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<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Dear Paul<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-US" style="color:windowtext">></span></b>Some of what you wrote is correct, but you go too far or leave out some important distinctions, thereby implying that some things are equal, that is, some are not really as worthy
and distinctive as others (Ron and Paul) have stated. <span style="color:windowtext">
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Of course there were things left out. I am happy you included below further refinements to the explanation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>1. Pyrolysis progresses (migrates) through a piece or pile of biomass as heat is able to penetrate. True. The Adam retort (and other retorts) heat the biomass from many sides, but there is no flame
(actual combustion) inside. It is a stretch of language to say that the pyrolysis in the retort
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="color:windowtext">>></span>has an MPF [migrating pyrolytic front] proceeding in a roughly horizontal direction.<o:p></o:p></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Au contraire. The Adam Retort (which heats the biomass from under a portion of the bottom of the pile, not multiple sides) does indeed have a MPF and the combustion is fed by oxidation using oxygen liberated
by the thermal decomposition of the fuel. There is no <i>added</i> oxygen, but oxygen there definitely is. There is enough oxygen in biomass to almost completely combust the hydrogen content. In practise the carbon and hydrogen are both involved in sustaining
the MPF. Once the fuel is hot enough, the MPF can move through the pile without any additional heat required.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
</blockquote>
<p class="MsoNormal"><span style="color:windowtext">></span>Sorry, that should say "has external heating proceeding inward from several directions from the sides toward the center."
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is an incorrect description of the Adam Retort. There are retorts that function in the manner you describe. His is not one of them.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>Furthermore, the processes in a retort are in sequential order during numerous minutes to 1) heat virtually all of the biomass to drive off the moisture, then 2) add more heat to virtually all of the
biomass to drive off the low-temperature volatiles to create torrified material, and than 3) to finally get the temperature hot enough to have actual pryrolysis, first in the 400 deg C range and then at higher temperatures if the external heating is continued.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is true for some retorts, not the Adams Retort.<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">></span>In sharp contrast, in a TLUD there is a distinctive zone of a few cm depth with actual small amounts of combustion (of some of the initial offgases). That zone migrates through the pile of biomass, heating mainly by radiation
a small layer of biomass below the MPF, then with pyrolysis at a rather uniform temperature (generally from 450 to 700 C, depending on USER CONTROLED
<span style="color:windowtext">[<i>sic</i>] </span>flow of primary air) to create the char as the gases move upward.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">The same also happens in a downdraft pyrolyser, and a bottom-pit updraft pyrolyser such as those produce by Hirendra Chakrabarti in India.<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">The addition of a control feature makes the process variable, however it does not fundamentally change how the system works.<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">></span>You may choose to try to equate the two descriptions above, but that would diminish your credibility as a precision-seeking scientist.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">There is no need for that kind of talk. First familiarise yourself with the systems under discussion. Seen from the side, an Adam Retort starts the MPF on the bottom right and it moves over a period of about
2 hours to the top left. Prof Lloyd can provide examples of sustained MPF’s moving horizontally underground in the Witbank area of South Africa without any addition of primary air. There are conditions where primary is required, and others when it is not.
Tiny stoves require it.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>And to equate a smouldering tree stump to MPF is a stretch beyond a stretch. Yes, there is fire there, and yes there is pyrolysis occuring. But such comparison is akin to saying that a ladybug and
a moose are the same because both are living creatures; and in fact both are animals. Even a petunia and a whale are both living organisms. Scientific comparisons need precision and detail.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is why the discussion is on principles not ladybugs. A dry tree stump can be ignited to char the stump and the roots underground, and in the 1800’s one could buy a kit for doing so. I was told of a different
method when I was young involving a steel pipe and kerosene. The point was to get the stump hot enough so that the pyrolysis would continue into the ground. The TLUD stove with an MPF is no more than a containerised version with controllable primary air.
<o:p></o:p></span></p>
<p class="MsoNormal"><br>
2. Ron correctly pointed out that in normal operation of TLUD stoves, there is zero O2 that gets past the MPF. That is vastly different from having so much primary air enter (as in Rocket stoves and other burners) that there is O2 moving upward above the
fuel (where the gases were created). <span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Ron is correct about the O<sub>2</sub>. It is indeed different (I don’t know about ‘vastly’ from stoves where the fuel and flames are ‘attached’ to the solid fuel and the gases oxidise as and when they can.
it is also true (but I didn’t expound on it) that within a fuel bed there are zones without no available O<sub>2</sub>, just as in the zone above the char.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>You are saying that is good as preheated secondary O2.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Functionally that is secondary air provided simultaneously, at least in some cases. My definitions are general cases and can be applied to the situation you describe.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>Maybe, but not really. It is simply inadequate combustion, with the results of undesirable emissions.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is speculation and cannot be true in all cases.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>The excessive primary air (which you state should be secondary air)<span style="color:windowtext">...<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Which I state has the function of providing secondary air…<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">>…</span>has had a cooling effect on the raw fuel that the combustion is trying to get hot enough to give off the pyrolytic gases.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is not a general case. It could happen.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>In other words, that secondary air that has passed over the fuel is part of the problem, not part of a solution because it has taken heat away from the fuel.<br>
<br>
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is not the case. What ‘problem’? Heat passed through a metal wall to secondary air is not ‘different heat’ from that gained by air passing through a fuel bed, or along a hot combustion chamber wall. There
are many roads to Rome. Air that is consumed after preheating is indifferent to hwo the heat was gained.
