[Terrapreta] Sustained Biochar
Gerald Van Koeverden
vnkvrdn at yahoo.ca
Tue Aug 28 07:28:52 EDT 2007
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
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
> To: Sean K. Barry
> Cc: Robert Klein ; terrapreta
> 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
>> To: 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
>>
>> 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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