Mr. Harris, I like your suggestion of smaller digesters. The problem is I have not been able to find a digester design robust enough yet cheap enough for a 100 cow dairy. Do you know where such a design exists? I have just about given up the notion that such a thing exists.
Thanks for your help with this. M. Charles Gould Extension Educator-Bioenergy and On-farm Energy Conservation Michigan State University Extension (C) 616/834-2812 On Jan 9, 2012, at 12:51 AM, "Paul Harris" <paul.har...@adelaide.edu.au<mailto:paul.har...@adelaide.edu.au>> wrote: 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.har...@adelaide.edu.au>mailto:paul.har...@adelaide.edu.au <http://www.adelaide.edu.au/directory/paul.harris>http://www.adelaide.edu.au/directory/paul.harris CRICOS Provider Number 00123M ----------------------------------------------------------- This email message is intended only for the addressee(s) and contains information which may be confidential and/or copyright. If you are not the intended recipient please do not read, save, forward, disclose, or copy the contents of this email. If this email has been sent to you in error, please notify the sender by reply email and delete this email and any copies or links to this email completely and immediately from your system. No representation is made that this email is free of viruses. Virus scanning is recommended and is the responsibility of the recipient. From: digestion-boun...@lists.bioenergylists.org<mailto:digestion-boun...@lists.bioenergylists.org> [mailto:digestion-boun...@lists.bioenergylists.org] On Behalf Of REX Sent: Sunday, 8 January 2012 5:26 PM To: <mailto:digestion@lists.bioenergylists.org> digestion@lists.bioenergylists.org<mailto:digestion@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 _______________________________________________ Digestion mailing list to Send a Message to the list, use the email address digest...@bioenergylists.org<mailto:digest...@bioenergylists.org> to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org for more information about digestion, see Beginner's Guide to Biogas http://www.adelaide.edu.au/biogas/ and the Biogas Wiki <http://biogas.wikispaces.com/> http://biogas.wikispaces.com/
_______________________________________________ Digestion mailing list to Send a Message to the list, use the email address digest...@bioenergylists.org to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org for more information about digestion, see Beginner's Guide to Biogas http://www.adelaide.edu.au/biogas/ and the Biogas Wiki http://biogas.wikispaces.com/
