[Digestion] 5000 dairy cow AD system

[Paul Harris]

G'day Rex,

 

Apparently a lot of the biogas comes from the fines/solutes in the liquid -
I noticed that with piggery effluent the raw effluent was almost impermeable
to water (it would hold puddles for quite a while) but after treatment the
solids were pretty free draining (water disappeared in minutes).

 

I will also raise my usual point in favour of distributed systems - why not
put smaller (cheaper!) digesters at each farm and if necessary pipe the
biogas to a central generator (depending on distance)? You will be spending
a lot of energy on trucking waste in and then you have to truck the
digestate out from the central facility again. The total capital cost may be
higher, with more units to maintain, but you can start with one or two and
spread the finances out a bit as well as helping local employment (I guess
people will be working on digesters instead of driving trucks!).

 

Happy digesting,

HOOROO

-- 

Mr. Paul Harris, Room 202, Charles Hawker 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

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 REX
Sent: Sunday, 8 January 2012 5:26 PM
To: digestion at lists.bioenergylists.org
Subject: [Digestion] 5000 dairy cow AD system

 

Hi All,

 

I have been approached to put together a proposal for a centralised AD using
the manure from 5000 dairy cows. The intention is to pre-concentrate the
dairy manure slurry and to truck the solids to a central processing unit. As
silage and grass is extensively used as feed, we would be able to co-digest
this with the manure to increase the gas output. Furthermore, it is intended
to use the exhaust gas and the AD liquor to grow macro algae or a plant such
as hyacinth (an indigenous variety that is not likely to become an invader
should it get out) which can be shredded and added back to digestion. We aim
to use the gas for power generation and to use the heat to keep the
digester(s) warm.

 

Questions:

1. By leaving the water behind, do we lose most/all/some of the FFA? What
impact would it have on gas production?

2. Can anyone recommend a supplier of technology for this size of plant?

3. 5000 cows is an arbitrary amount at this stage - 10 farms of 500 cows
each. Is there a better/more economical size?

 

Kind regards

Rex Zietsman

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