[Terrapreta] torrefaction vs. carbonization

[Gerald Van Koeverden]

Some more information...from the same report (link attached below  
quote).  Note property #2.  I wonder where they got the idea that  
charcoal wasn't resistant to fungal attack...?

"The product of torrefaction process is a solid product, which is  
torrefied biomass, has attractive properties
such as improved heating value, low moisture content and ease of size  
reduction. The
properties of torrefied biomass are as follows:
1. Lower moisture content and therefore higher heating value compared  
to biomass,
Due to lower moisture content, it is cheaper to transport the  
torrefied biomass
2. Hydrophobic nature: the material does not gain humidity in storage  
and therefore
unlike charcoal and biomass, it is stable and is resistant to fungal  
attack.
3. Easy burning and less smoke formation when burnt
4. Suitable for various application such as for cooking fuel,  
residential heating, raw
material for manufacturer of fuel pellets, reducer in smelters -  
steel industry,
manufacture of charcoal or activated carbon, gasification, co-firing  
with other fuels in
boilers etc.

http://64.233.167.104/search?q=cache:iqOOAZ556LIJ:cgpl.iisc.ernet.in/ 
site/Portals/0/Documents/FinalReportOnTorrifiedBamboo.pdf+wood 
+torrification&hl=en&ct=clnk&cd=7&client=safari

Gerrit


On 8-Dec-07, at 5:20 PM, Gerald Van Koeverden wrote:

> Nick,
>
> I had to look up what torrefaction was:
>
> "Torrefaction is mild pre-treatment of any biomass (including  
> bamboo) at a temperature between
> 200 and 250° C. During torrefaction the properties of bamboo  
> undergo changes, wherein the end
> product has much better fuel quality compared to biomass for  
> combustion application. The
> decomposition reactions during this process results in bamboo  
> becoming completely dry and
> loose its tenacious structure, also the hygroscopic nature of the  
> biomass is changed to
> hydrophobic material. Besides this, the process increases the  
> calorific value of the end product.
> The actual weight loss in this period would be about 20 to 25 %  
> whereas 90 % of the energy of
> the parent dry material is preserved in the torrefied matter. The  
> combustion process of this matter
> has less problematic volatiles and hence the process is closer to  
> that of charcoal. It can therefore
> be used as an alternate to charcoal in many applications. It also  
> makes the material immune to
> attack by fungi. Hence long term storage without degradation is  
> possible."
>
> Based on 15 minutes of research, it doesn't look promising.  It  
> would seem that this super-drying of wood makes it  
> hydrophobic...and if it stays that dry in the soil, it would be  
> difficult for nutrients to move through a soil solution into it.   
> Moreover, it doesn't sound like it is conducive for a 'fungal'  
> bridge between itself as a microhabit for microrganisms with the  
> soil;  in char mixed with composting material, the char actually  
> becomes a microhabit for fungus...
> However, this is only speculation.
>
> How closely have you examined the torrefied wood you have found in  
> the soil?  Does it 'house' microrganisms?  Has it absorbed soil  
> nutrients?  Or is it merely an inert material taking up space?
>
> gerrit
>
>
>
> On 8-Dec-07, at 2:21 PM, Nikolaus Foidl wrote:
>
>> Dear all!
>>
>> My charcoal costs at a charring efficiency of 42 % is around 35 US 
>> $ per ton
>> Charcoal. Now after analyzing 15 year old soil where huge amounts  
>> of forest
>> where simply burned and charred. Now excavating I find huge  
>> amounts of only
>> torrefied wood pieces which as well did not degrade, like the  
>> charcoal
>> chunks.
>> Now looking at this and if torrefied wood would do the same as is  
>> charcoal,
>> why not save a huge amount of additional CO2 and just torrefy the  
>> stuff and
>> mill it and then burry it? Cost per ton would drop to half, CO2  
>> taken out of
>> the atmosphere rise by 50 to 70 %.
>> Just an idea but maybe worth to be discussed.
>> Best regards Nikolaus
>>
>>
>>
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