[Digestion] % Water

[Duncan Martin]

I think these last two postings forget that the initial query was why a max 
% water is recommended *for a (bioreactor) landfill*.  In that context, 
there is no question of pumping or mixing.

Flooding CAN halt the process of anaerobic decay. I reckon it's because if 
acids build up, there is often nowhere for them to go.

I am not sure whether that mechansim is widely accepted. However, we have 
coal and peat to remind us of this effect - not to mention an occasional 
well-preserved human body in a peat bog once in a while. (There were two 
fine examples here in Ireland in recent years.)

Of course, if you plan to PUMP the stuff, you are in a completely different 
ball-park - just as the recipe for chicken soup is quite different from that 
for roast chicken!

In passing, I have written in the past (elsewhere) how amazingly little 
communication there is between researchers in AD and LFG/bioreactor 
landfills.

They are studying the very same process in a different context but they 
rarely speak to each other, read each other's papers or attend "the other's" 
conferences. The result is that they go off in opposed directions, 
unawares - and we get the silly statement that kicked off this discussion- 
that a high % water inhibits LFG production.

An undergraduate-level knowledge of AD would have sounded alarm bells to say 
that there must be some other mechanism than simple inhibition !!!

(I imply no criticism of the initial posting, which simply quoted "expert" 
advice - widely accepted expert advice too.)

Moral: beware of experts.....  and remember that I might be one myself!

Best regards

Duncan J Martin

Chair
Republic of Ireland Centre
Chartered Institution of Wastes Management

================================
CONTACT DETAILS
Duncan J Martin, PhD, CEng, CSci, MIEI, MCIWM, MIChemE
24 Townsfield, Cloughjordan, N Tipperary, Ireland
Mobile: +353 86 8377 906
Home: +353 505 42087
Email: duncanjmartin at eircom.net
================================




----- Original Message ----- 
From: "Katahdin Energy Works" <KatahdinEnergyWorks at verizon.net>
To: "'Peter Allison'" <pmallison at optusnet.com.au>; 
<digestion at listserv.repp.org>
Sent: Tuesday, October 09, 2007 1:34 PM
Subject: Re: [Digestion] supernatant water content


> Amen to this observation.
>
> Anything beyond a ratio of 12% solids and you run into serious manure 
> slurry
> pumping problems.
>
> Among the recommendations, besides limiting your solids to liquid ratio; 
> are
> using fairly wide PVC pipe, i.e. 6"; siting your digester so you can take
> full advantage of gravity---you have no idea how expensive it gets to pump
> manure slurries; eliminating any bends--a clogged PVC bend usually has to 
> be
> cut out, and replacing them with Tees that are capped for easy cleanout;
> obtain the best manure/feedstock chopper you can get, i.e. HOULE 
> electromix
> or a FAN system since the finer the emulsified slurry the easier it is to
> pump and digest.
>
> These are the 'professionally' designed systems; some will want to keep it
> simple and just fill the tank and heat it up; and let it 'cook'; then pump
> it out and deal with solids settling later.
>
> Frank.
>
> Frank J. Heller, MPA
> KATAHDIN ENERGY WORKS
> 12 Belmont St.
> Brunswick, ME 04011-3004
> 207.729.6090
> http://mysite.verizon.net/fjheller/
>
> -----Original Message-----
> From: digestion-bounces at listserv.repp.org
> [mailto:digestion-bounces at listserv.repp.org] On Behalf Of Peter Allison
> Sent: Wednesday, October 10, 2007 10:28 AM
> To: digestion at listserv.repp.org
> Subject: Re: [Digestion] supernatant water conten
>
> Charles,
> The water content of a biogas charge requires to be sufficient to mobilize
> the manure content to a slurry, about 1:1 with damp manure. Below this 
> ratio
> the slurry is too thick to move and too much water is a waste of space and
> diluted reactivity. The correct ratio reacts to stirring more like a gel
> than either a solid or liquid mix, just pourable.
> I believe the process has great benefit beyond just producing gas. It will
> reduce waste material handling problems, provide high response, 
> sustainable,
> agricultural fertilizers, a means to return carbon to the soil, several
> compounds that will absorb and remediate toxic waste and effectively
> scavenge oil spilled on water, provide raw feedstock for the carbon fiber
> industry and food supply for aquaculture. All from pure excrement. What 
> more
> could you want?
> Regards,
> Peter Allison.
> _______________________________________________
> Digestion mailing list
> Digestion at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> http://info.bioenergylists.org
>
>
>
> _______________________________________________
> Digestion mailing list
> Digestion at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> http://info.bioenergylists.org
>
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.488 / Virus Database: 269.14.5/1058 - Release Date: 
> 08/10/2007 16:54
>
>