Dear Ron
Quoting "Ronal W. Larson" <[email protected]>:
Tom - see notes below. I have little time for a few more weeks, but
will try to get back to this, if others haven?t already supplied enough of
a response.
On Dec 23, 2013, at 4:36 PM, Tom Miles <[email protected]> wrote:
Ron,
I didn?t mean anything quite so personal. :-/
[RWL1: See next response to Mark Ludlow. I was mostly trying to
get some humor injected - about my own ?cult?.
Most of the biochar research has focused on pyrolitic char and not on
combustion or gasification char. There is a clear bias toward
pyrolysis, or
low temperature char. Can anyone really say this is the way that the
Amazonians, or anyone else, created the charcoal that we find in the terra
preta soils? Or was it smoldering combustion, staged combustion (a la Alex
English), or a combination of pyrolysis, gasification and combustion? I
know that I have had a lot of bad slash and straw burns that have left a
lot more char on the ground than ash. Are there ?signatures? in the terra
preta char that point specifically to pyrolysis, gasification or
combustion?
[RWL2: I just spent half an hour trying to find something
definitive. I found one Ppt by three friends on this topic, but not
enough words to go with the pictures. I will check after Xmas.
I hope someone on this list has looked at efforts to mimic the Terra
Preta soils.
# KC: This seems to be "The Unspoken Elephant in the Room." Just how did
the Terrapretians actually make Terra Preta??? Did they actually make it on
purpose, OR did it just happen, when they disposed of wastes, either
``jungle wastes`` or ``domestic wastes``? What is the difference between
making "Terra Preta" and the Milpa Agriculture, as practised in Belize?
It seems clear they did much more than just put
out ash - which seems to have been what the vast majority of aboriginal
slash and burn cultures did.
# KC: The inorganic fraction of the char remaining from "slash and burn"
could be one possible explanation for the presence of charcoal in the soil.
I favor an argument that the
char came from what happened during and after cooking (If wood is easy to
come by, you can make a lot of char in a 3-stone arrangement.
# KC: Certainly, there was an excess of wood available.... a "jungle full
of wood." However, it was certainly not easily available... there would be
an enormous labour content requirement to cut down trees and prepare the
wood for use as a fuel, with only "Stone Age Implements and Technology."
The ``Amazonian Terrapretians`were no doubt just as smart and just as lazy
as Modern Day Men. Those who have chopped down a hardwood tree with a sharp
axe can appreciate the difficulty of chopping down jungle trees with a
relatively blunt stone age axe.
I have seen one argument for an approach like HTC.
# KC: The possibility of using the nutritious ``black goop`` from the
bottom of the Òxbow Lakes that are very common along the Amazon River has
been suggested as a source of fertiliing nutrients for Terra Preta on this
list in the past, and the concept was received with extreme disinterest. I
would suggest that the ``black goop``was made by the `LTAHTC Process``, ie,
the ``Low Temperature Anaerobic HydroThermal Carbon Process``
I see biochar production growing in stages. For the time being a large
quantity of char that is sold as Biochar is actually char from
gasification. As biochar markets grow we might expect to find more
pyrolytic char made ?for purpose? but now we have some pyrolitic char and
byproducts of gasification (including TLUDs) and combustion.
[RWL3: I wouldn?t couple the words ?TLUDs? and ?gasification?.
TLUDs look like pyrolysis to me.
# KC: Also in the past on one of these lists (Biochar...Gasification...
Stoves...) were extensive discussions on the subject of whether a TLUD was
a `Gasifier Stove`or not. The conclusion at the time seems to have been
that the TLUD was indeed a gasifier, that was close coupled to a stove .
Given that gases are produced in pyrolysis, it would seem fair to accept as
a fact that pyrolysis is a `gasification process.
The ?high temperature? gasifier char performs very well and in some
applications better than pyrolytic char. Several studies (and some
commercial producers) have found that conditioning the char through
partially oxidation (to higher temperature) enhances nutrient retention.
These products are for improving soil fertility , not necessarily to
replace activated carbon. So why not consider CO2 gasification as a
possible process step?
[RWL4: I need help on this. I am assuming that adding CO2 to hot
char is designed to leave little char. Doesn?t sound like a major help
for producing a biochar.
