Improved Cookstoves and Energy Saving Cooking Equipment

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What is a Stove?

The term ‘stove’ refers to a device that generates heat from an energy carrier and makes that heat available for the intended use in a specific application. Cook stoves are made to transfer the generated heat to food, with the purpose to get it cooked and edible for human consumption. Thus ‘a stove’ features the combination of heat generation and heat transfer to a cooking pot if the food is cooked in a liquid, or a griddle, plancha etc. if the food is baked on a hot surface or roasted without liquid.

What is an Efficient Stove?

Cook stoves are commonly called “improved” if they are more “efficient” than the traditional cook stoves. But what does “efficient” mean in this case?

Energy efficiency describes the heat transferred into the pot in relation to the overall energy generated by the stove within a defined task (e.g. water boiling test). For more details on stove testing see here.

But in most cases, this is not what is meant when the efficiency of stoves is discussed. From the perspective of a stove user, the core question concerning the efficiency of two alternative stoves is:
“With which of the two stoves do I use less fuel to prepare my meal?”


To answer this question, a number of factors beyond the stove design should be considered:

• the quality and characteristics of the fuel,
• the handling of the fuel,
• the handling of the stove,
• the management of the cooking process
• the cooking environment

In this broader sense, the entire cooking system has to be analysed in order to determine which stove has a higher “user efficiency”.

When we talk about the efficiency of stoves, we usually compare the specific fuel consumption of a specific energy to either (a) a benchmark or (b) the specific consumption of another stove. 

Examples:

• Stove A consumes less fuel (for a specific standardised task) as indicated in the benchmark (e.g. 80g of charcoal per kg food prepared in a controlled cooking test)
• Stove A consumes 40% less fuel than stove B per litre boiled water (in a 5l Water boiling test)

With focus on relative performances of stoves, the assessment of stove efficiency is circumstantial. A clay stove is perceived as an efficient stove in households with open fire places and as an inefficient stove in households which are using a rocket stove.
International standards on stove quality have been discussed for many years. While they are desirable to enable a global comparison of stove performances, there is a danger that cheap solutions for the very poor households are abandoned due to their low performance in relation to the global standards, when in fact they could still be a relevant improvement in comparison to the baseline situation of the poorest of the poor. That’s why a stratification of quality standards has been developed in the Lima consensus.

Improved biomass cook stoves are thus to be considered a fuel-efficiency technology rather than a renewable energy production technology. Nevertheless, they are clearly a form of rural renewable energy use, one with enormous scope and consequences of use. Cook stoves come in a variety of designs targeting various types of biomass and cooking techniques that take into consideration cultural diversities.   

Improved stoves have been produced and commercialized to the largest extent in China and India, where governments have promoted their use, and in Kenya, where a large commercial market developed.

Applications and Efficiency

Stoves can be largely categorised into domestic and institutional categories. This determines the design, size and cost.  Institutional stoves tend to be bigger, more robust and generally more expensive in comparison to domestic stoves.

Improved biomass stoves save from 10–50% of biomass consumption for the same cooking service provided and can dramatically improve indoor air quality.

Research, dissemination, and commercialization efforts over the past few decades have brought a range of improved charcoal—and now wood-burning—stoves into use. Many of these stove designs, as well as the programs and policies that have supported their commercialization, have been highly successful.

There are 220 million improved stoves now in use around the world, due to a variety of public programs and successful private markets over the past two decades. This number compares with the roughly 570 million households worldwide that depend on traditional biomass as their primary cooking fuel. China’s 180 million existing improved stoves now represent about 95% of such households. India’s 34 million improved stoves represent about 25% of such households.

In Kenya, the Ceramic Jiko stove (KCJ) is found in more than half of all urban homes and roughly 16–20% of rural homes. About one-third of African countries have programs for improved biomass cook-stoves, although there are few specific policies in place. Non-governmental organizations and small enterprises continue to promote and market stoves as well.

Policies and programs to promote efficient stoves are designed to improve the health, economic, and resource impacts of an existing renewable energy use and thus closely linked to sustainable forestry and land management.

Global Stove Diversity 

There are many different types of stoves across the world. This is natural, as a stove needs to accommodate the site-specific constellation determined by the available fuels, climatic conditions and preferences of users in the local culture. Thus, stove designs reflect global diversity. Please keep in mind: ‘One size fits some, but rarely all’.

