Biochar Production in Mobile Reactors

This Module expands the applicability of biochar Projects to contexts where biomass resources are spatially dispersed, seasonally available, or generated in volumes insufficient to justify permanent, fixed-location infrastructure. By enabling biochar production to occur close to feedstock generation sites, mobile reactors can reduce or eliminate the need for long-distance biomass transport, thereby lowering associated costs, emissions, and logistical barriers. Mobile reactors are becoming more common solutions to residue management^1,2,3. This approach supports flexible deployment across agricultural, forestry, and land management settings, while maintaining the potential for localized soil application and carbon removal benefits⁴.

This Module outlines the specific requirements for Projects that employ mobile biochar production reactors. Mobile reactor Projects are characterized by the relocation of production units across multiple operating sites over the duration of a Project, either as individual units or as coordinated groups. This includes reactors that can self-move, be easily transported, or deconstructed and rebuilt. Mobile reactor Projects may operate sequentially at multiple locations, processing site-specific feedstocks under variable operating conditions. These requirements ensure robust data integrity, traceability, and environmental safeguards equivalent to those required for stationary facilities, while accounting for the operational variability inherent to mobile reactor deployment models.

Project Proponents must meet all the requirements set out in the Biochar Production and Storage Protocol and relevant Modules.

Due to the potential variability in operating conditions, feedstock characteristics, and site-specific constraints associated with mobile biochar production, Projects utilizing mobile reactors may exhibit greater heterogeneity in the physicochemical properties of the resulting biochar. Such variability can influence biochar stability, degradation rates, and long-term carbon storage durability. Accordingly, Projects employing mobile reactors are only eligible for crediting under the 200-year option of the Biochar Storage in Soil Environments Module, unless otherwise specified in future methodological updates.

Isometric will not credit Projects utilizing unmodified pit, flame curtain, or Kon-Tiki–style kilns. These systems are ineligible as they are not designed to operate under controlled pyrolysis conditions, but rather to facilitate reduced-emissions combustion. As a result, they are not optimized for the production of consistent, high-quality biochar. The combustion-oriented design limits the ability to accurately measure and quantify carbon retention and losses, particularly through gaseous emissions, and introduces variability in biochar characteristics due to fluctuating operating and environmental conditions.

Project operations may occur across multiple and varied locations, with site-specific environmental, social, and regulatory risks differing between deployments. Project Proponents must comply with the relevant sections of the Isometric Standard and Biochar Production and Storage Protocol.

Project Proponents must include a high-level risk assessment for the expected area of operation that addresses:

• i) the full geographical scope The Project could operate in;
• ii) All specific biomes and environment types where operations will occur (e.g., agricultural lands, temperate forests, grasslands, degraded lands); and
• iii) Any particular areas of concern within the geographical scope identified in (i) that require enhanced safeguards, including but not limited to: protected areas (national parks, wildlife reserves, UNESCO sites), critical habitats for endangered or threatened species, Indigenous territories, culturally significant sites, water source protection zones, and areas with vulnerable or marginalized communities.

If a new deployment is not covered by the above assessment, a reassessment will be required, and assessed at the next verification. Project Proponents must update the environmental and social safeguard assessment to identify location-specific risks and provide evidence of regulatory approval through applicable permits.

In addition to the requirements set out in the Isometric Standard and the Biochar Production and Storage Protocol, projects must implement a framework for Free, Prior, and Informed Consent (FPIC) to maintain high social integrity. This ensures that all stakeholders, particularly landowners and tenants, understand the long-term implications of the Project and participate voluntarily without coercion.

The Project Proponent must demonstrate that consent was obtained through a process that is:

• Free: Consent is given voluntarily, without manipulation, undue influence, or pressure.
• Prior: Consent is sought sufficiently in advance of any Project activities or feedstock collection.
• Informed: Stakeholders are provided with clear, accessible information regarding the Project’s risks, benefits, and their right to withdraw.
• Consent Documentation: All consent agreements must be digitally archived in the dMRV system, including time-stamped signatures or, where appropriate, video-recorded verbal consent for low-literacy contexts.

