Improved solid biofuel stoves

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This page refers to stoves using a fuel, usually solid. For solar versions, see Solar cooking


Cook stove is a general term for stoves used in developing countries, often of a very simple designs.

Efforts have been made in recent years to design and promote more efficient stoves. These are known by various names: improved cook stoves, improved stoves, improved cookstoves, improved cook stoves, smokeless stoves and wood conserving stoves. These designs, when they work as intended, don't fill the home with harmful smoke (through more efficient burning to reduce smoke, and a chimney or venting to remove that smoke), and use less fuel. Several designs have been developed.

Health impact

Cooking and heating with solid fuels such as wood, dung, coal or crop waste over open fires or stoves without chimneys can lead to indoor air pollution. This indoor smoke contains carbon monoxide, benzenes, aldehydes, small soot and dust particles and other health-damaging pollutants.

A WHO assessment found indoor air pollution to be the 8th most important risk factor for disease. It is a particularly important risk factor for acute respiratory tract infections (ARI) including bronchitis and pneumonia. Each year, IAP is implicated in the deaths of 1.6 million people ( a death every 20 seconds). Because women and children spend the most time near the domestic hearth, they are especially vulnerable [1].

Use of cleaner burning fuels, access to improved stoves and/or behavior changes could substantially reduce exposure to indoor smoke and associated diseases [2].

Key design features

Some or all of these design features help make a stove more efficient and lower in health impact:

  • Chimney or vent - to remove smoke to outdoors, and improve airflow through the fire.
  • Controllable air inflow - requires the fire to be in an enclosure with an adjustable inlet - allows reduction of burning rate to match needs.
  • Use of a material with good insulating properties, for the inside walls of the stove - usually ceramic.
  • Afterburning - mixing the flue (exhaust gas) with a small amount of new air, to allow the last remaining hydrocarbons and carbon monoxide to burn without a flame.
  • Use of the flue gas heat for space heating (in cold climates) and/or water heating. To avoid leakage of flue gas into the room, a heat exchanger is needed. In an expensive product this may be a complex stainless steel device, or in a developing nation a simple metal flue pipe.Category:Suggested projects[expand]
  • Many societies cook only a few types of food and you should design the stove to meet their specific needs
  • If they stir a thick material, you will need a well supported base in order to keep the cooker stable
  • There is an optimal separation between the pot and the cooker to allow for the airflow to escape. Design the stove to match the pots and maintain this separation
  • If too much material is placed in the burner, not all of the hydrocarbons will be consumed, so consider limiting the amount of space for the flamable material. Also consider what type of material is burned locally when designing this burning area
  • In desnsely populated areas such as refugee camps, multipul households will want to share the stoves, so consider including insulated handles.
  • As always with appropriate technology, the stoves should be locally constructed with local materials, using local techniques. This way, you can seed euntprepreneurs to produce sell, and repair the stoves after you leave.

Ongoing research and development

Groups including the Kobus Venter's Vuthisa Technologies[3] and EWB San Francisco Professionals Chapter[4] are doing research into optimizing such stoves, including using briquettes made from waste biomass (e.g. agricultural waste) with a simple briquette press.

The fuel used can have a great impact on the smoke produced, as well as affecting the environmental impact. CharcoalDEPRECATED TEMPLATE - PLEASE USE {{W}} INSTEAD. is much cleaner burning than wood or dung, but is usually made from wood.

Amy SmithDEPRECATED TEMPLATE - PLEASE USE {{W}} INSTEAD. has done work on producing charcoal from other forms of biomass. To make the biomass stick together, a binder is used. (Another method of making briquettes more cohesive is to leave the biomass in water for a couple of days to decompose slightly.) The choice of biomass depends on what is widely available, but includes bagasseDEPRECATED TEMPLATE - PLEASE USE {{W}} INSTEAD. (sugar cane waste) bound with a paste of cassavaDEPRECATED TEMPLATE - PLEASE USE {{W}} INSTEAD. root (also called manioc or tapioca); and wheat or rice straw bound with a small amount of dung, in areas where pure dung is normally burnt.[5]

A program called CFD-GEOM can be used to model cookstove designs.

