[Terrapreta] Topic #3 - charcoal production: pulverizingcharcoal

[Greg and April]

Interspaced in Blue.
  ----- Original Message ----- 
  From: Sean K. Barry 
  To: Terra Preta ; Michael Bailes 
  Sent: Monday, May 19, 2008 20:39
  Subject: Re: [Terrapreta] Topic #3 - charcoal production: pulverizingcharcoal


  Hi Michael, Greg, Roy, et al.,

  This is great!  We are on topic here, right?  Pulverizing charcoal that is produced for charcoal-in-soil use is part of the topical element #3: charcoal production, right?  I just don't want the topic police to be messing with us.  DO YOU!?

  I figure so.

  Here are some questions, though?  Why pulverize it?  I suppose it might have a larger amount of surface area per kilogram as a result.  But, could it be pulverized too much?  I think that the original Terra Preta charcoal had a 3mm minus size to it, but I am not sure that occurred before or after it was made and put into the soil.  Maybe it just breaks up with cultivation?  Pulverizing the char will impart some cost, either to mince up the feedstock or the charcoal.  Agua Das and Tom Reed at the Biomass Energy Foundation did do some studies on particle size of feedstock, when it comes to efficiency of gasification, but not of charcoal product.  I think Dynamotive , which does Fast Pyrolysis, for gas, found that much smaller feedstock particle sizes results in more gas and less char product.

  Why pulverize char?    I can think of several reasons off hand.     Makes it easier to spread on fields ( or other places ) by different means.    Increases surface area.    Alows more even application.    In pulverized form it can more readlily added to animal feed.

  Partical size?    For direct application to the fields, I would hazzard to say that you are right with >3mm.    For use as a aquaculture growth medium, I would say 5mm - 20mm.

     

  If we said that the least expensive way to make charcoal was minimal processing of the feedstock, then pulverizing the charcoal product might be better than pulverizing the feedstock.  But, then this goes back to analysis of what the "best" particle size was for the charcoal, when used as a soil amendment.

  Not necessarily.    With a smaller partial size we can load retorts with less airspace ( although some airspace is needed - other wise it then acts as a single mass rather than a bunch of smaller pieces ), getting a more efficient burn and conversion ( using less fuel ).    I think it is safe to say that pieces in the 2-3 inch ( 50 - 75 mm ) range are probably the smallest size going in to a large retort - other wise packing will probably inhibit char formation ( barring the use of baffles to prevent packing ).    I highly doubt that we will find that large pieces ( over 2-3 inch ) is optimum ) so if we start with smaller material, the less effort we have to put forth to crush to the final size.    ( There is this, if we find that financing the operation is difficult we could also sell some of the char to the BBQ market and that requires pieces in the 2+ inch range )   


  Should I say field study?  Larry Williams and Richard Haard didn't pulverize the charcoal they used at 4CN, I don't think.  They just pushed it around some and made bucket dumps onto the ground, I thought.  I seem to remember some pictures of Richard all covered in charcoal dust, wearing a dust mask, and so I do think that he did some experimentation with pulverizing charcoal, though.  Maybe they will chime in and let us know what they think about charcoal lump size?

  Edward Someus and Richard both spoke about applying charcoal as a side band with seeding operations.  That discussion seemed to imply that fine grained charcoal was required (to get it through the seed drill injectors?).

  There is more than one way of side banding, but, I doubt that the tiny amount flowing through a seed drill, would prove to be of any effectiveness.    Slurry pumping I think would apply a more effective level of char.    

  Remember, effective TP soils are being measured at having 6% or more char - in establishing char in the field, I would probably opt for a variation of low till method, by opening a furrow, and slurry pumping a mix of organic sludge and char, seeding and then closing the furrow.    Alternatively a large hypodermic needle like device ( with a bore diam of no less than 1/4 -3/8 inch 5 -10 mm ) that would inject the same mix of organic sludge and char into the soil with the seed to follow in that exact particular spot - in fact there is no reason that the seed can not be added to the mix just at the point of pumping.    

  Yes, there is the need to develop some new equipment, but it reduces the need to try and get the char fine enough to get through a seed drill, and a fairly simple plunger system could be used - in fact you could probably use the hydraulic system that many ( most? ) tractors already have.


  Greg H. 
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