[Terrapreta] Low Temp Chars

[AJH]

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