This section explains the problem of traditional biomass cooking, the solutions provided by improved (or “clean”) cooking solutions (ICS), and the choices that The African Stove Company (TASC) makes when it designs and implements projects distributing ICS.

What are the problems with traditional biomass cooking?

Over 1 gigaton of carbon dioxide (CO2) is emitted each year by burning wood fuels for cooking [1]. That figure is approximately 2% of global emissions and comparable to the carbon footprint of the United Kingdom. The carbon footprint of traditional biomass cooking comprises emissions from the woodfuel supply chain, fuel combustion, deforestation, and forest degradation. Wood fuel harvesting and charcoal processing are primary drivers of regional forest degradation across the African continent [2]. Burning wood fuel also creates black carbon (BC) emissions, which are short-lived (8-10 days) but influence regional precipitation and temperature changes. 

Household air pollution (HAP) from cooking causes over 4 million premature deaths each year from conditions including lung cancer, chronic obstructive pulmonary disease, and ischemic heart disease. HAP exposure is responsible for 45% of pneumonia deaths in under-fives and it is a leading cause of blindness and low birth weight globally. It is worth noting that there is broad scientific consensus that the breadth of negative health outcomes and the number of ill-health episodes caused by inefficient cooking have likely been underestimated due to insufficient data.

In developing countries, women usually take responsibility for cooking. Their health, and that of their children, is disproportionately impacted by HAP. Inefficient cookstoves require more fuel to be collected and more time in attendance while food is cooked. The aggregate time spent in fuelwood collection and cooking is around 5 hours per day. Injury and violence are commonly overlooked risks of frequently arduous trips to collect firewood.

Traditional biomass cooking is a problem for public health, gender inequality, our climate, and the local environment. In Sub-Saharan Africa (SSA), where TASC’s work is focussed, the total cost of traditional open-fire cooking is over $330 billion a year: $186 billion on gender, $96 billion on health, and $47 billion on climate and environment [3]. Replacing traditional biomass cookstoves will improve women’s health, allow them greater economic and social freedoms, and reduce CO2 emissions.

What does TASC do?

TASC distributes ICS across SSA and monitors reductions in wood fuel use amongst recipient households. We register our projects with reputable international carbon standards to receive verified carbon credits.

Why do you distribute cookstoves?

We distribute ICS to address two acute needs: to reduce the environmental, social and economic impacts of open fire cooking; and to meet the demand for high-quality carbon credits to meet regulated or voluntary emissions reduction targets.

What is an improved cooking solution? Is it the same as a clean cookstove?

ICS include a range of interventions or appliances designed to improve fuel efficiency and emissions performance in cooking. Most are improved cooking stoves; however, the category also includes products like thermal insulation sleeves.

According to the World Bank Group (WBG) and World Health Organisation (WHO), a clean cooking solution, or clean cookstove, is an advanced ICS that lowers particulate matter and carbon monoxide emissions to near zero [4]. Clean cookstoves do not burn wood or charcoal but instead use feedstocks like processed briquettes, biomass pellets, liquid petroleum gas (LPG), methanol, or even electricity. The name ‘clean cookstove’ is often used to describe all manner of ICS, which can be confusing.

Which cookstoves do you distribute?

TASC distributes portable rocket stoves supplied by Burn Manufacturing of Kenya and RocketWorks of South Africa. We purchase different models depending on which country we are operating in and whether the target communities are predominantly wood or charcoal fuel users.

How do portable rocket stoves work?

The central feature of a rocket stove is an ‘L-shaped’ chamber that is designed to moderate airflow into the fire and maximise fuel combustion. Rocket stoves are open at the point at which wood is fed in, allowing lots of oxygen to be drawn into the unit. As the fire starts, rising hot air moves up through the chamber, drawing more air behind it. The insulated combustion chamber only has space for a small amount of fuel to burn at any given time, ensuring almost complete combustion prior to the flames reaching the cooking surface.

Why do you distribute portable rocket stoves?

Improved cookstoves vary widely in terms of the fuel feedstock, construction materials, methods of production, and performance. Some carbon projects distribute ‘basic’ artisan cookstoves or make permanent alterations to ‘legacy’ coal or biomass cookstoves. ‘Basic’ and ‘legacy’ cookstoves achieve minor efficiency gains and negligible reductions in local air pollution. These products are not quality tested, prone to malfunction or degradation, and are relatively expensive considering their overall impact.

