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<p>All,</p>
<p>I look at my Stove Tec charcoal stove and note that it has a
grate that lets air into the charcoal from below. This gives a
hotter and more lively flame than burning on a solid surface. The
rocks would do the same thing, providing better air flow.
Reducing the charcoal quantity would reduce the air flow
resistance through the fuel, again improving air flow. This
hotter more lively flame, with effective secondary air mixing,
will burn the CO better. Sam at Aprovecho has done a lot of
research on burning charcoal, and would be one of those to be
consulted. He also found that if the CO passes through a flame it
burns better, which makes sense because when it meets the
secondary air, it will be preheated and the flame will provide an
ignition source. Providing adequate air, space, time and heat to
keep a CO flame going above the charcoal will help eliminate CO
emissions. I don't see anything new with the rocks, just a good
application of existing knowledge.<br>
</p>
<p>Kirk H.</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 10/30/2019 4:13 PM, Ronal Larson
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:61A467FB-F7DF-4E61-B8AE-B76B0023002B@comcast.net">
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<div class="">Crispin, Kevin, List, cc Christa</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>Note
change in thread title. The previous were under the name “no
subject”- which wouldn’t help researchers not around for this
thread (which is going well).<span class="Apple-tab-span" style="white-space: pre;"> </span></div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span></div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>1.
My comments below were started before responding to a similar
message from Christa Roth - just sent. So later readers
please go back to that "no subject" thread that was started a
few weeks ago by Kevin - reporting on three simple tests in
three different African countries (also identified below - now
up to 4). All show major efficiency improvements when small
stones and/or a second grate are added to an existing
charcoal-using stove.</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>2.
The main points for Kevin and others are (and hope others
will disagree or add/subtract):</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
use a water boiling test - not a cooking test. The latter is
too subjective on the right termination time, and is difficult
to replicate. Also doesn’t give the needed comparative
information on power and efficiency.</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
use at least two standard fuel amounts; maybe 0.3 and 1 kg
(this now being the main discussion topic)</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
report something on the char - especially the size
distribution. (Which itself can be another test parameter).
Maybe a statement like “32 pieces in the 1 kg - with a
max/min range less than 2:1”</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
report on the details of starting the fire. (Amount of
Leaves, paper, alcohol, wax etc). See below on using a metal
tube.</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
details on the cook pot</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
the amount of water should match the stove’s intended use -
maybe 2 or (not and) 5 liters; of course measure the amount
boiled away. Report elevation, etc</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
times are important. Measure the time to get fire started and
put pot on, b) time to boil and stop the test- c) stop
time - maybe 1 hour max, and d) time to tend Don’t worry now
about hot and cold starts</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
assume 30 MJ/kg for the char, unless you have more
information. The right equations for per levels, energy used,
and efficiency are all over the place.</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
give several photos of the stoves - with dimensions. So
others can compare or try to duplicate</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
Its fine to use unskilled testers - to save money. Let
approved labs worry about CO, PM2.5 etc. Amateurs (school
kids) can do the above test outline well enough. </div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
your four reported tests could be improved, but almost anyone
using a stove can help with numerical data. We need a lot.
Your four reporters all did well.</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
cooking tests are not to be discouraged - but after water
boiling tests. After you’ve picked a best (which could
include economics on the costs (and benefits) of an extra
grate or two.)</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
next tests can/should progress to details on the number and
size of the (free) stones and the number of grates. Two extra
grates (and stones on one or both sides) may still improve the
efficiency further.</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
report little details - the sizes of the pot and stove (air
gaps both vertically and radially), etc</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
report the amount of time spent tending the fire. If there is
air control, explain that.</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>-
Lastly - plentiful details on the two main parameters now
needing study - the stones and the grates (materials,
thicknesses,- not just the diameter(s) and the number of
holes).</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>3.