# KC: The ``Pillar of Agricultural Biochar`` seems to be Terra Preta.
Perhaps someone could provide evidence of some sort showing how the
Amazonian Terrapretians controlled their char making temperatures.
One major producer of char in California uses a downdraft gasifier. In a
downdraft gasifier wood devolatilizes at or above the oxidation zone.
Volatile carbon is oxidized by the air injected from nozzles to make CO2.
The hot CO2 reacts with the char to form CO and H2. This occurs in the
?reduction zone?. The reduction zone is often shown as a deep bed
of carbon
but in fact it is usually only a couple of inches thick. Large
chips reduce
to powdered char in less than 2 inches where gas temperatures are
800-900C.
The resultant producer gas is a mixture of this CO from reducing char and
the devolatilized gas. Taking CO2 and reacting it with charcoal
at 800-900C
as Purdue has done is not a lot different so the qualities of the char
should be similar.
[RWL5: Still need help (not knowing enough about the term
?gasification?). In downdraft gasifiers, I have been assuming that the
injected air was reacting mostly with the char, not with the already
produced gases. The intent was to get rid of as much char as possible (and
I assume the same for the Purdue researchers). I understand that Purdue
is inputting CO2 and not air (in a second stage), but the intent in both
cases is (I presume) to leave as little char as possible. I just don?t
see how that fits into this list - interested in getting a lot of char. I
understand that part of the processing is to maximize CO and H2. I?ll
try to get back to this.
# KC: The problem seems to be when those interested in producing
``Biochar`` for Agricultural Purposes get into conflict with those who want
to produce ``Biochar```for ``Climate Change Purposes``, or other purposes.
A clear definition of ``The Various Biochars`` would indeed be helpful
I think we need to explore all avenues of producing char and energy
1. Slow pyrolysis ? 25%-30% char; 30% oil+gas
2. Fast pyrolysis ? 15% char; 60% oil
3. Gasification ? 5%-25% char; 75%-95% energy
4. Combustion ? 1-5% char; 95% heat
[RWL: Tom - the bottom two total near 100%, but not the top two; can
you add some more components?. I am surprised also to see gasification
char as high as 25%; who is getting this high - and how?.
# KC: There are indeed a lot of different kinds of chars that are produced
by various means, for various purposes, from various feedstocks, and at
various temperatures. It seems that there are still a lot of ``loose ends``
associated with ``Char``, ``Biochar``, etc.
Adding to this list might be the work of Mike Antal (and Mantria)
with added pressure. Also Cool Planet uses pressure and catalysts with the
term ?fractionator?. Retort char (zero oxygen) could be a little
different from your four - all of which involve some O2?. Maybe same for
char made with microwaves (heating from the inside of particles being
different)? Certainly HTC (hydrothermal carbonization) is very
different. Is the approach by Alex English different from any of these (I
think it is close to slow pyrolysis). Nat Mulcahy with World Stove has a
different approach with no oxygen flowing through the fuel bed. Jim
Mason?s BEK will be called gasification?
# KC: You make a very good case for the need for the IBI to clean up their
definition of ``Biochar``.
I heat my home partly with wood (mostly solar (except when cold and
cloudy), no gas) - and have pulled copious amounts of char out of my (open
front) stove - a lot more than 5%. I believe that has to be called
interrupted combustion - just the same as the whiskey maker Jack Daniels
does - combustion interrupted at the end of the pyrolysis stage and before
much gasification can have occurred. The difference seems to be whether an
O2 molecule can reach a hot char surface or not - because of still-exiting
pyrolysis gases getting oxidized first (mainly to CO and H2O).
# KC: With all this char being available to you, it would be interesting
to see your comments on tests that you have probably done, using this kind
of char as a soil additive for improving plant growth.
All in all I think it great that there are so many carbonization
approaches - hopefully enough for every combination of soil and plant
species. The big divider will be process temperature, it seems.
# KC: It would be very interesting to see your comments on which kinds of
chars are best for the various end uses to which the various chars can be
put.
Best wishes, for ``Biochar Clarification`in 2014``.
