the rocket stove: a very appropriate technology

With the help of our summer interns, we built our first rocket stove for use in the village a little over a month ago.  A rocket stove is a more efficient way of cooking with fire.  It uses smaller diameter wood — and less of it — but still cooks faster than a traditional open fire.

A rocket stove is incredibly easy to construct, and it can be made entirely out of materials already present in rural areas.

a banana stalk frame for a rocket stove. note the metal fuel shelf inside the cut horizontal stalk.  the stalks are removed after forming the stove.

Parts of a Rocket Stove

1. Chimney: the vertical hollow space on which the cooking pot rests and through which heat passes to escape
2. Fuel Magazine: the horizontal hollow space through which a) fuel and b) air travel into the combustion chamber
3. Fuel Shelf: a metal shelf in the fuel magazine on top of which fuel is placed and under which air flows
4. Combustion Chamber: where the fire burns; also where the fuel magazine and chimney meet
5. Heat Exchanger: some device which forces heat from the chimney to pass over the sides of the cooking pot

the lady interns mixing clay, sand, straw, and water (to make cob)

We use cob to build our rocket stoves, as all the ingredients are readily available in every village.  Cob is also fireproof and easy to repair.  Sorry I didn’t get any photos of us actually placing the cob on the banana stalk frame.  But I’m sure you understand the process.

adding fuel to the stove. air flows under the fuel shelf and into the combustion chamber. we even oriented our air intake to take advantage of the winds that usually come from a particular direction.

Probably my favorite advantage of the rocket stove is how little fuel it requires.  Deforestation is a big problem in our part of Sukuma land, and much of this is due to charcoal-making and firewood supply.  Rocket stoves allow families to harvest fallen and cut branches, rather than entire trees.  [I'm wanting to encourage families to begin coppicing (planting an area of fuel-providing trees which regrow limbs quickly after being cut).]

we set our cooking pot (not shown) on top of the vertical banana stalk in order to build the stove around it.  this ensures that our heat exchanger (the cob stove itself) is a good fit with the pot.

Many manufactured rocket stoves use a tubular sheet of metal as a heat exchanger.  It sits on top of the chimney, circling the pot, in order to force heat to remain in contact with the pot.  [I'm not sure if they're really called "skirts," but that's what I call them.]

We opted for making our heat exchanger out of cob, as a part of the stove itself.  The disadvantage to this is that our rocket stove works most efficiently with only one particular (size) pot.  But we felt like the advantages (many having to do reproducibility and the availability of materials — clay being easier to find than metal) won out in the end.

spiraling inside the heat exchanger

We made spiral cut-outs inside our heat exchanger (where the pot will sit) in order to keep heat in contact with the pot (and more sides of it) for longer.

yohana removing the fruits from our stove.  [this was actually during the curing process -- they couldn't wait to cook a little something.]  any guesses what i had for chai that morning?

After letting the the rocket stove dry for a week, and then curing it with a small fire, Christie organized (at the request of several women in the village) a class on making chapatis and pancakes.  All the cooking that day was done on the new rocket stove.

christie’s cooking class (though she’s not present in the picture, and — although i did man the fueling of the rocket stove — this was the only time i touched the cooking all day, but this pic is all we’ve got)

All our friends at Mwakiwasha seemed to really enjoy the new stove and how little wood it requires.  Several women were asking us to build rocket stoves at their homes.  Our answer: “No! Build it yourself.”*

 

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*But not in that way.  We explained that rocket stoves are super easy to build (and free if you’ve got a small scrap of metal anywhere), and that we’ll be happy to put on a training seminar to teach everyone how to build rocket stoves at their own homes.  It sounds as if, though, we’re actually going to have a little “Appropriate Technology Day,” in which we teach two or three different technologies that will be useful to everyone.

** There are no double asterisks above to correspond with this comment — I just thought I’d include it and didn’t know where to put it.  The Sukuma traditionally cook over an open fire around which three stones are set to hold the pot.  Not only is a great deal of heat lost cooking in this way (and therefore fuel burned), but lots of children in villages, at some point in their lives, fall into one of these fires (or its coals) and burn themselves badly.  This was something that one of the Tanzanians brought up when we were discussing the advantages of the rocket stove.

*** Yeah, these triple asterisks don’t really come from anywhere, either.  But if you want a good manual on building rocket stoves (slightly different than what we’ve done), see this manual from the Permaculture Research Institute of Kenya.
 

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