[Digestion] Biogas production

Jaime Marti Herrero tallerbiogas at hotmail.com
Tue Nov 13 07:20:59 PST 2012


Hi Kyle

about antibiotics i have been afraid from the beginning,
but after years dealing with those, the solution is just to be patient and
wait for the auto regulation of the slurry. I attach a paper about antibiotics,
and how they do not affect seriously the biogas production.

 

about your low biogas production...yes, looks low. my
reference number are 35 liters of biogas per kg of fresh manure, so in your
case should be something like 1400l/day. with your numbers, the digester have
40 days of retention time (HRT) for 19ºC of slurry temperature. Your SBP (m3CH4/KgSV)
looks low, but your BPR (m3CH4/m3/d) looks acceptable, so the conclusion is
that the digestion process is not efficient, and could be because the
antibiotics, but also because the HRT is low. 

so, i recommend you first wait a few weeks to looks
how is going the biogas production...and if nothing changes (you should get
something similar as 1400l/d for those 40kg of fresh manure), i recommend to give
more HRT to the digester, up to 60-65 days.

 

keep in touch

j-----

Jaime Martí Herrero

CIMNE (www.cimne.com). Building
Energy and Environment Group

Cochabamba · Bolivia

Tel. (+591)-73 090 621

 

BIOGAS AND BOLIVIA

-RedBioLAC:http://redbiolac.org/

-Taller Biogas Bolivia:http://tallerbiogas.blogspot.com  

-Video: Biodigester installation in bolivian Altiplano:http://es.youtube.com/watch?v=3Sl0XEN5Bgo-Manual gratuito-Biodigestores familiares: Guía de diseño y manual de
instalación: http://grecdh.upc.edu/publicacions/llibres/documents/2008_jmh_guia_biodigestores.pdf

From: kyle at takamotobiogas.com
Date: Tue, 13 Nov 2012 10:44:10 +0300
To: Digestion at bioenergylists.org
Subject: [Digestion] Biogas production

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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