Improved cookstoves and fuel conservation

The world's forests are shrinking under tremendous pressure from agricultural and lumbering activities. In some areas, the intensifying search for fuelwood, the primary cooking fuel for the South, is an important contributor to the problem. Most of this wood is burned in open fires or inefficient stoves. When wood is simply too expensive or too far away, animal manures and crop residues formerly returned to the soil as fertilizers frequently are burned as fuel instead. This practice, increasingly common in many parts of Africa and South Asia, adds to a downward spiral in soil fertility. Once the trees and vegetation on hillsides are removed, soil erosion proceeds rapidly with rain water runoff and flooding, and the land can be turned into a desert. Current patterns of daily firewood consumption around the world are thus important factors in an advancing environmental crisis.

Since the late 1970's, much work has been done on the design and dissemination of simple, low-cost improved cookstoves. Such stoves can save up to 40% of the wood fuel normally consumed in open fires, and 25-35% of the fuel consumed in typical traditional stoves. The collective experience of this work is described in Burning Issues. After much enthusiastic pursuit of a variety of strategies to encourage owner-building of stoves, experienced observers are concluding that the small industry production of stoves is one of the most promising routes to take. The advantages of this approach include better quality control and therefore higher efficiency and longer stove life than can be achieved with owner-building. Costing $1-5 each, the stoves can often pay for themselves in fuel savings within 1-2 months if the fuel is purchased. In rural areas where most fuel is gathered, very low-cost stoves can still be sold to some people, but the distribution problem is much more difficult, and clearly successful strategies have yet to be worked out.

Fuel conservation through improved cookstoves appears to be the cheapest way for a nation to invest in new sources of energy. The typical artisan-produced cookstove conserving 35% of fuelwood costs less than $5. Three improved stoves have the same effect on fuel supply as one family biogas plant (which would cost 40- 50 times as much) - both mean that one additional family's cooking fuel needs can be supplied. The capital investment will be higher for electric or kerosene stoves, and one must also consider the cost of adding to the electrical generating capacity and extending the electrical grid. Both electric and kerosene stoves have the added daily cost of fuel, which in the case of the improved stove is nil (because improved efficiency alone accounts for all of the gain). The common subsidies and the foreign exchange requirements make kerosene imports burdensome for the national economies of many countries.

The secondary effects of existing cooking systems must be understood before acceptable improvements can be made. In many places, smoke from indoor cooking fires is a significant contributor to lung and eye disease. Yet this smoke also serves to dry crops hung over the cooking area and to protect thatched roofs from insect damage. In highland regions and other colder areas, the space heating function of the indoor cooking fire may need to be included in cookstove design. Successful stove promotion efforts may depend on the availability of effective alterations for these secondary functions of the cooking fire.

Experience has shown that despite the need for wood conservation on a massive scale, adoption of improved stoves cannot occur immediately for an entire nation or region. It will, instead, depend on involvement of local people in careful, systematic work which emphasizes testing and cooking methods. Existing stoves and new prototypes can be tested with a minimum of equipment. Testing techniques are covered by several of the books in this section.

Most knowledgeable people have revised their estimates of the fuel savings possible with the typical new stove. A 35% savings is now considered a realistic figure for the better stove designs. Similarly, most agree that the distribution of improved stoves alone is not going to greatly affect the rate of deforestation in most places. Nevertheless, improved cookstoves are now considered to be a cost-effective component in reforestation programs in some countries, and clearly they have a role to play in improving the quality of life by conserving family resources of cash and time, and reducing smoke in the cooking area.

Many thanks to David Bartecchi of Village Earth for the initial content.

Improved Cookstoves in need of Entries on Appropedia

Footnotes and references

  1. World Health Organization
  2. Randomized Exposure Study of Pollution Indoors and Respiratory Effects (RESPIRE) Trial
  3. Vuthisa Technologies is a small company in Pietermaritsburg, Kwa Zulu Natal, South Africa, and Kobus Venter discussed (or discusses) the development of the design on the Biomass cooking stoves lists.
  4. EWB-SFP Appropriate Technology Design Team's blog, with a strong focus on improved stoves. See also Darfur Cookstoves - Updates May-December 2006
  5. MIT's Amy Smith on third-world engineering: TEDTalks - Video on YouTube.

See also

External links