[Stoves] Stoves Digest, Vol 4, Issue 13

frank frank at compostlab.com
Wed Dec 8 12:47:09 CST 2010


Stovers,

The pH of dung is dependent on the C/N (available C/ available N)  
ratio. A lot of  dung has a very high pH. If you smell ammonia you know 
you have high pH dung. Bacteria need available carbon and available 
nitrogen. One or the other will likely be the limiting factor, so if 
nitrogen is limiting (high C/N ratio above ~15) the excess carbon will 
form organic acids. and a low pH results. If carbon is limiting the 
nitrogen forms ammonia and the pH goes up releasing the ammonia into the 
air (smells). Finally enough goes off (lost nitrogen from the ag 
system), pH drops.

In the end it all comes out about the same. Excess carbon is a slow 
system as the nitrogen needs to recycle between dead and living 
bacteria. Carbon is lowered as CO2 goes off until a C/N ratio ends up 
~10. With excess nitrogen the nitrogen is lowers as it is lost as 
ammonia until the system ends up ~10 C/N. Acid conditions due to organic 
acids build up and high pH due to ammonium build up both slow down the 
system until pH is finally at a level optimum for the microbes.

Wood chips and other non-available carbon forms will results in high C/N 
ratios meaning the C/N ratio is really not very usable numbers because 
the only ones that count are the C and N in available forms when 
predicting proper mixes. Not easy to do.

The above is how I think of it today.

Frank





Anand Karve wrote:

> Dear Richard,
> the acidification of dung is only due to organic acids. It may change 
> the pH but should not have any effect on the organic substances like 
> cellulose, lignin or even mucus in the dung.
> Yours
> A.D.Karve
> On Wed, Dec 8, 2010 at 7:36 AM, Richard Stanley 
> <rstanley at legacyfound.org <mailto:rstanley at legacyfound.org>> wrote:
>
>     Good questions Kevin,
>
>      I am embarrassed to say that I have never pursued the issue, an
>     admission made worse by the fact of having extolled Biogas tech
>     widely in Tanzania through most of the 70's . Question is if the
>     bath is acid as Crispin implies through his description of the
>     mentioned peace corpsman,  what effect would  that have on the
>      fiber content of the dung so essential for wet process
>     briquetting ? We would need the fibers intact.
>     As also related to Crispin's story about the use of the decanted
>     liquid for solidifying clay: I'm just wondering Crispin; did you
>     get any idea of the thermal properties of the resulting
>     clay-cement ? Would it in other words be good for stove insulation
>     and/or structure ?
>
>     Richard
>
>     On Dec 7, 2010, at 7:58 AM, Kevin wrote:
>
>     > Dear Rajan
>     > ----- Original Message ----- From: <rajan_jiby at dataone.in
>     <mailto:rajan_jiby at dataone.in>>
>     > To: "Kevin" <kchisholm at ca.inter.net
>     <mailto:kchisholm at ca.inter.net>>; "Discussion of biomass cooking
>     stoves" <>>>
>     >>
>     >> Dear Kevin,
>     >>
>     >> Well, we also use biogas plants where animal dung is a major
>     feedstock.
>     >>
>     >> Here the energy part comes out as methane ( which is used as
>     fuel ) and the slurry from the plant contains all the nutrients (
>     without any loss ).
>     >
>     > I have no experience with biogas plants run on animal manure. Is
>     the slurry from a biogas plant filterable? If so, would it
>     potentially make a fuel equivalent or superior to dung that was
>     burned directly, with no washing?
>     >
>     > As I understand it, Richard Stanley uses a retting process on
>     biomass, to develop binding characteristics for his holey
>     briquette feed. Would the drained solids from a biodigester
>     perhaps have better "binder characteristics than freshly washed
>     dung? Perhaps Righard has already explored this avenue?
>     >
>     > Best wishes,
>     >
>     > Kevin
>     >
>     >
>     >>
>     >> Best Regards,
>     >>
>     >>
>     >> Rajan
>     >>
>     >>
>     >>
>     >>
>     >>
>     >> -----
>     >> No virus found in this message.
>     >> Checked by AVG - www.avg.com <http://www.avg.com/>
>     >> Version: 10.0.1170 / Virus Database: 426/3302 - Release Date:
>     12/07/10
>     >
>     >
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> -- 
> ***
> Dr. A.D. Karve
> President, Appropriate Rural Technology Institute (ARTI)
>
> *Please change my email address in your records to: adkarve at gmail.com 
> <mailto:adkarve at gmail.com> *
>
>
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-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
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(831) 724-3188 fax
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