General Kitchen Management Practices

--> Back to Overview Cooking Energy Compendium

General kitchen management 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!

Energy-saving Practices

Besides using energy-efficient technologies such as improved stoves, simple changes in behaviour can save substantial amounts of fuel; potentially as much as the use of an improved stove. Frequently the impact of simple behavioural changes is overlooked, or is not known to the project staff. Examples of energy-saving practices are:

Splitting the fuelwood into small sticks. Drying the fuelwood in the sun before using it. Starting the fire just before all other preparations are finished, but with enough time for the fire to heat up, thus avoiding the worst of the smoke. Ensuring a good contact between the fire and the pot. Reducing the fire intensity after the food has come to a boil, by feeding it with less wood. Using a lid on the pot. Soaking dried food (such as beans, pigeon peas etc.) prior to cooking. Extinguishing the fire immediate after use. One should not underestimate the energy-saving potential of these practices. Even drying fuelwood can save between 25 and 35 % of energy. Since most of these practices require only behavioural changes, households can save energy at little or no cost. Nevertheless, changes in cooking traditions are usually not easy to achieve, and therefore convincing people can be a difficult task.

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

Other links:

http://solarcooking.wikia.com/wiki/Integrated_Cooking_Method

http://solarcooking.wikia.com/wiki/Heat-retention_cooking

http://solarcooking.org/heat-retention/ (with examples from Tamil Nadu)

http://www.bioenergylists.org/en/node/245 with reference to many more examples on retained heat cooking from Bolivia,

http://cookinginabasket.blogspot.com/ with examples from Kenya

Pressure Cooking Pots

Pressure cookers are cooking pots with an airtight seal, which have a lid firmly fastened to the pot. The food is steamed at a pressure above atmospheric pressure. It is set on a shelf over the boiling water, which preserves the nutrients, as they do not leach into the water. The elevated pressure allows the temperatures to rise well above 100ºC which in turn reduces the cooking time. 

Pressure cookers have to be of aluminium or stainless steel, and cannot be produced in many developing countries. As a consequence they are much more expensive than a fireless cooker (prices vary between 17 US$ and more than 100 US$). Pressure cookers have been distributed mainly in India and to a much lesser extent in South Africa. Imported cookers from China are offered to other parts of Africa; however many of these models are equipped with an integrated hotplate and are exclusively designed for using electricity. To date, these limitations make the technology largely unsuitable for rural areas.

Advantages

• Pressure cookers are more versatile than fireless cookers.
• They are suitable for small quantities of food.
• Cooking is much faster and thus the pressure cooker can save considerable amounts of energy.
• It is possible to sterilise goods using a pressure cooker.

Disadvantages

• The initial investment is too high for most families.
• Opening the cooker must be done carefully since hot steam, under pressure, can force its way out as the cooker is being opened, injuring the cook.
• After a few years the seal between the pot and the lid wears out and must be replaced for the pressure in the pot to be maintained; this requires a service system to be in place.

Additional information resources

Roth, Christa: Foodwarmer File: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.
Fact Sheet Firewood Management Factsheet firewood management-probec-2004.pdf	This fact sheet is a compilation of energy-saving practices and was developed by the Integrated Food Security Project in Malawi. Every practice is explained in detail and addition is provided regarding the reasons of fuelwood savings and additional benefits).
	Mike Bridgewater: Heat Retention Cooking vs. Solar Cooking The Solar Cooking Archive: www.solarcooking.org