[Digestion] % water in landfills

[Duncan Martin]

Charles and all

I think the guideline that 38-40% H2O is best in landfills relates more to 
the need to avoid XS water, which greatly increases the volume of leachate 
to be contained and managed.

Saturation with water doesn't seem likely to inhibit the process - 
otherwise, how does conventional AD work? It's often said to do so but I 
think that's based on the widespread assumption that the reaction mechanisms 
in LFG generation are the exact same as in AD.

If you check out my research publications between 1999 and 2005, you'll find 
I propose an alternative that makes more sense: the Reaction Front (aka 
Microreactor in some earlier papers). The basic microbiology and 
biochemistry are the same but I think the major reactions in a landfill 
might take place INSIDE the solids.

One reason for this is that the liquid fraction in a real landfill (unlike 
many lab models) is usually very high in inhibitory VFAs (Volatile Fatty 
Acids), so it's hard to see how much reaction could take place in the liquid 
phase. If so, any inhibitory effect of liquid saturation in landfill might 
be due to the much greater mass of VFA it would contain.

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: "mrcdb" <mrcdb at charter.net>
To: <digestion at listserv.repp.org>
Sent: Monday, October 08, 2007 5:27 PM
Subject: Re: [Digestion] Digestion Digest, Vol 16, Issue 1


> Hello All,
>
> I am an Energy Consultant in Erie, MI,  USA
>
> I have been researching anerobic digestion lately as related to Municipal
> Solid Waste (MSW) landfills and landfill gas to electric plants.
>
> I am a member of the Solid Waste Association of North America (SWANA) and
> just completed their landfill gas ecourse.
>
> Anyway, in their course they state that "a moisture content, of the
> digestion material, of 38-40% is ideal for the most methane production" 
> and
> that "recirculating the leachate produces lots of gas"
> They say that a moisture content much over 40% is a saturated condition, 
> and
> will slow or stop methane production!
>
> So, it seems to me, that a digester full of water is not an efficient way 
> to
> produce methane?
>
> Does anyone have any thoughts on this subject?
>
> Thanks,
>
> Charles Bagwell
> President
> Zerwell Energy
> www.zerwellenergy.com
> Erie, MI
>
>
>
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>
>
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