[Stoves] TLUD and biochar production

[rongretlarson at comcast.net]

Frank, Josh, and list - see below 

Most of this was written before lunch and so only a bit of response below to Josh, who also answered Frank. Not exactly relevant, but I went down to the Colorado House (Ag committee) to support SB 13-273, which puts a little bit more state emphasis on removing beetle kill. (Minimize fire hazard) Passed the second chamber committee with only 1 "Nay" vote, so is sure of getting through the remainder. The only reason for going was to get the word "biochar" on the table. The Committee chair (Fischer - who knows biochar) helped by asking a question. 

More below, trying not to duplicate Josh 

----- Original Message -----
From: "Frank Shields" <frank at compostlab.com> 
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org> 
Sent: Monday, May 6, 2013 10:52:13 AM 
Subject: [Stoves] TLUD and biochar production 

Dear Stovers, 

It seems that a TLUD would make poor quality biochar. 
[RWL1: Th is is a strong statement that r equ ires more proof than you are giving. My contrary belief (based on what I read about improved ag production from char made in TLUDs) is that such char is very good. The reason is that such char is often measured to be around 600 C - near the supposed sweet spot. 

There are only two hot 
spots. One is the flame front and the second the flame heating the pot. 
[RWL2: The most important hot spot is a th ird one - at the (moving) pyrolys is fro nt .] 

As 
the flame front migrates down through new biomass volatiles come off and hit 
cooler conditions above in the left over char where I would think 
condensation of organics would occur. 
[RWL3: You should be using the term "pyrolysi s front" . The only "flame" ever traveling through the char is after the pyrolysis front reaches the bottom of the fuel bed (and that is w hen to stop) . The "cooler" char above the pyrolyss front is still very hot and not much condensation is occurring - as I understand it. In fact there may be more cracking in this hot char area. Very little CO2 gets through (which is ide al , as we want the CO that comes about because the char is hot enough). 

Josh Kearns has an earler response note on this, which I endorse. But it would be ideal to have someone report in detail. Plots I have seen of char temperature are quite constant over time, once the pyrolysis front has passed. There are always tars left, but as Josh sad, those are useful . T he char-making stove char hasn't received any bad press that I am aware of. There is a lot of good press. 

This is good as a cleaner gas goes up 
to the secondary air to combust and heat the pot. But the char is left with 
tars. This could be better for used as charcoal for other cooking but would 
make very poor biochar for the garden - if this is what happens. 

[RWL4: So my "If" response is that "this is NOT what happens". Anyone have contrad ictory ev idence? Ron] 

Regards 

Frank 


Thanks 

Frank Shields 

BioChar Division 
Control Laboratories, Inc. 
42 Hangar Way 
Watsonville, CE 95076 

(831) 724-5422 tel 
(81) 724-3188 fax 
frank at biocharlab.com 
www.controllabs.com 





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