Biochar application to soils

Module name

Module category

Carbon storage

Methodology name

Biomass carbon removal and storage (BiCRS)

Version

2.3

Methodology ID

RBW-BICRS-CS-BCSOIL-V2.3

Release date

January 21st, 2026

Status

In use

Glossary

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.

See more details on how modules are organized in the BiCRS home page.

How to use this module

BiCRS Methodology

Eligibility and scope

Eligible technologies

This module covers industrial biochar projects that meet all of the following requirements:

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 allows for issuance of 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.

Eligible end uses of biochar include application directly to soils or incorporation into soil-related products, such as soil additives, horticultural substrates, potting soils, fertilizer mixes, or compost.

This module also allows for issuance of avoidance RCCs on the basis of avoided horticultural products from the use of biochar (with strict proof of replacement, see the Baseline Scope section).

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.

Pyrolysis and gasification equipment manufacturers are not eligible Project Developers.

Certification requirements

Certification requirements for this module are defined in the BiCRS methodology. These cover crediting period duration, monitoring period duration, site audits, and versioning and project compliance.

Project scope

One project is defined as:

the operation of one or more pyrolysis units, across one or more sites,
within a single country,
using similar types of pyrolysis units,
using the same carbon removal measurement approach and durability claims, and
operated at sites that are under the oversight or data access of a single Project Developer, regardless of whether the developer directly owns or manages each site.

The project scope is cradle-to-grave and includes all processes that result from biochar production and application. This includes but is not limited to the following: all removals from biochar production, and all induced emissions related to biomass sourcing, leakage, upstream and downstream transport, embodied emissions from infrastructure and machinery, and onsite process emissions from biomass and biochar processing and energy use.

Any processes that would have occurred regardless of the biochar production and application activities may be excluded from the project scope.

Baseline scope

Several baselines may be applied depending on the type of credit issued:

Removal RCCs from biochar carbon removal:

the baseline shall include any permanent carbon removal that would have occurred in the absence of the project.
This includes but is not limited to permanent carbon storage from the alternate fate of the biomass feedstock used for pyrolysis.
It shall be assumed by default that no biomass feedstock would have been used to produce biochar in the absence of the project (i.e. there is no share of the project activity in the baseline scenario).

Avoidance RCCs from energy co-products:

the baseline shall include the equivalent amount of energy produced and exported by the project.
The type of energy selected for the baseline shall be representative of the energy produced by the project, and shall be specific and conservative.
All life cycle emissions from the baseline energy source shall be accounted for, including but not limited to raw material extraction, processing, upgrading, distribution, and if relevant, combustion.

Avoidance RCCs from horticultural products:

the baseline shall include the equivalent amount of horticultural products (e.g. peat, fertilizer...) produced and sold by the project.
The specific amount and type of avoided products must be provided by the Project Developer with project-specific documentation. It must show that the user of the biochar actually uses less of the horticultural product than they did previously, as a result of their use of biochar. This must be proven using, for example, operations tracking or invoices from the biochar user. 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.
All emissions from the baseline horticultural product life cycle that differ from the biochar life cycle shall be accounted for, including but not limited to raw material extraction and processing. If processes are equivalent between the biochar and horticultural product, such as transport delivery or packaging, they may be excluded from both the project and baseline scope for the purpose of quantifying avoidance RCCs from horticultural products.
By default, it shall be assumed that biochar application to soils does not replace any measurable, verifiable product.

The baseline scenario structure remains valid for the entire crediting period but may be significantly revised earlier if:

The Project Developer notifies Rainbow of a substantial change in project operations or baseline conditions, and/or
The methodology is revised, affecting the baseline scenario.

The specific values within the baseline scenario will be updated during each crediting period, using project data to accurately reflect the equivalent of the project’s operations.

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 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.

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%)

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.

Principles & requirements

The principles and requirements specific to this module are detailed in the sections below. Other principles and requirements shall be taken from the accompanying modules and methodologies:

BiCRS methodology

Additionality
No double counting
Environmental and social safeguards

Other modules

Co-benefits
No double counting
Environmental and social safeguards
Leakage

Durability

Durability threshold

All projects certified under this methodology shall prove durable carbon removals for at least 100 years. Project Developers may claim an extended durability threshold of 1000 years if they choose the 1000-year pathway for GHG quantification and measurements.

