Economic, Health, and Design Issues
Cooking food on an open, wood fire or an inefficient stove uses considerably more wood fuel than a properly designed wood cook stove. It will also take longer to cook. This inefficiency causes unnecessary degradation of forests and considerable time gathering wood or purchasing from a local vender. A properly designed wood cook stove like the D Best stove will use up to 75% less wood. In addition the size of the wood is very small—approximately 2 cm, which is just a little bigger than a twig. Many families spend as much as 20% of their disposable income on wood fuel.
An open wood fire or an inefficient stove creates substantial amounts of smoke that is inhaled by cooks and family members. Wood smoke causes numerous health problems such as coughing, asthma, headaches, COPD, cataracts, heart disease, cancer, high blood pressure, and implications in other health problems. It is estimated that 1.5 million people are killed annually from wood smoke. Some of the undesirable ingredients of wood smoke are benzene, butadiene, styrene, formaldehyde, dioxin, and methylene chloride. Smoke is caused by incomplete combustion; however, improved stoves such as the D Best Stove have almost 100% combustion. They are virtually smoke free except during start up and when the wood is pushed further into the fire (see User Guide).
The D Best Stove, which has been constructed in Guatemala, Honduras, and Uganda, incorporates all of the basic design features of the rocket stove, which creates a very hot fire.
- A chimney above fire creates a faster draft and greater efficiency.
- A shelf for the wood to rest on so air passes under wood to the coals.
- Use of a pot or pan skirt so the hot gases go around the pot or to the bottom of the pan and then out the flue pipe.
- A rebar grate eliminates the steel plate so hot gases do not need to heat the plate first.
- The input flow area equals the output flow area, although less output area increases the velocity of the hot gases.
- See User Guide for techniques to increase efficiency.
Recommendations for combustion chamber materials are as follows:
- Firebrick is the most expensive but will probably last the longest and may be the only choice in a particular country.
- Insulative brick is desirable when the number of stoves justifies its use, and facilities are available for curing.
- Baldosa tile is inexpensive and long lasting and would be desirable in Guatemala and neighboring countries in Central America.
By extending the base and the steel plate before the flue pipe, a second or warming pot area is constructed.