[Digestion] Effect of Surface Area

David david at h4c.org
Thu Nov 1 09:56:40 PDT 2012


On 11/1/2012 1:32 AM, Paul Muthui wrote:
> Good Day All,
> I read in an article that increasing the surface area inside the 
> biogas digester  (e.g. by introducing vertical structures), 
> increases the population bacteria population and consequently more 
> gas production.  By what percentage does this increase gas 
> production? And what's the most effective way to do it?

Methanogens are part of a complex ecology that likes to sustain itself 
by forming biofilms on any available surface. However, for most kinds 
of digestion-- that is, at any percentage of solids that one might 
"choose," rather than having it /imposed/ by the high water content of 
the substrate-- there is plenty of surface for the biofilms to form.

Adding surface to the inside of a digester, then, is almost 
exclusively done where the dilution of the incoming substrate is 
considerable (1%-2% or less). What happens where such substrates are 
digested with sufficient HRT is that floating consortia of microbes 
develop. These a bit like sponges, and are often referred to as "flocs".

You may be able to learn more by searching for [biogas dilute flocs] 
and adding any reference to the substrate you have in mind.

David William House
"The Complete Biogas Handbook" |www.completebiogas.com|
/Vahid Biogas/, an alternative energy consultancy |www.vahidbiogas.com

"Make no search for water.   But find thirst,
And water from the very ground will burst."
(Rumi, a Persian mystic poet, quoted in /Delight of Hearts/, p. 77)

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