[Digestion] slurry from Potassium hydroxide catalyzed glycerin

[David]

Douglas,

On 1/4/2012 7:15 AM, Douglas Renk wrote:
> Has anyone demonstrated the effect of introducing marine anaerobes 
> highly toleratant of sodium into glycerin by-product enhanced 
> digesters? Sodium may still be of concern for land application, but 
> perhaps the digester could remain stable. I recall some studies 
> about 20 years ago with Chynoweth at IGT for inoculum suited for sea 
> kelp digestion.
> Any experience with this may greatly help our biogas industry 
> with co-digestion of biodiesel glycerin. I find the industry 
> resistant to move away from sodium hydroxide catalyst.

In a study about the digestion of (apparently salty) Korean food 
wastes ("Effect of particle size and sodium ion concentration on 
anaerobic thermophilic food waste digestion" Water Sci Technol. 
2000;41(3):67-73), Kim et al found that

    ...methane gas production [was] affected by various sodium ion
    concentrations. The reaction was not affected until 5 g/L of
    sodium ion was added into the test reactor. The volume of methane
    gas produced from the test reactors decreased gradually according
    to the sodium ion concentrations applied when more than 5 g/L of
    sodium ion. In case of 20 g/L of sodium ion, the methane gas
    production was reduced to about 50% of theoretical gas volume.


Of course, as you imply, a good deal depends on the population in the 
digester, but given that glycerin is so easily acidified, that it is 
more easily produces stable digestion when other materials are added 
to the digester, and that it must in any case be fed slowly, it seems 
unlikely that the first problem one would encounter would be sodium 
ion concentration. In other words the circumstances that lead to 
stable digestion would tend likewise to reduce sodium concentration in 
the digester, except perhaps if it is fed kelp or a similar 
high-sodium co-digestate. As far as Wayne's question about ag use of 
sodium-"enriched" effluent, that I would think would depend primarily 
on the circumstances. Sodium would be a problem particularly in drier 
climates and soils.


d.
-- 
David William House
"The Complete Biogas Handbook" |www.completebiogas.com|
/Vahid Biogas/, an alternative energy consultancy |www.vahidbiogas.com

|
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"Make no search for water.       But find thirst,
And water from the very ground will burst."
(Rumi, a Persian mystic poet, quoted in /Delight of Hearts/, p. 77)

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