[Stoves] biochar in basic soils?

Anand Karve adkarve at gmail.com
Sat Dec 15 06:31:45 CST 2012


Dear Rolf,
I live in a region having vertisol soils, having pH >8.5. I must have
tested biochar at least 10 times, and never got any positive results.
Yours
A.D.Karve

On Thu, Dec 13, 2012 at 1:48 PM, Energies Naturals C.B. <
energiesnaturals at gmx.de> wrote:

> Hallo all,
>
> this is a question I have asked quite often, but perhaps never on the list
> .
>
> Whenever I read about the benefits of biochar, it is almost always in
> relation with distinctively acid soils.
>
> Does anyone know the effect of biochar, itself beeing mostly basic, on
> already basic soils ?
>
> Rolf
>
>
>
>
>
>
>
> Am 13.12.2012 05:10, schrieb Kevin:
>
> Dear Tom
>
> ----- Original Message -----
> *From:* Tom Miles <tmiles at trmiles.com>
> *To:* biochar-policy at yahoogroups.com ; rongretlarson at comcast.net ; 'Discussion
> of biomass cooking stoves' <stoves at lists.bioenergylists.org>
> *Sent:* Wednesday, December 12, 2012 2:18 AM
> *Subject:* Re: [Stoves] [biochar-policy] Re: Equipment required for
> testingstoves
>
>  Charcoal burns in direct contact with air well above 600 C so any fire
> at the charcoal stage would be above 500-600C.
>
>
>
> # There are two issues here:
>
> 1: The temperature at which charcoal burns
>
> 2: The average temperature experienced by the charcoal remaining after it
> was produced.
>
> Certainly, charcoal can burn at temperatures well above 600C in air.
> Surface temperatures of burning char can be very different than the core
> temperature.  Consider a flash fire, with high surface temperatures for a
> short time. Core temperatures of the wood or char remaining can be very
> much lower. This is a very complex heat transfer problem... unsteady state
> three dimensional heat transfer to bodies of irregular shape, with change
> in phase. What is important is the properties of the "unburned charcoal"
> remaining for potential use as biochar.
>
>
>
>  Higher temperature oxidized chars have great adsorption properties. They
> compost readily. Great way to make terra preta.
>
>
>
> # Certainly, such "designer chars" could have very superior properties,
> but at greater cost.  The "bottom line" for the Farmer or Grower is the
> "Benefit/Cost Ratio." Additionally, there may be special soil conditions
> that such "designer chars" can handle better than "regular biochar" that
> works adequately well for most common soil conditions.
>
>
>
> Best wishes,
>
>
>
> Kevin
>
>
>
> Tom
>
> *From:* biochar-policy at yahoogroups.com [
> mailto:biochar-policy at yahoogroups.com <biochar-policy at yahoogroups.com>] *On
> Behalf Of *Kevin
> *Sent:* Tuesday, December 11, 2012 8:18 PM
> *To:* rongretlarson at comcast.net; Discussion of biomass cooking stoves;
> biochar-policy
> *Cc:* Alex English; Tom Miles
> *Subject:* [biochar-policy] Re: [Stoves] Equipment required for testing
> stoves
>
>
>
>
>
> 
>
> Dear Ron
>
>  ----- Original Message -----
>
> *From:* rongretlarson at comcast.net
>
> *To:* Discussion of biomass cooking stoves<stoves at lists.bioenergylists.org>;
> biochar-policy <biochar-policy at yahoogroups.com>
>
> *Cc:* Alex English <english at kingston.net> ; Kevin Chisholm<kchisholm at ca.inter.net>; Tom
> Miles <tmiles at trmiles.com>
>
> *Sent:* Tuesday, December 11, 2012 2:09 AM
>
> *Subject:* Re: [Stoves] Equipment required for testing stoves
>
>
>
> Lists (adding biochar-policy also), Kevin, Alex,  Tom  (who I add, because
> he speaks Portuguese and might have caught an answer when we were in Manaus
> a few years ago)
>
>    See below
>
> *From: *"Kevin" <kchisholm at ca.inter.net>
> *To: *"Discussion of biomass cooking stoves" <
> stoves at lists.bioenergylists.org>, "Alex English" <english at kingston.net>
> *Cc: *"Discussion of biomass cooking stoves" <
> stoves at lists.bioenergylists.org>
> *Sent: *Monday, December 10, 2012 8:24:34 PM
> *Subject: *Re: [Stoves] Equipment required for testing stoves
>
> 
>
> Dear Ron
>
>
>
> Would you agree that the Amazonians made Terra Preta with low temperature
> char?
