# Sampling and measurements A summary of measurements and their frequency is outlined in the table below. See each corresponding section for more details.
Measurement frequencyParameters
Each Production Batch, on a single representative sample of biochar
  • H/C_{\text{org}} and organic carbon content (full description here)
  • Inertinite content (fraction of the distribution sample that has a random reflectance of 2% or higher) and residual carbon (if calculating 1000-year removals) (full description here)
  • Biochar moisture content, on at least 3 biochar samples (if measuring biochar amount via mass) (full description here)
Once per year, or anytime biomass feedstock changes
  • Methane emissions, on three runs representative of all other kilns in the same Production Batch (full description here)
  • Environmental pollutants of biochar, on one composite sample mixing biochar from each kiln run (full description here)
  • Dry bulk density of biochar, on at least one sample from each kiln (i.e. 20 different kilns, 20 bulk density measurements) (if measuring biochar amount via volume) (full description here)
  • Biomass to biochar conversion factor (if not weighing the biomass input of each kiln run) (full description here)
  • Updated biomass leakage assessment (full description here)
Each kiln run
  • Moisture content of biomass input (full description here)
  • Type of biomass input (full description here)
  • Amount of biomass input, via precise mass measurements if using a feedstock mix, or estimates if using a singular biomass (full description here)
  • Amount of any energy inputs used, for example for process ignition.
  • Mass or volume of fresh biochar produced (full description here)
  • Temperature curve measured in each kiln using real-time sensors, proving pyrolysis has occurred (full description here)
  • Sampling records (proof of setting aside a small sub-sample of biochar, to be combined with sub-samples from all other kiln runs in the same Production Batch) (full description here)
All biochar used
  • Proof of eligible, durable biochar end use, with names and GPS coordinates of spreading locations, among other information (full description here)
Once per year
  • Kiln Operator training (full description here)
  • Proof and findings from the visits of Kiln Supervisor to each Kiln Operator (full description here)
  • Proof of calibration and accuracy of onsite scales for weighing biochar to determine biochar amount (full description here)
Once per verification and credit issuance
  • Quality oversight report from the Project Developer (full description here)
  • Environmental sustainability and Leakage compliance of biomass feedstock (full description here and here)
## Production Batch definition A Production Batch is defined as the **biochar produced across multiple sites and kilns of the same technology type, with the same biomass feedstock type or mixture, quenching approach, and pyrolysis temperature curve**. See the [Eligible biomass feedstock](/methodologies/distributed-closed-kiln-biochar/eligibility-and-scope.md#eligible-biomass-feedstock-open) section for requirements on single and mixed feedstock definitions. It is assumed that all biochar from the same Production Batch has the same characteristics. The definition of **production batch is used to group the following measurements:** $$H/C\_{\text{org}}$$, organic carbon content, inertinite content (optional), and methane emissions. {% hint style="info" icon="lightbulb-gear" %} A Production Batch is **an accounting construct** used to group and track biochar produced under consistent conditions, rather than a discrete operational event. It represents a defined set of kiln runs sharing the same feedstock type, kiln type, and pyrolysis parameters, allowing that biochar to be characterized, sampled, and credited collectively. {% endhint %} **GHG quantification shall be done separately for each biochar** [**Production Batch**](#user-content-fn-2)[^2], 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 and credit issuance. A Production Batch is valid for **a maximum of 6 months operating time or 200 tonnes of biochar**, whichever comes first. After this period or mass threshold, the biochar is considered part of a new Production Batch, even if conditions remain unchanged. This means that after 6 months of operating time, the Production Batch ID resets, a new batch is created, and new monitoring requirements apply, regardless of whether 200 tonnes have been produced or if feedstock or pyrolysis conditions have changed. Where a project operates many kilns, Project Developers may choose how to designate subgroups of kilns that each contribute to their own distinct Production Batches. This allows projects to manage Production Batch validity periods more effectively, avoiding a situation where all kilns in a large project are tied to a single batch that reaches its validity limits quickly. Note