[Terrapreta] Low Temp Chars

[Sean K. Barry]

Hi AJH

I do not think microorganisms will digest or oxidize pure carbon.  Pure carbon in charcoal (that which is not part of the molecules of VM in charcoal) will not be decomposed by soil microorganisms sooner than the VM because partial oxidation of hydrocarbons and carbohydrates in the VM will release smaller amounts of heat when they are oxidized.  To oxidize pure carbon releases much more heat and there is no partial reaction.  The microorganisms might literally need to burst into flames in order to digest pure carbon.

Also, since the carbon is buried in soil, it is not likely to be oxidized with oxygen in the air, since in general there is very little air in soil, particularly moist soil.  Someone talked recently on the list about charcoal emitting "long-infrared rays".  It seems to me that this must be related to some kind of thermo-chemical reaction of the charcoal with air.  I suggested that it was slow oxidation of the carbon in the charcoal with open air exposure.  

Other evidence, perhaps more compelling, about the resilience of carbon in soil (in the form of charcoal) is the carbon dating of the charcoal in the Terra Preta.  This is how we know that the Terra Preta was formed as long ago as it was and it tells us also how long that charcoal has been in the soil.  Given that there is any charcoal in that soil which dates back that far (circa 2500-7000 years) suggests that all of the charcoal (which is more consistent in form than inconsistent) will have lasted as long.

Let me know what you think?

Regards,

SKB
  ----- Original Message ----- 
  From: AJH<mailto:list at sylva.icuklive.co.uk> 
  To: Sean K. Barry<mailto:sean.barry at juno.com> 
  Cc: terrapreta at bioenergylists.org<mailto:terrapreta at bioenergylists.org> 
  Sent: Thursday, April 26, 2007 3:35 PM
  Subject: Re: [Terrapreta] Low Temp Chars


  On Wed, 25 Apr 2007 22:12:03 -0500, Sean K. Barry wrote:

  >It is claimed that microorganisms decompose or digest bio-oils (VM, pyroligneous acids, acetic acid, wood vinegar, etc.) in charcoal
  >This may in fact be true and there maybe even some evidence to support those claims. But, I don't know if this precludes any sequestration of the carbon in those substances. 

  >
  This is what I'd like an answer to, I'm completely happy that adding
  char to a soil can enhance the soil by both changing growing
  conditions and supplying plant minerals in an easily assimilated form.

  I'm afraid I may be missing some gems on this list because I cannot
  keep up with the threads but if it is to be promoted as a means of
  carbon sequestration then we need to know what carbon remains long
  term in the soil. 

  Now plants respire CO2 as well as photosynthesise with it, it's just
  that they fix more than they use, so if someone tells me a microbe
  makes use of a volatile portion of the char then I assume it will
  involve some oxidation of it.

  Knowing we can make char with fixed carbon contents varying from 70%
  to 99% and that the yield of the original (woody) dry matter will vary
  inversely from 45% to 15% we need to know how much is sequestered long
  term before we start making a generic claims about the effect with no
  regard to the source or type of char.



  > When the microorganisms free up plant nutrients from the bio-oils, immediately when they decompose the bio-oils or when the microorganisms die, then the roots of plants will likely take them up.  These nutrients (N, P, K, S, Ca, Fe, Mg,  etc.), however, do not include carbon-C. Growing plants do not absorb soil-based carbon.  They get it from the atmosphere in the form of CO2.


  Yes, which is why I'm suggesting the microbes will be oxidising it or
  is there another explanation? Can an experiment that tests the
  remaining carbon from ancient terra preta soils be devised that
  relates the original mass of biochar (low temperature and agriwaste
  rather than wood I believe) to that which survives in the soil?


  AJH

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