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Dear Ron</div>
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I want to make sure you are aware of what the 9% number refers to. It is not the concentration of CO nor the CO/CO2 ratio. It is the energy loss at a certain combustion inefficiency. </div>
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For gas stoves operating indoors in Germany in standard housing the permitted CO/CO2 performance is 2%, same as kerosene stoves in South Africa. The energy loss is 1.5%. </div>
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The best available stove test is the CSI-WHT which is capable of making in the lab a prediction of future performance in the field. It also uses valid metrics and correctly reports fuel consumption. </div>
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You will be pleased to know that the test also reports recoverable charcoal mass. </div>
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Regards </div>
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Crispin </div>
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<div>List and ccs</div>
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<div><span class="x_Apple-tab-span" style="white-space:pre"></span>1. I think we should first try to answer the original question from Mr. Poehlmann - which I take to be whether it is better to burn char in the TLUD or in another device. I think the exchanges
below say clearly that the answer is the latter.</div>
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<div><span class="x_Apple-tab-span" style="white-space:pre"></span>But I would urge also taking a look at doing neither - but rather placing the produced char into soil. You have a char product that is clearly worth something in any/every market. If you care
about climate change, placing this char in the ground (then can be called biochar) will be worth more than dollars.</div>
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<div><span class="x_Apple-tab-span" style="white-space:pre"></span>2. I suggest that we follow the available stove testing literature - with the best I know of being that from a webinar given by EPA’s Jim Jetter.</div>
<div><a href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=307494">http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=307494</a></div>
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<div><span class="x_Apple-tab-span" style="white-space:pre"></span>Slide 22 shows total CO output by weight of less than 1% in an apparently well done test</div>
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<div><span class="x_Apple-tab-span" style="white-space:pre"></span>3. I am not up to date on CO mortality figures, but would personally be very scared of the 9% value offered as an average by Crispin. The values at one or two sigma away must have lethal potential
many places and we certainly hear of CO-caused deaths. Anyone following this closely?</div>
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<div>Ron</div>
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<div>On Aug 4, 2015, at 9:40 AM, Crispin Pemberton-Pigott <<a href="mailto:crispinpigott@outlook.com">crispinpigott@outlook.com</a>> wrote:</div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">Dear Rebecca and Paul</span></div>
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<span style="color:rgb(31,73,125)">RAV>…</span><span style="">I have always been worried about the CO level that is produced in wood burning stoves (3-stones, traditional and improved) that become charcoal burning at the end stage of cooking. I am specifically
referring to the traditional way rice is cooked in the Philippines to prevent it from burning at the bottom of the pot. First, the water is brought to boil at high power; then rice is added and stirred until most of the water is absorbed; and then any remaining
unburned wood is removed and the rice, in the covered pot above the stove, continues to cook to perfection the "palangay" way -- i.e., with the heat from the glowing embers of the charcoal remains. Alternatively, rice and water are brought to boil together
and then cooked the "palangay" way.</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">Understood.</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)"> </span></div>
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<span style="">Have you or anyone else taken CO/CO2 measurements under the above described cooking conditions, both indoor and outdoor?</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">I have taken many measurement of CO/CO2 at various stages and what I see is that in the late burning stage the CO/CO2 ratio is not as bad as many assume – even in a poorly sheltered
fire. The combustion of char tends to stabilise at 12-16% CO/CO2 with 14% being common in a ‘cold fire’. It is not true at all that the carbon mostly emerges as CO.</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)"> </span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">To get high CO one has to ‘force’ the production of it such as in a hot, choked, air-inadequate fire. Then one can see the CO/CO2 reach 30% or more. It is not uncommon to see
25% in poorly constructed stoves, but not at the end. Little well-aerated char fires stabilise in that 12-16% range.</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)"> </span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">It is often said that “the CO is really high”. That is relative true compared with a really good fire, but CO is highest in hot, bad fires where there is enough energy to create
a high burn rate and poor mixing or poor combustion.</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">Let’s use the example of 14.28% CO/CO2. I choose that because the CO as a fraction of C is 1/8<sup>th</sup>. The ratio of CO to CO2 is then 1:7 which is 14.28%. So we are burning
char with 1/8<sup>th</sup><span class="x_Apple-converted-space"> </span>of the carbon emerging as CO and 7/8 as CO2, OK?</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">If the char is 85% carbon (realistically, this is a reasonable guess) then the heat available is about 29.5 MJ/kg. We lose about 75% of heat for all CO produced instead of CO2.
