[Terrapreta] Sustained Biochar
Sean K. Barry
sean.barry at juno.com
Tue Aug 28 11:17:26 EDT 2007
Hi Gerrit,
All plant biomass is things like sugars, cellulose, hemi-cellulose, and lignin, basically carbohydrates. The ratio of # of atoms of carbon-C, hydrogen-H, and oxygen-O; C:H:O, is very close to ~1:2:1, as all carbohydrates are made up of multiples of CH2O molecular constructs.
Charcoal on the other hand is 93-95% pure carbon. It does often times still contain some small amounts (5-7%) of combustible hydrocarbons and carbohydrates. Usually this is called the volatile matter content of the charcoal. The C:H:O ratio in charcoal then is something more like ~95:10:5.
So, where did all the H2O part of the CH2O carbohydrates go? ... from within a "sealed" and pressurized vessel? The hydrogen and oxygen atoms cannot be transmuted into carbon atoms by this chemical process. The answer is, that the hydrogen an oxygen is all still there. It would not surprise me, either, if Dr. Antonietti's reactor did not vent some gases (perhaps CO2, H2, CO, N2, CH4, and O2?) upon opening.
The mass of a single carbon-C atom is 12 atomic units, 1 au for a hydrogen-H atom, and 16 au for an oxygen-O atom. So, in carbohydrates, where ratio of # of atoms, C:H:O is approximately ~1:2:1, then then mass ratio is 12:2:16. Then carbon-C makes up, at most ~40% (12/(12+2+16) = 0.40) of the total mass of any un-pyrolyzed, raw, biomass. It is NEVER possible to convert 100% of the mass of any plant material (biomass) entirely into carbon. 40% is the maximum achievable yield of fixed carbon (on a weight/weight basis) from the conversion of any biomass, regardless of the method used for conversion. Because charcoal is not entirely pure carbon (it contains volatile matter), then the actual maximum yield of charcoal is even less, perhaps 35%.
You might read some of the materials presented on this site my Dr. Michael J. Antal from the University of Hawaii. He has great experience with conversion of biomass into charcoal and he is also Bio-chemist ro a Bio-chemical engineering professor, so he understands and has written much about this subject (charcoal yield from conversion of biomass).
Regards,
SKB
----- Original Message -----
From: Gerald Van Koeverden<mailto:vnkvrdn at yahoo.ca>
To: Sean K. Barry<mailto:sean.barry at juno.com>
Cc: Robert Klein<mailto:arclein at yahoo.com> ; terrapreta<mailto:terrapreta at bioenergylists.org>
Sent: Tuesday, August 28, 2007 6:28 AM
Subject: Re: [Terrapreta] Sustained Biochar
Dr. Markus Antonietti (Max Plank Institute) writes it's just a matter of knowing when to stop the carbonization process. He produces materials that are 100% charcoal from any source of biomass in his steam cooker. I don't see how it would be possible to get a higher yield of charcoal through any other process.
http://www.mpg.de/english/illustrationsDocumentation/multimedia/mpResearch/2006/heft03/3_06MPR_20_25.pdf<http://www.mpg.de/english/illustrationsDocumentation/multimedia/mpResearch/2006/heft03/3_06MPR_20_25.pdf>
Gerrit
On 28-Aug-07, at 1:36 AM, Sean K. Barry wrote:
Hi Gerrit,
I have not heard or read specifically of what you call "hydrothermal carbonization". However, there is a process I read about on Wikipedia once, and in some referenced articles and texts, which might be similar? It is called "molecular de-polymerization" (look it up!) and it occurs as a chemical reaction in biomass, which has been ground up and mixed with water, and brought to a high pressure and high temperature, in a sealed vessel, for a short period of time. The result of the reaction is to turn the "biomass/water soup" in a refine-able bio-oil. There is no release of any "producer gas" with this reaction, I don't think.
It is certainly possible that any chemical reaction which occurs in a "sealed" vessel will not produce any gas phase reaction products, especially if its done under pressure. Even the strictly thermo-chemical process of pyrolysis can be done in such a way that it does not release gases (see the work of Brown et, al., at the University of Iowa and NREL, on the production of pyrolytic bio-oils).
The problem with using these processes that do not produce gases, as I see it, for Terra Preta purposes, is that they also do not produce large amounts of charcoal either. The destructive distillation of biomass which occurs in "hydrothermal carbonization" and "molecular de-polymerization" reactions can reduce a chunk of lignin/hemi-cellulose (wood) into a pool of black oil, without releasing any gases. But, if the biomass moisture content is low enough (<20% m.c. dry basis) to produce charcoal during pyrolysis, then "producer gas" will also be released in the reaction.
So, I would guess that "hydrothermal carbonization" might be an easier way to convert biomass into more usable energy forms (a refine-able bio-oil), but it won't be able to make charcoal from biomass for use in amending soil.
Regards,
SKB
----- Original Message -----
From: Gerald Van Koeverden<mailto:vnkvrdn at yahoo.ca>
To: Sean K. Barry<mailto:sean.barry at juno.com>
Cc: Robert Klein<mailto:arclein at yahoo.com> ; terrapreta<mailto:terrapreta at bioenergylists.org>
Sent: Tuesday, August 28, 2007 12:06 AM
Subject: Re: [Terrapreta] Sustained Biochar
Sean,
Do you have any idea of the production of gases in the process of hydrothermal carbonization which takes place at about 200C? I have just assumed that none would be produced in this process.
Gerrit
On 28-Aug-07, at 12:45 AM, Sean K. Barry wrote:
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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