General Kitchen Management Practices
--> Back to Overview Cooking Energy Compendium
General kitchen management practices
This section deals with technologies and techniques that can save substantial amounts of energy, regardless of the type of fuel and stove used.
Fuel preparation and handling of the stove offer a high potential to improve efficiency and limit resource use for cooking. One option for users is to adjust their behaviour and adopt efficient cooking practices regardless of the type of stove and the fuel.
Another option is to integrate energy saving devices into the household cooking system like pressure cookers or heat retainers, like thermos flasks, heat retaining boxes also called hay box or hot bag.
Fuel-saving cooking practices
Simple changes in the cooking practices of households can save substantial amounts of fuel. Like with any type of work: the overall-efficiency of a process depends to a great deal on how you plan it and manage each individual step. Although cooking is often done outdoors, these no-cost techniques are commonly called 'kitchen management practices'.
Often the impact of simple behavioural changes is overlooked, or is not known to the project staff or partner organisations. Since most of these practices do not require additional tools or devices, households can save energy at little or no cost. Nevertheless, changes in cooking traditions and habits are usually not easy to achieve, and therefore convincing people can be a difficult task, especially within projects.
Regardless of the region and the stove and fuel used the following guidance can be applied everywhere to save energy while cooking:
Don't waste fuel by running an empty stove
- Get all the ingredients needed for the dish readily prepared (collecting, washing, cutting, etc.) before you start the fire.
- Have all ingredients and utensils at hand close to the stove, including cooking tools, water, and spices.
- Don't waste time once the fire is started and avoid wandering off (e.g. to chat with your neighbour) while the stove is already on.
- Extinguish the fire when you have finished cooking.
Make the best use of the heat from the fire
- Ensure that the heat generated from the fire finds its way into the pot.
- If possible use a metal pot that conducts heat better than a clay pot.
- If possible use a pot with a flat bottom instead of round-shaped pots. The transfer of heat into a flat-bottom pot is higher.
- Shield the pot from wind e.g. with a skirt around the pot, otherwise the hot flue gases will be blown away and the pot will be cooled by the wind.
- Reduce the intensity of the fire once the food has come to a boil.
- Use a heat retaining devise after boiling.
- Use always a lid on the pot to prevent surplus steam escaping from the pot (steam is water heated beyond boiling point, so any steam leaving the pot is energy lost for the cooking process).
- Use small amounts of water for cooking: any water that is thrown away after cooking has consumed a lot of energy until it boiled. This practice not only saves fuel but also retains nutrients.
Shorten cooking times of certain foods
- Soak dried food (such as beans, peas, rice, etc.) prior to cooking.
- Cut food up into smaller pieces: e.g. cut smaller cubes or slices instead of boiling a whole potato or cassava root.
- Don't overcook food. Monitor the cooking process closely by testing regularly if the food is already cooked. Once the food is ready to eat, take it off the stove.
Efficient cooking practices do not only take place in the kitchen itself, but already start with fuel management. Therefore please read as well the chapter’s firewood management and other solid biomass fuels.
Additional information
Efficient cooking practices based on experience from Malawi in English and French |
|
| Efficient cooking practices based on experience from Burkina Faso in French |
|
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'.
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
Read more on how to make and use this low-cost technology to save household energy in the document with examples from Malawi (How to make and use a fireless cooker or the French version Cuisinière sans feu)
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:
|
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, online 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 special cooking pots that can be sealed airtight and allow pressure to build up inside: with a mechanical device (screws or interlocking parts) the pot-lid can be pressed firmly against the pot-body. A gasket in between the lid and the pot prevents steam to escape from the pot. With rising heat, the steam pressure inside the pot builds up beyond atmospheric pressure, allowing the temperatures to rise well above boiling point. To prevent explosions, regulators and safety valves let surplus pressure escape.
Fuel is saved (and subsequently emissions reduced) because
- Higher temperatures above 100 °C reduce the time needed to cook the food.
- Very little steam can escape between the pot and the lid, thus less water is needed to cook the food. Less water needs to be heated up and less energy invested to reach boiling.
- As steam is water heated beyond boiling point, any steam prevented from leaving the pot is heat preserved to cook the food.
Pressure cookers can be used with nearly any stove and fuel type. To use it on an open wood-fire, care should be taken that non-metal parts do not get exposed to the flames, otherwise they will melt or burn.
When a pressure cooker is used in combination with a fireless cooker, for some foods fuel savings can exceed 90%, e g. with some types of legumes, that need 4-5 hours to cook. In a pressure cooker only the energy needed to bring the food to the boil is consumed. If the pot is put into a fireless cooker before the pressure valve releases steam, no energy in form of steam is lost. The cooking can continue inside the fireless cooker for 4 hours with high enough temperatures for the beans to cook.
Pressure cookers are normally made from thick aluminium or stainless steel, which makes them heavier and more expensive than conventional pots. They might also be difficult to produce in many developing countries.
Prices are seldom below 20 US$, top-of-the range products easily exceed 200 US$. Pressure cookers are currently popular in urban areas, where the fuel has to be paid for in cash, and where the local foods can easily be cooked wiht pressures cookers: especially in Asia (China and India and to a much lesser extent in Latin America and South Africa. For economic reasons, they have not yet spread into many rural areas.
Yet they can bring advantages on fuel savings especially at higher altitudes, as reported from Tajikistan in http://www.hedon.info/BP57_PressureCookerTraining?bl=y:.
The pressure cooker is essential in the higher altitudes, because it creates a higher boiling temperature due to the steam pressure inside the cooking pot. The higher the altitude, the lower the atmospheric pressure and the related natural boiling temperature and hence, the longer it will take for food to cook. Several types of pressure cookers can have about 100kPa pressure increase over local atmospheric pressure, but models vary greatly. The required boiling time for softening the food is between one fourth and one fifth of the normal boiling time, depending on the altitude.
Advantages
- Pressure cookers can be used with most fuel types and stoves.
- At high altitudes where the boiling point is naturally low, they offer great advantages to raise the temperature above 100°C and prevent food to be left undercooked.
- 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.
- Pressure cookers are used for steaming. As steam builds up inside, they can not be used for frying or roasting.
- Pressure cookers can also not be used for foods that need to be stirred during cooking (like maize porridge).
- Opening the cooker must be done carefully since hot steam, under pressure, can escape with force and scald the cook.
- Pressure cookers are not appropriate for dishes, where different ingredients need to be added at different times, as they cannot easily be opened during cooking.
- 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.
This is an integrated cooking system that is often overlooked, yet with a big potential to increase fuel efficiency and reduce emissions from cooking. If seals can be replaced, the life span of a pressure cooker usually by far exceeds the lifespan of a stove. Decision makers and project implementers might want to consider options to facilitate access to durable pressure cookers that can be used with any stove-type, as alternative or complementing measure to a new stove technology and/or a new fuel.
Additional information resources
Roth, Christa: Retained heat cooker: "Fireless cooker" or "Foodwarmer"
|
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.Das sollte ovrher schon drin sehen und |
| 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
|
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. Christa, 20.7.2011:
|
| Mike Bridgewater: Heat Retention Cooking vs. Solar Cooking The Solar Cooking Archive: www.solarcooking.org |
