[Terrapreta] Sustained Biochar

[Sean K. Barry]

Hi Larry,

Conversion of biomass to charcoal in an "open air" retort, depending on conditions of moisture content, pyrolysis temp, and air flow, can retain as much as ~63% of the original carbon in the feedstock (giving ~25% charcoal on a weight of charcoal/weight of of dry feedstock basis).  Usually under best practices, more carbon can be retained in the charcoal, than is released in the exhaust gases.

The critical problem with the "open air" mound or retort is the release of UNBURNED methane (CH4), which can be a relatively small part of the producer gas output and contain a relatively small part of the original biomass carbon.  It not the amount of carbon that is the problem, though.  It is the methane (CH4) molecules that are the problem.  The reaction of burning methane is just

    CH4 + 2(O2) => CO2 + 2(H2O)

One methane molecule is oxidized (burned) with two oxygen molecules producing one carbon dioxide molecule, two water molecules, and heat.  So, when "burned" (or "flared" as it is called), the methane (CH4) puts one GHG molecule (the CO2) into the atmosphere.
This CO2 molecule has no more effect on the atmosphere than any of the other CO2 molecules that would have been released as part of the producer gas "exhaust" output from the pyrolysis reactor.

Left UNBURNED though, that one methane molecule, has a much more potent GHG effect than any single CO2 molecule.  Its GHG effect ranges from over 100 times more potent in the first 20 years to 30 some times more potent 100 years later, on average 62 times the potent than a CO2 molecule.

So, its 62 times more important to NOT release the carbon as methane (CH4), than it is to prevent the release of carbon as CO2 molecules.  If you retain 60% of the carbon in the charcoal and the rest goes into the air as CO2, then you will have taken more CO2 out of the atmosphere than would be released.  The exhaust gas CO2 would contain only 40% of the original carbon

Producer gas is roughly 20%-H2, 20%-CO, 10-15%-CO2, 40%-N2, 2-3%-CH4, plus some <<1% trace gases.  The 40% of the biomass carbon which is released in the producer gas, goes into 3 molecules CO, CO2, and CH4, in the ratio #CO:#CO2:#CH4 of 20:15:3.
So the methane can contain ~3-4% of the original biomass carbon, 40% x (3/(20+15+3)) = 40 x (3/38) = ~3-4%

3% x 62 = 186%!,   4% x 62 = 248%

So, this shows that the detrimental effect of releasing unburned methane(CH4) is 3 to 4 times (186%/60% to 248%/60%) the beneficial effect of storing all of the charcoal that could possibly be produced into the soil.  And, it would only reduce to being only this bad of a thing to do after 50-75 years!

The lesson for anyone making a "simple" charcoal retort is to BURN the or "Flare Off" the producer gas any way possible.


Regards,

SKB

  ----- Original Message ----- 
  From: Larry Williams<mailto:lwilliams at nas.com> 
  To: Adriana Downie<mailto:adriana at bestenergies.com.au> 
  Cc: Miles Tom<mailto:terrapreta at bioenergylists.org> 
  Sent: Tuesday, August 28, 2007 11:02 AM
  Subject: Re: [Terrapreta] Sustained Biochar


  Adriana, Terra Preta list members and my local Soil, Plant and Water list-------Earlier this year Rich and I posted pictures of our attempt to make charcoal. At that time I did not appreciate the significant increase of the greenhouse gases over the capture of carbon in producing charcoal. When I look at common practices in managing vegetation in the Pacific NW (the area that I am most familiar with) the scope of societal change to reduce the release of CO2 or CH4 boggles my mind. Know that I have had open fires my entire life the same as the society around me. 


  If the experiment to produce charcoal, that Rich and I accomplished, released more carbon to the atmosphere than it captured, at least, we captured some of the carbon. I admit that we could do better and will capture more of the carbon as we learn how to do that. Do pay as close attention to other sources releasing CO2 and CH4 also. If we need to get on our soapboxes to voice objections to societal releases of greenhouse gases, I am there on that box.


  Washington State Department of Natural Resources is about to burn debris from clearcut logging practices. In our locale, they would be a good place to begin the change of societal habits towards more responsible management of carbon. In the process of using charcoal as a soil amendment for growing more food and the sequestering of atmospheric carbon we cannot expect the largest producers of greenhouse gas to alone make a difference. Non-point pollution or rather very small point sources of pollution cannot be overlooked either, i.e. individual management of carbon.


  If a Douglas fir tree grows to maturity and the stump rot in place, it has the potential to be alive for close to seven hundred years and decompose over the next five to six hundred years. It has the potential to grow to a height of 200 feet. The accumulation of carbon grows and then is gradually released. If that same tree is used for lumber then the capture of carbon is released at a much faster rate. There are very few remaining homes that have any old growth lumber in them in the one hundred and thirty years of local logging. A good portion of that carbon has been released.