Reversal risk assessment

The major carbon reversal risks from biochar application to soil are:

Insufficient biochar stability, where biochar carbon is not sufficiently carbonized and is decomposed by microbes and soil organisms, resulting in re-emission of CO₂.
Failure to durably incorporate into soils, where biochar does not end up in a durable storage matrix (e.g. soil or soil-like material) and is instead burned or destroyed, intentionally or unintentionally (e.g. as fuel, in storage fires, or via waste incineration).

This methodology establishes the following mandatory project design requirements to mitigate these risks, detailed in the following sections:

measuring the durable carbon fraction
verification of biochar end use

Upon meeting these requirements for each verification and credit issuance, the risk of reversal is considered negligible for biochar application to soils. There are no further project requirements to assess reversal risks or conduct post-crediting monitoring for reversals.

All projects certified under this methodology shall contribute the default minimum 2% of their verified removal RCCs to the Rainbow Buffer Pool, as defined in the Rainbow Standard Rules.

Risk mitigation: Measuring permanent carbon fraction

Not all biomass carbon that is converted to biochar is expected to remain durably stored. The durability of biochar carbon depends on the its physicochemical stability, which is influenced by factors such as carbonization temperature and biomass feedstock.

Project Developers shall measure one of the following well-known proxy indicators of biochar durability for each production batch. These indicators serve both as eligibility thresholds, and as inputs to quantify the permanent fraction of carbon ( $F_{perm}$ ) expected to remain durably stored beyond the applicable durability threshold.

The fraction of permanently stored carbon shall be quantified using the models and equations specified in the GHG quantification section. Only this fraction shall be issued as removal RCCs.

Pathway

Indicator

Threshold requirement

100-year pathway

Hydrogen-to-organic-carbon atomic ratio ( $H/C_{\text{org}}$ )

$H/C_{\text{org}}$ must be less than 0.7

1000-year pathway

Random reflectance distribution

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 organic carbon.
Must also have $H/C_{\text{org}}$ less than 0.7

The distinction between the 100-year and 1,000-year durability pathways provides supplementary qualitative information and 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 quantification section.

These durability indicators shall be monitored for each production batch according to the Rainbow Sampling Requirements.

Issuing removal RCCs only for the verified, highly stable fraction of biochar carbon mitigates the risk of biological decomposition and re-emission after soil application.

Risk mitigation: Proof of biochar end use

Project Developers shall prove that all biochar has been used in the intended durable storage application (e.g. incorporated into soils, added to fertilizer mixes…). This shall be done in Biochar Application Verification Reports that 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.

Issuing removal RCCs only after verified incorporation into a permanent storage matrix mitigates the risk that biochar is burned, destroyed or otherwise re-emitted.

No double counting

See the BiCRS methodology No double counting 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.

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).

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.

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.

Co-benefits

Projects should support at least two quantifiable and verifiable environmental or social co-benefits, aligned with the UN Sustainable Development Goals (SDGs) framework. Any co-benefits claimed by the Project Developer shall be quantified, monitored, and audited for each verification and credit issuance.

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

Environmental and social safeguards

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, including but not limited to those related to pyrolysis, gasification, waste feedstock management, and biochar spreading on soils.

Feedstock sustainability risks shall be taken from the Biomass feedstock module.

Biochar applied to soils must be below the pollutant concentration thresholds outlined in Table 2, defined by the World Biochar Certificate Guidelines (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.

Substance

Limit amount (g/tonne dry matter)

300

200

100

1000

200

8 EFSA PAH

Disclaimer: The European Biochar Certificate (EBC) and the World Biochar Certificate (WBC) are independent certification programs designed to ensure the quality of biochar products. These certifications are administered and trademarked by Carbon Standards International (CSI) and are distinct from the Rainbow certification and the issuance of carbon credits.

The threshold values provided here are based on the voluntary guidelines of the World Biochar Certificate (WBC), reproduced with permission. While these values have been adopted by the Rainbow standard as pollutant thresholds, they are only indicative. Meeting these thresholds for Rainbow certification does not imply eligibility for or any association with the EBC or WBC programs. Project Developers certified under the Rainbow standard shall not make claims or use any trademarked materials from CSI, unless explicitly allowed by CSI.

Voluntary certification under the WBC and EBC schemes is overseen by CSI and includes additional requirements beyond pollutant thresholds.

Project Developers shall fill in the Rainbow Biochar application to soils risk assessment, 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
Health risks from exposure to harmful gasses and particles

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.

Any identified material risk (defined as issues with a risk score of moderate or higher) shall be subject to a 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.

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 substantial and sensitive GHG emission risks in the risk evaluation template.

All risk assessments must also address the Minimum ESDNH risks defined in the Rainbow Standard Rules.

