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

[Crispin Pemberton-Pigott]

Dear Friends

 

I am bringing to mind that these high temperatures and the presence of at
least two fluxes were discussed when we were looking at making ceramic stove
components. The same principles apply: if there are fluxes (CL, K) in the
clay (ash) Si melts at a lower temperature. Alex found to his dismay this is
pretty easy to do with a large scale grass burner.

 

Roger Samson, to his credit, found out how to get the Cl and K out of the
grass and dramatically reduce the problem. When we speak of 'char' and at
the same time 'biomass' and 'wood', it would do us well to keep in mind the
very different result obtained when heating them to 900-950 C. One is going
to produce fused ash immediately and the other is hardly going to produce
any at all.

 

With ceramics, it is common to add K to reduce the melting temperature. It
seems that with combustion, we want it out because of the problems caused.

 

Regards
Crispin

 

+++++

 

Paul,

  Attached is minimalist, two points, graph showing potassium volatility
beginning at 400C with a ~37% loss at 800C.

Courtesy of Preto and Hrbek;

 
<http://www.biochar.ca/files/Can%20Biochar%20Initiative%20Preto%20Dec08.pdf>
http://www.biochar.ca/files/Can%20Biochar%20Initiative%20Preto%20Dec08.pdf

 

Alex

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