Good question Rolf
I believer there has been little done with it. I have posited the same question
in the past as places like the Marshall Islands have nothing but
soils based on corals and coraline algae and dressing of humus topsoils built
up over the years. Biochar and even charcoal seem to help
I have been supplimenting small raised beds on an off for several year and it
seems good.
Michael N Trevor
Majuro
Marshall Islands
----- Original Message -----
From: Energies Naturals C.B.
To: Discussion of biomass cooking stoves
Sent: Thursday, December 13, 2012 8:18 PM
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 ?
Rolf
Am 13.12.2012 05:10, schrieb Kevin:
Dear Tom
----- Original Message -----
From: Tom Miles
To: [email protected] ; [email protected] ;
'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: [email protected]
[mailto:[email protected]] On Behalf Of Kevin
Sent: Tuesday, December 11, 2012 8:18 PM
To: [email protected]; 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: [email protected]
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" <[email protected]>
To: "Discussion of biomass cooking stoves"
<[email protected]>, "Alex English" <[email protected]>
Cc: "Discussion of biomass cooking stoves"
<[email protected]>
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: [email protected]
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" <[email protected]>
To: [email protected], "Discussion of biomass cooking stoves"
<[email protected]>
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, [email protected] 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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