[Terrapreta] Scientific American Story on Charcoal Decomposition

[Sean K. Barry]

Hi Andrew,

What rate was the charcoal added to the soil?  5-10 tons/year?  Charcoal-in-soil is said to have a half-life measured in millennia.  This even if sun-baked soils like that in the Amazon.  So, +10/year -2/year nets ~+8/year.  If that charcoal helps the soil hold more water and or more nutrients, then the cost of other soil amendments , like fertilizer and water, could be decreased.

Regards,

SKB
  ----- Original Message ----- 
  From: andrew<mailto:list at sylva.icuklive.co.uk> 
  To: terrapreta at bioenergylists.org<mailto:terrapreta at bioenergylists.org> 
  Sent: Sunday, May 11, 2008 9:08 AM
  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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