  Small Doug fir trees, as they are called, that don't make it to the saw mill are currently chipped in tub grinders (a hammer knife process) which will release carbon (rot) within ten years. Even old growth Doug fir stumps, trees cut one hundred years ago which are as solid as rock (so to speak) with pitch with hundreds of years of carbon storage remaining, when placed in a tub grinder will last as splinters for only ten years. Then if you consider Doug fir, any aged tree, cut for firewood then the release of carbon is immediate. Burning wood in open fires is what this culture is made of. I dare say that it is an addiction so the resistance to change will be hard to overcome. It is easy to see the different rates of carbon release. These releases are management decision. Most people and government do not appreciate the need for change.


  Carbon management is the focal point if we are not going to "crisp up" the only blue-green globe that we have found in the universe. I note that my personal universe has change from my hometown as a child to this blue-green globe in my life. I am a plant person as a landscaper and manage plant growth.


  The concept of Terra Preta has fascinated me for several years now and have witnessed some very significant changes, I believe, in plant growth in my garden and some very interesting, isolated, black soil associated with buried old growth Doug fir roots. These experiences have led to my acceptance of Terra Preta de Indio and to the possibility that black earth can occur as a result in other conditions also. 


  This is off the topic of managing carbon but then again there may be other conditions that increased soil fertility in a process similar to Terra Preta.


  As serious as open burning and making mound-fired charcoal are for the creation of greenhouse gases, the pyrolysing of wood needs, in my opinion, to be common event for the fields and the gardens. The process needs to be simple and effective at capturing carbon if used by the majority of the population to reduce greenhouse gases. An industrial process for making charcoal will not work for people who have little money. This likely includes many farmers in the western culture and what of farmers around the world?-------Larry






  P.S. The small retort that I am using captures carbon in the form of charcoal and wood condensates. With a little more work the remaining smoke will be burnt. At what point is more carbon captured than released?















  ------------------------------------------- 

  On Aug 27, 2007, at 10:47 PM, Adriana Downie wrote:


    Rich,

     

    Please go back and read Seans post. You are better to burn to CO2 than pyrolysis and release syngas. I think that promoting small scale pyrolysis is going backward and gives fuel to the sceptics.

     

    Adriana. 

     

    -----Original Message-----
    From: Richard Haard [mailto:richrd at nas.com<mailto:richrd at nas.com>] 
    Sent: Tuesday, 28 August 2007 3:21 PM
    To: Adriana Downie
    Subject: Re: [Terrapreta] Sustained Biochar

     

    Adriana

     

    Yes but ---- When neighbors on both sides are burning debris and logging operations on ridge 3500 feet above us are burning slash what is the big deal with making some charcoal for your own curiosity on the effects of charcoal in your garden and to make a convert who in the long term may help to educate others about the benefits of sequestering carbon on a larger scale if and when such charcoal  and charcoal making equipment becomes available on the market.

     

    Rich H

    On Aug 27, 2007, at 10:10 PM, Adriana Downie wrote:





    Thanks Sean,

     

    This is a very important point that really needs to be well understood. Those who are making char in a 44 gallon drum in the back yard and putting it on the vege garden are not doing the planet any favours. What is more, they are not doing themselves any favours either because not only do traditional methods have Greenhouse effects which far out weigh the benefits of sequestering char in soil they also have severe human health impacts which far out weigh any social benefit from improved agricultural yields. Particulate emissions are often the overwhelming detrimental effect when environmental LCAs are done, it is essential to manage these if this technology is to be of any benefit. No good saving the planet from global warming if in turn we give everyone respiratory diseases.

     

    Regards,

    Adriana Downie

    BEST Energies Australia

     

    -----Original Message-----
    From: Sean K. Barry [mailto:sean.barry at juno.com<mailto:sean.barry at juno.com>] 
    Sent: Tuesday, 28 August 2007 2:46 PM
    To: Robert Klein
    Cc: terrapreta
    Subject: Re: [Terrapreta] Sustained Biochar

     

    Hi Robert,

     

    I don't know where you get the information for your postings.  It seems sheer speculation.  Is it?  Isn't it?

     

    Making charcoal in earthen mounds will NOT reduce the global warming effect of green house gases (GHG).  This happens because all of the charcoal (~93-95% carbon) that could be sequestered into soil, rather than being released as CO2 (a complete combustion product and a GHG), still CANNOT reduce away the effect of releasing the even 2-3% methane (CH4), during the charcoal making process.  Open air charcoal kilns will release more GHG and exacerbate the global warming problem.  This will happen even with all the benefits that could be derived from burying the charcoal.  You will get reduced atmospheric CO2, but also increased atmospheric methane (CH4), by making charcoal this way.

     

    This is a critically important fact.  Ask any bio-chemist?  It will not be disputed.  Charcoal for "Neo Terra Preta" must be made in sealed reactor and the producer gas should not be released to the atmosphere like exhaust, or smoke.

     

    The producer gas from a pyrolysis of biomass reaction contains 1) complete combustion product gases; CO2, H2O, 2) combustible fuel gases; H2, CO, CH4, 3) inert + trace gases; N2, O2, Argon, etc., and 4) some suspended, vaporized, tars (longer chain hydrocarbons and carbohydrates, like ethane gas, methanol,  and acetic acid.  All together the "producer gas" can have an energy content of ~200-300 BTU/Nm^3).  The higher BTU density gases come come from low temperature pyrolysis (with very limited oxygen and lots of added heat).  These gases are rich in methane (CH4) and longer chain hydrocarbons.