Mobile Projects often operate on land with complex ownership or tenancy structures. To protect the rights of those managing the land, the following requirements apply:

• Where feedstock is collected from land managed by a tenant, the Project Proponent must obtain explicit consent from both the landowner and the tenant.
• Through the dMRV app, the feedstock for every batch of biochar produced must be linked to a land parcel where consent has been pre-verified.
• The Project must verify that the collection of biomass residues does not infringe upon the existing rights of local communities to use that biomass for traditional purposes (e.g., fuel, fodder, or mulch).
• Participants must be informed of their right to refuse feedstock collection at any time.

Mobile biochar reactors may be subject to different air quality and fire safety requirements across jurisdictions. Maintaining a log of applicable permits for each operating location ensures regulatory compliance, supports transparent verification, and demonstrates that production activities are authorized and conducted in accordance with local safety and environmental regulations.

The Project must maintain a log of local air quality and fire safety permits for every jurisdiction where the mobile unit operates.

Mobile biochar reactors are biochar production units designed to be mobile, and operated, across multiple sites over the duration of a Project, either individually or in groups.

A reactor must be defined as mobile and relocate at least once over the duration of a Project to qualify under this Module.

To streamline the MRV process for mobile reactor deployments, Project Proponents may group individual mobile production units into a Mobile Production Group. A Mobile Production Group is defined as one or more mobile reactors that demonstrate high operational consistency, allowing for representative composite sampling rather than unit-by-unit characterization.

Unlike fixed distributed Facilities, Mobile Production Groups are defined by operational equivalence rather than geographic proximity. Grouping is determined by reactor specification, operating parameters, feedstock category, and procedural consistency.

• Mobile Production Unit:**** A single mobile reactor, including its associated control systems, sensors, and dMRV instrumentation. Each unit is uniquely identified by a reactor serial number or asset identifier.
• Mobile Production Group:**** One or more Mobile Production Units of the same reactor model, operating under the same Standard Operating Procedures (SOPs), control parameters, and compatible firmware version, and processing feedstock within a single defined Feedstock Category. A Mobile Production Group is the mobile-reactor equivalent of a Facility.
• Deployment Site:**** A discrete geographic location at which a Mobile Production Unit operates. Each Deployment Site is identified by GPS coordinates, a site identifier, and the dates of operation.

To qualify as a single Mobile Production Group, the grouped units must meet all of the following criteria:

• All units within the Group must be the same reactor model, using the same materials, design, and production scale.
• All units must be operating under a compatible firmware or control-system version and the same set of operating parameters (temperature setpoints, residence time, airflow configuration).
• Any unit that has been materially modified, rebuilt, or had its control system altered must be treated as a new unit and cannot be included in an existing Group until it has completed a full recommissioning process and, where applicable, a new Method A baseline (see Section 4).

• Operators across all units within the Group must have undergone the same standardized training program, and follow identical SOPs.

• Units must have the same production process as defined in the Biochar Production and Storage Protocol.

• SOPs must include documented procedures for reactor start-up, steady-state operation, shutdown, feedstock preparation, biochar handling, sampling, and reactor relocation

• Each unit must be assigned a unique identifier by the Project Proponent and must be registered prior to use. Projects must maintain an active list of reactors. Reactors that are damaged or otherwise removed from service must be withdrawn from the active list.

• The Groups must operate within clearly defined regulatory and legislative boundaries, such that all biochar production activities are subject to consistent laws and regulations.

To ensure the environmental integrity and scientific rigor of carbon removal claims, the sourcing of feedstock for all reactors within a Group must be in line with the Biomass Feedstock Accounting Module. These requirements ensure that the carbon sequestration data remains accurate and verifiable across a distributed network of operations.

