GHG quantification

Calculations of GHG emissions for the baseline and project scenarios shall follow a robust, recognized method and good practice guidance. The overall methodological approach is a comparative life cycle assessment (LCA) at the project-scale, based on ISO 14064-2:2019.

This methodology shall be used in conjunction with the Rainbow modules listed below. Modules are like mini-methodologies that only cover a part of the project life-cycle. Combining the relevant modules for a project results in a complete picture of the required data, calculations, monitoring plans, and other information needed for a full GHG quantification.

Processing and energy use

Transportation

Infrastructure and machinery

GHG quantification shall be done separately for each biochar Production Batch, since each batch by definition has distinctly measured biochar carbon characteristics. The GHG quantification results of multiple Production Batches may be combined for one monitoring period.

System boundary

The system boundary of this quantification section starts at the procurement of biomass feedstock, and ends at the biochar end of life, after accounting for decay and re-emission in its end use application. Biomass feedstock production impacts are excluded because biomass is required to be waste or invasive species, and therefore not allocated any production or cultivation emissions. The system boundary includes the following key steps, also displayed in Figure 1:

• biomass collection

• biomass transport to the kiln

• biomass processing (including but not limited to drying and chipping)

• energy used to start the kiln (including high-quality wood, and any associated leakage emissions)

• energy used to combust methane emissions within the reactor

• embodied emissions from manufacturing the kilns, including their shipping to the pyrolysis site and end of life waste treatment

• methane emissions from the pyrolysis process

• biochar transport to the site of use

Figure 1 The system boundary of the distributed biochar quantification is summarized. Processes are grouped and color-coded according to the section below where they are described in detail.

Any steps that are fully manual do not incur any GHG emissions. Any steps that would have occurred anyway in the baseline scenario shall be excluded from the system boundary.

The following high-level equations shall be used to calculate carbon removals from distributed biochar projects.

Calculations: Removals

$\textbf{(Eq.1)}\ Net\ Removal = R_{baseline}-R_{project}-E_{project}$

where,

• $Net\ Removal$ represents the net removals from the project during the monitoring period, in tonnes of CO$_2$eq. Its sign is positive.

• $R_{baseline}$ represents any baseline GHG removals, representing permanent storage that would have occurred in the absence of the project, in tonnes of CO$_2$eq. Its sign is negative. Its value is zero, as outlined in the baseline scope section.

• $R_{project}$ represents the project's gross GHG removals, in tonnes of CO$_2$eq. Its sign is negative.

• $E_{project}$ represents the project's total induced GHG emissions across the project life cycle, in tonnes of CO$_2$eq. Its sign is positive.

$\textbf{(Eq.2)}\ E_{project} = {E}_{project,\ leakage} + E_{project,\ methane}+ {E}_{Transport,\ total}+ E_{infra,\ machinery} + E_{project,\ processing}$

where,

• $E_{project}$ was described in Eq. 1.

• $E_{project,\ leakage}$ represents the project's GHG emissions from leakage from use of biomass.

• $E_{project,\ methane}$ represents the total methane emissions from pyrolysis, in tCO$_2$eq, calculated in the Pyrolysis process section below.

• ${E}_{Transport,\ total}$ represents the project's GHG emissions from the Transportation module, including the energy use and embodied emissions involved in transporting all input and output materials.

• $E_{infra,\ machinery}$ represents the total emissions from the Infrastructure and machinery module allocated to the project for the monitoring period.

• $E_{project,\ processing}$ represents the total emissions from other inputs and outputs calculated in the Processing and energy use module.

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GHG quantification is performed for each Production Batch, based on the amount of biochar produced, but removal Rainbow Carbon Credits (RCCs) are issued on the basis of biochar delivery and application in an eligible end use. The following equation is used to determine the number of RCCs to issue per monitoring period, accounting for a potential delay in biochar use after production. See the Functional unit section for more details.

$\textbf{(Eq.3)}\ Removal\ RCCs= \frac{Net\ removal}{tonne\ or\ m^3\ biochar\ produced} \times tonne\ or\ m^3\ biochar\ delivered$

Where

• $Removal\ RCCs$ represents the number of removal credits to be issued at the end of the monitoring period.

• $Net\ removal$ was calculated in Eq. 1.

• $tonne\ or\ m^3\ biochar\ produced$ represents the amount of biochar produced in the entire Production Batch. Project Developers may choose whether to report it by mass or volume, in tonnes or in m³ of biochar.

