Tests protocols cookstoves

While the development process of the ISO/TC 285 [1] on clean cooking solutions is on-going, the test protocol for improved cookstoves working group is moving forward.

The work on this ISO began in 2012. When adopted, it will aim to allow countries to enforce the improved cookstoves standards (ICS) and labelling for efficiency and cleanliness. This policy should spur on stakeholders to design less polluting and more efficient cookstoves.

The working groups, including the one dedicated to test protocols, met last November. At the end of the process, they will submit their working documents to the ISO and to the country members for adoption. (For more information, read The cookstove challenge).


It is important to understand two tests in use in the improved cookstoves sector: the Water Boiling Test (WBT) and the Adapted Water Boiling Test (AWBT).

To justify the relevance of the product to the general population, producers/distributors, and funders, it is necessary to measure its performance. The GERES (an environmental NGO) team quickly realised that the testing protocol that is most commonly used at the international level does not provide a reliable picture of cookstove performance in Cambodia. Also, it is not representative of Cambodian cooking practices. That is why GERES developed a new testing protocol, based on the international WBT, that takes into account the culinary practices of the region: the AWBT.

It enables GERES staff to design more efficient cookstoves and meet the needs of Cambodian cooking habits; the New Lao Stove (NLS), ideally used with charcoal in urban areas; the Neang Kongrey Stove (NKS) for rural areas and ideally used with firewood; and a ‘rocket [2]’ stove, the KhRoS, targeting urban areas and used mainly with charcoal.

In 2013, the Global Alliance for Clean Cookstoves (GACC) commissioned the GERES Biomass Energy Laboratory (G-BEL) to conduct a study. They were asked research local cooking habits and the difference between the WBT and the AWBT further. The study sought to answer: 'How do we obtain results in a laboratory setting that more closely mimic those in the field? Which test, the WBT or AWBT, is the most trustworthy?'

The heart of the matter

GERES researchers begin the study with a reminder about cooking habits in Cambodia. High cooking power accounts for 90% of the overall cooking time for boiling, grilling, and frying in Cambodia. To control the heating power, the user adds or removes fuel during the cooking process. The AWBT has been developed for this particular situation. It takes into account more high-powered cooking in the testing procedure.

Then, researchers obtained data for two different stoves (the NLS and KhRoS) for every test protocol: the WBT, the AWBT, and the KPT.

The KPT?

The the Kitchen Performance Test (KPT), another test protocol, is essential for this comparison. It measures controlled, real situations performance and is used as a control test for this study. We deem this testing protocol to provide a reliable picture of performance in a real-life cooking situation. The degree to which the results of the WBT or AWBT align with the KPT will allow us to estimate the reliability of both tests.

We use this third test protocol because it is impossible to compare data from the WBT and AWBT. They are based on distinct criteria and use different units.

The researchers measured the performance gap between the two stoves, using each test. For example, they measured the NLS and the KhRoS using the WBT. They rated each stove based on the results. The difference between each rate is then translated into a percentage. Then, they repeat the same procedure for each test, the AWBT, and the KPT. Note that we consider the KPT results to be reliable. Thus, the value (percentage) that is closest to the KPT indicates the greatest reliability.

According to the KPT, the KhRoS is 22.5% more efficient than the NLS; per the WBT, the KhRoS is 12% more efficient than the NLS; and, according to the KPT, the KhRoS is 25% more efficient than the NLS. These results show a greater difference in the results between the different cookstoves than the AWBT and the KPT, whose results are relatively close.

Another conclusive comparison criterion is the fuel saved during cooking. For each test, the divergence in fuel consumption measured with the KhRoS and NLS is compared. This difference is also converted into a percentage for each test and compared. The study shows that the variation between the KPT results and AWBT is 11%, while those between the WBT and KPT reached 47%.

This discrepancy is explained by the heating power difference during the WBT and AWBT. The first test incorporates both high and low heat while the second reproduces the practices of the country; it maintains high heating power during 90% of the cooking time.

It should be noted that this high heating power is well represented in Asia, where they cook sticky rice, but also in West Africa, where rice is mainly steamed.

Given these elements, the authors, David Béritault and Jean-François Rozis, recommend paying particular attention to these power variations. Indeed, if we consider the WBT results in the design of a cookstove, it may have good results when used with low power. The design must also meet the specific power needs of the local context while respecting efficiency and cleanliness criteria. However, these differences in power are poorly addressed by the WBT. This is of particular concern when the WBT is used to collect the necessary field data to gain access to carbon finance. As shown in the study, the WBT does not give a reliable picture of energy consumption conducted in real-life situations. As a result, CO2 emissions reductions calculated with the WBT are not representative of actual emissions reductions.

ISO/TC 285 seeks to accurately answer these problems by offering criteria as representative as possible to the reality in the field.

For more information, read the study.

[1] http://cleancookstoves.org/events/160.html

[2] Type of Improved Cookstove