Monitoring

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)
Random reflectance ( $R_o$ ) mean and distribution, and residual carbon content (only for Approach 2: Estimating 1000-year removals using random reflectance)
Environmental and social safeguards: biochar pollutant measurements
Biochar Application Verification Reports, with names and GPS coordinates of spreading locations, among other information
Sampling records

Monitoring Plans for this module shall include, but are not limited to, tracking of the following information for each reporting period:

Number of Production Batches
Total amount of biochar produced per year, in tonnes of fresh biochar
Co-benefits

Monitoring Plans shall include the following information for each monitored parameter:

monitoring frequency
emission sources and sinks
data source
measurement methods/procedures, and their accuracy and calibration
quality assessment or quality control procedures
responsible party for collecting and archiving data

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.

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).

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 () *

Percent

Laboratory chemical analyses

GPS coordinates 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

The ecoinvent database version 3.12 (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.

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 shall be applied for allocating GHG emissions between co-products.

Assumptions

By default, biochar application to soils does not replace any product.
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.
All biochar from the same production batch has the same characteristics (e.g. , $H/C_{\text{org}}$ , $R_o$ ).

Baseline scenario

The baseline scenario for the purpose of Removal vs Avoidance RCCs issuance is detailed below.

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 during the mandatory methodology revision process, and any changes to this assumption would be applied to existing projects.

Note that baseline scenario carbon sequestration may be included for the project from the biomass feedstock module.

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 Durability section. A single approach must be used consistently throughout each monitoring period, though a different approach may be chosen for subsequent monitoring periods.

Approach 1: Modeling 100-year removals with $H/C_{\text{org}}$

This approach is based on research from Woolf et al., 2021, and the IPCC modeling method. 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 and the global soil temperature dataset from Lembrechts et al., 2021. The Rainbow Certification Team can provide soil temperature values for Project Developers based on the provided GPS coordinates.

For verification, Project Developers shall provide primary project data in the form of laboratory measurements for $H/C_{\text{org}}$ and following the 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.

Soil temperature (°C)

<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, 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.

$\textbf{(Eq.2)}\ R_{project,\ 100}= F_{perm\ 100}*{C_{org}*A}_{biochar}*(1 - M_{\%})*C\ to\ {CO}_{2}*-1$

where,

$R_{project,\ 100}$ 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 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.
It is multiplied by -1 to obtain a negative sign. Removals are reported as a negative value in the BiCRS methodology.

Approach 2: Estimating 1000-year removals based on inertinite fraction

This approach is based on the research from Sanei et al., 2024, 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 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.

For verification, Project Developers shall provide primary project data in the form of laboratory measurements for $R_o$ distribution, labile organic carbon content, and moisture content for each production batch, following the 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.

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.

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.

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.

$\textbf{(Eq.4)}\ R_{project,\ 1000}=F_{perm\ 1000}*{C_{org}*A}_{biochar}*{(1 - M}_{\%})*C\ to\ {CO}_{2}*-1$

where,

$R_{project,\ 1000}$ 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 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.
It is multiplied by -1 to obtain a negative sign. Removals are reported as a negative value in the BiCRS methodology.

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

Rainbow 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

An uncertainty assessment is presented below for all aspects of GHG quantification set at the methodology level. The findings from this assessment are then applied at the project level, where project-specific GHG quantification also undergoes an uncertainty assessment.

The overall project GHG quantification uncertainty is determined by qualitatively combining both the methodology-level and project-specific uncertainties for each identified source of uncertainty.

The three assumptions presented in the 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 horticultural material avoided must be proven by the Project Developer.

The equations and models have moderate uncertainty. The model for 100-year permanence from Woolf et al., 2021 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 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 and measurements

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; ensures one representative sample per production batch; addresses samples and composite samples amount and frequency; and ensures homogenization. The VVB and the Rainbow 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
European Biochar Certificate Guidelines Annex 4 Representative Sampling

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.

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

3 001 – 10 000

10 001 – 20 000

20 001 – 40 000

40 001 – 60 000

60 001 – 80 000

80 001 – 100 000

The European Biochar Certificate Guidelines Annex 4 Representative Sampling should be followed for taking composite samples. Those requirements are summarized below.

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.

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

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 3.12 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 assessment template

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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).

Description of the change

Justification

Date

Version changed to

Restructure sections: added Baseline Scope, renamed Eligible technologies to Eligibility and scope, renamed Eligibility criteria to Principles & requirements, moved Monitoring Plan to Principles & requirements