[Terrapreta] Charcoal properties

[Tom Miles]

If people who are doing Terra Preta experimentation are willing to have
their charcoal tested and report it here we can accumulate a database of
experience on the Terra Preta website. 

 

Tom Reed has a few charcoals on his BEF Woodgas site:

http://www.woodgas.com/proximat.htm

 

Proximate Analysis at a commercial lab here is $55 per sample. $12 for
sample preparation and $43 for the analysis. (Hazen Research, Golden
Colorado http://www.hazenusa.com/analytical-5.php ) There are many labs, we
just have used Hazen often. 

 

Some suppliers can probably provide a Proximate Analysis (Moisture, Ash,
Fixed Carbon, Volatile Carbon). 

See coconut shell charcoal
http://www.alibaba.com/catalog/11429503/Coconut_Shell_Charcoal.html

 

CEN (European) and ASTM (US) standard methods may differ slightly.  I found
CEN standard methods for analyzing for Moisture and Ash at:

http://www.crbnet.it/FisicaTecnica/File/Pubblicazioni/pdf/1248.pdf

This lab uses an Italian standard for Volatile matter.

 

If I recall there are European (or country) standards for different grade of
charcoal. 

 


FAO also describes Chapter 8. Quality control of charcoal and by-products


http://www.fao.org/docrep/X5555E/x5555e09.htm

 

The Phyllis database has several char analyses but of coarse they are not
linked to specific agricultural uses. 

http://www.ecn.nl/phyllis/

 

Tom Miles

 

 

 

 

 

 

 

 

 

 

From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of danny day
Sent: Friday, March 02, 2007 10:29 PM
To: Michael J. Antal, Jr.
Cc: terrapreta at bioenergylists.org
Subject: Re: [Terrapreta] Charcoal properties

 

Michael, thanks jumping in.
 You have as much experience as anyone I know in this field.

Everywhere I go people ask me how they can make their own char and I tell
them from my experience, make a small campfire and use a hose with a mist
nozzle to keep the charcoal in cool as it pyrolyzes.  Without instruments,
(and this is not a rule for all biomass sources)  a  charcoal  that sinks in
water was made too hot but  saying that any which floats is the best is not
accurate either.  We are all working on finding the best char but I believe
we will find it is much more complex than that.  The evolutionary
development of soil life and its interactions with char have some very
interesting revelation to come.  Michael, your lab is as qualified as any to
make standardized char.  One which support a biological response of the
microbial environment which can create an environment for a specific crop is
part of the knowledge base that we can help can contribute.  I trust soon
that we can begin to support labs around the world for providing the
analytical testing needed. 

It's exciting isn't it?

Danny Day

Eprida

On 3/3/07, Sean K. Barry <sean.barry at juno.com  <mailto:sean.barry at juno.com>
> wrote:

Hi Michael,

 

Thank you for your very interesting comments.  By what you have said in your
post, ...

 

"Tests by my colleague Professor Goro Uehara and his co-workers in CTAHR
have
shown that the addition of some charcoals to the soil can be harmful to
plant growth.  Our analyses of the properties of this "harmful" charcoal
indicate that it would have been perfect for barbeque."

 

and ...

 

"A good barbeque charcoal will have a VM content of 25 - 30%, whereas a
charcoal destined for metallurgical use often has VM content below 10%."

... would it be fair to infer, then, that relatively high volatile matter
content (25 - 30%) in charcoal probably does not make a good agricultural
use charcoal?  Has anyone tested metallurgical use charcoal (@ <10% VM) as
an AgChar?  What are the pyrolysis conditions under which metallurgical use
charcoal is made (feedstock, temperature, oxygen or air supply level, etc.)?
Are there any simple methods (not involving expensive gas chromatographs
and/or other equipment) to test for VM content?  Like, maybe does low VM
charcoal combust at a lower or higher temperature the higher VM charcoal?
Do they have a different densities?

 

You say, "This is not an easy job and there are no short cuts that I can
find."  So maybe my questions seem like naivete, but what I am interested in
learning from you is if a fuel scientists/chemical engineer like you really
does maybe know some possible simple methods to do proximate analysis of
charcoal or maybe some parts of it.  Not everyone interested in testing or
making Terra Preta has your kind of background, nor access to the kinds of
scientific equipment you do.  But, I suspect that there are low tech ways to
accomplish some of the things you are doing with your analysis of charcoal
properties.  Hopefully, you may be willing to at least discuss the
possibilities.

 

Would you be willing to put your papers online for the group?  I'm
interested, so if you like, send them to me.

 

 

Thank you and regards,

 

Sean K. Barry
Principal Engineer/Owner
Troposphere Energy, LLC
11170 142nd St. N.
Stillwater, MN 55082
(651) 351-0711 (Home/Fax)
(651) 285-0904 (Cell)
sean.barry at juno.com

----- Original Message ----- 

From: Michael J. Antal, Jr. <mailto:mantal at hawaii.edu>  

To: terrapreta at bioenergylists.org 

Sent: Friday, March 02, 2007 2:28 PM

Subject: [Terrapreta] Charcoal properties

 

Dear friends: terra preta is fascinating in part because it involves so many
disciplines.  My viewpoint is that of a fuel scientist/chemical engineer.
My laboratory produces well-characterized charcoals for a wide variety of
research endeavors, including carbon fuel cell studies, metallurgical
charcoal applications, activated carbon production, and terra preta research
(with my colleagues Dr. Goro Uehara, Dr. Jonathan Deenik, and Tai McClellan
in the University of Hawaii's College of Tropical Agriculture and Human
Resources).  With this message I wish to call your attention to the
elementary properties of charcoal that I think about when I am producing a
charcoal for one of our research endeavors.

