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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>How recalcitrant is tar to decomposition in soil? There is tar
and tar. The tar that is present in crude oil soon gets chewed up – think of
the slight effect of the Gulf of Mexico oil spill, and how fouled areas were
quite quickly cleaned naturally. But do a bit of heat treatment/oxidation, and
the tar becomes really stable. Our roads don’t generally disappear. So I would
guess that the tar in a charcoal would be resistant to biological attack.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hope that helps.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Philip[<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Stoves
[mailto:stoves-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Crispin
Pemberton-Pigott<br>
<b>Sent:</b> 02 April 2014 06:56<br>
<b>To:</b> stoves@lists.bioenergylists.org; Phillip Lloyd<br>
<b>Subject:</b> Re: [Stoves] Adding value to charcoal from TLUD stoves<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Arial","sans-serif";
color:#1F497D'></span><span style='font-family:"Calibri","sans-serif";
color:#1F497D'>Thanks Juli</span><span style='font-family:"Calibri","sans-serif";
color:#1F497D'>en<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";
color:#1F497D'>That was very helpful. <o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";
color:#1F497D'>Prof Lloyd, can you assist us answering Question 3 below?<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Arial","sans-serif";
color:#1F497D'></span><span style='font-family:"Calibri","sans-serif";
color:#1F497D'>Regards </span><span style='font-family:"Calibri","sans-serif";
color:#1F497D'><o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";
color:#1F497D'>Crispin <o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>Hello Rajan and all;<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>The point you raise about allowing for a few minutes of the
char-burning phase to heat the charred fuel and drive off any left over
volatiles is a good one.<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>The height of the TLUD combustion chamber is likely to be
important, because the top of a tall column of charcoal may not get hot enough
to drive off volatiles by char-burning. In addition, the top of a
tall column will have experienced a longer time for tars to condense
during the flaming-pyrolysis phases than a shorter column. I have made
some grimy wood-pellet biochar in a stove pipe TLUD.<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>Not driving off the volatiles will result in fine pore space
of the biochar being occluded. Perhaps that is what was going on
with the following research: <o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>Peterson, S. 2013.
Comparison of gasification and pyrolysis methods for preparing biochar from
corn stover and wheat straw. </span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'><a
href="http://biochar.illinois.edu/Peterson.pdf">http://biochar.illinois.edu/Peterson.pdf</a></span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>In this Powerpoint
presentation, he shows that TLUD biochar had a lower surface area than biochar
made by pyrolysis.</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>I think there are some
questions to answer:</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>1) Is it commonly the
case the a short period of char-burning will raise the temperature of the bed
of char sufficiently to drive off all condensed volatiles?</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>2) Is there any
difference between forced and natural draft TLUDs?</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>3) How
recalcitrant to decomposition is tar in soil, and in particular,
tar embedded on biochar? Is the occlusion of pore space long-term?</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>And a final comment.
Users of TLUDs will have to learn how to drive them properly if they want to
make good quality biochar.</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>Thanks, Rajan, for your
observations.</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>Cheers,</span><o:p></o:p></p>
<p><span style='font-family:"Tahoma","sans-serif"'>Julien.</span><o:p></o:p></p>
<p class=MsoNormal><br clear=all>
<br>
-- <o:p></o:p></p>
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<p class=MsoNormal>Julien Winter<br>
Cobourg, ON, CANADA<o:p></o:p></p>
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