• $tonne\ or\ m^3\ biochar\ delivered$ represents the amount of biochar delivered in an eligible end use in the monitoring period, for the given Production Batch. It must be reported in the same units as for the $tonne\ or\ m^3\ biochar\ produced$ variable.

Functional unit

The functional unit shall be 1 tonne of biochar produced or 1 m³ of biochar produced, depending on the project's chosen measurement method for the Biochar amount produced.

Input data shall be provided for all processes related to biochar production in the given Production Batch, and net project removals are first calculated for all processes across the entire duration of the Production Batch.

This is normalized to net removals per functional unit by dividing by the amount of biochar produced in the Production Batch.

The number of credits to issue in the given monitoring period is calculated by multiplying the amount of biochar delivered applied in an eligible end use, by the net removals per tonne or m³ of biochar produced.

This approach is detailed in Eq. 3 above.

Data sources

The required primary data for GHG calculations from projects are presented in Table 1. These data shall be aggregated for all kiln runs within a Production Batch, after being measured and reported in dMRV at the frequencies summarized in the Monitoring section, and made publicly available.

Note that the table does not include all information needed for project monitoring and verification: only the data inputs for ongoing GHG quantification. The full list of information is provided in the minimum requirements for a Monitoring Plan.

Table 1 Summary of primary data needed from projects and their source for GHG quantification. All primary data sources listed here are required to be monitored and updated during verification. *Note that only one approach is required for reporting transport data. See the Transportation module for more details. **See the Infrastructure and machinery module for more details.

Category	Parameter	Unit	Source
General, credit issuance	Volume or mass of biochar delivered in permanent end use	m3 or tonnes of biochar	Measured onsite, dMRV
Carbon storage	Volume or mass of biochar produced	m3 or tonnes of biochar	Measured onsite, dMRV
Carbon storage	Bulk density of biochar (only if using volume)	tonne of biochar/m3	Measured onsite, dMRV
Carbon storage	Biochar moisture content () (only if using mass)	Percent	Elemental analysis by accredited laboratory
Carbon storage	Biochar $H/C_{\text{org}}$	Ratio	Elemental analysis by accredited laboratory
Carbon storage	Biochar organic carbon content	Percent	Elemental analysis by accredited laboratory
Carbon storage	Fraction of $R_{O}$ distribution measurements above 2% (only if using 1000-year approach)	Fraction	Analysis by accredited laboratory
Carbon storage	Residual organic carbon ($C_{org,\ f\ residual}$) (only if using 1000-year approach)	Fraction	Analysis by accredited laboratory
Carbon storage	GPS coordinates of biochar spreading sites (for determining soil temperature)	coordinates	dMRV
Biomass leakage	Carbon sequestration rate (or use default 0.5%)	Percent	Secondary literature, models
Pyrolysis process	Methane emissions rate	g CH4/kg dry biochar	Analyses from accredited independent provider
Pyrolysis process	Energy or wood for starting pyrolysis (amount and type)	MJ, kWh, liters fuel, kg wood	Measured onsite, dMRV
Pyrolysis machinery	Item and material type, material amount, item lifetime**	kg, tonne, m3 years e.g. kiln made of 80 kg steel for 5 years	Technical specifications, bill of materials, invoices
Transport of biomass	Distance biomass transported by motorized vehicle*	km	Operational records, conservative justified estimates
Transport of biomass	Weight of biomass transported*	tonne	Operational records, conservative justified estimates
Transport of biomass	Vehicle type for biomass transport*	category	Operational records, conservative justified estimates
Transport of biomass	Fuel quantity consumed for biomass transport*	liters fuel	Operational records, conservative justified estimates
Transport of biochar	Distance biochar transported by motorized vehicle*	km	Operational records, conservative justified estimates
Transport of biochar	Weight of biochar transported*	tonne	Operational records, conservative justified estimates
Transport of biochar	Vehicle type for biochar transport*	category	Operational records, conservative justified estimates
Transport of biochar	Fuel quantity consumed for biochar transport*	liters fuel	Operational records, conservative justified estimates

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 methodology.

Assumptions

1. All biochar from the same Production Batch has the same characteristics (e.g. , $H/C_{\text{org}}$...).

2. All biochar made from the same feedstock has the same methane emission rate from pyrolysis.

3. The permanent carbon sequestration rate from biomass leakage, where the alternate fate is being left on the field to decompose, is at least 0.5%.

