[Digestion] Biogas production

Paul Harris paul.harris at adelaide.edu.au
Tue Nov 13 01:06:45 PST 2012

G'day Kyle et al,

My antibiotic experience is at a piggery where weaners were injected 
with Ivomec as part of the weaning procedure but the digester carried 
on, apparently quite happily. Then one day the whole herd was fed Ivomec 
in the feed mix (and of course some feed spills straight into the 
drains), which resulted in no gas - the good part is a few days after 
stopping pumping into the digester gas production restarted 
spontaneously. I doubt if a few cows would have a bad effect, that said 
I used cow manure where I found out the cows were fed antibiotics in 
another digester and got no gas for a few weeks, but when I returned 
from holidays a few weeks later gas production had commenced.

Are you talking dairy cattle or beef cattle and what is your operating 
temperature? You can use the attached model to try the variables.

Happy digesting,

Mr Paul Harris BEng (Ag) (Melbourne)
Visitor at The University of Adelaide

On 13/11/2012 6:14 PM, Takamoto 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 <http://www.takamotobiogas.com>
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