All units within a Mobile Production Group must:

• Be processing the same feedstock, i.e.:
  • Species group or biomass type (e.g., softwood forestry residues, hardwood forestry residues, agricultural straw, nut shells)
  • Physical form (e.g., chips, logs, pellets, loose straw)
  • Moisture content range
  • Ash content range
  • Contaminant profile thresholds (e.g., heavy metals, treated timber exclusion)
• Have consistent documentation and accounting outputs, in accordance with the Biomass Feedstock Accounting Module (e.g., $CO_2e_{MarketLeakage}$, $CO_2e_{Counterfactual}$).
• The feedstocks must be sourced from a single, defined region with similar ecological characteristics (e.g., biodiversity, as determined by regional authorities or a specific biodiversity classification system) and subject to the same legislative requirements throughout.

These requirements must be reassessed every time a mobile production unit relocates. A Mobile Production Unit that transitions to a different feedstock must be assigned to a different Mobile Production Group or a new Group must be created. Production from different Feedstock Categories must not be composited within the same Sampling Lot.

Feedstock moisture content is well documented to cause inefficient pyrolysis, leading to increases in CH₄ emissions. Thus, to mitigate the risk of high CH₄ emissions, feedstock preparation and monitoring is critical. As such The Project Proponent must:

• Ensure the moisture of a feedstock is quantified, using a digital moisture meter, ideally integrated into the dMRV application, immediately before starting biochar production.

• Moisture readings must be taken from randomly selected, spatially distributed locations across the feedstock load to ensure homogeneity is captured. The minimum number of measurements per production run scales with the wet mass of the feedstock processed, as follows:

  Feedstock per production run	Minimum moisture measurements
  ≤ 1.5 tonnes	15
  1.5 to ≤ 5 tonnes	20
  5 to ≤ 20 tonnes	30
  20 tonnes	40

  Sampling must be spatially distributed across the feedstock load (e.g. top, middle, and bottom of the pile; front, middle, and back of a container; outer and inner regions of a stack) such that localized wet pockets are likely to be detected. If any single measurement returns a moisture content above 20%, additional measurements should be taken in the surrounding area to determine whether the affected material can be segregated and removed, or whether pyrolysis must be postponed for the entire load.

If average measured feedstock moisture is greater than 20% pyrolysis should not be attempted.

To ensure consistency and safety across a mobile reactor Group, there must be a centralized governing document for site operations. This ensures that regardless of the location or the individual operator, the pyrolysis process remains within the optimized parameters required for high-quality carbon removal.

The Project Proponent must submit the required standard operating procedure (SOP) for the mobile kiln and expectations for how pyrolysis should be operated and take place.

This document must serve as a technical manual for operators ensuring that the pyrolysis process is standardized across reactors and sites of operation within a Project.

To ensure the precision of carbon removal data in a mobile context, specific safeguards against the physical stresses of relocation should be in place. These requirements ensure that the physical movement of reactors inherent to a mobile fleet does not degrade the accuracy of monitoring instruments.

Weigh scales and temperature sensors must undergo a visual inspection by the operator using certified weights or reference tools after the reactor is moved to ensure accuracy was maintained after transit, to ensure the equipment is performing within manufacturer tolerances.

Mobile biochar reactors are exposed to mechanical stresses during transport, including vibration and shock, which can compromise structural integrity and affect reactor performance. Undetected cracks or imperfections may alter heat transfer, gas containment, or process control, leading to safety risks, uncontrolled emissions, or deviations from the defined production process that undermine biochar quality and carbon accounting. Projects are required to undergo a visual inspection after each relocation by the operator, with any issues reported to the Project Proponent. Pyrolysis is prohibited until any damage is repaired, ensures reactors operate under controlled, verifiable conditions and supports the integrity, safety, and environmental safeguards of the Protocol.

Due to the mechanical stress of transport, reactors must undergo visual inspection for cracks or imperfections after every relocation. If the reactor is damaged, pyrolysis must not occur until adequate repairs have been undertaken.