Baseline scenario

There is no baseline 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 Standard Rules, this assumption shall be re-assessed at a minimum every 5 years, and any changes to this assumption would be applied to existing projects.

Project scenario

Biomass leakage

This section is only required if the feedstock's alternative use was to be left on the soil or reapplied to soils for nutrient recycling. This includes but is not limited to:

• mulching

• composting

• spreading fast-decaying cellulose-based residues (e.g. decay within 5 years)

Project leakage shall account for permanent carbon storage that would have occurred anyway in the absence of the project.

Although most biomass carbon would be released before the project's permanence horizon, a small fraction may be stabilized permanently as soil carbon. This portion is counted as leakage and deducted from the project's carbon removal capacity.

The uncertainty around biomass carbon being 1) naturally incorporated into the soil and 2) converted to a stable carbon form is high, influenced by factors such as climate, soil type, soil health, and land use, making it hard to estimate for individual projects. Thus, it is assumed that a default 0.5% of the carbon in the biomass feedstock left on the soil, or reapplied to soil, will be permanently stored in soils.

Project Developers may conduct a project-specific assessment and provide a different carbon sequestration rate, but the final rate used in calculations shall be 0.5% or higher.

Biomass diversion and replacement

Leakage associated with the diversion and replacement of the biomass from its alternative use shall be quantified for each biomass used.

Project Developers shall follow the Alternative use and Biomass diversion and replacement guidelines in the Leakage section to determine the type and amount of replacement/substitute product or process.

Project Developers shall provide a conservative and representative emission factor for the production and use of the replacement product.

Calculations: Biomass leakage, biomass amount, biochar amount

$\textbf{(Eq.4)}\ {E}_{project\ leakage}= E_{CF\ carbon\ storage}+ E_{replacement}$

Where,

• $E_{CF\ carbon\ storage}$ represents the biomass leakage from the monitoring period, in tCO$_2$eq. This value shall be applied to Equation 2.

• $E_{CF\ carbon\ storage}$ represents the permanent carbon removal in the baseline scenario in the monitoring period, in tCO$_2$eq.

• $E_{replacement}$ represents the leakage emissions from the diversion of biomass and replacement of its substitute, in tCO₂eq.

$\textbf{(Eq.5)}\ E_{CF\ carbon\ storage}= A_{biomass}\times C_{biomass} \times S_{biomass} \times C\ to\ {CO}_{2}$

Where,

• $E_{CF\ carbon\ storage}$ was described in Equation 4.

• $A_{biomass}$ represents the amount of biomass feedstock used in the monitoring period, in tonnes of dry matter. It may be weighed directly and converted to dry mass using biomass moisture content measurements, or calculated using Eq. 6 below

• $C_{biomass}$ represents the concentration of carbon in the biomass feedstock, in tonnes of carbon per tonne of dry matter. This value may come from secondary sources.

• $S_{biomass}$ represents the permanent sequestration rate of carbon applied to soils, which may be provided by the Project Developer from secondary sources, but shall be at least 0.5%, as described in the Assumptions section.

• $C\ to\ {CO}_{2}$ is 44/12 = 3.67, and represents the molar masses of CO$_2$ and carbon respectively, and is used to convert tonnes of carbon to tonnes of CO$_2$eq.

$\textbf{(Eq.6)}\ A_{biomass} = A_{biochar} \div CF_{biomass\ to\ biochar}$

Where,

• $A_{biomass}$ was described in Eq. 5.

• $A_{biochar}$ represents the amount of biochar produced during the monitoring period, in tonnes of dry biochar. It shall be calculated using either Equation 7, 8, or 9, depending on the project's chosen biochar amount measurement method.

• $CF_{biomass\ to\ biochar}$ represents the biomass to biochar conversion factor, as tonnes fresh biomass input $\div$ tonnes dry biochar output. It may be taken from secondary sources or measured for each project, as detailed in the Sampling and measurements section.

$\textbf{(Eq.7)}\ A_{biochar} = V * BD_{fresh}*(1-M_{fresh\%})$

where,

• $A_{biochar}$ represents the amount of biochar produced during the monitoring period, in tonnes of dry biochar.

• $V$ represents the volume of biochar produced in m³.

• $BD_{fresh}$ represents the bulk density of fresh biochar (as opposed to dry biochar), considering the mass of fresh biochar, in tonnes biochar/m³.

