[Terrapreta] What does Carbon Sequestration really mean?

[Sean K. Barry]

Hi Joe and 'terrpreta' listers, et al,

Yes, I think it is an equilibrium issue, too.  I believe that the the overall flux of carbon to/from the atmosphere and carbon from/to the living organic plants and animals on and in the soil is something which must already have reached its equilibrium some time ago.
The human activity component now of pumping CO2 into the atmosphere at a rate of 6 GT/year is not part of the equilibrium flux.
It is unnatural doing things like burning fossil fuels and degrading soil by killing the active microbes, plowing open fields of dead, decomposing matter, planting only food crops in so much land, and killing away the weed pests.  It is an outside force.  

Nature cycles an estimated 120 BT of carbon in/out of the atmosphere every year by itself.  Humans now throw up 5% more of that into the atmosphere every year!

Hysteresis is ...

hys·ter·e·sis  
      1. the lag in response exhibited by a body in reacting to changes in the forces, esp. magnetic forces, affecting it. 


We are seeing now, affects in the atmosphere, which are the results of this Human pump of carbon into the atmosphere.
Even if we can "sink" carbon at the crazy fast rate of 6 billion tons of carbon per year, it still looks like the results of that kind of activity will only begin to effect the atmosphere some 3 to 5 generations out (~150) years.  Paltry half measures or small fractional measures will only produce effects even further out.

But, the natural system will probably try to re-achieve the "equilibrium state" it was in (before the human push) or adjust itself to live another way modifying itself to the new "equilibrium state".  The concentration of GHG in the atmosphere is just part of the "equilibrium state", but it has a duration of hysteresis that humankind just has not dealt with much before.

To your question, Joe.  No, I do not equate charcoal carbon (more atomic carbon) with organic carbon in soil.  I do think charcoal is far more resilient in soil than organic carbon.  Organic carbon is carbon combined into complex molecules like carbohydrates.  Carbohydrates are the food source for most animals, insects, and microbiology in the soil.  This Kingdom of living things has a very well developed ability to decomposed organic carbon and harvest the chemical energy that is stored in the molecules.  This does not appear to be so true of more pure atomic carbon, like is found in charcoal.  I think this perhaps explains the resilience of charcoal in soil.

What I was trying to express, is that the existence of carbon in the soil, in the form of charcoal, seems to promote both soil microbes and plants.  This is some of what we talk about in on this list.  It is our hope that this can be demonstrated as true.  We want to believe this, so we can reap the benefits to agriculture from its reality.

Carbon in the soil seems to sort of "juice up" the normal cycling of carbon that the Biosphere already does.  This cannot be true of fossil carbon.  Fossil carbon lies well below the "living soil" zone.  It is in the very deep subsoil and it could not have the chance to make this "juicing up" occur.

The mere presence of carbon in the active living soil, will in my opinion, only raise the cycling number.  The Biosphere will begin to cycle more than 120 billion tons of carbon into and out of the atmosphere every year.  We may not see a reduction in the atmospheric levels of CO2, either.  Along with the increased cycling, there may just be a higher average concentration of CO2 in the atmosphere.  It seems like the increased presence of carbon, in any form, in the "living zone" (the Biosphere) will act like a positive feedback.
The increased levels of carbon will spread throughout the system, raise the concentrations everywhere, and keep them higher.

Raising temperatures are another positive feedback, too.  As they rise, decomposers will act more quickly.  As they rise, areas formerly of short growing season will begin to have longer growing seasons and more plant productivity.  Everything will again, begin to get "juiced up" more.

I hope someone can see what I am saying here.  I have struggled to make this message understood.  I think what it means is that we really need to understand what is means to really "Sequester Carbon".


Regards,

SKB

  ----- Original Message ----- 
  From: joe ferguson<mailto:jferguson at nc.rr.com> 
  To: Sean K. Barry<mailto:sean.barry at juno.com> 
  Cc: Kevin Chisholm<mailto:kchisholm at ca.inter.net> ; terrapreta<mailto:terrapreta at bioenergylists.org> 
  Sent: Saturday, September 22, 2007 3:21 PM
  Subject: Re: [Terrapreta] What does Carbon Sequestration really mean?


  This is an equilibrium issue, and since it results from a dynamic process, the time scale must be cranked into the calculation.

  Fro annual crop like corn/maize, the time scale is of the order of a year, and we'll hardly see a measurable impact on atmospheric CO2 concentrations.  For forest new growth starting from worn-out farmland. the time scale would be centuries, and we might possibly see an impact.  For carbon sequestered in the style of terra preta, the time scale is apparently on the order of at least millennia.  And since we seem to have got into the current difficulties within the past two centuries, I would believe that a partial solution with millennia time scales looks quite attractive.  So a recurring process of sequestering a goodly portion of the product of an annual crop, carried out for millennia, should have quit a cumulative impact.

  And a question:  When you use the phrase "carbon in the biosphere", are you assuming that atomic carbon within the root zone is somehow equivalent to organic carbon in the same place?

