I concur on Paul's preference for smaller systems. I have seen a handful of proposals based on trucking waste from a number of small to medium farms where they have tried to show energy balance (all the trucks are methane powered, etc.), but the numbers never add up. Specifically, de-watering this waste requires relatively well developed systems at each site, and likely still leaves you with a serious amount of waste water treatment for each site to achieve healthy discharge levels (in Mexico it is the water, not the solids that is the treatment challenge). The management system is also more complex and requires a high level of coordination. The alternative de-centralized option will likely have similar initial capital costs, but you can make a better case for farmer investment as they will reap the benefits. You then have much smaller long-term operating costs, and all that energy for trucking can go to good use (or maybe still trucking some effluent fertilizer to local fields). As Paul mentioned, the option to eventually pipe gas a larger distance for centralized use is an option that may make sense (but I have not seen it outside of the European context or large landfill gas context yet).
Cheers A On Sun, Jan 8, 2012 at 10:51 PM, Paul Harris <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 <paul.har...@adelaide.edu.au>**** > > 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] *On Behalf Of *REX > *Sent:* Sunday, 8 January 2012 5:26 PM > *To:* 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 > > 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/ > > > -- Alexander Eaton Sistema Biobolsa IRRI-Mexico RedBioLAC Mex cel: (55) 11522786 US cel: 970 275 4505 a...@irrimexico.org a...@sistemabiobolsa.com sistemabiobolsa.com www.irrimexico.org www.redbiolac.org
_______________________________________________ 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/