>      *[RWL1:  I think others may have an answer - maybe based on
> spectroscopy.  I will start looking but don't know that field well enough
> to know what others may have concluded about these ancient soils.  I fear
> that 500 years (minimum) in soil may hide the initial character that we can
> readily see in a University setting.  I know from being in several
> Amazonian biochar "pits" that it is pretty hard to find a piece big enough
> to test.  I think it entirely possible that char left over from simple
> three-stone fires could have been made at 500-600 C (or higher).  Would you
> call those temperatures high or low?] *
>
>
>
> *# KC1: Obviously, I am speculating, but I would speculate that Terra
> Preta was made with charcoal from a number of sources:*
>
> *1: Char residue remaining after charring or burning  of "wood waste from
> initial jungle clearing.*
>
> *2: Char residue remaining from charring or burning of agricultural waste
> and weeds*
>
> *3: Char and ash residue from cooking fires and possibly smudge pots*
>
> *4: Organic fertilizer supplements, from humanure, composted food scraps,
> and probably dredgings from oxbow lakes.*
>
> *I would consider 500-600 C to be a "low temperature char." I haven't
> seen any references to the existence of bellows technology in ancient
> Amazonia, that would be necessary to produce significantly higher
> temperatures.*
>
> *It is likely that the Amazonian Terrapretians would have quickly noticed
> if such low temperature char additions to their agricultural practises were
> causing poor results. If that was the case, they likely would have taken
> steps to avoid application of char to fields. They would be looking for
> short term benefits or harm. Given that they used char on a widespread
> basis, and that it was basically low temperature char, it would thus seem
> that Terra Preta worked with low temperature char, and it worked relatively
> quickly, not requiring an aging period of several years.*
>
>
>
>
> If so, are there any test results to show that an "intermediate
> temperature char" would give better results than the "low temperature char?"
>       *[RWL2:  I think that people like Dr. Johannes Lehmann and Evelyn
> Krull may be getting to an answer for some specific soil and species.  I
> keep looking for it.
>      My note below to Alex was to make it easier for users to know what is
> being used  Some of my favorite biochar scientists like Drs. Julie Major
> and Christoph Steiner were forced to use char bought off the side of a
> remote Amazonian road.
>        I haven't seen any data emphasizing tests with a range of
> temperatures.   Drs. Stephen Joseph (low) and Hugh McLaughlin (high)
> recommend different temperature regimes.]  *
>
>
>
> *#KC2: Is it perhaps likely that "basic low temperature biochar" is good
> for general agricultural applications, but that intermediate and high
> temperature chars may be better for addressing special agricultural
> problems. *
>
>
>
> I seem to recall that "high temperature char" and/or "activated char"
> gives inferior results in a biochar application.
>      *[RWL3:  How about giving a cite for that?] *
>
>
>
> *#KC3: Unfortunately, I cannot point to a specific cite.*
>
> Does this impression make sense to you?
>     *[RWL4:  No - certainly not as a universal truth/] *
>
>
>
> *#KC4: Universal truths are scarce and hard to find. :-) If you put
> yourself in the circumstances of an Amazonian Terrapretian of 3,000 years
> ago, what would you do differently?*
>
> If so, is there a "preferred char making temperature range"?
>     *[RWL5:  I am sure that it depends a lot on the intended recipient
> soil - and probably on the plant species.  #KC5:1 Certainly! Jungle woods
> can vary in density from balsa at about 10 lb/cubic foot, to Lignum Vitae,
> at about 68 pounds per cubic foot.*
>
>
>
> *My focus in this exchange below with Alex is to give soil researchers
> and stove users a better idea of even getting close to knowing what char-T
> they are using. *
>
> *#KC5:2 Char making temperature is easy to determine. It should thus be
> very easy to determine the importance, or lack thereof, of char making
> temperature. It would be very good to know this, to reduce variables in a
> test analysis.*
>
>
>
> * There is a good bit of information out there relating pH to production
> temperature - but pH also depends on fuel size and ash content and pH
> changes over time.   Who knows what else leads to a "preference"?
>      And we also hear from Dr.  Spokas that what happens after char
> production is maybe as much or more important.   I think it is absolutely
> amazing that we hear so many good reports (and few bad reports) when we
> know so little even about the char-production temperature - and even the
> wood species, etc, etc, etc.    Ron] *
>
>
>
> *#KC: With that many "good reports" and so few "bad reports", and with so
> many char variables, this would tend to downplay the importance of char
> variables. The "bad reports", presuming that they were competently done,
> could provide very important insights into what works, and what doesn't.*
>
>  Best wishes,
>
>
>
> Kevin
>
>
>
> Best wishes,
>
>
>
> Kevin
>
>  ----- Original Message -----
>
> *From:* rongretlarson at comcast.net
>
> *To:* Alex English <english at kingston.net>
>
> *Cc:* Discussion of biomass cooking stoves<stoves at lists.bioenergylists.org>
>
> *Sent:* Monday, December 10, 2012 9:46 PM
>
> *Subject:* Re: [Stoves] Equipment required for testing stoves
>
>
>
> Alex:
>
>   Thanks:
>
>   I see only a few remaining questions related to the thermocouples.  My
> interest is only in being able to report to the soil scientists the
> temperature at which the char was produced.
