[Stoves] why does coffee husk biochar smell like urine?

[Alex English]

Paul,
It is possible that the ash (elemental composition) contains 38% K20.  
Tom Miles et al. report on Alkali in Biomass
list;
http://www.trmiles.com/alkali/fuelsc7.html
Alfalfa stems 28%
Bana Grass 43%
Almond Hulls 53%

Alfalfa hay can have up to 3% K on a dry basis. K-potassium is a 
nutrient that plants will take up in "luxury consumption" when more is 
available. Rain can wash some out of the leaves of living alfalfa plants.

K will start to volatilize at fairly low temperatures with losses 
increasing with temperature. Other ash components will influence this 
rate and the form it takes.(example Sulfates and Chlorides) Some of the 
K is usually left within the char structure and some on the surfaces 
that will likely be quickly available to plants.

Odiferous char is often associated with  volatile organic compounds 
remaining in  or condensing on low temperature chars but they don't 
resemble urine to me.

Alex


On 15/10/2011 3:06 AM, Paul Olivier wrote:
> Christa,
>
> Do you have any idea why coffee husk biochar smells like urine?
>
> I just read that coffee husks contain 36% to 38% K2O.
> This supposedly accounts for the low melting point of its ash.
> That its ash has a low melting point makes sense to me,
> since, if I leave the fan on a bit too long after the gasification 
> cycle is finished,
> I see a stony yellowish/white ash at the bottom of the reactor.
>
> How is this possible that coffee husks could have so much K2O?
> What happens to the K2O when it is subjected to heat?
> I see that K2O has a melting point > 350C.
> If subjected to heat does it turn into K2O2 or even KO2?
> At what point does it turn into a gas?
>
> Does the presence of K2O account for its urine smell?
> What does this urine smell mean with regard to the value of coffee 
> husk biochar?
> Would coffee husk biochar be rich in potassium?
>
> Paul
> -- 
> Paul A. Olivier
> 27C Pham Hong Thai Street
> Dalat
> Vietnam
>
> Louisiana telephone: 1-337-447-4124 (rings Vietnam)
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>
>
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