[Stoves] Improving three stone stoves and finding out where wild jatropha grows

Mon Jul 9 01:14:38 CDT 2012

This sound really interesting and worth follow up
Adapting or modifying a used behavior is certainly likely to meet with more success.

Michael
Majuro
Marshall Islands

From: Crispin P-P 
Sent: Monday, July 09, 2012 4:47 AM
To: Discussion of biomass cooking stoves 
Subject: Re: [Stoves] Improving three stone stoves and finding out where wild jatropha grows

Dear Joyce 

There in Ethiopia three stone fires that are made using three hand made 'stones' formed from clay. 

These fires significantly outperform regular fires because the whole fire is more controllable. Basically the stones are C-shaped clay stands with a flat top and bring bottom so they can stand by themselves.  

As they stand on their own the can be moved in and out racially to support lots of different sizes and his staff different sized fires. When close together the form a small combustion chamber that is mostly vertical wall and just enough space to fit in some wood. 

Referring to your suggestion about the clay wall between the stones, what they can have a more than three clay supports. This means the stove is not optimized for one pot size, but can be set to suit any pot with ease. 

To burn jatropha seeds you will need a combustion chamber with highly restricted primary air. This need results from the oily nature of the fuel and it's tendency to make runaway fires.  Flames will probably not give toxic fumes but the smoke is probably pretty awful if the flames go out.  

If you try the jatropha branches I would be interested to know what you think of such a movable clay stone fire. 

Regards 
Crispin 

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From: "Joshua Guinto" <jed.building.bridges at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: July 8, 2012 11:38 PM
Subject: Re: [Stoves] Improving three stone stoves and finding out where wild jatropha grows

Dear Joyce

Have you seen the website of Jon and Flip on the Recho Rocket stoves. i thought it will be very simple to make and that even women could make them. http://www.rechoroket.com/%22How_to%22_Albums/%22How_to%22_Albums.html

Clay is a very versatile material to work with. It is very cheap and can be built on site even without electricity or welding machine and by women. 

I am now trying to make grills as fuel grates using clay. It would be a simple flat disc and then you punch holes through the wet clay while it is still soft. I think 2.5 cm thick is best. I mix clay with temper which could be carbonized rice hull or fine saw dust in a ratio of 2 parts clay to 1 part of temper. The website of Jon and Flip will tell you more about better recipes. But if your intention is to use it as a fuel grate, i would advice you to make a higher ratio of clay because you need durability than insulability for this function. 

 As soon as the disc is dried, you can use it to elevate the fuel to allow air to come beneath. The disc will :"self fire" meaning it will harden in fire as you use it intensely. I observe that intense use can "cook" the clay to as much as 1.5 cm deep. 

Still with clay, you can use it to make a skirt around the three stone stove. In fact you can use the same clay to make a three piece platform and make a sturdy and stable platform instead of the three stones which are irregular in shape. The same clay will self fire through time. 

But my wise guess is that this will be very smoky. You will need to create a higher coloumn of the fire box to create enough draft to pull in enough air so there will be enough to burn the gases, tars and oils. There is a certain ratio of fuel to air to attain the right combustion, 1 part fuel to five parts air (if im not mistaken). 

Just like nut shells, firing it from the top as in TLUD will give you better results. Dr. Paul Anderson has a lot of experience and materials on this. However, with the TLUD mechanism, you will have to raise the coloumn of the stove to create stronger draft and to create higher temperature so the oils, tars, particulate matters and other gases may be burned. Otherwise, with the basic three stone stove, it will produce a lot of smoke.

If you can be successful with this, why not try the next level - the recho rocket or maybe the holey roket by Rok Oblak?  www.holeyroket.wordpress.com. I undertook skills training with fisherfolks in a village of Sorsogon here in the Philippines. The participants were composed of men and women. I observe that the men are good in mashing the clay and cutting things but the women are better in design and the detailed plastering and finishing the stove body. The combination of men and women is best. 

Finally, with such stoves, you there is less worry about the fuel because the options will be expanded. Such stoves can be used with  a lot of fuel combinations  - wood sticks, palm fronds, grasses if you twist them tight and of course holey briquettes. Jathropa is  among the good options. I understand jatropha seeds would be a great fuel to bring along in camping and picnics because they contain a lot of energy. It would also be good to keep them in storage in anticipation of natural disasters. 

We have here jathropa in my neighborhood, here in the Philippines. People commonly use it as fencing material and the leaves to cure simple ailments.   However, i am still comfortable with the pili shell and green coconut shells around here that are more accessible. 

All the best Joyce and good luck. 

Jed 

2012/7/8 Joyce Lockard <rj.lockard at frontier.com>

  I wonder if it would help to fill in two of the spaces between three of the stones with curving walls of clay, leaving one open for the fuel.  Clay would reduce heat loss due to any horizontal air currents so help keep it hotter under the pot. The clay walls could come up to within an inch or so of the bottom of the pot, which would still be supported by sitting on the three stones, so that emissions and hot air would be deflected up the pot sides. And, very important, it is something that a woman could do herself without any expense.  

  I am trying to find out where (in what countries) jatropha is growing wild, so women could scavenge for the seeds.  Another question is whether there is a way to make a simple grate for three stone stoves to hold up the jatropha seeds.  I suppose they would burn if they were on the ground under wood. Would there be an advantage in lifting them above the wood, up close to the pot bottom?

  I have read that half of the people who burn wood/charcoal for cooking are using three stone stoves. Trying to help the poorest of women with simple, cheap or no-cost improvements in their three stone stoves is in line with the first Millennium Development Goal of relieving extreme poverty.  I would like to find colleagues to try this idea of adding clay walls. It is not something I can do at my home. Any suggestions of where I can find people to try it?  If it appears feasible to add the mud walls, then the challenge will be to make the idea known to those who need it.  

  Joyce M Lockard

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