[Terrapreta] new address to the simple kiln

[Ron Larson]

Folke:

    1.  I like your advance a lot - and suggest it may have considerable merit in third world cooking.  You did an excellent job in the photos and explanations. Some questions:

a.  What is the weight yield for char in the interior can?   A typical number for charcoal-making stoves is 25%.  Yours could be higher as there is no "flaming pyrolysis" (less carbon conversion to CO?) in the interior can. 
b.  What is the ratio of weights for the exterior combustable wood to the interior pyrolyzable wood (before the interior can stops pyrolysis gas emissions)?  I.e.  What is the minimum mount of exterior fuel required?
c.  How long did it take before you could see pyrolysis gases coming from the interior can?
d.  How long before the entire pyrolysis operation was completed?
e.  Have you tried leaves,grasses, and twigs packed tightly in the interior can?  These are hard to combust in stoves but still could become valuable biochar.

2.  Some background on how this relates to charcoal-making cookstoves:
    a.  The "sister" companion stoves list was started about a dozen years ago as an offshoot of Tom Miles' Bioenergy list.  Most of our first stoves-list discussion was a result of my describing experiments with top-lit stoves with controllable primary air supply.  Tom asked me to be the first stoves list coordinator, but one will also see some earlier charcoal-making discussion in the bioenergy list archives (assuming those still exist).
    b.  I think there must have been some discussion ten-twelve years ago of interior cans of the type you describe;  I certainly tried some, and they of course worked as you have described.  But I was not doing what you have described - as I had my mind fixed on top-lighting.  In those early days, we had some discussion of a well-known Indian researcher's (name forgotten) efforts to promote an inverse version on yours (a central flame within a toroidal outer pyrolysis chamber.  Top loaded - major difficulties in sealing.  The design never took off.
    c.  The top-lit charcoal-making stove has not taken off as I had hoped (in later years, for terra preta/biochar reasons).  There are three main reasons I think for that failure.  
        -  One is that a top-lit design is strictly batch operated; your design overcomes that because you can add more exterior fuel at any time   With some modifications in your approach, you could add new fuel at the bottom rather than the top.  I suppose that one could find a way to replace the interior can - maybe even have the second can move down from an early higher position (and itself be replaced by a third can).  It would be nice if the lower air supply could be made conrollable (commercial versions maybe using a speed-controlled fan??   I found that a ceramic conical "plug" in circular holes worked pretty well - compared to sliding "windows".
        - The second is that it is messy to shut down, assuming you have finished the cooking job with just the right amount of starting fuel (reference problem #1)  Lots of smoke when the pyrolysis front gets to the bottom -until you open up the lower primary air supply and start consuming the char (which we on this list want to save for soil augmentation).  Your design solves that problem also (assuming that you only see minimum noxious gases at the end??).
        -  The third problem is getting the charcoal out after cooking is over.  It is hard ( and messy and somewhat dangerous) to extinguish the hot charcoal when you have primary and secondary air ports and a flame exit.  Your design also solves that problem apparently.  As you note, the interior can can have a removable bottom "lid".

3.  This is to urge others to follow Folke's important suggestion about being able to cook with this alternative interior-pyrolysis-can design.  I spent some months in Ethiopia trying to perfect a charcoal-making design (batch type, top-lit, primary (with control) and secondary air supply) for the cooking of enjira.  This is a (delicious) thin sourdough flat bread cooked on a homemade thick ceramic disk (a "magogo"), of about 60 cm diameter.  Has to be one of the most inefficient cooking methods around.  I think there is a fair chance that Folke's approach could work there (steel (tefloned??) cooking surface being preferred), with this plate maybe sitting on top of the interior can.  This might also be applicable (at least outdoors) with the la plancha metal cooking surfaces used throughout the Spanish-speaking Americas.  There are probably ways to move this indoors with a chimney.
    I emphasize that my main justification for further research by this list is charcoal production.  But it is also a way of cutting costs (assuming future carbon credits) for the roughly 3 billion of the world's population cooking at least part of the time with wood.  (Also of course increased food production and use of scrap fuels not otherwise combustible and headed at least partly towards unwanted methane.)

4.  I kick myself for having been too top-lighting centric.  Congratulations to Folke.

Ron


  ----- Original Message ----- 
  From: folke Günther 
  To: 'Terra Preta' 
  Sent: Monday, May 26, 2008 8:01 PM
  Subject: [Terrapreta] new address to the simple kiln


  See http://terrapreta.bioenergylists.org/gunthersimple0508

  ---------

  A complete description of the simple charring methods for home garden is now at http://www.holon.se/folke/carbon/simplechar/simplechar.shtml 
  I saw that there is an older address at the terrapreta list. I use it to cook the dinner wok at the same time as I am burning the charcoal. 
  Sending you a picture of that too asap.
  YS
  FG

  -- 
  NB :Send your mails to folkeg at gmail.com, not to holon.se
  ----------------------------------------
  Folke Günther
  Kollegievägen 19
  224 73 Lund
  Sweden
  Phone: +46 (0)46 141429
  Cell: +46 (0)709 710306
  URL: http://www.holon.se/folke
  BLOG: http://folkegunther.blogspot.com/ 



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