that the 6-month validity clock runs on operating time. Production pauses during the rainy season do not count toward the 6-month limit, provided the 200-tonne threshold has not been reached. A 5-tonne tolerance buffer is allowed, permitting a Production Batch to reach up to 205 tonnes. This accounts for the on-the-ground challenges of predicting precise biochar output across multiple kilns over an extended period. {% hint style="info" %} For example, * A small project may only produce s of biochar evenly throughout the year. A new Production Batch would start at the 6-month mark, and biochar would start being added to a new Site Composite Biochar Pile. * A larger project may produce a total of 600 tonnes of biochar per year, with a total of 50 tonnes/month across all 10 kilns in the project, and 5 tonnes/month/kiln, operating year-round. The Project Developer could either: * keep all 10 kilns grouped together, and reach the 200 tonne mark within 2 months. This would result in 6 Production Batches in the year. Or, * split the kilns into two groups of 5 kilns each, and reach the 200 tonne mark for each group within 4 months. Two distinct production batches would be produced in parallel. They reset after 4 months, 3 times per year, for a total of 6 Production Batches. * A different project may produce 50 tonnes of biochar in January and February, then stop production for 5 months, and produce another 50 tonnes in August. The biochar produced in August may be grouped with the biochar produced at the beginning of the year in the same Production Batch, since the delineation is 6-months of operating time, not 6 calendar months. {% endhint %} Production Batches **may be non-contiguous**. {% hint style="info" %} For example, if Feedstock #1 if used on Day 1, a different Feedstock #2 on Day 2, and Feedstock #1 is used again on Day 3, the resulting biochar from Day 3 could be part of the same Production Batch as the biochar produced on Day 1. {% endhint %} ## Methane emissions Methane emissions shall be measured **anytime the biomass feedstock or feedstock mix changes, or annually if the biomass feedstock does not change**. See the [Feedstock composition and consistency](/methodologies/distributed-closed-kiln-biochar/eligibility-and-scope.md#feedstock-composition-and-consistency) section for the definition of a feedstock change. Measurements shall be conducted on three runs across three separate kilns of the same technology type and using the same feedstock, operated by different kiln operators where more than three operators are active in the project. Methane emissions testing, including results and photos of the process, may be handled in the dMRV app or in a separate report shared with Rainbow and the VVB. Methane emissions shall be reported in kg CH4/kg biochar. The **mean of all measurements plus one standard deviation** shall be used for [GHG quantification](/methodologies/distributed-closed-kiln-biochar/ghg-quantification.md#pyrolysis-process) of all biochar produced in that year using the same biomass feedstock, and shall remain representative of all kiln runs provided that: * the kiln type is the same, * the biomass feedstock type remains the same, and * biomass moisture content requirements are met for the methane-testing kiln runs, and are representative of expected moisture content during ongoing kiln runs (mean <20% for woody biomass; <15% for all other biomass; no individual measurement above 25%). #### Measurement timing Methane emission measurements shall be conducted once per 12-month period. Measurements must be completed before credits can be issued for any biochar produced within that period, but **may be conducted at any point during the 12-month period** to which they apply. If the representativeness conditions listed above are met, **measurement results may be applied both retroactively and prospectively** to kiln runs within the same 12-month period. {% hint style="info" %} For example, if biochar is produced from January through March, production then pauses, and resumes in November using the same biomass feedstock, kiln type, and operators, methane measurements from November may be applied to biochar produced in March of the same period. Credits for the January-March biochar cannot be issued in March because methane emission measurements would not be available at that time, but may be issued after the November measurement campaign, if adequate production records have been maintained demonstrating all representativeness conditions are satisfied. {% endhint %} #### **Measurement approaches** Methane measurements for closed kilns shall follow either the **carbon mass balance approach** or the **volumetric flow × gas concentration approach**, as described below. Proof of calibration and a measurement report signed by the independent provider must be submitted regardless of which approach is used.
NameDescriptionInstructions
Carbon mass balance

