[Stoves] Low temperature vs high temperature charcoal?

[Tom Miles]

Dan,

 

Since plants can't read we have to watch and listen to them to find out what
works. Unfortunately we're often better at talking (prescribing) than
listening.  Thanks for your observations. 

 

Tom  

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Carefreeland at aol.com
Sent: Sunday, June 16, 2013 5:35 PM
To: stoves at lists.bioenergylists.org
Subject: Re: [Stoves] Low temperature vs high temperature charcoal?

 

Tom, Tom, Listers, 

    I would think that there would be a reduction in tars in the higher temp
chars. This might have some advantages in less surface tension of water. The
tars, on the other hand may have some beneficial use in reducing, insects,
fungus or bacteria growth in chars used for soil enhancement. The chars
created in a gasifier or less efficient system such as an open fire or
various older systems of char making would all contain more ash. The extra
ash would have benefits as a nearly balanced fertilizer in the soil. Minus
only nitrogen. 

    It surprises me that higher temp chars would have a lower surface area.
Has anybody studied the relationship between the time it takes to cook the
char and the amount of surface area created?  I would think the higher
temperatures and faster cooking would rupture the cell membranes violently
and to a greater extent from flashing steam. Would this create more or less
surface area?  Would carbonized cells have a greater CEC with tiny holes in
them from slow cooking or larger more accessible ruptures from fast cooking?
Would some cells not rupture completely?  or be blocked in large chunks of
charcoal from acting to absorb water and minerals?     

    Obviously, the type of biomass would also be a great variable in the
surface area equation as cells rupture based on their design. Old gunpowder
makers knew this from experience that is why low ash, high surface area
Willow and Dogwood were favored. The Dogwood for dense, high octane powder
and the Willow for light, fast burninig powder. 

    I think that nature already has figured this out in a beautiful way- as
usual. Char for soil is best created in hot but inefficient forest fires.
Char for use as a fuel for man is best created with a high yield and lots of
hydrocarbons in a closed retort system. All other uses fall on a scale in
between. The Biblical saying "Render unto God what is God's" comes to mind.
And you thought it was just about taxes! 

    I like to burn my brush in a big cut open tank in the garden. All the
ash flies out into the air and lands well distributed all over the garden.
This saves me the task of spreading the ash. In forest fires the majority of
the char forms underground or under ash. Again, Nature is still one or many
steps ahead of us. 

    Only questions, no answers as usual. No lab or even a greenhouse anymore
to experiment with.  Have fun all you college types. Let me know what you
find. I do still read some of the letters now and then.

    Keep Charring and Stoving, 

    

    Dan Dimiduk 

    From the peanut gallery.  

    

In a message dated 6/16/2013 4:41:37 PM Eastern Daylight Time,
tmiles at trmiles.com writes:

Stephen Joseph should comment on the target "optimum" range set out by
Lehmann and others of 450-550 C which seems to have guided most research.
According to their work an increase in temperature to 500-700C would appear
to result in slightly lower yield and surface area. pH and CEC would be
about the same. Trials with different plants and soils since this early work
may tell us a different story. 

We have had good results with limited use of higher temperature pyrolysis
and gasifier chars, in the 500-700C range or even higher, when used in
erosion control, filtration, vermiculture and soil-less media. The main
drawback of a gasifier char is a lower char yield.     

Tom Miles

 

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