The 150% Gap: Why Charcoal Baseline Assumptions Are Becoming a Carbon Market Risk

For over a decade, clean cooking and biomass fuel-switch carbon projects have leaned on a single default value: the UNFCCC CDM Tool 33 wood-to-charcoal conversion factor (WCCF) of 4.0 kg wet wood per kg dry charcoal. This figure is embedded across CDM methodologies, Gold Standard TPDDTEC, and Verra VM0050 — it underpins baseline emission calculations for hundreds of registered cookstove projects.

But new peer-reviewed field evidence from Sub-Saharan Africa suggests this default may be significantly understating real-world biomass demand -- creating a structural risk for baseline emissions calculations, crediting volume integrity, and audit defensibility across the cookstove carbon project portfolio.

4:1

UNFCCC CDM DEFAULT (TOOL 33)

7.1:1

KILN-LEVEL FIELD MEASUREMENT

10.0:1

FULL VALUE CHAIN

The Field Evidence

A 2026 study by Dr. Nordica MacCarty — Associate Professor at Oregon State University and Executive Director of Aprovecho Research Center — measured 24 traditional earth-mound kilns across Malawi and Ghana during 2023–2024. Published in Biomass and Bioenergy (Vol. 209, 108914) and subsequently submitted to ICVCM as stakeholder input, the study quantified biomass losses at each stage of the charcoal value chain [1] [2].

At the kiln level, the average WCCF was 7.1:1 (7.3:1 in Malawi, 6.9:1 in Ghana). When the system boundary was expanded to include harvesting, transportation, and distribution losses, the full value chain conversion factor rose to 10.0:1 (9.5:1 in Malawi, 10.6:1 in Ghana).

The critical finding: approximately 18% of total biomass losses occur outside the kiln stage — during harvesting, transport, and distribution. Most existing methodologies define system boundaries at the kiln stage only, leaving this loss category unaccounted for in baseline calculations.

Not an Isolated Finding

The MacCarty study is consistent with a broader body of evidence. FAO (2017) documented country-level carbonization ratios across Sub-Saharan Africa that range far above the 4:1 default [3]:

Even the FAO's own general default of 6:1 — established as a conservative cross-country average — is 50% higher than the CDM value that most carbon projects still use today.

Methodology Landscape Is Already Shifting

Registries and standard-setting bodies are beginning to respond. Gold Standard's revised RECH v5.0 and MECD v2.0 methodologies, published in May 2026, updated the default WCCF from 4:1 to 6:1, aligning with FAO's general default [4]. Verra's VM0050 v2.0 consultation, open through August 2026, is reviewing fNRB and conversion factor parameters as part of a broader methodology overhaul [5].

ICVCM has received stakeholder submissions on WCCF accuracy from both the academic community (MacCarty, July 2026) and the clean cooking industry (Gachugi, July 2026), indicating that the Core Carbon Principles review process is actively engaging with this parameter [2] [4].

"The trajectory is unambiguous: defaults are converging toward field-measured values. Projects that continue to rely on 4:1 may find their baseline assumptions challenged during the next validation cycle."

What This Means for Carbon Project Economics

If a project's baseline assumes a 4:1 WCCF while real-world conditions approach 10:1, the implications cascade across multiple dimensions:

The System Boundary Problem

Most cookstove methodologies define the system boundary at the kiln: wood enters, charcoal exits, and the difference is counted as the conversion efficiency. But the MacCarty study demonstrates that nearly one-fifth of total biomass losses happen before wood reaches the kiln and after charcoal leaves it.

Harvesting losses include branch trimming, breakage, and selective felling. Transport losses include breakage during loading, transit vibration, and spillage. Distribution losses include degradation at retail points and moisture changes. None of these are captured by kiln-only system boundaries.

For projects that involve improved charcoal stoves, fuel-switch interventions, or REDD+ adjacency, this gap has a direct accounting implication: if the charcoal baseline WCCF is understated, the baseline emissions against which the project's reductions are measured are also understated -- potentially inflating or deflating credited volumes depending on project type and methodology.

