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<font face="Microsoft JhengHei UI">Hi Kevin<br>
<br>
Many thanks for that clear and detailed response.<br>
<br>
Best regards<br>
Robert<br>
</font><br>
<br>
<br>
<div class="moz-cite-prefix">On 22-Jun-22 1:29 PM, K McLean wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CALxcr-uOLWgWGeg=p_JLfx3zWfaeLB=QZ9WU9vwRnrqNk8GAiQ@mail.gmail.com">
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<div dir="ltr">
<div class="gmail_default" style="font-size:small">Good
question, Robert.</div>
<div class="gmail_default" style="font-size:small"><br>
</div>
<div class="gmail_default" style="font-size:small">Other sizes
work. 25x25x25 cm works well with maize stalks in home
kitchens. We recommend 45x45x30 for school kitchens for more
firepower.</div>
<div class="gmail_default" style="font-size:small"><br>
</div>
<div class="gmail_default" style="font-size:small">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.</div>
<div class="gmail_default" style="font-size:small"><br>
</div>
<div class="gmail_default" style="font-size:small">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.</div>
<div class="gmail_default" style="font-size:small"><br>
</div>
<div class="gmail_default" style="font-size:small">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.</div>
<div class="gmail_default" style="font-size:small"><br>
</div>
<div class="gmail_default" style="font-size:small">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.</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Jun 22, 2022 at 1:17
AM Robert Taylor <<a href="mailto:rt@ms1.hinet.net"
moz-do-not-send="true" class="moz-txt-link-freetext">rt@ms1.hinet.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div> <font face="Microsoft JhengHei UI">Hi Kevin<br>
<br>
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?<br>
<br>
Best regards<br>
<br>
Robert<br>
</font><br>
<div>On 22-Jun-22 5:13 AM, K McLean wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_default" style="font-size:small">
<div class="gmail_default">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.</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">We found that most woody
biomass bigger than thin twigs burns well in the <a
href="https://youtu.be/DmzQFCp2kNI"
target="_blank" moz-do-not-send="true">cooking
hole</a>. 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 <a
href="https://drive.google.com/file/d/15V4vTJxO1Lcm0wFzB96pQT9jvgjaXkwh/view?usp=sharing"
target="_blank" moz-do-not-send="true">video</a>. </div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">Thick twigs burned without
tending for 1.5 hours. Thick twigs and small
branches are abundant and unused in much of Africa.</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">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
<a href="https://youtu.be/DmzQFCp2kNI"
target="_blank" moz-do-not-send="true">training
video</a>.</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">Women can:</div>
<blockquote style="margin:0px 0px 0px
40px;border:none;padding:0px">
<div class="gmail_default">- All but stop collecting
firewood.</div>
<div class="gmail_default">- Leave the kitchen to do
other things once they start the fire.</div>
<div class="gmail_default">- Make biochar.</div>
</blockquote>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">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.</div>
<div class="gmail_default"><img
src="cid:part1.07hyYa2J.32ItEmMs@ms1.hinet.net"
alt="2 burner drawing.jpg" style="outline: 0px;
margin-right: 0px;" class="" width="338"
height="263"><br>
</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">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 <a
href="https://drive.google.com/file/d/1b2WvePKX_ofnELUWhexqQZR4NyCrXxnH/view?usp=sharing"
target="_blank" moz-do-not-send="true">video</a>.</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">Kevin McLean</div>
<div class="gmail_default">Sun24</div>
</div>
</div>
<br>
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