We distribute the specific models of rocket stoves because they:

  • achieve the highest fuel efficiencies for biomass stoves (over 50% improvement on traditional stoves)
  • achieve, on average, 60 percent HAP reduction [4], which is the highest combustion efficiency for biomass stoves
  • are manufactured in special purpose factories to maximise durability and consistency
  • are reported to last from 7-10 years
  • are financially viable for use in carbon credit projects; and
    allow people to cook traditional meals using fuel that is readily available in their community.
Why don’t you distribute LPG or electric stoves?

LPG and electric stoves are difficult to distribute for two reasons:

    • There isn’t suitable fuel supply in remote rural communities, and;
    • The products are too expensive to distribute under a carbon credit methodologies.

However, we are monitoring methodological updates to determine when it would be feasible to implement LPG and Electric cooking projects. LPG and electric stoves can improve HAP reductions from 60% to over 90%.

What are the traditional cooking solutions that you are replacing?

Most families in our project areas use ‘3-stone’ fires, where pots are balanced on rocks, or ‘Os’, which are a circular metal pot stand. 3-stones are most common amongst rural, wood fuel users. In peri-urban and urban areas we find basic charcoal stoves called ‘Mbalula’, which resemble an old washing machine drum, or a metal bin with holes drilled through the sides.

Which areas does TASC work in?

We are currently active in South Africa, Zambia and Zimbabwe.

What is the level of need in these countries?

In Sub-Saharan Africa (SSA), approximately 729 million people, or 73% of the regional population, have no access to any ICS [1, 3].

  • 88% of rural Zambian households have no access to electricity and just 2% have an electric cooker. In total, over 83% of households cook with biomass; 46% burn wood on 3-stone fires, and over 36% use Mbalula, mainly with charcoal [5].
  • 95% of rural Zimbabwean households rely on firewood or charcoal for daily cooking. 66% of urban households are connected to the grid but unreliable supply forces many to employ charcoal stoves as the primary mode of cooking [6, 7]. ICS are beyond the reach of most household budgets, due to the upfront cost.
  • South Africa has high rates of electrification and most of the population does not rely on biomass fuel. Nevertheless, disparate rural communities live a world apart from the urban centres and receive little to no social support from the national government. Thus, we have identified communities where SA citizens and economic migrants face the same issues as in Zambia and Zimbabwe.

All the areas in which we operate suffer from high annual increases in deforestation, combined with high proportions of woodfuel use. The link between woodfuel consumption and deforestation is highly localised and, charcoal supply in particular, is considered a primary cause of deforestation [8].

How does TASC distribute the cookstoves?

Distribution starts with sensitization, which is the dissemination of information about the proposed project to local communities. The objectives of pre distribution sensitization meetings are to maximize the adoption of the new stove and eliminate the use of traditional stoves. Sensitization meetings are arranged through local tribal authorities, which helps ensure the project is promoted in a culturally appropriate fashion. Attendees receive a presentation on the benefits of the efficient stove, how to cook with it, and how to obtain one. Afterward, the names and addresses of those who would like a stove are collected. Only one cookstove is allowed per household.

Several days later, our team will return to each village to distribute the stoves. They use a mobile application to collect data on the recipients, including full name, social security number, proof of identity, address, family size, GPS location etc. The recipients also sign an End User Agreement. The agreement confirms that they understand that TASC retains the rights to monitor the stove usage and the ownership of any carbon credits that may be obtained by doing so.

Why do you give the cookstoves away for free?

We give stoves away in exchange for the exclusive right to monitor them and sell carbon credits associated with their performance. We find this is the most efficient method of distribution. Demanding any cash payment – upfront, financed, or concessionary –dramatically reduces uptake because our target beneficiaries cannot afford it. Contrary to popular belief, we do not find beneficiaries to be less willing to look after stoves that they didn’t pay for. Our experience is supported by academic research [9].

How do you measure the performance of the cookstoves?

The primary measurement of cookstoves’ performance is reduction in fuel use and, consequently, the reduction in carbon dioxide equivalent (CO2e) emissions. This is how the issuance of carbon credits is determined. CO2e savings are calculated by following methodologies by the Gold Standard or the Verified Carbon Standard. The Gold Standard provides guidance on how other project impacts – health and gender – can be extrapolated from the data on stove usage.

Each year, the project scenario is compared with the baseline scenario to calculate the average fuel savings per unit (stove/household). Both scenarios are determined by a conducting a habit survey and a kitchen performance test (KPT) to understand how households cook before and after the introduction of new stove, and to calculate fuel usage.

The habit survey is used in both baseline and project scenario to determine household cooking habits, stove usage, and household demographics. The KPT is used to directly measure fuel consumption over a 24-hour period. The KPT is performed over 4 consecutive weekdays. Project field officers randomly select households from the database and visit them every 24 hours to weigh a stockpile of fuel and measure the change from day to day. The field officers instruct the participant households to consume fuel using all cooking technologies that they would normally use. If secondary biomass stoves are used, their emissions are included in the results.

