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.
  

These are technologies that can save substantial amounts of energy, but not 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 prevents the heat to leave the pot. The simmering process of the meal 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.
  
  

Fireless.JPG

Food can be kept warm even for up to 6 hours if people come back late home from the field or the market.
Or if visitors are expected and they don’t come in time, the buffet can be kept warm, decorative baskets can be put directly on the table.

The construction and functionality of the heat-retaining box, hay box, and hot bag, are essentially the same. Each one comprises an insulated box or a bag insulated with locally available insulating materials such as using polystyrene beads, vermiculite, fibres or locally available residues such as hay, sawdust, cotton waste, waste paper, or even dried banana leaves. An insulated lid or cushion closes the box or bag.

 

Photo: C. Roth/GIZ

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'.

The temperature of the food is sufficient to complete the cooking process at temperatures at little below boiling point. Depending on the type of food cooked, using hot bags can reduce fuelwood consumption by up to 50 % (as shown in the following case study from Tanzania). Other organisations report up to 80 % reduction, 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. A

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 hot bag 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 tend to be less burned and less smokey. Hence the taste is changing. 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.

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

Pressure Cookers

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.