Concentrate all tests and discussions on stones and extra
grates. They are the issue now - not the amount of char to be
loaded or where the best location for air holes, stove
materials, etc. We need examples of dozens if not hundreds
of stove designs - if we are ever going to figure out how to
optimize the main new parameters - stones and grate numbers.</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Kevin
- thanks for putting all you time and energy in on these
mods that don’t seem in any way possible to pay for your
expenses to date (including going to Nairobi - please keep us
informed on whether this subject came up with anyone.)</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>And
next we can talk about charcoal-making stoves - which should
make money, not just save it.</div>
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</div>
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</div>
Ron</div>
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</div>
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<div><br class="">
<blockquote type="cite" class="">
<div class="">On Oct 27, 2019, at 1:28 PM, Crispin
Pemberton-Pigott <<a
href="mailto:crispinpigott@outlook.com" class=""
moz-do-not-send="true">crispinpigott@outlook.com</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div id="response_container_BBPPID" dir="auto"
style="font-family: Helvetica; font-size: initial;
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<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">Dear Kevin </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">This is an
interesting exploration that may yield consistent
benefits is someone is using that rather dreadful
device. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">There are
dozens of charcoal combustors in Africa and the one
shown is one of the worst. Given that there are far
better devices for burning charcoal, not to mention
better ways to load the fuel, I am too surprised that
just about anything you do would not improve it. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">Cecil Cook
and I assisted GTZ's ProBEC North in the period
2007-2010 to improve the appalling charcoal waste in
Lusaka. Cecil came up with an interesting analysis
which was the result of interviewing users about how
much money they could save before their pockets "grew
holes". It was a bout 10 days income. Any stove that
costs more than that was unlike to sell no matter what
it did. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">A second
thing observed was the widespread used of a metal tube
as a chimney to speed the ignition. It seems the
second test was conducted without lighting the fuel
properly. I wonder if the tube was used for these
tests. </div>
</div>
</div>
</blockquote>
<div><span class="Apple-tab-span" style="white-space:pre"> </span><b
class="">[RWL: This is an important practical piece of
advise. Can probably save 10 minutes in the testing</b></div>
<br class="">
<blockquote type="cite" class="">
<div class="">
<div id="response_container_BBPPID" dir="auto"
style="font-family: Helvetica; font-size: initial;
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none;" class="" contenteditable="false">
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">Two
additional things that would make testing more
convincing. First, there is far too much fuel in the
stove. Do people really use a kg and light the whole
thing to cook a meal? I would expect something between
500 and 700 g. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">Second is
that one should never have a pot sitting directly on
the charcoal. It cannot possibly burn properly with
the pot sitting on the fuel extinguishing the flames. </div>
</div>
</div>
</blockquote>
<div><span class="Apple-tab-span" style="white-space:pre"> </span><b
class="">[RWL: I think you have to place the pot on the
char if that is local practice. Can do both. </b></div>
<br class="">
<blockquote type="cite" class="">
<div class="">
<div id="response_container_BBPPID" dir="auto"
style="font-family: Helvetica; font-size: initial;
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<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">That stove
usually has the pot sitting on top of the lip of the
stove with the fuel burning under it. The pot seals to
the stove and the gases exit through the holes. That
is why (in part) it is such a terrible cooker. It has
poor aeration and very high CO contributing to its
performance. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">More than
ten years ago a much better stove was introduced, a
metal version of the Maputo Ceramic Stove developed by
a retired German metal worker from the MCS. This costs
more than the one in the report, which I recall sells
for about $1.50. </div>
</div>
</div>
</blockquote>
<span class="Apple-tab-span" style="white-space:pre"> </span><b
class="">[RWL: Any cite possible?</b><br class="">
<blockquote type="cite" class="">
<div class="">
<div id="response_container_BBPPID" dir="auto"
style="font-family: Helvetica; font-size: initial;
color: rgb(64, 96, 191); font-style: normal;
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none;" class="" contenteditable="false">
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">If that is
the device someone is using, and the addition of the
stones improves performance consistently, by all means
continue. I'd like to see it operated with half the
fuel loaded to represent more closely the typical
pattern of use. I can't see the theoretical basis for
the additional plate making any difference save that
if it is loose, air can flow around the edge perhaps
burning off some of the CO generated in the midst of
the fire. As can be seen in the photo, elevating the
fuel above the lip gets it into the open air where it
can burn better. It's is still pretty awful, though. </div>
</div>
</div>
</blockquote>
<b class=""><span class="Apple-tab-span" style="white-space:pre"> </span>[RWL:
I can’t yet see the theoretical reasons either - which is
why I am pushing this thread (I keep saying Kevin has
brought us two new important ideas - backed up by four
reports working with very different stove (and earlier with
wood-burning. This list can make this discovery get moving
faster. Kevin’s report this year on stones with the 3-stone
fire is already reported to have been adopted by million in
one small part of one small country - saving 40-50% of the
wood!</b><br class="">
<blockquote type="cite" class="">
<div class="">
<div id="response_container_BBPPID" dir="auto"
style="font-family: Helvetica; font-size: initial;
color: rgb(64, 96, 191); font-style: normal;
font-variant-caps: normal; font-weight: normal;
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start; text-indent: 0px; text-transform: none;
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none;" class="" contenteditable="false">
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">The
Malgache stove popular in West and Central Africa is
better from several points of view including that it
elevates the pot above the fuel. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">If you want
to burn charcoal reasonably well there should be 50mm
vertical space between the fuel and the pot. That
region should be sheltered from cross winds and
aeration should be provided that reaches almost to the
centre, if possible. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">As to the
retention of heat in the stones, there is no doubt
they will get hot. The main benefit of stored heat in
a stove is to keep the char burning more completely as
the fire dies. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">How a bout
trying the experiment again using 350 g of charcoal
and break it up so it can burn at a rate high enough
to provide the cooking power needed. The fuel particle
surface to volume ratio defines this. If you want more
power, get more surface area burning at the same time.
