[Digestion] Attachment to previous Article - More scientific based research and questions

Alexander Eaton alex at sistemabiobolsa.com
Thu Oct 7 16:00:17 PDT 2010

HI Paul,

Thanks for the last post, but you left me with a question.  Our data has
shown pig manure is generally (roughly) between 20-25% TS, but the VS is
often 70-80% of the TS, so between 10-20% of the total mass of the wet
manure.  This corresponds with other data I have seen (right in front of me
House uses 20% TS and VS of 70% of TS for cow manure)  You mention VS of
only 10% of TS.  Did you mean of the total, or is this a different type of
manure, or am I missing something.

On another note, related to the standards we had discussed earlier this
year, can anyone comment on using TOC to evaluate waste streams and biogas
potential versus using COD?  We were buy some new equipment for the lab, and
the equipment salesman put the hard sell on for using TOC instead of COD to
evaluate waste.  Any thoughts?  The immediate disadvantage I see is
comparing past data with new data.


On Thu, Oct 7, 2010 at 4:09 PM, Paul Harris <paul.harris at adelaide.edu.au>wrote:

>  G’day All,
> In the discussion below I see the term TS (Total Solids) used, and it is
> important to remember that flour and sugar TS will be almost 100% VS
> (Volatile Solids) and equate to very high COD per kg. It is VS/COD that is
> available as substrate for anaerobic digestion, so when comparing other
> substrates we really need a VS figure (or VS as % of TS) as a measure of
> digestibility – manure VS is about 10% of TS so there will be huge
> differences.
> I also noticed in an earlier post the comment about methanogens being
> present in our digestive tract (I agree that they are), but why? I think it
> has been suggested they balance the H+ and H2 system so our digestive system
> can operate (so they may be “good” bugs) but it may also be that we provide
> an environment for their survival so they compete for nutrients. I know
> CSIRO have done work on reducing methane emissions from cattle so I will try
> to follow that up and I will also ask a gastroenterology colleague here as
> well, but comments are welcome.
> Happy digesting,
> Mr. Paul Harris, Room S116b, Waite Main Building Faculty of Sciences, The
> University of Adelaide, Waite Campus, PMB 1, Glen Osmond SA 5064 Ph    : +61
> 8 8303 7880      Fax   : +61 8 8303 4386
> mailto:paul.harris at adelaide.edu.au <paul.harris at adelaide.edu.au>
> http://www.adelaide.edu.au/directory/paul.harris
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> *From:* digestion-bounces at lists.bioenergylists.org [mailto:
> digestion-bounces at lists.bioenergylists.org] *On Behalf Of *Alexander Eaton
> *Sent:* Friday, 8 October 2010 3:30 AM
> *To:* For Discussion of Anaerobic Digestion
> *Subject:* Re: [Digestion] Attachment to previous Article - More
> scientific based research and questions
> Thanks All for the background documents.  These are extremely useful.
> Best,
> A
> On Thu, Oct 7, 2010 at 7:56 AM, David Fulford <davidf at kingdombio.com>
> wrote:
> Hello Alex and Listers,
> The best independent papers on the ARTI system are by EAWAG (
> www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_swm/<http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_swm/index_EN#owm>)
> who have also looked at the digestion of food residues from markets in
> Kerala, South India. While food residues have an average TS of 50% or less,
> Dr Karve bases his results on starch residues (e.g. flour dropped on the
> floor from milling). Suich residues have a TS of almost 100%. This means
> that we need to consider his gas production results as per kg total solids,
> rather than per kg of wet material.
> As the assessor from Ashden Awards who visited ARTI in 2006 (see
> www.ashdenawards.org/winners/arti06), I had to evaluate Dr Karve's
> statements.and his technology. The biogas plant uses simple cylindrical
> drums, so there is nothing special about the design. The major difference is
> the use of food residues rather than dung as the feed material. Since an
> animal has used as much of the input energy in the food as it can before it
> evacuates the rest, the gas production from undigested food is likely to be
> much higher than that from dung. Processed food (flour, sugar and cooked
> food) is likely to have a higher gas output than raw food, as much more of
> the material is accessible to the microbes. There are several other biogas
> projects in India using food residues as feed material, that started at
> about the same time as the ARTI one. I have visited the first Biotech Ltd
> project in Kerala (www.ashdenawards.org/winners/biotech) about which the
> EAWAG report was written and another in Mumbai called the Nisargruna system
> developed by BARC (see www.green-ensys.org/site/Biogas_Plant.html), which
> uses a two-stage digestor design.
> Looking at the basic thermodynamics of the process, it seems quite feasible
> to generate 1 kWh of electrical energy from 1 kg of starch, as Dr Karve
> suggests, although it does suggest a very high efficiency for the conversion
> of starch to biogas. However, in practice, a 1 cu.m ARTI biogas plant is too
> small to run an ic engine, as small ic engines are not very efficient.
> Regards,
> David Fulford
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Alexander Eaton
Sistema Biobolsa

Mex cel: (55) 11522786
US cel: 970 275 4505

alex at sistemabiobolsa.com
alexanderb.eaton at gmail.com
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