[Digestion] Biogas production

[Murali Krishna]

Good day Kyle,

We have been running digesters using cow dung as feed stock for the last
ten years. On an average, we are getting 1 m3 of biogas from 15 to 20 kgs
of cow dung.  The cows are grazing outside no concentrates were given.  If
we add cow urine to the dung the biogas increase at least by 25%.  The
urine quantity is roughly 30% of the feedstock.  The dilution of cow dung
and water is 1:1.

Our digesters are built for 45 days HRT and now we are reducing the HRT to
30 days.

Most of the intensive care cow farms are using antibiotics but I do not
think the digesters are stopping or under performing.  Of course, if the
dose of antibiotics is quite high, perhaps it may effect the production.

Krishna.

On Tue, Nov 13, 2012 at 1:14 PM, Takamoto <kyle at takamotobiogas.com> wrote:

> Dear Biogas List,
>
> I have been testing a plastic (LLDPE) floating drum digester with cow dung
> and found that the biogas production was lower than expected (pH 7, 19˚C)
> at around 0.5 cubic meters of biogas per day at 67% methane. The reactor
> volume is 3.2 cubic meters. I discovered that our dung supplier had
> recently used the antibiotic Tetracycline for a few of his cows so there is
> a chance of contamination, though at this point, I feel like the antibiotic
> concentration would be very low and should not affect gas production. Does
> anyone have experience with the effect of antibiotics? Also, what gas
> production should I expect from a 3.2 cubic meter reactor that I add 40 kg
> of cow dung to per day (plus 40 kg of water)? If I assume 15% TS and 80% of
> TS are VS then the Organic Loading Rate is around 1.5 kg -VS/m3/day and our
> specific methane yield is 0.07 m3 CH4/kg-VS and our digester efficiency is
> 0.1 m3 CH4/m3 reactor/day. Does this sound reasonable?
>
> I have also been reviewing research articles on gas production from cow
> dung but the results vary widely and sometimes I am not sure if the
> reported results are accurate. Also, research papers often use CSTR
> (continuously stirred tank reactors?) at 37˚C which makes comparing their
> results to my results rather difficult. We are getting a new load of
> non-contaminated cow dung today to see if that makes a difference. I'll let
> you know.
>
> I am sure this topic has been discussed before, so I am sorry if I have
> repeated the topic. I am newish to the forum so I haven't seen anything on
> this yet.
>
> Thanks for your advice,
>
> Kyle
> Managing Director
> Schutter Energy Ltd.
> www.takamotobiogas.com
>
>
>
>
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>
>
>


-- 
Regards.

Murali Krishna
Chairman
Hyderabad, Andhra Pradesh, India.
Ph:+91-40-24339999, 24333333,243355555, 24333555
www.villagevisionindia.com
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