Follow the approach outlined in relevant scientific publications.

The difference in the mass of known carbon input (via biomass) and output (in the form of biochar) is assumed to be emitted as gas. The concentrations of CH4, CO, CO2, and other carbon-containing species are measured continuously throughout the kiln run, using instruments including but not limited to non-dispersive infrared (NDIR) sensors. The total amount of each gas species is calculated by multiplying the relative fraction of each species by the total mass of carbon-containing gas emitted.

Gas concentration measurements shall

  • be taken across the entire kiln run, from start up through the end of quenching (if applicable), and
  • use instruments calibrated in accordance with manufacturer specifications and relevant ISO standards for the gas species being measured, and
  • be conducted by an independent measurement provider with demonstrated technical competence in field emissions measurement.
Volumetric flow × gas concentrationGas flow rate is measured at a defined point in a chimney or flue stack, and gas concentration is measured simultaneously. Methane mass emissions are calculated as the product of the two.
Gas flow rate may be measured using portable instruments inserted into or clamped onto the stack, such as a thermal mass flow meter or pitot tube manometer, or using fixed laboratory-grade instrumentation installed by an accredited testing body.
This approach is only allowed if there is one sole exit point of flue gas from the closed system (i.e. a single chimney).

Gas concentration measurements shall

  • be taken across the entire kiln run, from start up through the end of quenching, and
  • be measured simultaneously at the same point in the stack, and

  • use instruments calibrated in accordance with manufacturer specifications and relevant ISO standards for volumetric flow and for gas species concentration, and