Both the feedstock and the process (i.e. pyrolysis) conditions influence the
properties of the charcoal product.  For example, oak wood has little ash;
consequently its charcoal also has little ash.  On the other hand, rice
hulls have much ash (nearly pure silica), and so does its charcoal.
Likewise corncobs produce a highly macroporous charcoal, whereas sucrose
charcoal lacks a macroporous structure.  But unfortunately, the properties
of the feedstock do not completely determine the properties of the charcoal.
For example, if pyrolysis is carried out at a high temperature, some of the
volatile ash components leave the charcoal.  In our work it is not unusual
to find that the charcoal contains as little as 20% of the amount of ash
that we expected on the basis of the feedstock ash content.  One carbon
company produces an ash-free carbon for metallurgical applications by simply
heating a fossil carbon (usually coal) to such a high temperature that
virtually all the minerals in the fossil carbon vaporize.

Likewise the pyrolysis temperature (usually called the "heat treatment
temperature" or HTT) exerts a big influence on the properties of the carbon.
Fuel scientists employ proximate analysis to measure this influence.  Let's
be clear: there is nothing approximate about proximate analysis!  Proximate
analysis determines the moisture content (mc), volatile matter (VM) content,
fixed carbon (fC) content, and ash content of a charcoal (or fossil carbon).
A good barbeque charcoal will have a VM content of 25 - 30%, whereas a
charcoal destined for metallurgical use often has VM content below 10%.
Increasing HTT lowers the VM content of the charcoal, but there is not a
simple relationship between the HTT and the charcoal's VM content.  Why?
The simplest explanation is that the thermocouple used to measure the HTT
measures the temperature of the pyrolysis environment: it does not measure
the temperature of substrate during pyrolysis!  Pyrolytic reactors designed
to maximize "oil" (or gas) yields - and minimize the charcoal yield - employ
high heating rates.  Under these conditions the pyrolysis reactions are
endothermic; consequently there is a large temperature difference between
the charcoal and its environment (i.e. the temperature of the charcoal can
be hundreds of °C lower than its environment).  On the other hand, a
pyrolytic reactor that is designed to maximize the charcoal yield will evoke
exothermic pyrolysis reactions in the substrate, since the reactions that
form charcoal are exothermic.  In this case the temperature of the charcoal
can be much higher than its HTT.  I can provide some interesting papers on
this subject for anyone who is interested.

In summary, both the feedstock and the pyrolysis process conditions
influence the properties of the charcoal product, but they do not determine
the properties (i.e. knowing the feedstock and process conditions is not
enough to predict the properties of the charoal).  The only way to determine
the charcoal's properties is to actually measure them.  We do proximate
analyses of all our charcoals.  Often we do gas sorption measurements to
determine the carbon's surface area and pore volume distribution.  Sometimes
we obtain an elemental analysis of the carbon, or an analysis of its ash
content.  For our carbon fuel cell work we measure the carbon's electrical
conductivity, and with colleagues in the Hungarian Academy of Sciences we do
temperature-programmed desorption of biocarbons used in our fuel cell.  We
have done XRD, NMR, ESR, and MALDI-TOF MS analyses of some of our charcoals.
We have plans to expand our analysis capabilities into other areas soon.

Tests by my colleague Professor Goro Uehara and his co-workers in CTAHR have
shown that the addition of some charcoals to the soil can be harmful to
plant growth.  Our analyses of the properties of this "harmful" charcoal
indicate that it would have been perfect for barbeque.  This illustrates the
dangers of working with an uncharacterized charcoal purchased from your
local grocery store.  Professor Uehara and his co-workers will have more to
say on this subject in the near future.  In the meantime I emphasize that
our understanding of charcoal's beneficial and detrimental effects on plant
growth must rest (in part) upon measurements of the charcoal's properties.
This is not an easy job and there are no short cuts that I can find.

Like most of you, at present my terra preta research is not funded, so the
best I can do is provide well-characterized charcoals to my colleagues here
at UH.  In the future I may have the resources to provide well-characterized
charcoals to other terra preta researchers as well.  I will let you know
when this becomes possible.

Best wishes, Michael.

Michael J. Antal, Jr.
Coral Industries Distinguished Professor of Renewable Energy Resources
Hawaii Natural Energy Institute
School of Ocean and Earth Science and Technology (SOEST)
1680 East-West Rd., POST 109
University of Hawaii at Manoa
Honolulu, HI 96822

Phone: 808/956-7267
Fax: 808/956-2336
http://www.hnei.hawaii.edu  <http://www.hnei.hawaii.edu> 






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-- 
Danny Day
President
EPRIDA
404-202-6105 Cell
706-621-7651 Office 

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