Therefore we get as a loss:</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">0.75 x 1/8 x 29.5 = 2.765 MJ</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)"> </span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">So instead of getting 29.5 we get 26.73 MJ/kg, which is a loss of 9.375% or 9-3/8<sup>ths</sup><span class="x_Apple-converted-space"> </span>per cent at 14,28% CO/CO2.</span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)"> </span></div>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">So in round numbers it is reasonable to assume you are losing 10% of the heat energy in the form of uncombusted carbon.</span></div>
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<sub><span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)"> </span></sub></div>
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</span><span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)">PSA></span><span style="font-family:Helvetica,sans-serif">Concerning the issue of what is the heat lost (not liberated) if CO from charcoal escapes instead of being burned, you have
illuminated my (our) understanding.</span><span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)"></span></p>
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<span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)">></span><span style="font-family:Helvetica,sans-serif">In a "typical" charcoal stove that is generating dangerous amounts of CO, what percentage of the consumed carbon is "well burned" (and
becomes CO2) versus the carbon that is only transformed into CO? </span><span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)"></span></p>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">It is highly dependent on the kitchen conditions. In a well-ventilated kitchen CO is not an issue, first because low level CO is not all that dangerous, and second because one
doesn’t have to breathe the CO or the smoke, just because it comes out of the stove. In a real kitchen the smoke rises strongly to the top and most leaves by way of ventilation holes or gaps. In other words a ‘single box model’ of kitchen emissions being spread
evenly around the room at all times is unreasonable. Kitchens don’t work like that. There is some advanced mathematical modelling done by KK Prasad at Eindhoven University in the 80’s on this matter. CO and PM are strongly concentrated above the stove, and
are not spread around the room. Thus the exposure is affected much more by the kitchen than the actual emitted mass.</span></p>
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<span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)">></span><span style="font-family:Helvetica,sans-serif">The reply might need to give some range of values or qualify the responses relating to a "high heat" charcoal fire versus a "low heat"
charcoal fire, probably with the latter being proportionately much more of the carbon ending up as CO, with a corresponding 75% loss of the heat value for that amount of charcoal.</span><span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)"></span></p>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">The CO emitted by a charcoal stove on high power is usually more than the same stove at low power even if the combustion conditions at the end are poor. However, modern charcoal
stoves are far better at combusting the fuel than the old and new ‘Jikos’. I am hoping to be able to point to a new charcoal stove product soon that has been waiting in the wings for launch. It has greatly reduced CO production throughout the burn. We need
some examples like this to stimulate the industry. We have been setting targets too low.</span></p>
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<span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)">></span><span style="font-family:Helvetica,sans-serif">There is a big difference between (hypothetical numbers follow) 50% of carbon going to CO instead of CO2 (with the loss of 75% of the
heat value of half of the carbon [75% of 50% = 38% lost heat) versus only 5% of carbon going to CO (75% of 5 % = 4% lost heat). Of course, it is the CO that can kill you that is more important than some amount of lost heat.</span><span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)"></span></p>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">CO as a hazard is always going to be a hazard. On the other hand don’t over-sell a danger. If the 2-hr exposure limit is met, that’s OK. Remember that we have emission targets,
it is not a contest/race (though we love those too). Having no CO at all is great – better efficiency, no health risk. In practice however, people produce CO all the time and we don’t die from exhaling our own air. People have a CO/CO2 ratio of about 1.6%.</span></p>
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<span style="font-family:Helvetica,sans-serif">Comment: We are discussing "char-gasification", the oxidation of solid carbon (but as charcoal it is not necessarily pure) into either CO or CO2. The O2 that enters as primary air can result in either CO or
CO2. The role of secondary air is a very different story for char-gasification than it is for the combustion of pyrolytic gases as in the context of TLUD micro-gasifiers.</span><span style="font-family:Helvetica,sans-serif; color:rgb(31,73,125)"></span></p>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">I don’t have much add to that. It is important to recognise that CO2 produces at the pyrolysis front is often converted to CO endothermically in the char bed above it. CO<sub>2</sub><span class="x_Apple-converted-space"> </span>happily
goes back and forth several times to CO in a fire, or even to C<sup>++</sup>. It is not simple and direct. Similarly water in the fuel can be split into H<sub>2</sub><span class="x_Apple-converted-space"> </span>and O. When measuring the content of unburned
gases from a gasifier, you can find all sorts of strange totals of C and O<sub>2</sub><span class="x_Apple-converted-space"> </span>and water vapour and H<sub>2</sub>. Wouldn’t you be surprised to find that the total of the O in the gas is CO, CO<sub>2</sub>,
H<sub>2</sub>O, NO, NO<sub>2</sub>, SO, SO<sub>2</sub>, and O<sub>2</sub><span class="x_Apple-converted-space"> </span>is higher than the concentration in air?</span></p>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">Regards</span></p>
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<span style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(31,73,125)">Crispin</span></p>
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