All field testing and surveys measure real cooking habits and fuel use in a statistical sample of participant households, chosen using a randomised selection technique. The habit survey sample size is determined by using the “Sampling and surveys for CDM project activities and programmes of activities” document. Projects over 1000 devices are required to have a minimum sample size of 100 surveys but we oversample to 120 to account for possible anomalies and/or survey errors. For KPTs, the following guidelines apply. A statistically valid sample can be used to determine parameter values, as per the relevant requirements for sampling in the latest version of the CDM Standard for sampling and surveys for CDM project activities and programme of activities. 90% confidence interval and a 10% margin of error requirement shall be achieved for the sampled parameters unless mentioned otherwise in the methodology. In any case, for proportion parameter values, a minimum sample size of 30, or the whole group size if this is lower than 30, must always be applied.

As we are following the 90/10 approach with a covariance of 0.4, we are required to do a minimum of 45 samples. However, it is suggested to oversample to at least 60 tests to provide the ability to remove outliers and exclude any tests where experimental errors have occurred.

After sampling, fuel savings per device are calculated by comparing the project scenario against the baseline scenario. Fuel savings are multiplied by CO2 and non-CO2 emission factors as well as the fraction of non-renewable biomass (fNRB) and divided by 365 to calculate the total tonnes of CO2e reduced per device per day. This value is multiplied by the total number of technology days – the sum of days all devices have been active in the monitoring period – resulting in the gross emission reductions (in tCO2e) for the monitoring period.

TASC takes several steps to ensure project success, including:


  • our own proprietary cloud-hosted database for collecting records of stove distribution, including contact information, GPS locations, archived stove purchase agreements, financial accounts and distribution records, all of which is used for spot checking and cross referencing by a third-party auditor.
  • In-house monitoring (beyond verification or compliance monitoring) and community engagement is conducted throughout the project lifespan to identify where and when stoves may be underused and inform where additional training is required to maintain a high usage of stoves.
What is thermal efficiency? Why is it different to fuel reduction?

Thermal efficiency (TE) describes the fraction of heat energy that is put to work. In this case, it is the fraction of heat transferred to the cooking pot. The TE of our ICS is approximately 40%, while TE of an open fire is approximately 10%. That means 90% of the heat energy is lost in an open fire. We can estimate overall fuel savings by calculating the percentage difference between the old and new TE, as follows:                                               


(1-(10/40))*100 = 75%

The higher TE of the ICS means that ~75% less fuel is needed than cooking the same meal on an open fire. It should be noted that this fuel saving estimation is only done for ex-ante purposes and actual fuel savings in the implemented project is calculated by doing field consumption tests (i.e. KPTs) in the baseline and project scenarios.


[1] Bailis et al. 2015. The carbon footprint of traditional woodfuels. Nature Clim Change 5, 266–272 (2015).

[2] Hosonuma et al. 2012. An assessment of deforestation and forest degradation drivers in developing countries. Environ. Res. Lett. 7 044009. Available online:

[3] Energy Sector Management Assistance Program (ESMAP). 2020. The State of Access to Modern Energy Cooking Services. Washington, DC: World Bank. License: Creative Commons Attribution CC BY 3.0 IGO. Available online:

[4] Energy Sector Management Assistance Program (ESMAP). 2015. The State of The Global Clean and Improved Cooking Sector. Washington, DC: World Bank. License: Creative Commons Attribution CC BY 3.0 IGO. Available online:

[5] Luzi et al. 2019. Zambia – Beyond Connections: Energy Access Diagnostic Report Based on the Multi-Tier Framework (English). Energy Sector Management Assistance Program (ESMAP) Washington, D.C. World Bank Group. Available online:

[6] Johnstone, Kevin. 2020. Stoking Finance for Affordable Cookstoves: Experience from Malawi and Zimbabwe. International Institute for Environment and Development. Available online:

[7] Zimbabwe National Statistics Agency. 2017. Inter-censal demographic survey. Available online:

[8] van Dijk et al. 2019. Assessing the land-energy nexus in Southern Africa: An integrated assessment and scenario approach. In: EGU General Assembly 2019, 7-9 April 2019, Vienna, Austria. Available online:

[9] Bensch, Gunther; Peters, Jörg (2012) : A Recipe for Success? Randomized Free Distribution of Improved Cooking Stoves in Senegal, Ruhr Economic Papers, No. 325, ISBN 978-3-86788-374-0, Rheinisch-Westfälisches Institut für Wirtschaftsforschung (RWI), Essen,