Kevin
Ron
Tom
From: [email protected] [mailto:[email protected]] On
Behalf Of Ronal W. Larson
Sent: Monday, December 23, 2013 2:53 PM
To: Biochar; Tom Miles
Cc: Crispin Pemberton-Pigott; Gasification-Request
Subject: Re: [biochar] Pine char gasification
Tom etal:
1. I?m not sure I want to accept the ?philia? part of this message
(?philia? goes with ?abnormal? and pedophilia at one google site). I
found the word agape - but that sounds presumptuous. But I do admit to
being at the non-sensical end of the char spectrum. Maybe charphilia is
apt.
2. I know close to zero about any part of gasification, but I can
understand why one would promote the idea of recycling the CO2 to get more
gas (eventually the Purdue group wants liquid, it seems). But that has to
result in less char - and apparently leaves much higher temperature char.
Eventually it is almost all CO2, for gasification, but I worry that the
char produced this (high temperature) way might only be suited to replace
AC = activated carbon.
3. Since Alex English name came up today, we should note that he also
recycles CO2.
4. The dogma of the cult I am in says more char beats more heat, gas
or liquid, so I will look forward to some proof that is not correct.
Good luck to the Purdue folk.
Ron
On Dec 23, 2013, at 12:58 PM, Tom Miles <[email protected]> wrote:
Ron,
This work is very important for both the biochar and gasification lists.
Biochar will be produced at the large, or even small, scale as a
co-product
of energy (liquid fuels and/or power). The most efficient way to generate
power from the gases and vapors from slow pyrolysis (50% of the energy) is
probably through charcoal gasification (e.g. run the pyrolysis gases
through a charcoal gasifier). There are commercial systems under
development to make char and power in this way. There are also commercial
systems under development to make liquid fuels through combinations of
pyrolysis and gasification. The char products from these and fast
pyrolysis
processes run from 0% to about 15% of fuel input. I don?t know the fuel or
char yield for Cool Planet.
This particular study prepared the char with high temperature (826 C)
nitrogen. Wood particles (chips, sawdust) and resultant char particles in
this study are larger than for other char studies. Obs
ervations about BET surface area, particle size and the char morphology
are very interesting. The char morphology looks different than the SEM
images that we typically see. From gasification and pyrolysis we know that
pine carbonizes differently than hardwood so it is interesting to see the
shredded fibrous appearance of the pine char in this study compared to the
neat geometric structures that we often see, which is probably from
hardwood chars. The authors observe that the macropore volume is
significantly greater than the mesopore or micropore volume of the char.
They observe ?numerous wide tunnel protruding into the char particles. . .
[that] may provide pathways for bulk transport of CO2 into the particle.?
Char conversion numbers are interesting. Only 10-12% of the char was
gasified at 726 C (BET 391 m3/g) while 98-100% was converted at 896 C.
Surface area increased with conversion but not much greater than
the 35-47%
conversion at 776 C so CO2 gasification could be used to increase surface
area at the expense of half of char (660 m3/g). Meso and micro pore volume
doubles at the higher rate but stays pretty constant above 776 C.
Researchers conclude that a significant proportion of the pore volume is
within macro pores although the majority of the internal surface area is
within micro pores. They point out that the mass loss with surface
gasification occurs within the smaller pores leading to pore widening.
Researchers explain that the char gasification process involves three
steps: (1) adsorption of the gas-phase species to the char surface, (2)
surface reactions, and (3) desorption of the gasification
products from the
surface. The latter is the rate limiting process.
Recycling CO2 from gasification to gasify the char is an interesting
concept that may apply to modifying char properties (e.g. increase surface
area) from pyrolysis or recovering energy (heat, power, syngas) in an
industrial setting.
There is very little information about gasification or combustion chars.
Sometimes it helps to step back from our char-philia (and gaso-phobia) to
see what products combined pyrolysis and gasification can produce.
Tom
RL> don?t see any relevance to the biochar list. (Except if this work
shows that char is more valuable in the ground and/or that an
approach like
Cool Planet?s is more efficient.) On the biochar list, we should
want BOTH
high value fuels and charcoal.
This Purdue work is all about gasification of char - not pyrolysis.
I am not sure whether the topic is appropriate for
?gasification? either,
since that list seems to want gases for engines, not liquids.
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