[Stoves] ***SPAM*** Cooking Hole Modification to Three Stone Cookstove - Update

[Robert Taylor]

Hi Kevin

Many thanks for that clear and detailed response.

Best regards
Robert



On 22-Jun-22 1:29 PM, K McLean wrote:
> Good question, Robert.
>
> Other sizes work. 25x25x25 cm works well with maize stalks in home 
> kitchens.  We recommend 45x45x30 for school kitchens for more firepower.
>
> Different sizes may work better depending on the fuel and cooking 
> needs.  25x25x25 seems to be a good general recommendation since we 
> train on a mass scale and cannot customize based on the specific needs 
> of a family or community.
>
> Squared holes work best with stacked fuels like maize stalks. For a 
> 25x25x25 hole, the stalks should be cut to about 23 cm and stacked in 
> crisscrossing layers.  This method seems to get the most fuel in the 
> hole while allowing air to circulate within the pile. Cylindrical 
> holes would work better for fuels like wood shavings and cow dung patties.
>
> Generally, the area across the top equals firepower and depth equals 
> burn time.  25x25 area across the top gives good heat with maize 
> stalks.  If the depth is more than 25 cm, the fire goes out before the 
> bottom fuel burns.
>
> Denser fuels burn longer.  For example, normal size firewood burns 
> over three hours in a 25x25x25 hole.  This is much longer than 
> needed.  We will put common bricks in the hole to raise the floor, 
> reduce the burn time and save fuel.
>
> On Wed, Jun 22, 2022 at 1:17 AM Robert Taylor <rt at ms1.hinet.net> wrote:
>
>     Hi Kevin
>
>     Very interesting. What's the significance of the hole size and
>     shape, 25 x 25 x 25 cm? Is it optimal for good combustion, or
>     simply convenient based on pot size and fuel quantity?
>
>     Best regards
>
>     Robert
>
>     On 22-Jun-22 5:13 AM, K McLean wrote:
>>     Adding a 25x25x25 cm hole to traditional open-fire cookstoves may
>>     end the collection of firewood from forests in many areas. By
>>     piling fuel in the hole beneath the cookpot and lighting the pile
>>     on the top, the fuel burns long, hot, with no tending and with
>>     less smoke.  And by quenching the embers, cooks make biochar.
>>
>>     We found that most woody biomass bigger than thin twigs burns
>>     well in the cooking hole <https://youtu.be/DmzQFCp2kNI>. 
>>     Firewood the size that is typically burned in unmodified three
>>     stone cookstoves burns for three hours without tending.  Much
>>     less smoke is emitted than from an unmodified three stone
>>     cookstove.  A colleague estimates that the amount of wood in the
>>     cooking hole would burn for 30-40 minutes in an unmodified three
>>     stone cookstove. Here's a video
>>     <https://drive.google.com/file/d/15V4vTJxO1Lcm0wFzB96pQT9jvgjaXkwh/view?usp=sharing>.
>>
>>
>>     Thick twigs burned without tending for 1.5 hours.  Thick twigs
>>     and small branches are abundant and unused in much of Africa.
>>
>>     The cooking hole also works with crop waste (maize stalks and
>>     cobs, cassava stems, banana peels, bean stems, ...), elephant
>>     grass, bamboo, large sawdust and wood shavings, sawdust
>>     briquettes, dung patties and more. Depending on the fuel, the
>>     fire will burn without tending for 20 minutes to several hours. 
>>     Here's our training video <https://youtu.be/DmzQFCp2kNI>.
>>
>>     Women can:
>>
>>         - All but stop collecting firewood.
>>         - Leave the kitchen to do other things once they start the fire.
>>         - Make biochar.
>>
>>
>>     And 8-12 common bricks can support two cookpots over one cooking
>>     hole allowing two meals to be cooked with the same amount of fuel
>>     and time it takes to cook one meal.  The time to boil is only a
>>     few minutes longer than for one pot.
>>     2 burner drawing.jpg
>>
>>
>>     In much of Africa, most people know how to make bricks.  We show
>>     them how to make free custom bricks to line the cooking hole.
>>     Here is a video
>>     <https://drive.google.com/file/d/1b2WvePKX_ofnELUWhexqQZR4NyCrXxnH/view?usp=sharing>.
>>
>>     Kevin McLean
>>     Sun24
>>
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>
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