Almost 1/3 of the world’s population, about 2.7 billion people, continue to cook food in the traditional way on an open fire. This method has negative environmental and socio-economic consequences, especially for women and children involved in the cooking process. Firstly, the likelihood of such diseases as childhood pneumonia, chronic obstructive pulmonary disease (COPD), ischemic heart disease, stroke, and lung cancer increases. Secondly, for women and children, cooking on an open fire requires weekly time spent collecting fuel, which could otherwise be more usefully spent on income generation, education, or other activities. Thirdly, traditional cooking leads to about 2% of global greenhouse gas emissions, damaging climate resilience, and to the loss of non-renewable biomass due to wood burning.
The volume of emission reductions achieved as a result of replacing traditional stoves with clean ones is influenced by a wide range of parameters. One of them is the fraction of non-renewable biomass — fraction of non-renewable biomass (fNRB).
fNRB is the share of woody biomass considered non-renewable in the total amount of fuel used for cooking. This occurs when biomass is harvested faster than it regenerates. The higher this indicator, the greater the climate effect that can be obtained by replacing traditional stoves with clean ones.
The result of carbon unit issuance from stove replacement projects is most sensitive to the adjustment of the fNRB indicator, since baseline greenhouse gas emissions can change significantly. The problem is that the value of fNRB is specific to each region, even within one country. At the same time, this indicator cannot be measured directly. All existing approaches to assessing fNRB are based on modeling.
Project developers use fNRB values according to the tools and methods specified in the project implementation methodology. In 2017, country-specific fNRB values were approved. Later, they were used in the tools TOOL30 and TOOL33, as a result of which it became possible either to use 30% by default or to calculate fNRB values. These sources were the main ones for choosing the fNRB value of each specific project. At the same time, within carbon credit programs, under which carbon credits are issued for these projects, the UN, the scientific community, and non-governmental organizations (NGOs) constantly work together to refine this indicator to avoid overestimating carbon credits.
Against the backdrop of scandals around clean cookstove projects in 2023–2024, the process of revising the methodologies and parameters used accelerated. In October 2024, Verra released the methodology VM0050 Energy Efficiency and Fuel-Switch Measures in Cookstoves methodology, which replaced all previous methodologies under the Verified Carbon Standard (VCS). Also in 2024, the first version of the new methodology — Comprehensive Lowered Emissions Assessment and Reporting (CLEAR), developed by the Clean Cooking Alliance, was published. Based on it, projects can be implemented within the carbon crediting mechanisms of the Paris Agreement. Amid methodology updates, clean stove project developers began preparing for a significant reduction in the issuance of carbon credits.
Currently, the trend is such that project developers are recommended to move away from the default fNRB value of 30% according to TOOL30. And within the Gold Standard (GS) program, its use will be prohibited from 2026. GS allows the use of TOOL30 and other tools that will be revised within the Paris Agreement mechanism. These include TOOL33, updated in June 2025 based on the Modelling Fuelwood Saving Scenario (MoFuSS), as well as data from the MoFuSS platform itself.
“For AIM Carbon, the main principles in the implementation of any project are its high quality and an accurate approach to assessing the potential issuance of carbon credits. Therefore, despite the potential reduction in the issuance of carbon units, from the very beginning of project development, it was decided to use the most conservative and accurate MoFuSS estimates to avoid overestimating the project's climate effect. In addition, if the applicable climate standard allows this and relevant data are available, AIM Carbon uses fNRB indicators with regional accuracy rather than country averages. This makes it possible to more accurately take into account local features of fuel use and, as a result, increase the reliability of assessing the climate effect of the project,” says “BURN” project manager Alexander Makarov.
The MoFuSS platform, whose data is developed by scientists from Mexico and the USA, was launched in May 2025. As of August this year, it is considered the most accurate source of the fNRB indicator. However, some project developers opposed the MoFuSS values, claiming that they significantly underestimate fNRB in some African countries.
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