     

    One molecule of methane (CH4) has a GHG equivalent effect the same as 62 molecules of CO2!  This is a startling fact.

     

    If open air pyrolysis retains as much as 25% of the original carbon in the biomass, then 75% of all of the carbon from the biomass is expelled from the reactor into the producer gas, as part of both carbon monoxide (CO - ~20% of producer gas) and carbon dioxide (CO2 - ~10-15% of producer gas) gases.  Burnt or simply released, it is still 75% of the carbon from the biomass goes into the atmosphere.  Because of the potency of methane (CH4) as a GHG, it is far worse to release methane (CH4), than it is to burn it;

     

        CH4 + 2(O2) => CO2 + 2(H20)

     

    Rich BTU producer gas contains ~3% methane (CH4), so the producer gas contains only ~10-11 times as many carbon containing molecules  as methane molecules (CH4), (~0.30-0.35/0.03) = ~10-11.  The charcoal contains 1/3 the amount of carbon (25%/75%) as the gas; so the number carbon atoms in the charcoal compared to the number of methane (CH4) molecules is ONLY (((~0.30-0.35+0.03)/3)/0.03) = ~4:1.

     

    RELEASING THE METHANE contained in the producer gas (unburned), then has the same effect on the atmosphere as releasing 15 TIMES AS MUCH CARBON AS THERE IS IN ALL OF THE CHARCOAL YOU COULD POSSIBLY BURY (62/4 = ~15)!

     

    The point is then, that open air charcoal kilns CANNOT make charcoal fast enough without making the atmospheric GHG conditions worse even faster.  It is absolutely imperative the charcoal making devices should be "sealed" and the producer gas should at minimum be "flared" off, or the fuels it contains completely combusted and the resultant energy used.

     

    Any simpler just make charcoal out in earthen kilns plan will poison the atmosphere even faster than doing nothing, so we might cook the planet well before we could realize any of the agricultural benefits of putting charcoal into the ground.

     

    Regards,

     

    SKB

     

     

      ----- Original Message ----- 

      From: Robert Klein<mailto:arclein at yahoo.com> 

      To: terrapreta at bioenergylists.org<mailto:terrapreta at bioenergylists.org> 

      Sent: Monday, August 27, 2007 3:15 PM

      Subject: [Terrapreta] Sustained Biochar

       

      I cannot help but think that the methods used to
      produce the black soils must be self sustaining and
      indigenous to the farm itself.  I also see the use of
      fairly large pieces of charcoal that will be difficult
      to pulverize properly.  Remember that grinding has a
      natural sizing limit, past which a great deal of
      effort is needed.

      Without question the use of corn stover to build
      natural earthen kilns is a great solution when we are
      relying on hand labor alone.

      See:http://globalwarming-arclein.blogspot.com/2007/07/carbonizing-corn-in-field.html<http://globalwarming-arclein.blogspot.com/2007/07/carbonizing-corn-in-field.html>

      We also can conclude that corn stover is the best
      available source of large volume biochar. It needs to
      be central to any program simply to ensure 100%
      coverage of the fields with sufficient biochar.

      Is there a way to do this in the field with equipment?

      Let us return first to best hand practice. From there
      we can speculate on how this can be made easier with
      power equipment.

      We do not know how the Indians in the Amazon did this
      but we certainly know how they grew corn everywhere
      else.

      In North America, they used a trinary system.

      That meant that they cleared a seed hill, likely two
      plus feet across, perhaps slightly raised, in which
      they planted several corn seeds and also several
      beans.  These hills would have been at least two feet
      apart.  this means that twenty five percent of the
      land was been cropped in this way.  They also planted
      every few hills a few pumpkins.  This provided ground
      cover for the seventy five percent of the land not
      been directly cropped.

      An interesting experiment would be to now grow alfalfa
      in between the hills in order to fix nitrogen and
      provide a late fall crop.  It unfortunately would
      likely take too much water.

      This Indian system is ideal for hand work and for the
      production of terra preta by hand.

      In September,after the corn,beans, and pumpkins are
      picked, it is time to remove the drying corn stover
      and bean waste.  The pumpkin waste will be trampled
      into the ground fairly easily by now.

      Hand pulling the stalks from one seed hill gives you a
      nice bundle to carry off the field to where a earthen
      beehive is built for the production of Terra preta.

      How do we accomplish the same result with the use
      equipment is a difficult question.  Using a stone boat
      or wagon is obvious.  A hydraulic grabber of some sort
      to pull the bunch associated with a hill would be very
      helpful.  Tying the bundles would also be helpful.

      This would allow two workers to clear a larger field
      quite handily.

      After the earthen field stack is set up, the rest is
      fairly simple.  A wagon full of biochar is taken to
      the field and each hill is replenished with biochar
      before planting.  Still a lot of labor but much easier
      than the most basic system.

      To do this with row agriculture will mean the creation
      of some fairly complex lifting and baling machinery. 
      At least we are on the right track.





             
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