[Terrapreta] Strong warning against "simple" charcoal kilns

[Sean K. Barry]

Hi Kurt,

You are wrong.  You assume that ALL of the pyrolysis gases are burned.  You do not know this and you cannot state it as an observation made by anyone else, either.  Correct me if I'm wrong, but there is 10 times as much CO and 10 times as much H2 in "producer gas", than there is Methane-CH4.  Correct me, also, if the heat of formation of CH4 is not higher than for that of either H2 or CO.  Ergo, CO and H2 will burn first is and use up the oxygen first, is my assessment.  They will use up the oxygen available at the bottom of the outer barrel, and the Methane-CH4 will eject, unburned from the top of that "charcoal-in-a-barrel" retort.

Regards,

SKB
  ----- Original Message ----- 
  From: Kurt Treutlein<mailto:rukurt at westnet.com.au> 
  To: Undisclosed-recipients:<mailto:Undisclosed-recipients:> 
  Cc: terrapreta<mailto:terrapreta at bioenergylists.org> 
  Sent: Sunday, April 27, 2008 11:45 PM
  Subject: Re: [Terrapreta] Strong warning against "simple" charcoal kilns


  Sean K. Barry wrote:

  A flood of verbiage. Somebody correct me if I'm wrong, but I don't think 
  he took into account that in the two drum system that Folke proposed, 
  all the pyrolisis products are burnt (except the charcoal of course), so 
  the CH4 gets burnt as well, so the only significant gaseous product of 
  the operation is CO2 and H2O. I don't think temperatures get high enough 
  for any NOx to be produced.

  Kurt
  reaching for the paracetamol for the verbiage generated headache.