  Sean K. Barry wrote: 
    Hi Kevin & the terrapreta list,

    This discussion we all have been having about increased plant growth with increased CO2 concentration and the supposed increased microbial growth with charcoal in the soil, etc. has had me thinking very hard this morning.   I've been digging a trench out in the yard for four hours now.  Its amazing what looking at dirt and mud and rocks can do for cerebral activity.

    What I have been pondering is how Terra Preta could possibly do anything to change the CO2 concentration in the atmosphere.
    I've spent some time in these recent few days, typing postings to this list, trying to say that I do not think increased plant growth is going to reduce atmospheric CO2 levels.  Plants grow faster with higher CO2 concentrations.  I knew this.  I agreed with this when people were trying to beat me over the head about it.  Nonetheless, even with all the increased growth that increased CO2 concentration in the atmosphere could bring, I do not see that it can reduce the atmospheric concentration of CO2.  Plants live finite lives.  Then they decompose.  Decomposers expire CO2.  Decomposition of a living tree occurs at a higher rate than a tree grows.
    Ergo more outgo.  Get it?

    Focus for a bit on an observation that the living ecology of plants, animals, microbes, and soil actually expires CO2 into the atmosphere as well as inspires it.  There is a graph of continuous atmospheric CO2 readings.  It has been made rather famous by Al Gore, in his movie, "An Inconvenient Truth".  One of his college professors had started and been recording atmospheric CO2 levels since some time in the early 60s.  The graph has a SAWTOOTH appearance and an overall rising slope.  The sawtooth is clear evidence that the influx and outflux of CO2 to/from the atmosphere follows a seasonal pattern.  He said this in the movie.  Brian and Jon have both pointed out recently, that CO2 probably cycles diurnally as well.  The rising slope of the graph indicates that there is more carbon in the atmosphere than there was previously.  Feel free to argue any of these points with me.

    CO2 is part of the living respiration of the Earth.  If there is more carbon available to the living Bipsphere, then I think the concentrations of carbon in ALL parts of the overall system will increase.  The living systems just kind of push carbon around, passing it in and out of the atmosphere.   Plants are always performing photosynthesis in the spring and early summer, combining CO2 and H2O, with energy from the sunlight, to get at some of that energy, and they build carbohydrate structures (made with carbon bearing molecules) to get at more of that energy.  They slow at this in the fall and winter, releasing CO2 and/or not inspiring so much as at other times.  Animals and microbes are always pulling off the energy that is carried in complex carbon bearing molecules.  We all eat carbohydrates and expire CO2.  Humans "burn" hydrocarbons and expire CO2, also.

    Now, I come to something Kevin Chisholm said some time ago.  He was saying that carbon has to be removed from the Biosphere in order to be sequestered.  I hope this is an acceptable paraphrasing of your statement, Kevin?  I understood this to mean that carbon could not be sequestered, if it was still somehow involved in the living systems.  In light of this recent discussion about CO2 off-gassing by soil fauna and animals and CO2 uptake (and/or off-gassing) by flora, I have begun to believe that we cannot just invest carbon (in the form of charcoal) into living soil, and hope that it will somehow reduce atmospheric concentrations of CO2.

    It may force carbon to reside for a while in soil, but the overall affect of TP soil to increase both plant growth and soil microbiological growth, may not necessarily change the flux of carbon into/out of the atmosphere.  It is not absolutely clear, either, that charcoal stays permanently in the soil.  It seems to have a much longer half-life in soil than carbohydrates, though.

    Fossil carbon fuels are the difference.  The carbon they contain (in complex hydrocarbon molecules) had once been in the Biosphere.
    Fossil fuels are fossils of plants that grew on the Terra Firma once.  But, they have been buried, very deep, in the subsoil, below the livng soil, and out of the living Biosphere for a very long time (circa 300 million years).  Does everyone realize that humans have actually SET the half-life of fossil fuel carbon in the ground at circa ~300,000,150 years?!  Here it is now, with us and the rest of the animals and the plants, up here, above the lifeless subsoil ground, and all participating again in the global climatic cycling of carbon.

    Methinks, that putting it only as deep as Terra Preta, only as deep as the living part of the soil, IS NOT going to change the concentration of it in any part of the living Biosphere.  The living soil and the atmosphere, and the plants and animals are all part
    of the Biosphere together.  The carbon concentrations are up.   They are likely to increase everywhere.

    We CANNOT "Sequester Carbon", if we sequester it where there is life.  This is just my considered opinion.  You people can kick it all apart, as many of you are want to do.  This realization of mine has diminished my enthusiasm somewhat for Terra Preta.
    I hope to hell someone soon will be able to prove that Terra Preta soils do not need as much fertilizer as other soils to grow productive crops.  This may be its only redeeming value.  I am retracting my staunch statements of belief that Terra Preta can "Sequester Carbon".  I don't believe it can provide "carbon negative" energy, either.




    Regards,

    SKB
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