<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">></span>3. Tertiary air: Defined as either 1) the needed secondary air that did not get into the combustion zone soon enough (meaning that there was poor stove design)
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">I see this as inaccurate on two counts: 1) the secondary air may be added in a way that decomposes complex gases further before final combustion, and 2) the bit about poor design is unfair comment. There are
many good designs you may not know about.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">>…</span>or 2) excess air that will lower the temperature of the hot gases (meaning that this "tertiary air" was NOT needed nor part of the combustion process).
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Tertiary air may be provided for a number of reasons, but normally to provide the oxygen needed to complete combustion with a desirable level of free O<sub>2</sub> in the gases. Under certain circumstances,
for example natural gas boilers, the level of free O<sub>2</sub> is very low (1% by volume). To maintain such a low level of excess air it may be necessary to have tertiary or even more air injection points.<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">></span>Either way, the concept of "tertiary air" is bogus in the context of cookstove combustion.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is opinion only, contradicted by existing technologies that use it. One of the highest performing stick-burning stoves available has tertiary air injection – the Rocketworks stoves from Adrian Padt in
Durban, tens of thousands of which are sold each year.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>The objective is to get the combustion to be complete with the proper amounts of primary and secondary air at the correct times and places.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is true in some cases and not in others. Most Rocket stoves (per Aprovecho design guides) have only a single air entrance. The Rocketworks stoves have three distinct times and places.<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">></span>4. You wrote: <span style="color:windowtext">
<o:p></o:p></span></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="color:windowtext">>></span>This [MPF} process is ... how the Terra Preta soils in the Amazon were created over 20,000 years of slash and burn agriculture.
<o:p></o:p></p>
</blockquote>
<p class="MsoNormal"><span style="color:windowtext">></span>The origins of Terra Preta are still being debated by the experts in that field, which is certainly not your claimed field of expertise.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">I am sorry to hear you talk about ‘fields of expertise’. Facts in evidence speak for themselves and are not invalidated by any messenger claims.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="color:windowtext">>></span>The Amerindians cultivated land that was already productive, they did not create it
<i>de novo</i>. Cecil confirms they farm patches of land that are already productive, not random areas. He observed this when he was doing PhD field research while at Harvard.
<br>
<br>
<o:p></o:p></p>
</blockquote>
<p class="MsoNormal"><span style="color:windowtext">></span>I have great respect for Cecil Cook. But somehow what you have attributed to him and his work has not reach my attention previously.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">So what? <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>And I do not accept your statements.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">I don’t care. I cared to know, by interviewing him, how the Amerindians farmed and what role char had in their agriculture. I reported this previously to this list. Maybe you forgot. It is in the archives.
At the time Ron replied that did didn’t accept the observational reports from Cecil who lived in the jungle for 4 years learning how their agricultural society functions.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>What happened thousands of years ago was not witnessed by Cecil. He could only observe the current day activities on lands that somehow became fertile.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">He reported observations, the most important of which is that they do not practise slash and burn farming over whole areas, but only the fertile bits. The practice of slash and burning creates a lot of char
in the ground, something contested by Ron at that time and diminished by your message regarding the tree stumps burning in California. If you don’t believe me, you can visit the area right now and witness the MPFs moving into the ground to charcoal the root
systems. A major part of the work of firefighters is extinguishing these MPFs. This is sufficient to convince me they exist. If they exist, they are producing biochar in the ground.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>You can take that topic to the Biochar Listserv, if you want to discuss it further.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">I have no interest in discussions on another list. I receive information from the Biochar-Ontario group.<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">></span>Sorry, I reject much of what you wrote. <span style="color:windowtext">
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Don’t be sorry. Learn and be happy! We are sharing perspectives here.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>I would not want you to be instructing people about TLUD stoves and char making and Terra Preta.
<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">That is none of your business over which you have no control.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>IMHO, your comments about pyrolysis in different devices reflect poorly on your credibikity
<span style="color:windowtext">[<i>sic</i>] </span>regarding your other strongly expressed positions, but that is a topic for others to discuss.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">And I feel sometimes you could learn a thing or two before posting comments about other technologies. Like everyone else, I find your contributions worthy and partially correct.
<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">Perhaps there is something you could answer: Is there something about char making that requires or drives their proponents to make completely unnecessary personal attacks and derisive, inaccurate speculations about motives? Outside
the agricultural sector and the production of char-enhanced fertilisers, I find the biochar enthusiasts as a group to be cloistered and fanatical, frequently engaging in divisive speech about something they have recently discovered.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">I should take a minute to compliment you, Xavier, Julien, Jonas Haller and Dr Nurhuda for being very open to exchange with me advice, explanations and observations without reservations about how or where the
information originates. All of you have produced very interesting and effective products suited to certain communities.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Best regards for a better burn<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
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