    • be taken by a measurement organization accredited with either ASTM D7036, ISO 17025, or approved by state or regional authority, or
    • for the use of portable equipment, be taken by a reputable independent instrument provider
## Biomass ### Biomass moisture content Kiln operators shall demonstrate that for each kiln run, the average moisture content of biomass is: * <20% (w/w) for woody biomass, or * <15% (w/w) for any other biomass, including any mixture with non-woody biomass. These thresholds serve two purposes: * ensuring that pyrolysis **methane emissions remain consistently low**, and * ensuring that annual methane emission measurements (conducted under the same moisture conditions) **remain representative** of all credited kiln runs. These thresholds are based on research[^7] demonstrating that below 15% moisture content, all biomass types produce reliably low methane emissions, and that for woody biomass specifically, methane emissions remain consistently low at moisture contents up to 20%. Moisture content shall be measured using a calibrated handheld moisture meter immediately prior to pyrolysis. A photograph of each sensor reading must be uploaded to the dMRV platform as evidence. Measurements shall be taken at a rate of one measurement per 100 kg of dried, ready-to-pyrolyze feedstock, with a minimum of 10 measurements per kiln run. Measurement points shall be evenly distributed across the biomass pile, covering both its surface area and depth. The mean of all measurements must not exceed the applicable threshold above, and no individual measurement shall exceed 25%. ### Biomass amount used The amount of biomass used serves two purposes: * quantifying counterfactual biomass carbon storage, where applicable, and * providing a rough validation check on the photographed biomass quantity against the reported biochar output. It shall be determined for each kiln run using one of the following approaches: * **Direct weighing** of biomass inputs for each kiln run, with moisture content subtracted using the biomass moisture content measurements. * **Calculation** by dividing the dry mass of biochar produced by a feedstock-specific biochar yield conversion ratio. Where the calculation approach is used: * **Amount of biochar produced** may be provided by weighing directly as dry mass, or derived from volume or quenched mass measurements using Equation 6 or 7 in the [GHG quantification](/methodologies/distributed-closed-kiln-biochar/ghg-quantification.md#calculations-biomass-leakage) section. * The **yield conversion ratio** may be drawn from reputable and transparent secondary sources, and must correspond to the project's specific configuration of kiln type, feedstock type, pyrolysis temperature, and duration. Where no suitable secondary values exist, the ratio shall be measured across at least three representative kiln runs. ## Biochar ### Biochar sampling procedure Kiln Operators and Kiln Supervisors shall follow the general biochar sampling procedure outlined below: {% stepper %} {% step %} **Each kiln run** After each kiln run at a given site, a defined quantity of biochar is set aside from that run, and added to the **Site Composite Pile**. The Kiln Operator continuously adds biochar subsamples to this single site-level pile throughout the entire Production Batch duration. The Site Composite Pile is stored in a protected and dry space. {% endstep %} {% step %} **Mixing the site's biochar, once per Production Batch** The Site Composite Pile shall be thoroughly mixed by the Kiln Operator to ensure homogeneity. Once per Production Batch, a representative sample of biochar is then taken from this mixed site-level pile by the Kiln Operator or the Kiln Supervisor. This is called the **Site Composite Sample**. {% endstep %} {% step %} **Combining all sites' biochar, once per Production Batch** The Site Composite Samples are combined from each site into a **Production Batch Composite Pile** representing biochar production across all sites for the Production Batch. {% endstep %} {% step %} **Taking a representative sample** The Production Batch Composite Biochar Pile is thoroughly mixed by the kiln supervisor, and a representative sample— the **Production Batch Representative Sample**— is taken and sent to an accredited laboratory for measurement of organic carbon content, permanence indicators (i.e. H/C ratio and/or inertinite content), and, once per year, environmental pollutants. {% endstep %} {% endstepper %} Biochar from all kiln runs throughout the entire Production Batch duration must be added to the Site Composite Pile before the composite sample is taken and sent for laboratory analysis. The Site Composite Sample may only be taken once the Production Batch is complete, either at the end of the 6-month validity period or upon reaching the 200-tonne threshold. Taking the sample earlier, while kiln runs are still ongoing, would mean the sample is not representative of all biochar in the batch. Specific protocols within this approach may vary depending on the project type and the kiln size. The [**suggested detailed approach**](#user-content-fn-8)[^8] is provided below, but Project Developers may propose their own approach if it: * is detailed in the PDD; * ensures one homogenized and representative composite sample per Production Batch; * describes the amount and frequency of subsamples and composite samples. The