Mobile reactor deployment conditions can vary significantly between sites, and uneven or unstable ground can introduce systematic errors in mass measurements, and biochar yield determination. Even small deviations from level operation may affect load cell performance, material flow, and residence time, leading to inaccuracies in production data. Requiring documented procedures to ensure stable, level setup helps maintain measurement accuracy and process consistency, supporting reliable monitoring, reporting, and verification under the Biochar Production and Storage Protocol.

Projects must provide documentation of procedures for ensuring the reactor is operated on stable, level ground (±2° tolerance), to prevent process inaccuracies in mass measurement.

Note this section supersedes Section 8.3.1, Section 8.3.2.1 and Section 8.3.2.2 of the Biochar Production and Storage Protocol. However, all testing that must be done is in accordance with the biochar characterization set out Section 3 of the Biochar Storage in Soil Environments Module.

This section outlines the requirements for sampling biochar in mobile production environments. To ensure statistical representativeness while maintaining operational efficiency, this Module moves from time-based triggers to mass-based composite sampling.

When units are aggregated into a Mobile Production Group, biochar characterization (e.g., carbon content, H:Corg ratios) may be conducted on a composite sample representative of the Group’s output, provided that:

• The dMRV system confirms that all batches contributing to the composite sample remained within the ±10% temperature (both mean and maximum) and duration variance thresholds.
• Biochar is sampled from all active units within the Group for every Reporting Period to create the composite laboratory sample, regardless of the geographic location of each unit.
• Composite samples only aggregate batches from the same Feedstock Category and the same operating parameter set.
• Chain-of-custody documentation traces each sampling increment back to a specific reactor (by serial number), Deployment Site (by GPS coordinates and site identifier), and Production Batch.
• A Sampling Lot must be closed and submitted for analysis within 6 months of the first increment being collected, regardless of whether the mass threshold has been reached, to prevent degradation of stored increments

• Production Batch (pp):
  • A discrete mass of biochar produced from a consistent feedstock and pyrolysis process. In mobile systems, this typically represents the output of a single kiln cycle or a single day’s production from one unit.
• Sampling Lot:
  • A defined cumulative mass of biochar (defined in Section 4.1.3) from which a composite sample is formed and sent for analysis.
  • If using the Grouping, then the Sampling Lot must consist of representative samples from cumulative production from all eligible batches within the defined Facility (i.e., multiple Production Batches from sites within the Facility).
  • Only Production Batches that meet the Facility's digital MRV thresholds (±10% temperature/duration) are eligible to contribute increments to the Composite Sample.
  • The mass of any batch triggering an anomaly (e.g., temperature deviation) must not be counted toward the Sampling Lot, and no increment from that batch shall enter the composite bucket.
• Composite Sample:
  • A single analytical sample created by combining volume-based increments and homogenizing from every Production Batch within a Sampling Lot.
  • The Project Proponent must demonstrate a physical homogenization process (e.g., ribbon blender) that ensures the final laboratory aliquot is representative of the entire Facility’s output.

In mobile production systems, the Composite Method must be used. This ensures all biochar produced is represented in the final laboratory analysis.

For every Production Batch ($p$) produced, an appropriate sample must be collected using a randomized cross-sectional method. These increments must be stored in a moisture-proof, sealed container until the Sampling Lot mass threshold is reached. The Project should also archive an appropriate mass of sample in case re-analysis is required.

Once the cumulative mass of the Sampling Lot ($L$) is achieved:

1. Dry-masses of all stored samples are combined. Each stored sample must correspond to a distinct production batch from the mobile reactor, such that the composite reflects the full range of batches produced at the production group during the sampling period.
2. The combined material should be thoroughly homogenized.
3. A final representative sample is extracted from this mixture and sent for laboratory analysis, at minimum, in triplicate.

The mass of the composite sample shall be sufficient to account for the volume capacity of the mobile reactor and the total number of production batches contributing to the Sampling Lot. The composite must not be dominated by material from any single batch; equal dry-mass contributions ensure that batch-to-batch variability, arising from differences in feedstock, operating conditions, or reactor performance across the production campaign, is captured in the analytical result.

