[Terrapreta] Durability of charcoal as carbon sink?

[Sean K. Barry]

Hi Christoph and All,

Would you think something like measured weights of vermiculite, NPK fertlizer, charcoal, maybe come clean sand? , and water might be the mixture to test?  Would the control for the experiment work as a growth medium, if it were the same mixture, sans the charcoal?  Would this experiment be conducted in a container separate from soil, but in the open air?  

My thinking went like this; that you could take a few measurements of any soil/charcoal mixture and get a baseline of "input carbon from charcoal" into the system.  The ATSM "proximate analysis" test says it measures moisture content, %fixed carbon, %VM (volatile matter), and %ash.  The test can be conducted on soil or charcoal samples.  The weight of the "input carbon", the to be "sequestered carbon from charcoal", should be measured separately.

With the "proximate analysis" measurement and a weigh scale, measure these things;

    1) get a proximate analysis of a sample of just the charcoal (used in the mixture), separately, 

    3) weigh the charcoal,

    3) get a proximate analysis of any sample of the well mixed soil/charcoal mixture,

    4) weigh the soil/charcoal mixture, which is all going into a closed system container, and

    5) compute the weight of the "sequestered carbon from charcoal" as the the weight
        of the charcoal times ( 100 - %VM(charcoal) - %ash(charcoal) ) / 100.

If we assume the water is maintained in the soil and control at a certain moisture content, the greenhouse is ventilated in open air, and with atmospheric CO2 levels where they are at now (CO2 @ 469 ppm?), then the control and the test sample would be in the same environment (unless you separated them a great distance).

I don't think the flow of carbon dioxide gas in/out or oxygen out matters in this experiment.  These relate to the photosynthesis activity of the plants, the biologic respiration of the soil microbiology, the decomposition rates of the soil organic matter (and VM), and nutrient uptake by the plants, etc.  These do not effect the "sequestered carbon from charcoal" (Do they?).  But, I would expect these might/will change the net carbon and the %C(soil) versus that of the baseline soil sample.

But, there is a simplification I thought of for this experiment.  What we are only interested in is measuring the carbon level (regardless of source or in/out flux rate of carbon to/from the soil or the system).  We expect, by hypothesis, for it to stay at the baseline level (as it was on the "carbon sequestration incept date").  The amount of carbon in the soil could/should get larger in the soil, but it also should never drop below the baseline "sequestered carbon from charcoal" level.  This is a statement the hypothesis, again.  Just measure the charcoal level in the soil.

If the level drops, then the hypothesis was not met, and the experiment is over.  The result of the experiment would then be "sequestered carbon from charcoal" is "not resilient", but rather, "decaying".  We might then try to determine the "rate of decay".  The hypothesis says, we expect the soil should stay at the baseline level or grow in carbon content continuously (regardless of other inputs and/or outputs) for a long period of time.

In other words, we are determining only if the baseline level of just the "sequestered carbon" is resilient over time?  We don't care about the flows of any other carbon.

As long as we don't "disturb" the system too much, or take anything in or out of that closed system, I expect the natural carbon cycle would maintain that soil "always" at or above the baseline level.  Do you think?  Even growing plants in that soil and harvesting them continuously is not going to reduce or change the "carbon from charcoal" content in the soil.

I am assuming, by hypothesis, that the "fixed carbon in charcoal" is NOT DECOMPOSED by microbes (but the VM may be), and that the "fixed carbon" is NOT TAKEN UP in any way by plant roots (plants only get carbon from gaseous CO2 in the air and/or water).  We're not mining it out or letting it wash away from the experiment, either.  So, the soil carbon content and soil organic matter may well or will go up (mostly, and possibly down?), but the "sequestered carbon from charcoal" will stay, and the soil carbon content (weight of soil*%C(soil)) WILL NEVER GO BELOW THE BASELINE "SEQUESTERED CARBON FROM CHARCOAL" LEVEL (weight of charcoal*%C(charcoal)).  Isn't that all we are trying to show?

Do any external fluxes matter at all, if we are only interested in measuring if the carbon that we put in soil goes away?

I think if any random "proximate analysis" of the soil/charcoal mixture were made on any date after the "sequestration incept date" and then compared to the baseline measurements, then it can show whether or not the "sequestered carbon from charcoal" is reslient over time.  No other measurements would be needed.

The results will show the hypothesis is met

    (weight of mixture*C%(mixture post)) / (weight of charcoal*C%(charcoal)) always > 1.0 ?

Or, they will show it isn't met.

Do you think this will work?  Did I miss something?

Duane, do you think a successful, continuous, long term experiment like this, which would validate this hypothesis, will suffice for
proof that "sequestered carbon from charcoal" stays in the soil for a very long period of time.

There is another argument to lend support to this hypothesis, which can be made, I think too;  Since soil carbon content is significantly greater in the original 2500-6000 year old Terra Preta than in the surrounding native soils, then the "carbon in the form of charcoal, which was added to the soil" by the ancient Amazonians is all still mostly there.  We can see it. 
We can see it in the Terra Preta soil (which has the high carbon%) and we don't see it in the control (native soils right next to it with low C%).  There is carbon from the charcoal along with probably a whole lot more in the enhanced soil organic matter in the Terra Preta soil.  If you could take all of the "carbon from charcoal" out of the original Terra Preta, then it may still have more carbon in the soil organic matter left, than the native soils do.  Bottom line is, no matter how you cut it, there is still as much carbon in the original Terra Preta as was in all of the charcoal that was put into it, and then some more from later growth by soil microorganisms.  This growth in soil organic matter didn't happen in the native soils.  It begins to look fairly obvious; putting carbon from charcoal in soil isn't going to make carbon decay out of the soil, its going to make the soil hold even more carbon.  The carbon is just a stable catalyst, not a reactant or a product in the phenomenon.

I say those seeking earnings from "carbon credits" can say,

"Pay me only for what carbon I put in the soil now and I can promise that soil will hold even more carbon in the future.  That's gratis."

They could become a very rich person selling a deal like that.  Don't you think?

It's proven!  Q.E.D.  Let's get the CDM Executive Board to see this and change the rules now.  Chop! Chop!



Regards,

SKB
----- Original Message ----- 
  From: Christoph Steiner<mailto:Christoph.Steiner at uni-bayreuth.de> 
  To: Sean K. Barry<mailto:sean.barry at juno.com> 
  Sent: Saturday, June 02, 2007 11:53 AM
  Subject: Re: Durability of charcoal as carbon sink?


  Dear Sean,

  I got more than 50 answers to my latest post, therefore I need to be
  short. Do you intend to measure CO2 fluxes? If so you need to consider
  that you have quite a big external impact. Soil and charcoal came from
  external sources. Maybe it would be possible to plant in inorganic
  substrate (like it is done in hydroponics). The only organic carbon source
  is the charcoal. This might make it easier to distinguish between the
  different carbon sources.

  Best,
  Christoph


  > Of course those designing an accounting system will want proof that
  > charcoal does keep the sink out of the atmosphere with no significant
  > return through decay or conversion back to greenhouse gases in any way in
  > a time period for which the future value remains significant.
  >
  >
  > Duane
  >
  >
  >
  >


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