It should fit into the space under the pot when it is
sitting on the stove lip. </div>
</div>
</div>
</blockquote>
<span class="Apple-tab-span" style="white-space:pre"> </span><b
class="">[RWL: See my comment above on reporting on fuel
sizes.</b></div>
<div><b class=""><br class="">
</b></div>
<div><b class="">End </b></div>
<div><b class=""><br class="">
</b></div>
<div><b class="">Ron<br class="">
</b>
<blockquote type="cite" class="">
<div class="">
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style="font-family: Helvetica; font-size: initial;
color: rgb(64, 96, 191); font-style: normal;
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none;" class="" contenteditable="false">
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">It is can
cook with 200 g there would still be lots left. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">Incidentally
when burning a kg of charcoal and stopping with most
of it left over, you should report the energy
liberated as that of the charcoal ash-free (AF). This
is because all the original ash in the fuel is still
there at the end, which means the missing mass is
combustible, not "average charcoal". Suppose the ash
is 10%. Then the missing 200 g mass has the energy of
200/0.9 g = 222 g of charcoal with ash in it. </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">Regards </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class="">Crispin </div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
<div name="BB10" id="BB10_response_div_BBPPID"
dir="auto" style="width: 1015px;" class=""><br
class="">
</div>
</div>
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10pt;" class="">
<div id="from" class=""><b class="">From:</b><span
class="Apple-converted-space"> </span><a
href="mailto:info@sun24.solar" class=""
moz-do-not-send="true">info@sun24.solar</a></div>
<div id="sent" class=""><b class="">Sent:</b><span
class="Apple-converted-space"> </span>October
27, 2019 9:01 AM</div>
<div id="to" class=""><b class="">To:</b><span
class="Apple-converted-space"> </span><a
href="mailto:stoves@lists.bioenergylists.org"
class="" moz-do-not-send="true">stoves@lists.bioenergylists.org</a></div>
<div id="reply_to" class=""><b class="">Reply
to:</b><span class="Apple-converted-space"> </span><a
href="mailto:stoves@lists.bioenergylists.org" class=""
moz-do-not-send="true">stoves@lists.bioenergylists.org</a></div>
<div id="subject" class=""><b class="">Subject:</b><span
class="Apple-converted-space"> </span>Re:
[Stoves] (no subject)</div>
</div>
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</tr>
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</div>
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<div class="">
<div dir="ltr" class="">
<div class="gmail_default" style="font-size: small;">Here
is a<span class="Apple-converted-space"> </span><a
href="https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.google.com%2Fdocument%2Fd%2F167i50oweyfe23bRMnDSeJwlu0eM4IgTek6IO2C6JPes%2Fedit%3Fusp%3Dsharing&data=02%7C01%7C%7C5adb9b35eb164c863d8e08d75addc36c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637077780832681885&sdata=YpL%2BDV4Jv3JJn7EOBjT5EA3jWIjF3B8CQkFz2NMriU0%3D&reserved=0"
class="" moz-do-not-send="true">report from
Zambia</a><span class="Apple-converted-space"> </span>indicating
that the rock bed and second metal grate improve
the efficiency of the Zambian mbaula (all-metal)
charcoal jiko by 41%. Cooking time is also
greatly reduced. While these testers have no
training, their results are consistent.</div>
<div class="gmail_default" style="font-size: small;"><br
class="">
</div>
<div class="gmail_default" style="font-size: small;">This
is such a simple modification that dissemination
could be very rapid. I hope some of you can try
this. </div>
</div>
<br class="">
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Oct 10,
2019 at 1:37 PM K McLean <<a
href="mailto:info@sun24.solar" class=""
moz-do-not-send="true">info@sun24.solar</a>>
wrote:<br class="">
</div>
<blockquote class="gmail_quote" style="margin: 0px
0px 0px 0.8ex; border-left-width: 1px;
border-left-style: solid; border-left-color:
rgb(204, 204, 204); padding-left: 1ex;">
<div dir="ltr" class="">
<div class="gmail_default" style="font-size:
small;">
<div dir="ltr" class="">
<div class="gmail_default">Listmates,</div>
<div class="gmail_default"><br class="">
</div>
<div class="gmail_default">Has anyone tried
this?</div>
<div class="gmail_default"><br class="">
</div>
<div class="gmail_default">
<div class="gmail_default">We seem to have
significantly increased the efficiency
of charcoal jikos by putting a bed of
rocks on the jiko's grate and putting
second metal grate on the rock bed. The
charcoal goes on the second metal
grate. 2-3 cm rocks work. It works in
all metal jikos and clay jikos that
we've tested. </div>
<div class="gmail_default"><br class="">
</div>
<div class="gmail_default">Our testing is
early and unscientific, but consistent.
