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

[K McLean]

I would add that it is okay if the heat is lower later in the cooking
session.  This would be a natural turn down when moving from boiling to
simmering.

On Wed, Jun 22, 2022, 10:25 PM Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

> Dear Kevin
>
> The TLUD restaurant stove may have been a response to local economic
> conditions. It was probably developed in 1984 and popularized in '85. In
> those days commercial cooking used electricity, wood, kerosene or charcoal.
> Maybe all of them became unobtainable.
>
> A round hole is harder to dig but easier to line with a metal can.  I am
> not sure but I think standing fuel is faster than layering it.  Loading a
> pre-formed bundle is fastest.
>
> The idea behind mixed fuels is to get a higher density fuel load. Low
> density fuels tend to burn rapidly. Denser twigs will tend to burn slower
> and make more char which can extend the usefulness of the fire.
>
> A good point was made by another contributor: what about the heat transfer
> when the fire is so far below the pot?
>
> Because the fire in the hole has no under-air supply, the excess air ratio
> in the fire, or above the fire, is much lower than a three stone fire. This
> means a higher temperature fire (flame) and a higher heat transfer
> efficiency. Yes, the fire is further away which can create a loss, but it
> has inherent advantages as well.  The proof is in the burning.
>
> Regards
> Crispin
>
> *From:* kmclean56 at gmail.com
> *Sent:* June 22, 2022 12:31 PM
> *To:* stoves at lists.bioenergylists.org
> *Reply to:* stoves at lists.bioenergylists.org
> *Subject:* Re: [Stoves] ***SPAM*** Cooking Hole Modification to Three
> Stone Cookstove - Update
>
> Dear Crispin,
>
> Thanks for your observations.  I wonder why the cylinder method in Uganda
> is no longer being used.  It sounds much better than unmodified three stone.
>
> A cylinder cooking hole should be more efficient.  We tried putting maize
> stalks upright in the cooking hole.  It worked but horizontal was easier.
> And liner bricks bricks are easier to make for a square hole.
>
> Why do you say mixed fuel will work better?  We will try it.  But if I
> know the reasoning, our testing will be more efficient.
>
> Kevin
>
>
> On Wed, Jun 22, 2022, 5:40 PM Crispin Pemberton-Pigott <
> crispinpigott at outlook.com> wrote:
>
>> Dear Kevin
>>
>>
>>
>> This is another fine piece of work. I looked at all the videos and the
>> techniques are clearly explained.
>>
>>
>>
>> I suggest that it is possible to make a round hole and to bundle the fuel
>> with string or grass such that it is prepared in advance and fills the hole
>> completely.  This method of cooking with grass and reeds was in use in
>> Ugandan restaurants in 1986 or perhaps 1985.  Fuel vendors prepared the
>> fuel for sale in “cylinders” which were dropped into the stove and
>> top-lit.  The difference is that the fuel was standing up, not
>> cross-layered and horizontal.  I understand they tied the reeds into long
>> bundles with multiple strings and then sliced then like a sausage so one
>> string held one bundle.
>>
>>
>>
>> You might try it to see if it is more convenient than hand-laying the
>> pieces.
>>
>>
>>
>> I am sure a mix of fuels would be better than one alone.  Twigs and
>> stover, for example.
>>
>>
>>
>> Realizing that this is potentially wasteful, but have you tried burying a
>> bucket in the ground and using that? You can douse it and lift it out by
>> the handle.  In some places buckets are hand made from roofing as a
>> cylinder, not tapered.  That might be ideal.
>>
>>
>>
>> Many thanks for your original ideas and extensive field work.
>>
>>
>>
>> Best regards
>>
>> Crispin
>>
>>
>>
>>
>>
>>
>>
>> *From:* Stoves <stoves-bounces at lists.bioenergylists.org> *On Behalf Of *K
>> McLean
>> *Sent:* Tuesday, June 21, 2022 15:13
>> *To:* Stoves and Biofuels Network <stoves at lists.bioenergylists.org>;
>> Ronal Larson <rongretlarson at comcast.net>
>> *Subject:* [Stoves] ***SPAM*** Cooking Hole Modification to Three Stone
>> Cookstove - Update
>>
>>
>>
>> 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://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FDmzQFCp2kNI&data=05%7C01%7C%7Cd03ae001820d4003d6a708da547d689c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637915194870399245%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=HY8uScDFhxbkYEkSPamiS1X2qeAVJYsAKnMQQgVeMag%3D&reserved=0>.
>> 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://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F15V4vTJxO1Lcm0wFzB96pQT9jvgjaXkwh%2Fview%3Fusp%3Dsharing&data=05%7C01%7C%7Cd03ae001820d4003d6a708da547d689c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637915194870555500%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=309kxjNHFmYkismlcUAUSeaNbEqrsg1212ClSq33bp4%3D&reserved=0>
>> .
>>
>>
>>
>> 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://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FDmzQFCp2kNI&data=05%7C01%7C%7Cd03ae001820d4003d6a708da547d689c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637915194870555500%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=31vM9fsRvcg%2B590zfI9zx4N8jp7%2BIzLmCw8m%2BVt9vCA%3D&reserved=0>
>> .
>>
>>
>>
>> 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.
>>
>>
>>
>>
>>
>> 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://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F1b2WvePKX_ofnELUWhexqQZR4NyCrXxnH%2Fview%3Fusp%3Dsharing&data=05%7C01%7C%7Cd03ae001820d4003d6a708da547d689c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637915194870711716%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=MKX4SEd2BynwMQrzsftdQ0uevOgty73pmmkfY7qiY4g%3D&reserved=0>
>> .
>>
>>
>>
>> Kevin McLean
>>
>> Sun24
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>>
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