Cooking with rocks, measuring significant fuel savings through simple solutions


A new cooking innovation, involving the deployment of a simple and free solution to improve the efficiency and fuel savings of traditional stoves, was tested by SNV as part of its partnership with the non-faith based non-profit Sun24.

More than three billion people rely on biomass fuels every day as an energy source to satisfy their cooking necessities. This limited access to modern energy services, known as energy poverty, creates a significant social and environmental affliction among those trapped in it.

On average, a household in developing countries spends 7% of its income on cooking and lightning fuel. Furthermore, collecting fuelwood has an often overseen footprint in the productivity circles of dwellings as households can spend between 30 minutes to over six hours each day to conduct this task.

Impacting women and children

These usually impact women and children who are predominantly leading figures in households for collecting firewood and preparing meals. Moreover, cooking with traditional fuel sources and stoves can impair children involved in fuel collection by limiting their educational opportunities, providing inadequate nutrition levels due to limited income, and living under unhealthy conditions in the presence of household air pollution.

Guy cooking

10,600 deaths annually

Previous studies evidenced the constant obstacles faced by improved cooking technologies throughout its dissemination. Willingness to adapt and change traditional traits on cooking, coupled with upfront costs faced in acquiring a cooking technology, can become significant barriers in the adoption of these innovations.

With no one-fit-for-all solutions in place to fully replace traditional cooking patterns and technologies, an alternative path was explored to achieve the goal of scaling up cooking conditions with little or no cost while complementing current cooking dissemination campaigns.

Scalable solution

Sun24’s Rocks Bed Cooking Innovation uses small round stones or broken bricks spaced in between as a layer on which fuelwood is placed. This setup improves the efficiency of a cookstove by increasing the air flow throughout the cooking process, pre-heating the air used in the combustion, and by burning most of the embers. In fact, Sun24 already disseminated this concept to 1.5 million households so far in several countries in Africa and Asia.

This solution provides an accessible, scalable and cost-free approach to current traditional stoves that would improve their performance. Findings from a user survey with 99 women conducted by Sun24 in Africa suggested that this intervention was allowing cooks to prepare their meals with lower smoke emissions and higher thermal efficiencies in their traditional 3-stone stoves.

Stove visual

Accordingly, and to gather additional evidence on the real impacts of the Rocks Bed Cooking Innovation, SNV conducted laboratory tests and a subsequent Kitchen Performance Test (KPT) to quantify the differences in stove emissions, fuel use and stove efficiency attributed to this intervention.

The laboratory tests followed SNV’s Simplified Water Boiling Test (SWBT) to assess fuel consumption, Particulate Matter (PM) and Carbon Monoxide (CO) emissions. The results showed that fuel consumption was 30% lower in traditional iron bar stoves with the rock bed. In addition, stoves with this setup had a reduction of 35% and 45% in PM and CO emissions respectively. The promising results from the rock bed innovation motivated Sun24 to entrust SNV with a pilot test involving 30 households in rural Hanoi for a period of two weeks.

Following the existing KPT protocol, the study applied a survey to measure fuel consumption before and after the introduction of the cooking innovation. Throughout the test, households were instructed to cook normally. Additionally, households would receive training on how to setup and prepare the innovation for each cooking task.

Set up of stove for BEFORE and AFTER (with rocks bed) phase testing

Set up of stove for BEFORE and AFTER (with rocks bed) phase testing

Less smoke, faster cooking

Applying the rock bed innovation showed an average reduction of fuelwood consumption of 3.1 kilograms per day. This is equivalent to a reduction of 28.5%. Furthermore, statistical analysis of the fuel consumption per standard adult person (SA) or person meal indicated a mean 0.51kg/SA reduction (with a statistical range of +/- 0.29 due to uncertainty) after the innovation; equivalent to 34% savings (with a statistical range of +/- 20% due to uncertainty).

In addition to the empirical data collected from the KPT, qualitative data from the surveys showed a very positive feedback from cooks (90% of which are women) on using the rock bed cooking innovation. Every participating household observed less smoke emitted with the rock bed, lower fuel consumption and a faster cooking speed than before. Moreover, 73% of respondents argued that the smoke levels were significantly lower once the rock bed cooking innovation was in place. The high satisfaction levels found on every household were reflected on the willingness to conduct future cooking tasks with this innovation. 100% of the participants expressed their desire to continue using the rock bed concept in their traditional stove.

Lastly, 25 out of 30 households felt compelled to share their experiences with neighbours and friends in the area. In this case, word-of-mouth becomes a vital component that indicates an opportunity to scale up this cooking innovation. Lessons from previous dissemination efforts and campaigns on cooking suggest that it is necessary to provide a portfolio of alternatives to tackle energy poverty. This progressive approach enables and encourages implementing different contextualised solutions to a wide array of cooking needs and surroundings. Cooking dissemination efforts are not bound to quantum leaps alone. Simple, potentially scalable and virtually cost-free alternatives, such as the rock bed cooking innovation, can deliver gradual steps in the right direction by providing more efficient cooking experience in the short term.

Detailed report on KPT result can be found here.