Biochar Production in Combustion Co-product Systems

This is a Capture and Conversion Module associated with the Production of biochar. In some cases Project Proponents may seek to produce biochar as a co-product of a combustion process. These “combustion co-product” biochar systems may produce high stability biochar as a co-product, alongside other products such as bioenergy, heat, syngas, bio-oil, or combined heat and power^{1, 2, 3, 4, 5}.

These systems may include, but are not limited to:

• Biomass gasification systems that co-produce biochar with bioenergy (heat and electricity) through staged combustion processes where volatile gases are captured and converted to energy, while biochar is harvested as a solid product.
• Pyrolysis reactors or retorts where biomass is thermally decomposed with limited oxygen, producing biochar alongside pyrolysis oils and gases. The gases and oils may be combusted to provide heat for the process and can also be further processed into fuels or chemicals.
• Combined Heat and Biochar (CHAB) systems designed to generate thermal energy for heating or cooling applications while producing biochar.
• Modular bioreactors to convert biowaste streams (e.g., wood waste, cattle manure) into electricity and simultaneously produce biochar.
• Methanol autothermal reforming (ATR) systems that co-produce hydrogen and biochar with heat recovery as an advanced method.

These systems may be characterized by:

• Variable oxygen levels with less consistent control of pyrolysis conditions.
• Co-mingling of a heterogeneous biochar/ash mixture. If biochar and ash are co-mingled then the Project Proponent must detail the method through which additional carbon is quantified.
• Monitoring setups focused on boiler safety and emissions compliance, rather than systematic data collection on biochar formation.

The eligibility of combustion co-product pyrolysis technologies for inclusion of crediting under this Module will depend on their operating profiles, monitoring capacity, and emissions characteristics, as these may significantly differ from dedicated pyrolysis units.

In addition to all other requirements, to be eligible for crediting under this Module combustion co-product pyrolysis systems must meet the following criteria;

• Biochar is a defined, intentional output of the process, and not solely an incidental residue. I.e., the biochar produced must comply with the Additionality requirements set out in Section 2.5.3. of the Isometric Standard.

• The boiler system produces a reproducible and consistent biochar product that can be sampled and characterized in accordance with the requirements of the Biochar Production and Storage Protocol.

• Boiler operations meet or exceed the minimum performance and emissions thresholds required of pyrolysis reactors (e.g., stable operation within target temperature ranges, controlled feedstock handling), during the operating periods where biochar is being produced.

The same framework described in the Biochar Production and Storage Protocol will apply for production batch definition, sampling, and durability assessment to biomass boilers as to dedicated pyrolysis reactors. Where deviations are necessary, projects must clearly document these exceptions and provide a detailed justification demonstrating that monitoring and verification requirements are met with an equivalent or greater level of rigor. As an additional requirement in systems that operate continuously, Isometric requires at least 30 consecutive days of sampling and analysis for biochar characterization data to establish the stability of the production process.

Given the distinct characteristics of combustion co-product systems, Isometric has additional requirements on both production batch definitions and sampling methods. Unless otherwise stated, Project Proponents must still refer to all other requirements listed in the Biochar Production and Storage Protocol and relevant storage Module.

For initial sampling under Method A, a production batch is defined as biochar produced every 7 days (or if triggered by any of the ‘deviation’ criteria listed below). The maximum duration maintains sufficient measurement accuracy given the quantities of biochar produced. Note, a new Production Process is counted only if the variations listed below persist for > 6 hours, or otherwise listed.

• Fire box average temperature (Based on a rolling average of the prior 24 hourly temperatures across active boilers).
  • Above 450°C, ± 75°C (842°F, ± 167°F) should be the maximum temperature deviation.
  • Below 450°C (842°F) , temperature variation should be less than ± 20%
    • Depending on the biochar characterization data, this may be increased subject to agreement with Isometric.
• Feedstock
  • Any time the feedstock changes material or source, as defined in the Biomass Feedstock Accounting module, and/or the feedstock composition shifts by ± 20%.
• Feedstock residence time in reactor
  • If the feedstock residence time deviates from ± 20% of what is defined in the Project Design Document (PDD) for a typical production process
• Oxygen dosing
  • Oxygen levels must not exceed 8% in the fire box.
    • Depending on the biochar characterization data, this may be increased subject to agreement with Isometric.

These thresholds align with Isometric’s general framework for defining Production batches in Biochar Production and Storage Protocol, whereby the unique characteristics of the biomass used, the pyrolysis process, the produced biochar characteristics, transportation distances, and storage site characteristics will be the same for all of the biochar within a Production Batch. The exact values of these thresholds will remain flexible and may be adjusted as additional data on biochar chemistry is provided.

Suppliers must follow the sampling requirements outlined in the Biochar Production and Storage Protocol, with the following exceptions:

• Method A, sampling every batch for 60 samples (e.g., a minimum 3 samples per batch from the first 20 batches), this is to establish the variability of the Production process, before transitioning to Method B which will follow the same guidelines laid out in the Module.
  • As detailed in Biochar Production and Storage Protocol, the first 30 samples of the 60 need to include the ‘full suite’ of analysis detailed in the table of the appropriate Biochar Storage Module.
    • Three samples from the first 30 also need to include heavy metals, Polychlorinated Biphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Dibenzo-p-dioxins (PCDDs), and Volatile Matter or Fixed Carbon.
    • The remaining 30 samples under Method A only need to include those parameters needed for CO₂e [removal](#definitions-and-acronyms-removal quantification which will continue under Method B.

1. Afshar, M., & Mofatteh, S. (2024). Biochar for a sustainable future: Environmentally friendly production and diverse applications. Results in Engineering, 23, 102433. https://doi.org/10.1016/j.rineng.2024.102433 ↩

2. Siddiqui, S. (2025). Unlocking the environmental potential of biochar: Production, applications, and limitations. Frontiers in Sustainable Food Systems, 9, 1569941. https://doi.org/10.3389/fsufs.2025.1569941 ↩

3. Chen, W.-H., Teng, C.-H., Chein, R.-Y., Nguyen, T.-B., Dong, C.-D., & Kwon, E. E. (2025). Co-production of hydrogen and biochar from methanol autothermal reforming combining excess heat recovery. Applied Energy, 381, 125152. https://doi.org/10.1016/j.apenergy.2024.125152 ↩

4. Yaashikaa, P. R., Kumar, P. S., Varjani, S., & Saravanan, A. (2020). A critical review on the biochar production techniques, characterization, stability and applications for circular bioeconomy. Biotechnology Reports, 28, e00570. https://doi.org/10.1016/j.btre.2020.e00570 ↩

5. Deng, X., Teng, F., Zhang, X., Fan, J.-L., Forsell, N., & Reiner, D. M. (2025). Co-deploying biochar and bioenergy with carbon capture and storage improves cost-effectiveness and sustainability of China's carbon neutrality. One Earth, 8(1), 101172. https://doi.org/10.1016/j.oneear.2024.12.008 ↩