[Digestion] AD for cow manure

[Paul Harris]

G'day Rex,

If you have a lagoon check the likely Retention Time - it may be so long
that you don't have to worry about mesophilic/heating and so save the
cost/complexity. Dairies need hot water for washing, so that will use some
of the heat.

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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-----Original Message-----
From: digestion-bounces at lists.bioenergylists.org
[mailto:digestion-bounces at lists.bioenergylists.org] On Behalf Of Rex
Zietsman
Sent: Saturday, 11 June 2011 6:21 PM
To: digestion at lists.bioenergylists.org
Subject: [Digestion] AD for cow manure

Hi Steve,

It has been a long time since we last communicated. I hope you are well. I
see that you are still experimenting as ever. As you can see, it appears
that I am back in the AD business for my neighbour and another farmer in the
district. 

You are spot on with respect to being caught between two sizes - hence my
use of second hand 3 litre motors driving generators. Brent has come up with
a number of suggestions that I believe have merit and should be able to help
keep the overall cost down. So I will look at those for sure. The fact is
that all of the dairies have existing lagoons and if we can modify them, it
makes life a lot easier. I agree with your idea of pre-heating the charge
before feeding it to the lagoon. This means that there has to be a large
intake pit to take all of the washings in one go, heat them up and let them
go to the lagoon. I believe that the cost of this should not be exorbitant
and it will allow the lagoon to operate in the mesophilic range. 

Surprisingly, I have been involved with dry digestion over the past year
with the objective of generating biogas for transport purposes. The gas is
upgraded to about 92% CH4 before compression, chilling and liquefaction. The
bio LNG is then pumped into cylinders in cassettes. The cassettes are
mounted on trucks and the gas reduces the diesel consumption. The empty
cassettes are swapped out for full ones as required.  Clearly this is on a
much larger scale than farm digestion and the capital is much larger as
well. The requirement for the biomass raw material is that it must be able
to ferment. Essentially, the rule of thumb is: "if a cow will eat it, we can
ferment it". So your grass attempts are not far off the mark. How well does
the fixed film work?

Kind regards
Rex