[Terrapreta] Scientific American Story on Charcoal Decomposition
andrew
list at sylva.icuklive.co.uk
Sun May 11 09:08:00 CDT 2008
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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