[Digestion] heating the fermenter

[Duncan Martin]

Heat IS generated but so slowly that it is a very minor factor in most 
digesters.

The dominant factors in the heat balance tend to be:
- heat losses to the air and ground (except in VERY warm climates or with 
VERY good insulation or at VERY large scale)
- heat losses in the digestate (maybe offset by using it to preheat cold 
feedstock)
- heat losses to the feedstock (it is often well below the digester temp and 
if it isn't very strong you'll be adding a large volume every day) OR
- heat gains from the feedstock (if it's hot - but that's much rarer)
- any compensating heat input from a source of waste heat (sometimes 
available in industry)
- finally the balancing heat input from burning of some of the biogas (a 
waste of good fuel but often unavoidable)

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
Email: duncanjmartin at eircom.net
================================




----- Original Message ----- 
From: "adkarve" <adkarve at pn2.vsnl.net.in>
To: <Digestion at listserv.repp.org>
Sent: Monday, October 30, 2006 2:59 PM
Subject: Re: [Digestion] heating the fermenter


Dear members,
I still seek an answer to my question as to whether methnogenesis in a
biogas plant was an exenergonic reaction or not. The claim made by Mr.
Hatoum that a biogas plant with a moving dome was open at the top and
therefore not amenable to being insulated, is not acceptable to me.The top
of the fermenter is not open, but is covered by the gas holder. The gas
holder is made of moulded plastic. The plastic as well as the biogas inside
the gas holder are both poor conductors of heat. Since the fermentation
takes place inside the fermenter vessel, I feel that it would be meaningful
to insulate the fermenter vessel.
Yours
A.D.Karve
----- Original Message -----
From: Socrate Hatoum <socrate at hatoum.com>
To: adkarve <adkarve at pn2.vsnl.net.in>
Sent: Monday, October 30, 2006 4:27 PM
Subject: Re: [Digestion] heating the fermenter


Dear Dr Karve

With all due respect. your type of digester is impossible to
insulate, since it is opened at the top. due to the floating dome.
The later is functional in the tropics. But "thanks" to the global
heating the tropics are moving north...
Best regards
S. Hatoum

Le 29 oct. 06 à 02:51, adkarve a écrit :

> Dear Mr. Simon,
>
> in my starch based biogas plant, I add daily only 10 litres water
> and 1 kg starchy material to a fermenter having a volume of 1000
> litres.
>
> Is methanogenesis an exenergonic reaction? If that were so, and if
> the fermenter were insulated, there should be no need to heat the
> fermenter during winter.
>
> Yours
>
> A.D.Karve
>
> _______________________________________________
> Digestion mailing list
> Digestion at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org




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