[Digestion] Digestion Digest, Vol 6, Issue 4

[frank at compostlab.com]

Dear All,

This all depends on the test method to determine BOD and COD to be related to what the anaerobic microbes can use during the anaerobic process and time it takes place. COD is a hard hitting chemical reaction that reading will include things not broken doun during the AD process and BOD is just the oposite. A water solution in  an aerobic environment run for 5 days - both very different.

Frank Shields

On Mon, 14 Feb 2011 02:07:18 +0100, Markus Schlattmann wrote
> Hi all,
> 
> yes, that's true.
> But it seems that Mel already is in knowledge of the removed/degraded COD. 
> So in this case the lignocellulosic material would stay as undegraded COD is not relevant COD-input for this estimation.
> 
> Markus
> 
> Am 14.02.2011 01:29, schrieb Anand Karve:

> Dear All, 
>  The amount of methane produced by a substrate would depend upon the nature of the organic matter in it. The organic matter in the dung of herbivores would consist to a large extent of lignocellulosic material, which cannot be digested in anaerobic digesters. The organic matter in domestic sewage, on the other hand, would consist of material that would be more easily digested by the methanogens. Therefore, with the same quantiy of organic matter, the two substrates would yield different quantities of methane. 
> Yours 
> A.D.Karve
> 
> On Mon, Feb 14, 2011 at 3:24 AM, <finstein at envsci.rutgers.edu> wrote:
> Thanks Marcus for your response to my query:
> 
> > All,
> >
> > Do you know of (have) a way to "translate" BOD and/or COD to methane
> > potential? It would of course have to be in terms of BOD/COD removed
> > giving rise to so much methane.
> >
> > Mel
> 
> Hi Mel,
> >
> > if you consider the removed COD is completely transferred to CH4 in the
> > Biogas (CO2=0 COD) you can calculate:
> >
> > 1g COD removed ->  0,25g CH4
> > Or 1g COD removed -> 0,35 L CH4 (273K, 1013 mbar).
> >
> > If you want to estimate more exactly you may consider that some fo the
> > removed COD flows into H2 and microbial biomass.
> >
> > Markus
> 
> Your calculation, however, is at odds with the statement in Grady et al.
> 1999, page 600 in "Biological Wastewater Treatment 2nd edition" Marcel
> Dekker. The statement is that 4 kg COD removed generates 0.35 m3 of
> methane (0.35 L CH4/4 g COD removed). Also that figure or nearabouts is
> found in other documents. Apparently it was derived from theoretical
> calculation (not understood by me) and also from serious observation of
> real systems. If repetition = validity, thhan th figure is usable.
> 
> Perhaps others can weigh in on the theoretical end, or report other
> "sightings of the translation.
> 
> Mel
> 
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> for more information about digestion, see
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> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
> 
> 
> 
> -- 
> ***
> Dr. A.D. Karve
> President, Appropriate Rural Technology Institute (ARTI)
> 
> *Please change my email address in your records to: adkarve at gmail.com *
> 
>
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> 
>--

Mit freundlichen 
Grüßen,
Markus 
Schlattmann

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-- 
Frank Shields 
Soil Control Lab 
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www.greenrooflab.com
 
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