The resulting diversity of stoves can be described in different categories such as:

• Fuel types (solid, liquid or gaseous fuels from renewable biomass or fossil sources)
• Pot sizes (from small to big individual households sizes, medium to large pots for restaurants, enterprises or social institutions)
• Pot shapes and materials (round bottom/flat bottom pots, clay or metal, pots with or without handles and/or legs, frying pans,  etc.)
• Numbers of pots to be used at a time (pot holes for one or several saucepans)
• Numbers of fires (one fire-box or several fires)
• Batch-feeding or continuous feed of fuel
• Natural draft or forced convection with a ventilator
• With or without a built-in chimney to remove emissions from a kitchen
• Transportability (from built-in models that have to be constructed on site to portable stoves built elsewhere)
• Affordability (to suit the range of economic means of users from low-cost to more expensive)
• Place of manufacture (national production or imported)
• Cost (mainly determined by the type of building material and the level of sophistication of a stove)
• Other uses of a stove e.g. space heating, lighting

Stove designs also depend on the cooking habits. For instance, in many Latin American countries, tortillas are a traditional staple food baked on a hot metal plate ('plancha'). In Ethiopia the staple food is a pancake baked on a large ceramic plate. Stoves need to incorporate these essential features for people to prepare their staple foods. Otherwise the stove will not be acceptable in that area.

Beatrix Westhoff and Dorsi German compiled a comprehensive overview on global stove diversity in 1995 in the publication 'Stove Images - a Documentation of Improved and Traditional Stoves in Africa, Asia and Latin America'. It is available in English, French and Spanish at

• http://www.gtz.de/en/themen/umwelt-infrastruktur/energie/32777.htm

Not all stove types comply with criteria required to qualify as 'improved stoves'.
Promising stove types that are performing well within the GIZ-supported project areas are presented in the Stove Fact Sheets published by GIZ HERA.

The following chapters present stove types for different fuels and cooking practices according to the following structure:

Household Cooking Energy Diversity 

Household cooking energy is often discussed as a “one fuel - one stove” system. The archetype of this idea is the rural household using firewood in a 3-stone fireplace. On a second look, this picture is often a drastic simplification of the reality. Many households, particularly in (peri-) urban environments, are actually using several fuels and/or several stoves for a variety of reasons:

• Different traditional meals require different types of heat (e.g. Ethiopia: the large pancake-style injera, sauce, and coffee ceremony);
• Seasonal variation of availability or affordability of fuels (e.g. biomass as back-up if fossil fuels or electricity is not available, increasing prices or money shortages at the end of the month);
• Variation of convenience needs (e.g. fast cooking in the morning, slow cooking in the evening);
• Different abilities of cooks (e.g. expensive fuels and stoves shall not be used by the young daughter, so she is using firewood);
• Different cooking needs (e.g. preparation of meals for the family on a different stove as the preparation of animal feed or processed food for the market);
• Different types, shapes and sizes of cooking utensils (cooking pots, pans etc.) require different stove shapes or sizes.

Cooking energy interventions should be based on a clear understanding of the household cooking energy diversity of their target groups before activities are planned. It must be clear which part of the “traditional” (= baseline) cooking system shall be addressed.

Fuel Switching and the “Energy Ladder”

A favoured development model for household energy is described with the term “energy ladder”. The basic idea is that with increasing wealth, households are ‘progressing’ from stickwood to charcoal, kerosene, LPG and finally to electricity. Each step on the ladder is linked to a fuel switch which implies the permanent and complete change from the use of “traditional” fuels to “modern” fuels.

However, as indicated above, the introduction of “modern” alternatives often contributes to an enlargement of the complexity of parallel utilised cooking systems (the “cooking energy mix”) rather than a complete fuel switch in the sense of climbing a ladder.

Furthermore, in recent years, more and more observations have been made that users of “modern energy” like electricity or LPG are “going down the ladder” if a removal of subsidies increases the cost of cooking and/or the availability of the fuel. Hence the picture of “switching the fuel” is in many cases rather a matter of “increasing the diversity of options” than a permanent change of behaviour.

Generally it is easier to convince households to increase the efficiency of use of their traditional fuel(s) rather than to learn how to use a new fuel. It is also easier to only deal with the establishment of a supply-demand system for a stove rather than establishing a new fuel supply system as well. Fuel is needed on a daily basis; a stove needs to be replaced only once in a while.

It may seem that urban and better educated households are more open to innovations as compared to rural households with less education. However, this is a decision by the target group which can be surprisingly different than our assumptions. In a field test of a plant oil stove in Tanzania, even rural firewood using households have managed to operate a plant oil stove successfully.

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Links to Further Reading

http://www.bioenergylists.org/en