One of the characteristics of humankind is the ability to control fire and utilise it to prepare food. The oldest cooking fuel is firewood in the form of logs and branches from trees. Charcoal is the fuel derived from wood by pyrolysis in the process of carbonisation: the wood looses the volatile contents and the lighter yet energy-dense char remains. Due to the ease of transport and use, charcoal has become a prevalent cooking fuel in many urban areas of this planet, while firewood is more prevalent in rural areas.

As firewood and charcoal have very different burning properties they need different devices (stoves) for cooking. This section deals with both fuel-types seperately. Other types of biomass feature in the next chapter Cooking with other Biomass Fuels. (link reinsetzen)

Cooking with Firewood
woodfuel stove types (HH, SME, SI)
Cooking with Charcoal
Stoves designed to burn carbonised biomass
Cooking Practices for Woodfuel Users
fuel management, stove usage
Testing of Woodfuel Stoves

Cooking with other Biomass Fuels

Not all biomass comes in the form of logs and thicker branches of trees, that have been used as cooking fuel since humans learned how to prepare food with the help of a domesticated fire. The efficient and clean use of other types of biomass as fuels requires some preparation, processing and refining of the fuel. Some fuel types need specific set-ups and burners to combust well and generate heat that is useful for cooking. Thus, this section is structured by the types of biomass fuels, including the devices needed for cooking with each fuel. You find information on other fuels that are not based on biomass (solar, fossil fuels) in a separate chapter. Please note that most households do not only rely on one type of fuel only. Mostly households have cater for the household energy needs wiht a mix of different fuels. People make choices depending on many factors like the availability, affordability, convenience and safety of a fuel.

Cooking with Other Biomass Fuels (1. dung 2. unprocessed residues 3. processed fuels)
Cooking with Liquid Biomass Fuels (1. alcohol fuels (methanol, ethanol) 2. plant oils)
Cooking with Gas from Biomass (1. biogas 2. woodgas)

Cooking with Nonbiomass Fuels

Cooking with Sun
Cooking with Fossil Fuels (1. kerosin, 2. fossil gas, 3.coal)

General Cooking Practices

How efficiently cooking can be done in a household not only depends on the stove technology in use. Often the way the fuel is prepared or the stove is used and handled offers an even greater potential to improve efficiency and limit resource use for cooking. One option is for users to adjust their behaviour and adopt efficient cooking practices or techniques.

Another option is to integrate other energy saving devices and technologies into the household cooking system:

Pressure cookers enhance the cooking process, so that the same cooking can be done faster and with less energy input
Heat retainers like thermos flasks or 'fireless cookers' (also called the heat-retaining box, the hay bag or hot bag) maintain the heat and can do both: keep on cooking without a heat source and keep food or liquids warm over time.

This section deals with technologies and techniques that can save substantial amounts of energy, regardless of the fuel type and stove that is used. But they cannot substitute a stove. In order to retain heat, that heat needs to be put into the food first!

General kitchen management practices

Cooking with retained heat, without additional fire

Thermos flasks

Thermos flasks are an inexpensive way to maintain water, beverages or liquid food hot over time. In places, where food preparation is based on pouring hot water over food items like e.g. in Tibet, thermos flasks can be a major game-changer in the cooking system of a household: Alongside solar cookers, families own up to five thermos flasks and store the water heated by the solar cooker during the day. The hot water is used for preparing both morning and evening meals (mainly soup and porridge) enabling the solar cooker to fulfil almost all the household energy needs. However, this represents a rather specific case, which may not be transferable to many other countries. Yet, thermos flasks are currently underutilised and could probably play a more important role.

Retained Heat Cookers or 'Fireless Cookers'

The fuel consumption in the process of food preparation on a fire is not constant. A lot of fuel is required to heat up the content of a cooking pot. Once it is boiling, it only takes little energy to keep it hot and maintain the temperature at boiling point. Some foods like legumes, (sweet) potatoes, cassava or rice etc. do not require any stirring. The content of the pot has to be heated once to the boiling point and then kept at simmering level on a little flame without having to open the lid of the pot. If you open the lid of the pot and stir the content, the temperature goes down quickly and more fuel is needed to get it back to boil.
The small fire basically replaces the heat that is lost to the environment through the surface of the cooking pot and the closed lid. If you don’t use a lid, the heat loss will be even bigger and you need more fuel.
So there are two ways of maintaining the heat in the cooking pot:

either by keeping the pot on a slow fire and constantly adding energy
or by preventing the heat to escape from the cooking pot: instead of keeping the pot for a long time on a small fire, you can also wrap the cooking pot in an insulative cover (heat retainer = fireless cooker) which retains the heat in the pot. The simmering process of the food continues inside the wrapping. No further external heat supply or 'fire' is required. This is why this is called 'fireless cooking'. Based on the experience of the cook with cooking times of the specific foods, the food stays in the heat retainer (fireless cooker) until it is served.

How to do this: Bring food such as rice, beans or meat stews to the boil, then transfer the entire pot with the lid quickly into the insulated box or bag, where it is left undisturbed for several hours to finish 'cooking'.