>
>     Q1.  I think we should be able to say that a time average of a central
> thermocouple measurement showing a slight drop over time of the highest
> numbers is a pretty good estimate - that could be reproduced for "any"
> similar "flaming pyrolysis" approacd.  The properties (pH, surface areas,
> labile component, etc) of such char should be compared  (a Master's
> thesis?) with char produced via other means.  I think Nat Mulcahy's
> non-flaming pyrolysis approach can produce varying temperature char.  An
> all-electric heating approach in any oxygen-free environment , operated at
> different temperature should also be used to compare the char properties
> with those from stoves.  Maybe that data is already out there??
>
>    Q2.  I think there could be some influence of the initial fuel moisture
> content.  Do you (anyone) have an opinion on that?   I am trying to avoid
> having to always measure temperatures, but still be able to give an
> indication of the "likely" char temperature, by knowing how long a specific
> volume or weight of fuel lasted.
>
>    Q3.   I wonder if the char temperature as measured by a thermocouple
> system like yours would also be a function of the fuel itself  (species,
> characteristic size, shape, etc.)
>
>    Q4.  I am pretty sure that the top and bottom char will be
> significantly different in a typical cooking cycle, where a very high flame
> temperature is desired at first (affecting only the top part of the fuel
> load), and then a much lower temperature desired later (affecting only the
> lowest portion of the fuel load).   My question, for anyone, is whether an
> average temperature is at all valuable, if the average (obtained from the
> total duration of the pyrolysis) covered a wide range of production
> temperatures.  Actually I have heard so many different opinions on the best
> production temperature - maybe a mixture of char temperatures might be an
> advantage.  Thoughts?
>
>
> Ron
>
>  *From: *"Alex English" <english at kingston.net>
> *To: *rongretlarson at comcast.net, "Discussion of biomass cooking stoves" <
> stoves at lists.bioenergylists.org>
> *Sent: *Monday, December 10, 2012 4:38:56 AM
> *Subject: *Re: [Stoves] Equipment required for testing stoves
>
> Ron,
>
> On 09/12/2012 8:33 PM, rongretlarson at comcast.net wrote:
>
>  Alex etal
>
>   Thanks for the cite.  I think I understand most of the plot - which was
> of amazing duration!.   I am especially amazed at how uniform (and high)
> the flame temperature was in the late time plot, even as the other plots
> were dropping.
>
> It is a very steady gas producer. Conditions are constant except for the
> distance and path composition between the pyrolysis front and the burner.
> If it can be done over 100cm then why not 200 or 300.
>
>       a.   Since you have this one from 2000, you probably have quite a
> few more - from which I/we might extract a good bit more information/  Any
> other similar plots around that you can post?
>
> No I don't.
>
>
>      b.   I am surprised that the "pyrolysis gas temperature" was so much
> lower than the temperature of the char. Where was the probe for this
> measurement - and had there been some mixing of secondary air at this
> point?
>
> No mixing of secondary air at that point. That occurs in and above in a
> 5cm burner mixing pipe.  The tmperature difference is largely due to the
> nature of unshielded thermocouples in gas.For the most part thermocouples
> radiate away heat according to the temperatures of the surfaces that make
> up the sphere around them. A thermocouple buried in the pellets that are
> all carbonizing at 700C will give a fairly accurate measurement. A
> thermocouple in the gas above the top of the pellet bed will radiate to the
> pellet bed and, in this case the uninsulated container walls. The more that
> pellet bed shrinks the larger the portion of the radiant sphere that is the
> cool container walls. The larger the thermocouple, the greater the radiant
> cooling , the lower the measurement. The higher the temperature the greater
> the radiant loss, to the forth power. All the gas is also radiating and
> convecting heat to the container walls. So there are two reasons for a slow
> drop in gas temperature, and one reason for not trusting either. The same
> holds true for the absolute value of  post combustion measurement.
>
> There are gas-*aspirated pyrometers which shield a thermocouple with
> ceramic layers that approach gas temperatures and give better numbers. We
> will soon be using an 10 footer to probe the chain grate stoker gasses in
> carbonizer- pyrolysis-gasifier mode.*
>
> *Grate fun.*
>
>
>      c.  What is the present disposition of this equipment?
>
> Its in the recoverable bone yard. I should have shown it to Crispin when
> he was here.....or perhaps not:)
>
> Alex
>
>
> Nice work
>
> Ron
>
>
>
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-- 
***
Dr. A.D. Karve
Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)
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