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, <[email protected]> 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, > [email protected] 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 > > > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://stoves.bioenergylists.org/ > > > -- 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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