Harvesting → Transport → Kiln → Distribution → End Use

←——— 18% of losses unaccounted in kiln-only boundaries ———→

Recommendations for Project Developers

As the voluntary carbon market shifts from default-based to measurement-based integrity, parameter accuracy is becoming a financial variable — not just a technical one. For projects involving charcoal baselines, the following actions warrant consideration:

1. Reassess the 4:1 default against geographic evidence. FAO country-level data and the MacCarty study provide region-specific references that can be used to test whether the CDM default is defensible for a given project geography.

2. Clarify the system boundary. Determine whether the methodology permits — or requires — inclusion of pre-kiln and post-kiln losses. Document the boundary definition transparently in the PDD.

3. Consider targeted field sampling. For projects seeking premium pricing or CCP eligibility, field-based WCCF measurement at the project site provides the strongest defense against validation challenges.

4. Monitor methodology revisions. Gold Standard RECH v5.0, MECD v2.0, and Verra VM0050 v2.0 are all updating WCCF parameters. Projects using legacy methodologies should assess migration pathways.

5. Document assumptions. In the PDD, explicitly state which WCCF value is used, its source, and the rationale for selecting it over alternatives. Transparency is the first line of defense in validation.

Technology as the Integrity Layer

Baseline parameters like WCCF determine how much emission reduction a project can claim. But the underlying physical intervention — the cookstove itself — determines whether those claimed reductions actually materialize in the field.

This is where the fuel-switch logic becomes critical. Whether a project involves improved charcoal stoves, wood stoves, or pellet systems, the underlying technology determines whether the claimed emission reductions actually materialize. Improved combustion efficiency means less fuel consumed per cooking event -- regardless of fuel type. That translates directly into measurable fuel savings, lower emissions, and stronger MRV evidence.

At SSM Eco, 47 years of cookstove development and manufacturing have contributed to 16,798,244 tons of CO2 reduced and 20,152,703 tons of fuel saved. These figures reflect cumulative engineering performance -- combustion efficiency, material durability, and manufacturing consistency -- across wood, charcoal, and pellet stoves, representing real-world fuel demand reduction rather than modeled estimates.

As the market tightens, the projects that survive will be those whose data chain — from baseline parameters through technology performance to MRV evidence — can withstand increasing scrutiny.

High-quality carbon assets are built on high-quality data. And high-quality data begins at the field level — not in a default factor table.

ABOUT SSM ECO

With nearly five decades of clean cooking experience, SSM Eco manufactures wood, charcoal, pellet, and institutional cookstoves, with capacity of up to 2 million units annually. We work with energy companies, carbon project developers, NGOs, and other partners to deliver sustainable, customized cooking solutions and measurable emissions reductions.

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SOURCES & REFERENCES

[1]. MacCarty, N.A. (2026). "Quantifying charcoal conversion factors throughout the value chain in Malawi and Ghana." Biomass and Bioenergy, 209, 108914. DOI: 10.1016/j.biombioe.2025.108914

[2]. MacCarty, N.A. (2026). "Independent Research Findings on Charcoal Kiln Efficiency and the Wood-to-Charcoal Conversion Factor (WCCF)." ICVCM Stakeholder Submission, 15 July 2026.

[3]. FAO (2017). "The Role of Wood Energy in Africa." FAO Forestry Department. Country-level carbonization ratios.

[4]. Gachugi, N. (2026). "Revisiting the Wood-to-Charcoal Conversion Factor (WCCF) and Direct Charcoal Emission Factors." ICVCM PD Submission, 31 July 2026.

[5]. Verra (2026). VM0050 v2.0 Major Revision Consultation.

[6]. CDM Tool 33 v03.1. "Default values for common parameters." UNFCCC.

[7]. CIFOR Sustainable Woodfuel Brief #1. "Carbonization 2.0: How to produce more charcoal with less wood and emissions."