GIZ HERA Cooking Energy Compendium

This is 'work in progress': Until mid 2011 the compendium will be revised.

Basics about Cooking Energy

• Facts on Cooking Energy
  
• Frequently Asked Questions

Policy Advise on Cooking Energy

• Background - Cooking Energy Crisis
• Policy Challenges in the Woodfuel Sector
  
• Assessing Woodfuel Supply Potentials
  
• Cooking Energy Intervention Strategies 

Designing and Implementing Cooking Energy Interventions

Scoping and Inception Studies for Cooking Energy Interventions 

• Scoping Cooking Energy Systems
• Inception Studies for ICS opportunities 
• Inception Studies for Biomass Energy Supply Opportunities

• Carbon Funding for cookstoves
  

Designing and implementing ICS Supply Interventions

• Enhancing Production of ICS siehe alter links: (2.2 Production of Woodfuel Stoves und Intervention A: Introduction)
  (Product devolpment, production and marketing systems (incl. trainers)
• Commercialisation of Cookstoves
• Creation of Public Awareness
• User Training
• Financing Mechanisms for Cookstove Dissemination
• Quality Assurance of ICS
  national standards
• Scaling-up Strategies
• Result Based Monitoring
  outcome monitoring, impact assessment, methodology
• Sustainability of Cookstoves
  sustainability assessment, exit

Designing and implementing Woodfuel Supply Intervention

• Woodfuel Production Options
• Charcoal Production
  

Cooking Energy Technologies and Practices

• Global stove diversity

Cooking with Woodfuels (Firewood and Charcoal)

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!

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 Cookers

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 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.

This is an integrated cooking system that is often overlooked.

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.