Fireless.JPG

Food can be kept warm for up to 6 hours, e.g. if people come back late home from the field or the market. Construction and functionality of the heat-retaining box (fireless cooker, hay box, hot bag etc. ) depend on the insulative properties of the material used. The underlying principle of insulation is that air does not conduct heat as well as solid metal (e.g. a cooking pot), water or soil. The more insulated pockets of air you can create between the cooking pot and the outside, the more heat will be retained inside the pot. Insulative materials can be locally available organic residues such as hay, sawdust, cotton waste, or dried leaves, e.g. from banana plants. Other materials are waste paper, polystyrene beads, or vermiculite. An insulated lid or cushion closes the box or bag.

Photo: C. Roth/GIZ

For more information on how to make and use this low-cost technology to save household energy consult the document with examples from Malawi (link How to make and use a fireless cooker

Depending on the type of food cooked and the traditional cooking practices, using hot bags can reduce fuelwood consumption to a great extent. Some people report that they can save up to 80 % of their fuel, depending on the food and the efficiency of the insulation. An added benefit is that slow cooking retains many more of the food’s nutrients and vitamins than if prepared on a constantly hot fire. The following case study from Tanzania claims average savings of 50% of fuel: http://www.sunseedtanzania.org/home.php

Hot bag cooking in Tanzania
A pilot project implemented by the organisation Sunseed in Tanzania showed the advantages of heat retention cooking using a hot bag:

Women spend less time cooking and are less exposed to smoke.
There is a saving of about half the fuel.
Food cannot burn.
Food can be left unattended in the hot bag, leaving women more time for other activities.
Food can be kept warm for more than 24 hours.
Women can reduce the frequency of cooking by preparing enough food for two meals and putting half of it in the hay box to keep warm.

Disadvantages of fireless cooking:

The technology is not applicable to all types of food; it is limited to dishes that are cooked slowly in liquid. (beans, rice etc.).
Change of taste: if beans are prepared in a fireless cooker, theý don't aquire the smokey taste as if they were cooked on a fire. They might be healthier, but they taste different and are sometimes rejected for that reason.
It is not advisable to keep the food warm longer than six hours. Otherwise it might promote the growth of microorganisms in the food which puts the health at risk.

Fireless cookers have been successfully introduced for taking care of sick people. Patients often can not eat one big meal but have to eat or even drink often small portions of food or tea. Without a fireless cooker, this would require frequent food preparation. In a retained heat cooker, food can be kept warm near the bed of a sick person who can take hot food or tea at a time of his convenience for a periode of 3-4 hours. This has particular relevance for taking care of HIV/AIDS patients.

By combining the fireless cookers with any other energy-efficient technology it can increase the energy efficiency by up to a further 50 %.

In the case of solar cookers, the technology reduces the time needed for using the cooker, and thus can extend its use to those days when the weather would not allow pure solar cooking. It can also allow the solar cooker to be used for food eaten in the evening, if the hot food from the solar cooker is transferred to the fireless cooker and left till evening.

An example from South Africa shows that with a clever usage metering device, retained heat cookers can qualify to generate carbon credits. More information on

http://www.naturalbalancesa.com/

Further information:

Retained Heat Cooker Guide
The Guide to Designing Retained Heat Cookers was written by Don O'Neal, Vice President of HELPS International and Special Projects Director. The development of the HELPS International Retained Heat Cooker was funded by a grant from the United States Environmental Protection Agency to further the mission of the Partnership for Clean Indoor Air, to improve health, livelihood, and quality of life by reducing exposure to air pollution, primarily among women and children, from household energy use. You can download an electronic copy in PDF format by clicking on the link below. If needed, you can download the current version of Adobe Acrobat reader free from Adobe's website.

You may order a free copy of the Guide to Designing Retained Heat Cookers, EPA-402-K-06-004, on-line at www.epa.gov/epahome/publications.htm. You may also order by fax at 513-489-8695. You will need to provide the publication name and number, your complete mailing address (i.e., name, organization, street address, city, state, zip code, country) and phone number.

Attachment Size
Guide to Designing Retained Heat Cookers (Spanish) 2.05 MB
RHC Guide English.pdf 600.54 KB

Additional information resources

Roth, Christa: FoodwarmerFile:Foodwarmer malawi croth-2004.pdf Foodwarmer malawi croth-2004.pdf	An illustrated step-by-step description from Malawi showing how to build a food warmer/fireless cooker using a basket, cloth and dried banana leaves. Two recipes for local dishes are included. It is a very helpful document.
Pan Africa Conservation Education: Make a fireless cooker	This step-by step instruction for building a fireless cooker is supplemented with background information on the cooker and its use. It can be downloaded under www.paceproject.net. This homepage provides a number of other helpful documents on resource protection at grassroots level.

Extra/ Bonus tracks

Cooking Energy in Refugee Situations

Space Heating with Stoves

Glossary

Imprint

Search

GIZ HERA Cooking Energy Compendium

Preface

Basics about Cooking Energy

Policy Advise on Cooking Energy

Designing and Implementing Cooking Energy Interventions

Scoping and Inception Studies for Cooking Energy Interventions

Designing and implementing ICS Supply Interventions

Designing and implementing Woodfuel Supply Intervention

Cooking Energy Technologies and Practices

Cooking with Woodfuels (Firewood and Charcoal)

Cooking with other Biomass Fuels

Cooking with Nonbiomass Fuels