25-50% less fuel used. Here are three
reports. The Sierra Leone report has
good photos at the bottom.</div>
<div class="gmail_default"><span
id="gmail-m_7143231675533950200m_4206997578200011798gmail-m_-5379600863218226737gmail-m_-1297279476715938052gmail-m_1825955397064429865gmail-docs-internal-guid-10e1cdb9-7fff-27f8-efcc-c921a0e5cc06"
class="">
<div style="line-height: 1.38;
margin-top: 0pt; margin-bottom:
0pt;" class=""><a
href="https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F12MvBKjxq6PCGCcCHAjSYSeVXXvl7jWjD%2Fview%3Fusp%3Dsharing&data=02%7C01%7C%7C5adb9b35eb164c863d8e08d75addc36c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637077780832691902&sdata=MqY7JaMTSg6tod8s%2BlvxR09foMAMqHWo2jqMdgCklfs%3D&reserved=0"
class="" moz-do-not-send="true"><span style="font-size: 10pt; font-family: arial; background-color: transparent; vertical-align: baseline; white-space: pre-wrap;" class="">Sierra
Leone</span></a></div>
<div style="line-height: 1.38;
margin-top: 0pt; margin-bottom:
0pt;" class=""><a
href="https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Fopen%3Fid%3D1zQIY49E1vrfjYl7t5V_shvw70d67QirGWUrbW51tDxo&data=02%7C01%7C%7C5adb9b35eb164c863d8e08d75addc36c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637077780832701907&sdata=agj%2F%2BbtHo6x%2FmUbUkLDYsXFkDWtBy89LwA7wrlnlBQo%3D&reserved=0"
class="" moz-do-not-send="true"><span style="font-size: 10pt; font-family: arial; background-color: transparent; vertical-align: baseline; white-space: pre-wrap;" class="">Uganda</span></a></div>
<div style="line-height: 1.38;
margin-top: 0pt; margin-bottom:
0pt;" class=""><span style="font-size: 10pt; font-family: arial; background-color: transparent; vertical-align: baseline; white-space: pre-wrap;" class=""><a href="https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Fopen%3Fid%3D1MPwHCwKEVqJvuybKB5Yj39nr8fbcopBP&data=02%7C01%7C%7C5adb9b35eb164c863d8e08d75addc36c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637077780832711912&sdata=xQLz%2FJ6%2FdVVAD%2FkEfaX3r5phX01diAfAeimEmNph6Mo%3D&reserved=0" class="" moz-do-not-send="true">Kenya
(very few rocks)</a></span></div>
<div style="line-height: 1.38;
margin-top: 0pt; margin-bottom:
0pt;" class="">(The report authors
are untrained and not native English
speakers. Especially the Kenya
report contains many errors. Please
focus on the consistent final
conclusion that a rock bed and
second metal grate significantly
reduce firewood usage.)</div>
</span><br class="">
</div>
<div class="gmail_default">This may be a
very low cost, very easy way to greatly
improved the efficiency of charcoal
jikos. I'd like to hear if there is
already a body of work on this. Here is
my rough drawing:</div>
<div class="gmail_default"><br class="">
</div>
<div class="gmail_default">
<div class="">
<div class=""><span
id="cid:ii_k1kzflrt1"><20191010_133359.jpg></span><br
class="">
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<div class="">Thank
you,<br
class="">
</div>
<div class="">Kevin</div>
<div dir="ltr"
class=""><i
class=""><br
class="">
</i></div>
<div dir="ltr"
class=""><i
class="">Kevin
McLean,
President</i></div>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
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