In all cases a minimum of three analytical replicates must be performed per composite sample to ensure that analytical uncertainty can be accounted for.

The frequency of laboratory analysis is determined by the total mass of biochar produced.

Projects must collect a minimum of 10 composite samples, corresponding to 1 composite sample made up of samples from every batch/cook every 50 tonnes of production output from the kiln, for a total of 30 samples.

For every group of reactors, Projects must collect a minimum of 10 composite samples corresponding to 1 composite sample from every batch/cook every 50 tonnes from a single kiln, covering all kilns up to a maximum of 5 kilns, for a total of 30 samples. Where more than 5 kilns are in operation within a group, Projects must select the 5 kilns with the highest individual production volume and must be chosen in agreement with Isometric.

Projects must collect and archive samples from every batch from every kiln for the duration of the Project. For analysis, Projects must collect a composite (sampling lot) from a randomly selected 10% of kilns for each verification, subject to a minimum of 3 kilns. The random selection process must be documented and reproducible. If operating 3 kilns or less, then Projects must composite samples from all kilns.

Note: For a Project that intends to operate fewer than 6 kilns within a group, the number of samples required from each available kiln in order to complete Method A, and transition to Method B, must be agreed upon with Isometric to achieve the 30 sample threshold. Note: Method A ‘multiple kiln’ must be completed even by Projects that have already undergone method a single kiln. Projects may include the already sampled kiln in this method.

For Sampling Lots where the composite is analyzed, the resulting organic carbon ($C_{org}$​) value is applied. However, to account for variance in mobile systems, the following conservative estimates are applied to the final determination of $C_{biochar}$:

$$C_{Biochar} = \mu_{CC} - \sigma_{\overline{CC}}$$

$$\sigma_{\overline{CC}} = \frac{\sigma_{CC}}{\sqrt{n_{samples}}}$$

Where:

• $\sigma_{\overline{CC}}$: The standard error of the mean of carbon content across all eligible samples.
• $\sigma_{CC}$: The standard deviation of carbon content across all eligible samples.
• $n_{samples}$: The number of eligible samples for this Production Process.
• $\mu_{CC}$: The mean carbon content of all eligible samples.

The Project Proponent must include the following in their PDD:

• Definition of the exact mass taken from each batch (e.g., 100g taken for every 500kg produced).
• Detailed description of how the composite sample is mixed to ensure representativeness.
• Procedures for tracking increments from multiple distributed sites to the central compositing location.

The mean results from analysis must be used in calculations, and all supporting data must be documented.

Each mobile unit must be equipped with sensors and have an established monitoring framework to aid the verification of carbon removal, including:

• Each pyrolysis unit must be geolocated (e.g. GPS) at the start of a production run, to verify the kiln location and ensure no double counting or kiln movement.

• Each pyrolysis unit must be equipped with a minimum of two independent temperature sensors, allowing for design redundancy so that mid-batch sensor failures do not result in ineligible crediting, located in the pyrolysis chamber, flue stack, or a combination of both, positioned to capture the temperature regime relevant to the pyrolysis process.

• A timer or similar mechanism must track the production duration of each batch.

In terms of quantification of pyrolysis emissions:

• Real time monitoring of both the flue gas flow and composition is recommended in accordance with Section 10.1.1.1 of the Biochar Production and Storage Protocol.

• In the absence of real-time data, Projects must conduct annual emissions testing in accordance with Section 10.1.1.2 of the Biochar Production and Storage Protocol, measuring gas flow and emissions for all units covered by the Project's chosen testing pathway (defined below). Each emissions test must be representative of the full pyrolysis operation of the kiln, including quenching where appropriate. Portable emissions monitoring equipment from a reputable independent instrument provider may be used, provided adequate proof of calibration (and re-calibration, as appropriate) and standard operating procedure for measurement, is supplied.

