment with Rainbow Standard Rules V6.	September 2024	V2.0
Remove Rebound Effect and Independently Validated criteria	Alignment with Rainbow Standard Rules V6.	September 2024	V2.0
Added uncertainty assessment section	Alignment with Rainbow Standard Rules V6.	September 2024	V2.0
Infrastructure and machinery quantification expanded and specified, simple option added	Simplification, results not sensitive to impacts	September 2024	V2.0
New Leakage requirements	More rigorous eligibility criteria, and clear requirements and instructions for Project Developers	September 2024	V2.0
Allow option for 1000 year removals, measurement of random reflectance	Updated research	September 2024	V2.0
Added verification of end use reports	Increased rigor to ensure biochar is used as claimed	September 2024	V2.0
Added precise sampling requirements	Provide Project Developers with clear expectations, ensure representative sampling	September 2024	V2.0
Allow option to monitor data and quantify GHGs per production batch	Facilitate data collection and reporting for Project Developers	September 2024	V2.0
Biomass feedstock shall only be waste and biomass cultivated from sustainable production is not allowed	Increased stringency, following best practice and scientific recommendations	September 2024	V2.0

[^1]: *EBC (2012-2023) 'European Biochar Certificate - Guidelines for a Sustainable Production of Biochar.' Carbon Standards International (CSI), Frick, Switzerland. (). Version 10.3 from 5th Apr 2022.* [^2]: Inertinite is a type of maceral. Macerals are the organic compounds in materials like coal and shale, and are extremely permanent. They are analogous to mineral carbon in rocks. [^3]: * Schmidt, H.-P., Kammann, C., Hagemann, N., Leifeld, J., Bucheli, T.D., Sánchez Monedero, M.A., Cayuela, M.L., 2021. Biochar in agriculture – A systematic review of 26 global meta-analyses. GCB Bioenergy 13, 1708–1730.[ https://doi.org/10.1111/gcbb.12889](https://doi.org/10.1111/gcbb.12889) - Joseph, S., Cowie, A.L., Van Zwieten, L., Bolan, N., Budai, A., Buss, W., Cayuela, M.L., Graber, E.R., Ippolito, J.A., Kuzyakov, Y., Luo, Y., Ok, Y.S., Palansooriya, K.N., Shepherd, J., Stephens, S., Weng, Z. (Han), Lehmann, J., 2021. How biochar works, and when it doesn’t: A review of mechanisms controlling soil and plant responses to biochar. GCB Bioenergy 13, 1731–1764.[ https://doi.org/10.1111/gcbb.12885](https://doi.org/10.1111/gcbb.12885) [^4]: Goddin, J., Marshall, K., Pereira, A., Tuppen, C., Herrmann, S., Jones, S., Krieger, T., Lenges, C., Coleman, B., Pierce, C., Iliefski-Janols, S., Veenendaal, R., Stoltz, P., Ford, L., Goodman, T., Vetere, M., Mistry, M., Graichen, F., Natarajan, A., Sullens, W., 2019. Circularity Indicators: An Approach to Measuring Circularity, Methodology. [^5]: Ellen Macarthur Foundation, ANSYS Granta, 2019. An approach to measuring circularity. Published in 2015, adapted in 2019. [URL](https://emf.thirdlight.com/link/3jtevhlkbukz-9of4s4/@/preview/1?o) [^6]: WBC (2023): World Biochar Certificate – Guidelines for a Sustainable Production of Biochar and its Certification.' Carbon Standards International, Frick, Switzerland, (), version 1.1 from 20th December 2024. [URL](https://www.european-biochar.org/media/doc/2/wbc_1_1.pdf). [^7]: The coordinates are used by Rainbow Certification Team to obtain the average soil temperature (°C) where the biochar is spread. [^8]: Wernet, G., Bauer, C., Steubing, B., Reinhard, J., Moreno-Ruiz, E., Weidema, B., 2016. The ecoinvent database version 3 (part I): overview and methodology. Int J Life Cycle Assess 21, 1218–1230. [^9]: Woolf, D., Lehmann, J., Ogle, S., Kishimoto-Mo, A.W., McConkey, B., Baldock, J., 2021. Greenhouse Gas Inventory Model for Biochar Additions to Soil. Environmental Science & Technology 55, 14795–14805.[ https://doi.org/10.1021/acs.est.1c02425](https://doi.org/10.1021/acs.est.1c02425) [^10]: IPCC 2019. Appendix 4 Method for Estimating the Change in Mineral Soil Organic Carbon Stocks from Biochar Amendments: Basis for Future Methodological Development. 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 4 Agriculture, Forestry and Other Land Use. [URL](https://www.ipcc-nggip.iges.or.jp/public/2019rf/pdf/4_Volume4/19R_V4_Ch02_Ap4_Biochar.pdf). [^11]: Lembrechts et al., Global maps of soil temperature (2021). Global Change Biology. DOI: [10.1111/gcb.16060](https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.16060). [URL](https://zenodo.org/records/7134169). [^12]: Azzi, E.S., Li, H., Cederlund, H., Karltun, E., Sundberg, C., 2024. Modelling biochar long-term carbon storage in soil with harmonized analysis of decomposition data. Geoderma 441, 116761. [^13]: Sanei, H., Rudra, A., Przyswitt, Z.M.M., Kousted, S., Sindlev, M.B., Zheng, X., Nielsen, S.B., Petersen, H.I., 2024. Assessing biochar’s permanence: An inertinite benchmark. International Journal of Coal Geology 281, 104409[ https://doi.org/10.1016/j.coal.2023.104409](https://doi.org/10.1016/j.coal.2023.104409) [^14]: International Committee for Coal and Organic Petrology (ICCP), 2001. The new inertinite classification (ICCP System 1994). Fuel 80, 459–471.[ https://doi.org/10.1016/S0016-2361(00)00102-2](https://doi.org/10.1016/S0016-2361$00$00102-2) [^15]: determined by e.g. thermogravimetric analysis (TGA) or Rock-Eval 6 [^16]: A percentage of verified Rainbow Carbon Credits eliminated from each project and never issued. This acts as a safeguard against uncertainty in GHG reduction quantifications and overestimated carbon removal/avoidance. [^17]: Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down rules on the making available on the market of EU fertilising products and amending Regulations (EC) No 1069/2009 and (EC) No 1107/2009 and repealing Regulation (EC) No 2003/2003 (Text with EEA relevance), 2024. [URL](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:02019R1009-20240703) [^18]: *EBC (2012-2023) 'European Biochar Certificate - Guidelines for a Sustainable Production of Biochar.' Carbon Standards International (CSI), Frick, Switzerland. (). Version 10.3 from 5th Apr 2022.* [*URL*](https://www.european-biochar.org/media/doc/2/version_en_10_3.pdf) [^19]: *EBC (2012-2023) 'European Biochar Certificate - Guidelines for a Sustainable Production of Biochar.' Carbon Standards International (CSI), Frick, Switzerland. (). Version 10.3 from 5th Apr 2022.* [URL](https://www.european-biochar.org/media/doc/2/version_en_10_3.pdf)