  And sorry about this but I thought it advisable to quote his whole text


  > Hi Richard,
  > "Burning" 500 pounds of biomass down to nothing but ash produces 
  > complete combustion byproducts, with very nearly an entire consistency 
  > of only CO2 and H2O. This plus lots of heat. Pyrolizing 500 pounds of 
  > biomass to produce 150 pounds of charcoal will (because of the reduced 
  > amount of oxygen available [reduced air] during pyrolysis) generate 
  > "producer gas", as I describe below. The Methane-CH4 content in 
  > "producer gas" is the most important difference between these 
  > resultant emissions.
  > Biomass basically consists of molecules with a chemical composition of 
  > N x (CH2O). For the nit pickers, it’s not exactly that, but its close!
  > "Burning" generates "complete combustion byproducts" only
  > n(CH2O) + n(O2) => n(CO2) + n(H2O)
  > Pyrolysis generates "producer gas"
  > n(CH2O) + m(O2) => ~2n * [0.20(CO) + ~0.20(H2) + ~0.13(CO2) + 
  > ~0.05(H2O) + ~0.03(CH4)], where m < ~0.25n
  > The GHG Methane-CH4 makes up ~2-3% of the "producer gas" content. 
  > Methane-CH4 is non-existent in "complete combustion byproducts".
  > 150 pounds of charcoal @ ~90% carbon is 135 lbs of carbon.
  > So, bury the 150 lbs of charcoal and you offset the emissions of ~495 
  > lbs of CO2 [0.90 * 150 lbs * (12 + 16 + 16) / 12, (12 + 16 + 16) is 
  > the atomic weight of CO2]. Since the feedstock has molecules with an 
  > atomic weight of ~(12 + 1 + 1 + 16 = 30) and the carbon in the 
  > charcoal has an atomic weight of 12, then ~12/30 (~0.40) of the total 
  > weight of the biomass is carbon. So, the weight of the original carbon 
  > in the 500 pounds of biomass is then about ~200 lbs (= 0.40 * 500 
  > lbs). The weight of the carbon retained in the charcoal is 135 lbs 
  > (0.90 * 150 lbs). With a "fixed Carbon" yield of 135/500 = 0.27, the 
  > yield of carbon from that pyrolysis would be quite high (0.27/0.40) = 
  > ~68%!. This would be outstanding for "open air" pyrolysis, but let's 
  > go with it.
  > "Producer gas" released during pyrolysis has in it (~20% CO + ~13% CO2 
  > + ~3% CH4). The ratio then of carbon in Methane-CH4 molecules in the 
  > "producer gas" to carbon NOT in Methane-CH4 molecules (that is CO or 
  > CO2) in the gas is then, conservatively, about 9% (= 0.03/(0.20 + 
  > 0.13) = 0.03/0.33 = ~0.09). This results, then, in 65 lbs (= 200 - 135 
  > lbs) of carbon being released in the "producer gas" with ~6 lbs (0.09 
  > * 65 lbs) of that as carbon in Methane-CH4 molecules.
  > On the weight vs weight balance then, it looks like 135 lbs of carbon 
  > sequestered into the ground and only ~65 lbs of carbon released into 
  > the air, with ONLY ~6 lbs of that carbon being in Methane-CH4 
  > molecules. Cool, huh?
  > NOT QUITE! On a molecule vs molecule basis Methane-CH4 is a far more 
  > potent contributor to the green house warming effect than CO2 is.
  > A molecule of Methane-CH4 is 62 times more potent than a molecule of 
  > CO2 in the first 10 years of life in the atmosphere. Methane-CH4 is 23 
  > times more potent than CO2 over a 100 year life span in the 
  > atmosphere. Methane-CH4 (contrary to what some believe) is a long 
  > lived gas in the atmosphere. It has a half-life of ~12 years. This 
  > means that after ~12 years only half will be gone. It can linger in 
  > the atmosphere for many decades, even upwards of 100 years for some of 
  > it. It DOES NOT just all disappear in a few years!
  > Now, use the "greenhouse warming potential" scale and balance these 
  > emissions versus the buried carbon. 135 lbs of carbon into the ground.
  > 59 lbs (= 65 lbs - 6 lbs) of carbon in CO or CO2 molecules and 6 lbs 
  > of carbon in CH4 molecules. Let's say all the CO burns (or decays) to 
  > CO2, then the 59 lbs of carbon will look like only ~216 lbs of CO2 (= 
  > 59lbs * 44/12) released to the atmosphere. Carbon monoxide-CO burns 
  > more readily than CH4 and is decays (intoCO2) much more readily in the 
  > atmosphere than does CH4 (into CO2 and H2O).
  > Still we buried 135 pounds of carbon in charcoal (sequestered it) into 
  > the ground.
  > The ~6 lbs of carbon in the ~8 lbs of Methane-CH4 (= 6 lbs * (12 + 1 + 
  > 1 +1 +1 )/12) is also potentially ALL released in "open air" pyrolysis.
  > That 8 lbs of Methane-CH4 will effect the atmosphere like adding ~1364 
  > lbs of CO2 into the air (= 62 * ~6 lbs (44/12)) for ten years.
  > It will be like adding ~506 lbs oc CO2 (= 23 * ~6 lbs (44/12)) for one 
  > hundred years.
  > The GHG balance is then 65 lbs of carbon emitted out into the 
  > atmosphere, which acts like 1580 lbs of CO2 (= 216 + 1364 lbs) for the 
  > next 10 years, and like 722 lbs of CO2 (216 + 506 lbs) for the next 
  > 100 years. In neither case (1580 * 12/44 = 430 lbs), nor (722 * 12/44 
  > = 196 lbs) will the negative effect of carbon containign GHG molecule 
  > introductions (as CO2 and CH4) to the the atmosphere be LESS than 
  > benefit to be had for burying the 135 lbs of carbon.
  > ANYONE who would like to challenge me on this analysis, feel free to 
  > do so. I think it is sound and it does point out very emphatically, 
  > that we cannot pyrolyze biomass in "open air", semi-open-air", or 
  > "charcoal-in-a-barrel" kilns and EVER hope to manage GHG 
  > concentrations in the atmosphere and bring them down. If we hurry up 
  > and do this anyway, ignoring what I suggest, then the immediate future 
  > will get far worse much faster than it is even now.
  > Regards,
  > SKB
  >
  >     ----- Original Message -----
  >     *From:* Richard Haard <mailto:richrd at nas.com<mailto:richrd at nas.com>>
  >     *To:* Sean K. Barry <mailto:sean.barry at juno.com<mailto:sean.barry at juno.com>>
  >     *Sent:* Sunday, April 27, 2008 8:11 PM
  >     *Subject:* Re: [Terrapreta] Strong warning against "simple"
  >     charcoal kilns
  >
  >
  >     On Apr 27, 2008, at 5:23 PM, Sean K. Barry wrote:
  >
  >>     Now, the "charcoal-in-a-barrel" kiln? Well, when biomass if
  >>     pyrolyzed in open air (or limited amounts of air). This pyrolysis
  >>     reaction generates "producer gas" (H2:~20~, CO:~20%, CO2:~10-15%,
  >>     H2O:~5%, Methane-CH4:~2-3%, and Nitrogen gas-N2:~40-45%)
  >
  >
  >     I'm still puzzled by this. Today we burned tree debris that came
  >     down in winter storms. little or no charcoal. Lets say 500 lbs of
  >     debris. Now it' s all ash'
  >
  >     If we would have pyrolysed this with 30% yield then we would have
  >     about 150 lbs of charcoal and the fire would have consumed 350 lbs
  >     of wood. Seems like no matter how you slice this one any kind of
  >     pyrolysis is better than burning debris ??
  >
  >     Rich
  >
  > ------------------------------------------------------------------------
  >
  > _______________________________________________
  > Terrapreta mailing list
  > Terrapreta at bioenergylists.org<mailto:Terrapreta at bioenergylists.org>
  > http://tech.groups.yahoo.com/group/biochar/<http://tech.groups.yahoo.com/group/biochar/>
  > http://terrapreta.bioenergylists.org<http://terrapreta.bioenergylists.org/>
  > http://info.bioenergylists.org<http://info.bioenergylists.org/>


  _______________________________________________
  Terrapreta mailing list
  Terrapreta at bioenergylists.org<mailto:Terrapreta at bioenergylists.org>
  http://tech.groups.yahoo.com/group/biochar/<http://tech.groups.yahoo.com/group/biochar/>
  http://terrapreta.bioenergylists.org<http://terrapreta.bioenergylists.org/>
  http://info.bioenergylists.org<http://info.bioenergylists.org/>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: /attachments/20080428/7706bcbd/attachment-0001.html