[Stoves] biochar in basic soils?

Rolf Uhle energiesnaturals at gmx.de
Fri Dec 14 05:34:50 CST 2012


Thanks Kevin,

for your answer.

I am quite aware of most of these factors and of their interdependance.

That´ s why I ask for practical experience.

Chemistry, soil science and technology are very interesting, but they cannot 
replace the practical, hands on experiments with varying conditions.

Therefore I ask again if anyone has practical experience with biochar 
application on carbonate derivated soils with some loess mixed.

Thanks again and have a nice WE

Rolf 






Am Donnerstag, 13. Dezember 2012, 15:02:18 schrieben Sie:
> Dear Rolf
>   ----- Original Message -----
>   From: Energies Naturals C.B.
>   To: Discussion of biomass cooking stoves
>   Sent: Thursday, December 13, 2012 4:18 AM
>   Subject: [Stoves] biochar in basic soils?
> 
> 
>   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 ?
> 
>   # I would suggest that the reason why your question has not been answered
> already is that it is much more complex than it first appears. # Firstly,
> the method of testing biochar for pH is very important. If a given biochar
> is added to distilled water, and a pH reading is taken, this pH reading
> will probably not be a meaningful indicatior of the degree to which a
> biochar will modify soil pH. For one thing, there may be no indication of
> the quantity of biochar added per litre of water used in teh pH test.
> 
>   # Secondly, the amount of biochar added to a given soil is very
> important. Clearly, the impact of 1 Tonne per HA will be less than an
> addition of 10 tonnes per HA.
> 
>   # Thirdly, the nature of the soil to which the biochar is added will heve
> a large effect on the pH change. A given addition of biochar to a sandy
> soil will have a very much larger effect on pH than would the same rate of
> addition have on a clay soil with a large buffering effect.
> 
>   # Fourthly, the species of material responsible for the pH increase is
> very important. If a soil was basic because of relatively high calcium,
> but was deficient in potassium, a biochar with a high potassium content
> could result in a significant benefit to plant growth, greater than the
> detriment associated with a rise in pH.
> 
>   # Fifthly, the species of biomass and its preparation prior to conversion
> to biochar can be very important. Biochar made from fresh grass and leaves
> would be expected to have a higher pH than would biochar made from leaves
> and grasses that were weathered. Biochar made from de-barked wood would be
> expected to have a higher pH than would biochar made from de-barked wood.
> 
>   Sixthly, the process used to manufacture biochar could have a significant
> effect on its pH. A process with a high yield of biochar may have less
> "free ash" available for changing the apparent pH of the char.
> 
>   Seventhly, post-processing of a biochar can have an influence on pH.
> Biochar that is screened to remove ash would be expected to have a lower
> pH than would biochar that was not screened for ash removal. similarily,
> such screenings would be expected to have a significantly higher pH than
> would the coarser char particles remaining on the screen.
> 
>   There are likely other important factors impacting on the pH effects that
> biochar additions could bring to a given soil.
> 
>   Best wishes,
> 
>   Kevin
> 
> 
>   Rolf
> 
> 
> 
> 
> 
> 
> 
>   Am 13.12.2012 05:10, schrieb Kevin:
>     Dear Tom
>       ----- Original Message -----
>       From: Tom Miles
>       To: biochar-policy at yahoogroups.com ; rongretlarson at comcast.net ;
> 'Discussion of biomass cooking stoves' 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] 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 ; biochar-policy
> 
>         Cc: Alex English ; Kevin Chisholm ; Tom Miles
> 
>         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
> 
>           Cc: Discussion of biomass cooking stoves
> 
>           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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