[Terrapreta] Scientific American Story on Charcoal Decomposition

[Sean K. Barry]

Hi Lloyd,

I think this all goes back to what was the experimental protocol.  If the interest is in changes to soil carbon content, then soil carbon content should be measured first in the charcoal amended plots, before charcoal is put into the soil, and then after the amendments are made and during the test period (several times over the ten year study?).  Controls should also be maintained and measured as well.
With baseline and control measurements of soil carbon content, then adequate measures of change will be measured.  Fluxes of CO2 emissions from soil mean nothing when analyzed in the absence of total amounts (of carbon in the soil).

Regards,

SKB
  ----- Original Message ----- 
  From: Lloyd Helferty<mailto:lhelferty at sympatico.ca> 
  To: 'andrew'<mailto:list at sylva.icuklive.co.uk> ; terrapreta at bioenergylists.org<mailto:terrapreta at bioenergylists.org> 
  Sent: Wednesday, May 14, 2008 7:09 AM
  Subject: Re: [Terrapreta] Scientific American Story on Charcoal Decomposition


  How much extra carbon has been added to the soil by the addition of the C
  (char)?  IF it is more than 2 tonnes per ha per year then it is net
  positive, if not then we have produced a negative effect on soil carbon.  We
  can't forget the contribution of the char itself!

  Lloyd Helferty


  -----Original Message-----
  From: terrapreta-bounces at bioenergylists.org<mailto:terrapreta-bounces at bioenergylists.org>
  [mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of andrew
  Sent: May 11, 2008 10:08 AM
  To: terrapreta at bioenergylists.org<mailto:terrapreta at bioenergylists.org>
  Subject: Re: [Terrapreta] Scientific American Story on Charcoal
  Decomposition

  On Sunday 11 May 2008 13:35, Lloyd Helferty wrote:
  > I note that the author only indicated that using Charcoal (black
  > C) for enhancing ecosystem C sequestration ... can be "partially 
  > offset by its capacity to stimulate loss of native soil C". The 
  > important point is that the carbon sequestration capacity of Char is 
  > only Partially Offset by losses elsewhere (from humus) ~ which would 
  > mean the net carbon sequestration potential is still positive.

  It may be that organic matter rich soils should be avoided for neo tera
  preta schemes. We do know that soil organic matter (som) is respiring to CO2
  and Water more rapidly as soils become warmer in any case, so there's
  already a positive feedback mechanism working against accumulation carbon in
  the soil.

  Can we have a stab at some figures for a typical mineral arable soil,
  neglecting any benefits to growth that char additions may bring?

  Perhaps someone can add better figures for this assumption:

  How about a hypothetical soil with 4% som to plough depth of 23cms, That's
  2300m^3 of soil per hectare, on an oven dry basis can we allow that to be
  3500 tonnes of soil? Which yields a som of about 140 tonnes and carbon of
  about 82 tonnes. If soil carbon is recycled over a 40 year period then it's
  half life is 20 years ( matmeticions please correct me where I'm wrong), say
  adding an amount of char doubles the rate of respiration and reduces the
  half life to 10 years. Then by adding the char we're increasing the
  respiration of soc (soil organic carbon) by 2 tonnes per ha per year, what
  benefits offset this?

  AJH

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