  Projects must apply a default methane deduction of 0.672 tCO₂e per tonne biochar to all biochar batches. The deduction is based on the best available peer reviewed literature (see Appendix 1).

  • Testing every kiln. Projects testing every registered kiln must apply the default deduction until all registered kilns have completed their first emissions test, after which the test result yielding the highest CO2e emissions per batch must apply to all subsequent batches for the duration of the Project. Subsequent annual test results do not refresh this baseline.
    • Projects must screen first-round test results for statistical outliers using an established method (e.g. Grubbs' test, Tukey's fences) before selecting the result with the highest CO2e emissions per batch. The chosen method, threshold, and treatment of any identified outliers must be documented in the Project records and justified relative to the sample size. This screening requirement applies only to every-kiln testing.
  • Testing a representative kiln. Projects testing only a representative kiln per mobile production group must apply the greater of the default deduction or the representative kiln's first emissions test result to all batches for the duration of the project. Subsequent annual test results may refresh this baseline.

• Black Carbon is a potent climate-forcing aerosol produced by the incomplete combustion of biomass, characterized by a Global Warming Potential nearly a thousand times greater than $CO_2$. In mid-tech kilns, Black Carbon is a critical consideration because fugitive emissions typically occur during unstable phases like "cold starts" or quenching, even when the system is otherwise performing well. In all Projects the production of black carbon should be minimized. To maintain high environmental integrity, a conservative uncertainty deduction of 0.0328 tCO₂e per tonne biochar to account for these particulate emissions and their significant impact on both atmospheric warming and surface albedo will be applied to all systems unless an appropriate emissions control system, such as a secondary burn chamber, cyclone separator or scrubber, is present, or Black Carbon is directly quantified. Further details of this calculation can be found in Appendix 2.

The resulting mass of biochar produced must be measured and recorded for each batch using calibrated scales (e.g. crane scales or a high capacity balance) of an appropriate accuracy, these must be tared on a flat surface, where appropriate. Dry mass must be traceable for each batch. Therefore, weighing should be performed before quenching, or it can be done after quenching if the batch-level moisture content can be measured. These records, along with the kiln sensor data, must be submitted to the dMRV system.

All biochar produced by mobile reactors within The Project must be deployed through the same approved storage pathway and tracked using a unified dMRV system to ensure consistent traceability and verification.

The Biochar Production and Storage Protocol requires a rigorous digital Monitoring, Reporting, and Verification (dMRV) framework. This infrastructure ensures that every data point is captured within a system that minimizes human error and prevents unauthorized data manipulation.

This includes tracking where the carbon removal took place, to confirm feedstock sourcing area, preventing overcrediting and ensuring supply chain transparency.

GPS batch tagging: every production batch must be automatically geotagged with precise coordinates in the dMRV system.

To prevent data gaps and ensure data reliability and integrity:

• The dMRV system must be capable of secure, offline data logging with tamper-proof timestamps for use in remote areas, ensuring data is synced immediately upon regaining connectivity.
• The system must be programmed to automatically flag data anomalies, such as sensor readings that fall outside of calibrated physical ranges or batches with incomplete records.
• All locally stored data must be uploaded and verified within 30 days of production. Batches for which dMRV data has not been uploaded and verified within this window must be treated as anomalies (i.e., excluded from credited production and from Sampling Lots).
• During offline storage all data must be encrypted.
• The Project Proponent bears the ultimate responsibility for data integrity and must investigate any flagged instances or anomalies and provide a documented justification or corrective action before the data is submitted to Isometric for final verification.

In mobile biochar production environments, high-precision syngas monitoring is often technically or economically infeasible. To maintain a conservative carbon removal claim, a blanket methane (CH₄) deduction is applied to the gross carbon sequestration of each tonne of biochar produced.

This appendix takes the empirical approach: the deduction is anchored directly on field-measured stack emissions from operational closed retort kilns in mobile settings. No parametric breakdown of methane generation and combustion efficiency is performed, the empirical measurement integrates both factors directly.