• $M_{fresh\%}$ represents the moisture content of fresh biochar, on a weight basis (%w/w), so $1-M_{fresh\%}$ converts to dry mass of biochar.

$\textbf{(Eq.8)}\ A_{biochar} = mass_{fresh}*(1-M_{fresh\%})$

where,

• $A_{biochar}$ represents the amount of biochar produced during the monitoring period, in tonnes of dry biochar.

• $mass_{fresh}$ represents the mass of fresh or quenched biochar directly measured with scales at each kiln, in tonnes.

• $M_{fresh\%}$ represents the moisture content of fresh biochar, on a weight basis (%w/w), so $1-M_{fresh\%}$ converts to dry mass of biochar.

$\textbf{(Eq.9)}\ A_{biochar} = mass_{bone\ dry}$

where,

• $A_{biochar}$ represents the amount of biochar produced during the monitoring period, in tonnes of dry biochar.

• $mass_{bone\ dry}$ represents the mass of dry biochar directly measured with scales at each kiln, in tonnes. Since it is measured on biochar immediately after exiting the kiln, it is assumed to be bone dry (i.e. 0% moisture content).

$\textbf{(Eq.10)}\ E_{replacement}=A_{biomass}*F_{conversion}* EF_{alternative \ use}$

where,

• $E_{replacement}$ was described in Equation 4.

• $A_{biomass}$ was calculated in Eq. 5.

• $F_{conversion}$ represents a conversion factor for biomass replacement of its substitute.

• $EF_{alternative \ use}$ represents the conservative and representative emission factor for the replacement product of the biomass, in tCO₂eq/appropriate unit.

Biomass processing

The Rainbow Processing and energy use module shall be used to quantify the emissions from energy or material use for preparing biomass for pyrolysis. This includes but is not limited to drying and chipping biomass.

Transport of biomass and biochar

If biomass is transported to a pyrolysis site, or biochar is transported to its end-use point, using a vehicle that is not manually powered, transport emissions shall be accounted for using the Transportation module to calculate ${E}_{Transport,\ total}$ used in Eq. 2.

For this distributed small-scale technology type, it is expected that direct proof of transport will be unavailable (e.g., distance transported or fuel use during delivery). Therefore, Project Developers may provide justified and conservative estimates of transport distance, fuel consumed, and transport method.

Pyrolysis process

Any energy used to start the kiln (including high-quality wood and any associated leakage emissions), as well as energy used to combust methane emissions within the reactor, shall be included in the project’s total induced GHG emissions quantification. These emissions shall be calculated using the Processing and energy use module.

Methane emissions from pyrolysis shall be accounted for using direct methane measurements on a subset of representative kiln runs, following the Sampling and measurements requirements, and using the following equations.

Calculations: Pyrolysis methane emissions

$\textbf{(Eq.11)}\ {E}_{project,\ methane}= A_{biochar}* E_{bioCH_4}\div 1000*GWP_{bioCH_4}$

Where,

• $E_{project,\ methane}$ represents the total methane emissions from pyrolysis, in tCO$_2$eq. It shall be used in Equation 2.

• $A_{biochar}$ represents the amount of biochar produced during the monitoring period, in tonnes of dry biochar. It shall be calculated using either Equation 7, 8 or 9, depending on the project's chosen biochar amount measurement method.

• $E_{bioCH_4}$ represents the emission rate of biogenic methane from the pyrolysis process, in gCH₄/kg dry biochar, measured according to the Sampling and Measurement requirements.

• ${GWP}_{bio\ CH4}$ represents the global warming potential of biogenic CH$_4$ over 100 years, which is 27 tCO$_2$eq/t CH$_4$.

• Divided by 1000 to convert from gCH₄/kg dry biochar to tonne CH₄/tonne dry biochar.

Infrastructure and machinery

The Rainbow Infrastructure and machinery module shall be used to quantify the embodied emissions of kilns.

Biochar carbon storage

Project Developers shall choose between one of two approaches to quantify the gross 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.

1. Modeling 100-year removals using bulk measurements of $H/C_{\text{org}}$, or

2. Estimating 1000-year removals using random reflectance measurements as proxies for inertinite.

Approach 1: Modeling 100-year removals using bulk measurements of $H/C_{\text{org}}$

Project Developers shall quantify the gross carbon removals from their biochar project by modeling 100-year removals using bulk measurements of $H/C_{\text{org}}$. These measurements shall be done once per Production Batch. The measurements shall be done on the Production Batch Representative Sample, mixing biochar from each kiln run. See Sampling and measurements for more details.

