[Digestion] Digestion Digest, Vol 5, Issue 9

Tue Nov 14 09:14:17 CST 2006

Hi all!
Another important question is what you mean by high rate. Is it a high conversion efficiency och a high production per digester vessel volume.   These things are also in opposition to each other. To use smaller digestion vessels and not aim for the highest convesion efficiency of the digestible matter can be a more economical choice as the in vestment will be less. 

The highest possible solid concentration you can work with is what we call digestion cells. This is simply that you build up a kind of pile or landfill in a more scientifc way, put in drainage pipes and a system for circulating the liquid through the whole body and then you cover the the whole thing with a resonably tight membranene that could be made from heavy plastic tarpaulins or well packed clay. After that you suck out the gas through drainage system. When the gasproduction has become too small you stop and dig it out or you just leave the cell to become a landfill. This has been and is done in a few places in this country for municipal solid waste and it works. However it is not a nice job to dig out afterwards and if you leave it you must pay land fill tax so it is not very popular any more. It works however and the investment cost is reasonable. You may loose the plant nutritional value but you get the gas. Usually it is the gas that has some commercial value. Another way when it comes to food waste is to mash it, mix with some water and put it in the digestion section of a waste water treatment plant. Of course this is a rather low solid system and you loose the plant nutrition but you still get the gas. Again - the commercial value is more in the gas. The gas can be purified, upgraded and sold to a local natural gas supplier or be used for the local bus transport system.

These two more rough ways of doing it are realistic alternatives in competion with other methods like digesting in specially dedicated large vessels when it is question about large scale treatment of digestible waste from whole urban areas but it seems they are not so much dicussed in the scientific community. It seems that conversion efficiency can still be reasonable if the processes are given enough time but of course the main driver is not the energy nor the plant nutrition but instead the treatmen of streams of waste.
Regards to all
Bjorn Dahlroth
The Stockholm County Association of Local Authorities

-----Ursprungligt meddelande-----
Från: digestion-bounces at listserv.repp.org [mailto:digestion-bounces at listserv.repp.org] För Duncan Martin
Skickat: den 13 november 2006 15:23
Till: finstein at envsci.rutgers.edu; digestion at listserv.repp.org
Kopia: stuart at oaktech-environmental.com
Ämne: Re: [Digestion] Digestion Digest, Vol 5, Issue 9

Good to hear from you again Mel - but I have a question for you....

WHY are "High Solids and High Rates mutually exclusive"

Is that a law of nature or just an artefact of how we've been doing things up to now?

Clearly, the highest rates will be obtained with 100% soluble substrates, which are inherently incompatible with very high solids concns.

However, for the SAME substrate, I am not convinced.

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
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----- Original Message -----
From: <finstein at envsci.rutgers.edu>
To: <digestion at listserv.repp.org>
Cc: <stuart at oaktech-environmental.com>
Sent: Saturday, November 11, 2006 6:45 PM
Subject: Re: [Digestion] Digestion Digest, Vol 5, Issue 9

Greetings to all subscribers,

Regarding "high solids content" digestors alluded to below, please note
that in fact High Solids and High Rates are mutually exclusive. The point
is thoroughly explored elsewhere: <www.oaktech-environmental.com> click on
"news & events", then click on the item dated 29 January 2006 - see
especially Part 3.

The posted abstract on the Oaktech website reads:

"ArrowBio USA Represented by Professor Melvin Finstein submitted his
response to the URS Reports on future waste technologies for Los Angeles.
Mel's response is critical to a report that bundles all anaerobic
digestion systems into the same category and discounts the clear benefits
of advanced anaerobic digestion."

It might be noted that ArrowBio is a semi-finalist contender in Los
Angeles County and elsewhere. Much background material is given in the 29
January 2006 "Critique."

Regards to all,

Mel Finstein

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>    1. high rate digester (AKBAR SHABANI)
>    2. Re: high rate digester (Bjorn Dahlroth)
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> Message: 1
> Date: Fri, 10 Nov 2006 21:05:27 -0800 (PST)
> From: AKBAR SHABANI <a_shabanikia at yahoo.com>
> Subject: [Digestion] high rate digester
> To: "ÔÈ~å È&#1740,æÇÒ&#1740," <digestion at listserv.repp.org>
> Message-ID: <20061111050527.66358.qmail at web52208.mail.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
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> dear hi   I want to make digesteres  for biogas production from high
> concenterate matterial  with totale solides about 20-40 %.if it possible
> please help me
>
>   with thank
>   A - SHABANIKIA

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