The default emission factor in this appendix reflects the best published evidence available at the time of writing. It is intended to evolve as the underlying science evolves.

This Module assumes 15% feedstock moisture content (dry basis) as the operational standard.

The protocol adopts as the default methane emission factor the mean stack-measured CH₄ emission factor for mobile retort kilns reported by Sparrevik et al. 2015⁵:

$$EF_{biochar} = 24 \text{ g CH}_4 \text{ per kg biochar produced}$$

Sparrevik et al.⁵ measured n = 5 batch runs across operational rural retort kilns in Indonesia using consistent instrumentation. The reported value of 24 ± 17 g CH₄ / kg charcoal integrates: (a) methane generation during pyrolysis, (b) primary combustion of pyrolysis gases in the kiln's firebox, (c) all in-batch operational losses including start-up and shutdown phases, and (d) any fugitive emissions captured in the stack flow.

This value is supported by:

• The IPCC 1996⁶ production-process default of 30.8 g CH₄ / kg charcoal.
• The reduction range of 29.6–47% reported by Bedane et al.⁷ for improved retort kilns relative to traditional kilns, which, applied to the Pennise et al. ⁸ traditional kiln baseline of 32–62 g CH₄ / kg charcoal, implies improved kiln emissions of ~17–44 g/kg.
• The Cornelissen et al.⁹ aggregated retort kiln literature value of ~35 g/kg.

The empirical emission factor from Sparrevik et al.⁵ is already reported in units of g CH₄ per kg biochar produced — i.e. it natively integrates feedstock-to-biochar yield variability across the measurement set. No conversion through feedstock mass is required.

$$EF_{biochar} = 24 \text{ g CH}_4 \text{ per kg biochar}$$

The methane mass is multiplied by the 100-year Global Warming Potential (GWP₁₀₀) of methane of 28 (IPCC AR6¹⁰):

$$D_{CH_4} = EF_{biochar} \times \text{GWP}_{100} = 24 \text{ g CH}_4/\text{kg biochar} \times 28 = 672 \text{ g CO}_2\text{e per kg biochar}$$

$$D_{CH_4} = 0.672 \text{ tCO}_2\text{e per tonne biochar}$$

Project Proponents must apply the following fixed deduction to their gross carbon sequestration claims for every dry tonne of biochar produced:

This deduction is applied to the biochar output mass. For example, if a Project produces 100 dry tonnes of biochar, 67.2 tCO₂e must be subtracted from the total carbon removal Credits generated.

The empirical anchor in this appendix is valid only for Projects meeting all of the following conditions. Outside these conditions, primary measurement is required.

1. Feedstock moisture: <15% w/w (oven-dry equivalent).
2. Feedstock type: Woody biomass (twigs, dimensional wood, agricultural prunings). Fine-grained feedstocks (rice husk, coffee husk, nut shells, sawdust) are excluded, as Jayakumar et al. ¹¹ documents CH₄ emissions of 179 g/kg for coffee husk versus <5.5 g/kg for woody biomass in the same kiln class.
3. Kiln class: Closed retort kilns with integrated firebox combustion of pyrolysis gases (Adam retort, Casamance, Green Mad Retort, MRV, Mark V, or equivalent designs).
4. Start-up handling: Kiln operator demonstrates secondary combustion zone is lit and functional within 30 minutes of feedstock ignition.

The CH₄ emission factor adopted in this appendix (24 g CH₄ / kg biochar) is anchored on a single primary field study (Sparrevik et al.⁵, n = 5 batch runs in a single geography) supported by a small set of corroborating literature values. This represents the strongest empirical evidence currently available for the technology class in question, but the underlying evidence base is acknowledged to be modest.

This appendix will be updated as the science evolves. Triggers for review include:

• Publication of new field studies measuring CH₄ stack emissions from mobile retort kilns at sample sizes meaningfully larger than Sparrevik et al.⁵ (n = 5).
• Field measurements that characterize variance across kiln designs (Adam, Casamance, Green Mad, MRV, Mark V), feedstock types, and geographies not represented in the current evidence base.
• Updates to the IPCC default emission factors for charcoal production.
• Material changes in the kiln designs in widespread use across mobile biochar Projects.

