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.

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 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 the same 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 Section 8.3.1. 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 se spatially constrained and operate within clearly defined regulator 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) and subject to the same legislative requirements throughout.

These requirements must be reassessed every 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.
  • Measure a specified number of moisture readings be randomly taken per production run to ensure moisture homogeneity. A minimum ratio of 1 sample per 100 kg of feedstock must be used to account for heterogeneity, with a minimum total number of 15 measurements per production run.

To ensure that methane quantification is conservative on all batches within Groups when feedstock moisture is variable the following discount will apply:

• 2.8 kg CH₄/tonne dry feedstock

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

Detailed calculations and underlying assumptions are found in Appendix A.

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 and homogenizing increments 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 facility 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.

This initial high frequency sampling and analysis is required to generate sufficient data to estimate the carbon content of future biochar production with an appropriate level of statistical confidence, understand variance, and establish a stable Production Process.

For a new Production Process or feedstock, the Project Proponent must establish a baseline:

• This method must be used for the first 500 dry tonnes of production with one composite sample (a Sampling Lot) being sent for analysis every 50 dry tonnes of biochar produced per kiln or Group.

Until this threshold is reached, the consistency of the Production Process has been demonstrated and agreed with Isometric, Method A must be used, this will be for a minimum of 30 samples total (10 Sampling Lots with three replicates).

Once the initial characterization threshold is met, the sampling frequency may be reduced:

• One composite analysis must be performed for every 250 tonnes of biochar produced.
• While lab analysis is periodic, the equal mass allocation (sampling every batch) remains mandatory for every batch within the Sampling Lot.

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 PPD:

• 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.

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).
• 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.

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.

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 Developer. 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, to prevent process inaccuracies in mass measurement.

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 location deviates from above assessment, Project Proponents must update the environmental and social safeguard assessment to identify location-specific risks and provide evidence of regulatory approval through applicable permits or demonstrate compliance with enhanced safeguard measures, where required.

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.

A reference baseline is defined as the operating condition at which baseline methane formation and methane slip parameters are specified. In this analysis, a feedstock moisture content of 10% (dry basis) is used as the reference baseline, representing typical steady-state pyrolysis operation. Methane emissions at other moisture contents are calculated by applying conservative linear moisture-dependent adjustments relative to this baseline.

Table A1: Assumptions for calculations.

Where:

• $Y_{gas}$ the syngas yield is the volume of non-condensable gas produced during pyrolysis per unit of dry feedstock processed, expressed at normal temperature and pressure.
• $ρ_{CH4}$ the methane density is the mass per unit volume of methane gas at normal temperature and pressure (0 °C, 1 atm).
• $x_{10}$ the baseline methane fraction is the volume fraction of methane in dry syngas at the reference feedstock moisture content of 10% (dry basis), under steady-state operation.
• $f_{10}$ the baseline methane slip fraction is the fraction of methane generated in syngas that is not destroyed by combustion or flaring and is emitted to the atmosphere, at the reference moisture condition of 10%.
• $k_M$ the moisture sensitivity of the methane fraction quantifies the change in methane volume fraction in syngas per unit increase in feedstock moisture content, relative to the reference baseline.
• $k_s$ the moisture sensitivity of methane slip quantifies the change in the methane slip fraction per unit increase in feedstock moisture content, relative to the reference baseline.
• $M_{ref}$ the reference moisture is the feedstock moisture content used as the baseline operating condition for defining baseline methane formation and methane slip parameters.

$$E_{CH4} = Y_{gas} × x_{CH4} × ρ_{CH4} × f_{slip}$$

Equation (1)

Where:

• $E_{CH4}$ = methane emitted (kg CH₄ per tonne dry feedstock)
• $Y_{gas}$ = syngas yield (Nm³ per tonne dry feedstock)
• $x_{CH4}$ = methane volume fraction in dry syngas (–)
• $ρ_{CH4}$ = methane density at normal conditions (0.716 kg/Nm³)
• $f_{slip}$ = fraction of generated methane emitted (–)

$$x_{CH4} = x_{10} + k_M × (M − 0.10)$$

Equation (2)

Where:

• $M$ = feedstock moisture content (dry basis, fraction)
• $x_{10}$ = methane fraction at 10% moisture (0.04)
• $k_M$ = moisture sensitivity of methane formation (0.20)

$$f_{slip} = f_{10} + k_s × (M − 0.10)$$

Equation (3)

Where:

• $f_{10}$ = baseline slip fraction at 10% moisture (0.1424)
• $k_s$ = moisture sensitivity of slip (0.75

Step 1 — CH₄ fraction in syngas

$$x_{CH4} = 0.04 + 0.20(0.20 - 0.10)$$

$$x_{CH4} = 0.06$$

Step 2 — Slip fraction

$$f_{slip} = 0.1424 + 0.75(0.20 - 0.1)$$

$$f_{slip} = 0.2174$$

Step 3 — Methane emissions

$$E_{CH4} = 300 × 0.06 × 0.716 × 0.2075$$

$$E_{CH4} ≈ 2.8 kg CH_4/t dry$$

Result: $E_{CH4}$ = 2.8 kg CH₄/tonne dry feedstock (20% moisture)

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