[Stoves] Low temperature vs high temperature charcoal?

[Josh Kearns]

High draft/high temp. chars are superior from a sorption perspective:
http://www.wcponline.com/pdf/October2012Kearns.pdf

The lower mass yields are more than offset by greater-than-proportional
increase in sorption capacity. For water treatment/water quality
applications 85-90%, or even a little more, mass loss is optimal.

We'll have several papers coming out over the next couple of years filling
in a lot of the details on research into a lot of the questions that have
been brought up by Dan and others here....sorry, everyone, academic
publishing is so painfully slow.....

Josh



On Sun, Jun 16, 2013 at 8:34 PM, <Carefreeland at aol.com> wrote:

> **
>  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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-- 
Josh Kearns
PhD Candidate, Environmental Engineering
University of Colorado-Boulder
Visiting Researcher, North Carolina State University

Director of Science
Aqueous Solutions
www.aqsolutions.org

Mobile: 720 989 3959
Skype: joshkearns
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