Biochar’s capacity to enhance soils and store carbon has positioned it as a valuable nature-based solution. Yet despite growing scientific consensus and market interest, biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More remains underutilized in carbon markets.

One critical barrier is the absence of a universally recognized carbon sequestration coefficient index, a standardized tool to quantify how much carbon biochar reliably sequesters over time. Without this, uncertainty persists, deterring investment, slowing project validation, and undermining biochar’s integration into climate finance.

The Case for a Coefficient Index

Biochar’s carbon stability depends on several variables: feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More type, pyrolysis conditionsThe conditions under which pyrolysis takes place, such as temperature, heating rate, and residence time, can significantly affect the properties of the biochar produced.   More, application method, and environmental context. This variability has made it difficult to define consistent metrics. Current standards, such as Verra’s VM0044 or the European Biochar Certificate (EBC), provide methodological guidance, but they rely on bespoke testing and project-specific assumptions that hinder scalability and comparability.

A carbon sequestration coefficient—expressed as the proportion of carbon in biochar that remains stable in soil over time—would provide a reliable basis for issuing carbon credits, similar to emissions factors used in forestry and energy. The IPCC (2019) laid the groundwork by publishing a table (see below) of feedstock organic carbon contents, but this early attempt stopped short of offering usable sequestration coefficients or linking to field performance. The organic carbon content level was measured before application, which fails to account for the reactivity and thus stability of the char in soils.

Recent research by Adhikari et al. (2024) highlights why this matters. Their study found that while pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More methods (e.g. ‘simple’ vs. ‘advanced’ systems*) produced similar stability outcomes, feedstock type was the dominant factor influencing long-term carbon sequestration. This reinforces the feasibility of building an index stratified by feedstock and adjusted for production and soil conditions.

Why Current Methods Fall Short

The sector’s reliance on proxies like H:Cₒᵣg < 0.4 or O:Cₒᵣg ratios has limitations. These indicators, though useful, were developed from limited datasets and often underestimate biochar’s stability. They also fail to reflect real-world differences in land management or microbial activity.

Emerging methods—such as the Recalcitrance Index (R₅₀) and long-term field trials—offer a more nuanced picture of how biochar performs over time. But in the absence of a formal index, these data remain fragmented, limiting their value for investors, certifiers, and policymakers.

The Market Opportunity

According to McKinsey (2021), voluntary carbon markets could exceed $50 billion by 2030. Meanwhile, Supercritical (2025) forecasts a 30-fold increase in biochar supply over the next four years. Yet without standardised sequestration metrics, biochar risks being sidelined in these rapidly growing markets.

A robust coefficient index would:

• Streamline validation and verification, reducing transaction costs.
• Enable consistent crediting across regions and registries.
• Build investor confidence through measurable, transparent performance.

Key benefits of a Coefficient Index include:

1. Quantifiable Carbon Credits: An index would allow accurate, standardized accounting of CO₂ removals per tonne of biochar, supporting credit issuance and comparability.
2. Investment Certainty: Clear metrics would make projects more financeable, unlocking private and blended capital.
3. Policy Alignment: Governments could better integrate biochar into climate strategies and inventories with consistent benchmarks.
4. Research Efficiency: A shared framework would highlight data gaps and guide targeted research, accelerating innovation.

Addressing the Drawbacks

A central concern is that averages may misrepresent high- or low-performing projects. However, this can be managed by offering upside verification—where project developers submit lab-verified results if they expect to outperform default coefficients.

There’s also a risk that producers could favor low-temperature pyrolysis to increase yield at the cost of carbon permanence. But this can be mitigated by comparing biochar density to volume, as high-carbon biochar tends to be lighter and less volatile.

Finally, while some fear over-crediting of low-quality biochar, this is unlikely if the index is stratified by feedstock and management type, and if conservative default values are applied.

Biochar could sequester up to 2.6 billion tonnes of CO₂e annually if deployed at scale (Reverse Carbon, 2022). But realizing this potential requires structural reforms. A standardized carbon sequestration coefficient index would provide the clarity and credibility needed to move biochar into the climate finance mainstream.

As the world races to achieve net zero, bridging this knowledge and standardization gap is far from just academic – it is essential. Unlocking biochar’s carbon value through a standardised index could transform it from a promising soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More to a cornerstone of global climate strategy.

Questions to Consider

• What level of certainty should be required before biochar earns carbon credits—should the system prioritise accessibility or rigour?
• Is it more effective to use conservative averages to scale carbon removal quickly, or bespoke measurements to ensure accuracy?
• Who should lead the development of a global biochar coefficient index—research institutions, certifiers, or industry coalitions?
• What role should field-based measurement and digital MRV technologies play in validating or challenging fixed sequestration coefficients?
• Should policymakers start treating biochar as a formal carbon sink now, or wait until standardization catches up?

References

Adhikari et al. (2024) Comparative analysis of biochar carbon stability methods and implications for carbon credits, Science of the Total Environment 914 (169607). DOI: https://doi.org/10.1016/j.scitotenv.2023.169607

IPCC (2019). Appendix 4, 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 4: Agriculture, Forestry and Other Land Use. Accessible at: https://www.ipcc-nggip.iges.or.jp/public/2019rf/pdf/4_Volume4/19R_V4_Ch02_Ap4_Biochar.pdf 

McKinsey & Company (2021). A Blueprint for Scaling Voluntary Carbon Markets to Meet the Climate Challenge. Accessible at: https://www.mckinsey.com/capabilities/sustainability/our-insights/a-blueprint-for-scaling-voluntary-carbon-markets-to-meet-the-climate-challenge 

Supercritical (2025). The Biochar Boom: 30x Growth Ahead. Accessible at: https://gosupercritical.com/blog?p=biochar-market-outlook-2024 

Reverse Carbon (2022). Biochar -potential to remove 2.6 billion tonnes co2. Accessible at: https://www.reversecarbon.com/blog/ipcc-biochar-potential-to-remove-26-billion-tonnes-co2