The protocol owner will review this appendix at minimum every 24 months and at any time a triggering publication or change is identified.

This Module applies a mandatory black carbon (BC) deduction to all eligible Projects that lack integrated, industrial-grade Continuous Emission Monitoring Systems (CEMS). Technologies permitted under this Module may employ secondary combustion to mitigate particulate matter; where this is the case, the default deduction, which is intentionally conservative, may be reduced on the basis of empirical data and in consultation with Isometric.

This deduction accounts for three primary factors:

• Startup/Shutdown Phases: Periods of incomplete combustion before the unit reaches the steady-state temperatures required for full syngas oxidation.
• Atmospheric Forcing: The high Global Warming Potential (GWP) of black carbon (soot) over a 100-year horizon.
• Measurement Uncertainty: The inherent difficulty in quantifying particulate matter in non-industrial or decentralized settings.

To our knowledge, no published study directly measures black carbon emissions from biochar/charcoal kilns. The BC emission factor is therefore derived in two steps, both expressed on a per-kg-biochar basis:

1. A representative TSP emission factor is taken from kiln studies, on a biochar mass basis.
2. A BC/TSP fraction from Akagi et al.¹², for the "charcoal making" category, is applied to convert TSP to BC.

Because both reference values are reported per kg of biochar produced, the derivation requires no assumption about biochar yield.

Sparrevik et al.⁵ report a mean TSP emission factor of 12 ± 18 g/kg charcoal for retort kilns — the most directly relevant mid-tech technology class permitted under this Module. Cornelissen et al. ⁹ report PM10 emissions of 11 ± 15 g/kg biochar for flame-curtain Kon Tiki kilns, equivalent to 15.4 g TSP/kg biochar after the PM10-to-TSP conversion factor of 1.4 applied in both studies; Kon Tiki kilns are themselves ineligible under this Module but the data is retained as informative context for the upper range. A central value of 12 g TSP/kg biochar is adopted, anchored on the eligible-technology data.

Akagi et al. ¹² report for the "charcoal making" category a BC emission factor of 0.02 g BC/kg charcoal and a TSP emission factor of 0.7–4.2 g TSP/kg charcoal (midpoint 2.45). This yields a BC/TSP fraction specific to charcoal-making combustion regimes:

$$f_{BC/TSP} = \frac{0.02}{2.45} \approx 0.008$$

Applying this fraction:

$$EF_{BC} = 12 \text{ g TSP/kg biochar} \times 0.008 \approx 0.096 \text{ kg BC per tonne biochar}$$

The deduction is calculated using the 100-year Global Warming Potential of black carbon ($GWP_{BC}$ = 342):

$$\text{Deduction} \approx 0.096 \times 342 \approx 32.8 \text{ kg CO}_2\text{e per tonne biochar}$$

1. Uotila, K., Vikki, K., Uusitalo, M., Rasa, K., Leinonen, I., & Hagner, M. (2025). Mobile-manufactured biochar in mine closure, costly yet carbon-negative – A techno-economic and life cycle assessment of growing media value chains. Cleaner and Circular Bioeconomy, 12, 100173. https://doi.org/10.1016/j.clcb.2025.100173 ↩

2. Puettmann, M., Sahoo, K., Wilson, K., & Oneil, E. (2020). Life cycle assessment of biochar produced from forest residues using portable systems. Journal of Cleaner Production, 250, 119564. https://doi.org/10.1016/j.jclepro.2019.119564 ↩

3. McAvoy, D., Dettenmaier, M., & Kuhns, M. (2018). Mobile pyrolysis for hazardous fuels reduction and biochar production in Western forests. The Journal of Extension, 56(1), Article 14. https://doi.org/10.34068/joe.56.01.14 ↩

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