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 temperature.

Temperature shall be obtained in the following ways:

• Biochar application to soil or mixing into horticultural products: Soil temperature shall be obtained for the end use location of each biochar spreading or mixing 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.

• Biochar mixing into concrete: Average annual air temperature at the location where biochar is mixed into concrete shall be used. It shall be taken from reputable public databases.

Table 2 Soil temperature ranges are categorized and their corresponding c and m regression coefficients are presented, which are used in Eq. 10 below to calculate $F_{perm}$. Values are taken from Woolf et al., 2021.

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: Biochar carbon storage

$\textbf{(Eq.12)}\ F_{perm\ 100} = c - m*H/C_{org}$

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 2 for the corresponding project location's soil or air temperature.

• $H/C_{org}$ represents the ratio of molar hydrogen to organic carbon in biochar, measured via elemental analysis by an accredited laboratory for each production batch.

$\textbf{(Eq.13)}\ R_{project}= F_{perm\ 100}*{C_{org}*A}_{biochar}*C\ to\ {CO}_{2}*-1$

where,

• $R_{project}$ represents the total carbon removals from biochar during the monitoring period, in tonnes of CO$_2$eq. This value shall be applied to Equation 1 to calculate total project removals.

• $F_{perm\ 100}$ is calculated in Equation 12.

• $C_{org}$ represents the concentration of organic carbon in biochar, on a dry weight basis.

• $A_{biochar}$ represents the amount of biochar produced during the monitoring period, in tonnes of dry biochar. It is obtained using Equation 7, 8 or 9 depending on the project's chosen measurement method.

• $C\ to\ {CO}_{2}$ 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.

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.

Project Developers shall provide $R_o$ distribution, labile organic carbon content, and moisture content for biochar from 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 2a and 2b.

Figure 2a An example of a random reflectance frequency distribution diagram, with an analysis described below.

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.

Figure 2b An example of a random reflectance frequency distribution diagram, with an analysis described below.

Example 2: This biochar sample has more 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

$\textbf{(Eq.14)}\ F_{perm\ 1000} = {Sample\ fraction}_{> 2\%\ Ro} \times C_{org,\ f\ residual}$

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.

$\textbf{(Eq.15)}\ R_{project,\ 1000}=F_{perm\ 1000}*{C_{org}*A}_{biochar}*C\ to\ {CO}_{2}*-1$

where,

• $R_{project,\ 1000}$ represents the total carbon removals from biochar during the monitoring period, in tonnes of CO$_2$eq. This value shall be applied to Equation 1 to calculate overall project removals.

• $F_{perm\ 1000}$ is calculated in Equation 14.

• $C_{org}$, $A_{biochar}$ and $C\ to\ {CO}_{2}$ are described in Equation 13.

• It is multiplied by -1 to obtain a negative sign. Removals are reported as a negative value.

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 uncertainty of assumptions are assessed below:

Assumption	Uncertainty
All biochar from the same Production Batch has the same characteristics (e.g. , $H/C_{\text{org}}$, inertinite content).	In principle this assumption has low uncertainty, but the ability of Kiln Operators to maintain consistent pyrolysis conditions across sites and across kiln runs is moderately uncertain.
All biochar made from the same feedstock has the same methane emission rate from pyrolysis.	In principle this assumption has low uncertainty, but the ability of Kiln Operators to maintain consistent pyrolysis conditions across sites and across kiln runs is moderately uncertain.
The permanent carbon sequestration rate from biomass leakage, where the alternate fate is being left on the field to decompose, is 0.5%.	High uncertainty, but the total net project removals is not sensitive to this assumption, so a low overall impact.

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

Estimates may be used for the amount of processing and energy use inputs and the transport steps, rather than providing direct proof of each step. This is expected to introduce negligible to moderate uncertainty, depending on the level of justification provided for each project. For example, it may be negligible if the process is entirely manual/not motorized, requiring no transport or energy inputs. The uncertainty of these estimates and specific input data shall be assessed at the project level.

The uncertainty at the methodology level of the above-mentioned points are estimated to be moderate. This translates to a minimum discount factor of at least 6% for projects under this methodology.