VVB and the Rainbow Certification team must validate the rigor and representativeness of the proposed sampling approach. Records shall be uploaded to dMRV at each step, and track the date and time, location, the kiln ID/QR code, the Production Batch ID/QR code, and visual proof of the steps taken. #### Suggested detailed biochar sampling approach * **Sampling each kiln run for Site Composite Pile:** Set aside a biochar sub-sample from each kiln run, by taking a small amount from 3 different spots in the biochar from the most recent kiln run. Continuously add these small samples to the Site Composite Pile throughout the Production Batch. * **Mixing for Site Composite Sample:** Grind the biochar to a size of approximately <3 mm. Mix the ground sample by shoveling the pile three times from one pile to another. A sub-sample is taken from 10 spots in the mixed pile. The 10 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, 10 subsamples should be taken at 10 different spots in the pile and combined. The remaining biochar in the Site Composite Pile may be used in an eligible permanent end use and credited. * **Mixing for Production Batch Composite Biochar Pile:** Collect all Site Composite Samples from different sites grouping their biochar into the same Production Batch. Combine all Site Composite Samples into one pile. Shovel the pile three times from one pile to another. Take a sub-sample of 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. * **Taking a representative sample:** From the mixed pile of the combined sub-samples, 10 subsamples should be taken at 10 different spots in the pile and combined. This final sample is the Production Batch Representative Sample, and shall be sent to an accredited laboratory for measurement of organic carbon content, permanence indicators (i.e. H/C ratio and/or inertinite content) and environmental pollutants. * **Maintain a Retention sample**: Keep the remaining biochar in the Production Batch Composite Pile in a protected area, separate from all other Production Batch Composite Piles, to be used as the retention sample. Retention samples must be stored for a minimum of two years. ### Biochar amount produced Project Developers shall choose one of the two following approaches for measuring the amount of biochar produced: **volume or mass**. The same measurement approach shall be used for all biochar, across all kilns for a given Production Batch. The options are outlined in the figure below, and detailed in the following sections.
#### Biochar volume Volume of biochar must be converted to mass of biochar, because laboratory measurements of organic carbon content and are provided on a dry w/w% basis (i.e. in g organic carbon/kg dry biochar). Biochar volume is **converted to dry mass using dry bulk density measurements**, which require **a critical biochar drying step**. All components are detailed below. * **Volume:** Project Developers shall establish a standardized container type (e.g. box or bag, rigid or loose material) for use across all project sites. All container volumes shall be predefined and tracked in dMRV. Kiln Operators must record the number of containers filled with biochar and applied to permanent end uses. Biochar volume must be measured for each kiln run. * **Dry bulk density**: Onsite measurements are required for bulk density and shall be conducted by the Kiln Supervisor. As part of their annual site visit, they shall collect a representative sample from the [Site Composite Pile](#user-content-fn-9)[^9] at each site. One biochar bulk density measurement must be established for each site per year, unless the feedstock changes. The dry mass of the sample for the bulk density measurement shall be obtained using one of the following methods: * Directly weigh bone-dry biochar upon exit from the kiln. Since this does not involve mixing a composite and representative sample, it must be done on at least 3 separate runs per kiln. * Weigh fresh biochar mass, and adjust by the measured moisture content, described below. * **Biochar drying and moisture content:** Biochar must be sufficiently dried to 0% moisture content to obtain accurate dry bulk density measurements. It shall be dried using one of the following methods: * Moisture analyzer: use a laboratory-grade [moisture analyzer](#user-content-fn-10)[^10]. * Oven drying: dry the biochar in a ventilated oven at at least 110°C for a minimum duration of 48 hours. Subtract the final mass from the initial to determine moisture content and confirm complete drying. * Where oven drying is used, the VVB shall conduct or oversee cross-check measurements of moisture content using a laboratory-grade moisture analyzer during the annual [site audit](/methodologies/distributed-closed-kiln-biochar/eligibility-and-scope.md#site-audits), covering biochar samples from at least 3 different production sites. These cross-checks serve to verify that oven drying achieved complete moisture removal. * Where the VVB's measurements differ materially from the kiln supervisor's records in a direction that would result in fewer credits being issued, the VVB's measurements shall supersede the Kiln Supervisor's records for crediting purposes, and the Project Developer shall investigate and document the discrepancy. * Where the VVB's measurements would result in the same or greater number of credits, the Kiln Supervisor's records may continue to be used.

Kiln Supervisors shall take and prepare the biochar sample following these steps:

  • Take a mixture of biochar sampled from the bottom, middle, and top of the Site Composite Pile, already set aside by the Kiln Operator for sampling.
  • Transport the biochar from the Kiln Operator’s site to the location with measurement equipment, taking measures to protect the biochar from breaking during transport (if applicable, depending on project design)
  • Keep biochar samples from each site separate.

  • If using fresh biomass, dry the sample using

    • a ventilated oven at at least 110°C for a minimum duration of 48 hours, or
    • a laboratory-grade moisture analyzer, described above.

Kiln Supervisors shall conduct and report bulk density measurements as follows:

  • Use containers of a standard material and predefined volume size.
  • Use scales with proven calibration and high accuracy (e.g., digital readings; if non-digital, values rounded down).
  • Conduct measurements separately for each site (samples from different sites shall not be mixed, and measurements shall not be taken on composite samples).
  • Outliers may be excluded from the bulk density dataset (defined as any individual measurement that is 3 standard deviations above or below the mean of the dataset).
  • The final bulk density value used for GHG quantification of each Production Batch shall be the mean minus one standard deviation of all measurements within that batch.
Photos shall be uploaded to dMRV at each step. Project Developers shall prove that all measurement instruments used, such as scales and/or moisture analyzers are calibrated at least once per year. The VVB shall review **all records** related to biochar drying and bulk density measurements to ensure that: * **Drying:** biochar was fully dried to 0% moisture content prior to measurement. * **Transport and handling:** the biochar sample used for bulk density measurement is similar to, and representative of, the biochar initially sampled, and has not been excessively damaged during transport or handling. * **Representative subsample:** the biochar sample used for bulk density measurement has a bulk density consistent with the larger biochar retention sample pile from which it was taken. #### Biochar mass If biochar mass is used as the main indicator of biochar production and use, Project Developers shall provide Kiln Operators with accurate and calibrated measurement scales. The biochar output of all kiln runs shall be weighed upon completion of pyrolysis. Biochar mass may be measured either before quenching (bone dry) or after quenching. If biochar is **weighed before quenching**, the recorded mass already reflects the dry mass of biochar produced and may be used directly to calculate carbon removals (see Eq. 9 in the [GHG quantification](/methodologies/distributed-closed-kiln-biochar/ghg-quantification.md#calculations-biomass-leakage-biomass-amount-biochar-amount) section). If biochar is **weighed after quenching**, the moisture content of the biochar must be measured and accounted for. Moisture content must be measured on at least 3 separate samples for every biochar Production Batch (see Eq. 8 in the [GHG quantification](/methodologies/distributed-closed-kiln-biochar/ghg-quantification.md#calculations-biomass-leakage-biomass-amount-biochar-amount) section). Moisture measurements shall be conducted using one of the following methods: * By the Kiln Supervisor, following the oven drying or [moisture analyzer](#user-content-fn-10)[^10] approach described above for biochar drying. Measurements must begin on the same day the biochar is produced and weighed (i.e. within 24 hours). Time-stamped photos shall be uploaded to dMRV at each step. * By sending biochar samples to an accredited independent laboratory for moisture content measurement. Samples shall be sent on the same day the biochar is produced and weighed, and must be protected to minimize moisture loss, including at a minimum wrapping the biochar in three layers of sealed plastic bags. Photos shall be uploaded to dMRV at each step, including time stamps showing that biochar is produced, weighed and sent on the same day (i.e. within 24 hours), and including photographic evidence of sealing the biochar sample. Project Developers shall prove that all measurement instruments used, such as scales and/or moisture analyzers are calibrated at least once per year. The VVB shall review all records related to biochar drying and moisture content measurements, if taken. ## Accredited labs Proximate and elemental analysis of biochar 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. [^1]: A production batch is defined as the biochar produced across multiple kilns of the same technology type, with the same biomass feedstock type or mixture, quenching approach, and pyrolysis temperature curve.
A production batch is valid for a maximum of 6 months operating time or 100 tonnes of biochar, whichever comes first. [^2]: A production batch is defined as the biochar produced across multiple kilns of the same technology type, with the same biomass feedstock type or mixture, quenching approach, and pyrolysis temperature curve.
A production batch is valid for **a maximum of 6 months operating time or 200 tonnes of biochar**, whichever comes first. [^3]: * Lotz, S., N.Hagemann, D.Hölscher, and H.-P.Schmidt. 2026. “Methane Emissions From Flame Curtain Pyrolysis (Kon-Tiki).” GCB Bioenergy18, no. 4: e70108. . * Cornelissen, Gerard, et al. “Flame Curtain Kilns Produce Biochar from Dry Biomass with Minimal Methane Emissions.” *Science of the Total Environment*, vol. 903, 1 Dec. 2023, pp. 166547–166547, . [^4]: * ISO 12039:2019: Stationary Source Emissions — Determination of the Mass Concentration of Carbon Monoxide, Carbon Dioxide and Oxygen in Flue Gas — Performance Characteristics of Automated Measuring Systems * ISO 25140:2010: Stationary Source Emissions — Automatic Method for the Determination of the Methane Concentration Using Flame Ionisation Detection (FID). * ISO 25139:2011: Stationary Source Emissions — Manual Method for the Determination of the Methane Concentration Using Gas Chromatography. [^5]: Some of this difference in carbon mass is actually lost as aerosols and particulate matter rather than gas, but treating it entirely as gaseous carbon may slightly overestimate total gas-phase emissions, making this a conservative assumption. [^6]: * ISO 16911-1:2013: Stationary Source Emissions — Manual and Automatic Determination of Velocity and Volume Flow Rate in Ducts — Part 1: Manual Reference Method. * ISO 16911-2:2013: Stationary Source Emissions — Manual and Automatic Determination of Velocity and Volume Flow Rate in Ducts — Part 2: Automated Measuring Systems. * EN 15259:2007: Air Quality — Measurement of Stationary Source Emissions — Requirements for Measurement Sections and Sites and for the Measurement Objective, Plan and Report. [^7]: * Cornelissen, Gerard, et al. “Flame Curtain Kilns Produce Biochar from Dry Biomass with Minimal Methane Emissions.” *Science of the Total Environment*, vol. 903, 1 Dec. 2023, pp. 166547–166547, . [URL](https://www.sciencedirect.com/science/article/pii/S0048969723051720). * Lotz, Simon, et al. “Methane Emissions from Flame Curtain Pyrolysis (Kon‐Tiki).” *GCB Bioenergy*, vol. 18, no. 4, 13 Mar. 2026, . [URL](https://onlinelibrary.wiley.com/doi/10.1111/gcbb.70108). [^8]: The recommended approach sampling requirements are based on the following sources: * [EU Fertilising Products Regulation (EU) 2019/1009](#user-content-fn-10)\[^10] * [European Biochar Certificate Guidelines Annex 4 Representative Sampling](#user-content-fn-11)\[^11] [^9]: After each kiln run at a given site, a defined quantity of biochar is set aside from that run, and added to the **Site Composite Pile**. Biochar subsamples are continuously added to this single site-level pile throughout the production batch duration. [^10]: Specifically a thermogravimetric moisture analyzer using the loss-on-drying (LOD) method. As opposed to a handheld moisture sensor. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.rainbowstandard.io/methodologies/distributed-closed-kiln-biochar/sampling-and-measurements.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.