[Digestion] Digestion Digest, Vol 16, Issue 4
Vishwas Gokhale
g_vishwas at vsnl.com
Thu Oct 11 02:10:34 EDT 2007
The quantity of water in the digester is really irrelevant. Completely
clarified effluents are known to produce biogas. For example Dr Lettinga's
UASB digesters are known to work without any suspended solids content in the
feedstock and that too with retention time as low as 6 hours. It is also
known that no fermentation is possible with completely dry organic solids.
But fermentation is possible with green biomass without any water addition.
The real consideration in the digester design is the amount of feed stock (
biodegradable matter) and the quantity of bacterial mass and how well the
optimum ratio is maintained.
There are number of techniques used to retain biomass ( bacterial mass)
inside the digester, control the pH and maintain the temperature so that the
anaerobic digestion works more efficiently.
The landfills normally do not employ these techniques. That is the essential
difference between a digester and a landfill.
Vishwas Gokhale
Principal Consultant
GIT Associates
1034/2/B, 6, Annapurna, Model Colony,
Pune 411016, India
http://www.gitassociates.com
-----Original Message-----
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Sent: 11 October 2007 10:32
To: digestion at listserv.repp.org
Subject: Digestion Digest, Vol 16, Issue 4
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Today's Topics:
1. Re: supernatant water conten (Bruno M.)
2. % Water (Duncan Martin)
3. Burning food waste (Duncan Martin)
4. Re: Burning food waste (Katahdin Energy Works)
5. Digesting MSW (Zietsman, Rex)
----------------------------------------------------------------------
Message: 1
Date: Wed, 10 Oct 2007 18:01:55 +0200
From: "Bruno M." <brunoM1 at telenet.be>
Subject: Re: [Digestion] supernatant water conten
To: Digestion at listserv.repp.org
Message-ID: <20071010160154.A314041C9 at europa.telenet-ops.be>
Content-Type: text/plain; charset=iso-8859-1; format=flowed;
x-avg-checked=avg-ok-5E5F65B4
Depending on the feedstock you do not always have
to make a liquid soup to do AD.
like in the Dranco process.
See ( for English version:
www.ows.be/pages/index.php?menu=69&choose_lang=EN
[ site is also viewable in German (Deutsch),
French ( Fran?ais) and Dutch ( Nederlands)]
Click e.g. on " Dranco " ... dry anaerobic digestion ...
Grts
Bruno M.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 14:27 10/10/2007, you wrote:
>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
>
>
>
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>
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Message: 2
Date: Wed, 10 Oct 2007 19:50:02 +0100
From: "Duncan Martin" <duncanjmartin at eircom.net>
Subject: [Digestion] % Water
To: <fjheller at verizon.net>, "'Peter Allison'"
<pmallison at optusnet.com.au>, <digestion at listserv.repp.org>
Message-ID: <014f01c80b6e$66c0f950$4033869f at Dell1>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
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
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>
------------------------------
Message: 3
Date: Wed, 10 Oct 2007 19:54:28 +0100
From: "Duncan Martin" <duncanjmartin at eircom.net>
Subject: [Digestion] Burning food waste
To: Bj?rn Dahlroth <bjorn.dahlroth at telia.com>, "'mrcdb'"
<mrcdb at charter.net>, <digestion at listserv.repp.org>
Message-ID: <015101c80b6f$02f22c40$4033869f at Dell1>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Yes, it might be reasonable to burn food waste at 40% H20. But that's not
the scenario here.
The initial posting was about a landfill, which contains only a small % of
organic waste (tending to zero in the EU). Landfills can burn, of course -
but it's not recommended!
Duncan
----- Original Message -----
From: "Bj?rn Dahlroth" <bjorn.dahlroth at telia.com>
To: "'mrcdb'" <mrcdb at charter.net>; <digestion at listserv.repp.org>
Sent: Wednesday, October 10, 2007 4:29 PM
Subject: Re: [Digestion] Digestion Digest, Vol 16, Issue 1
Hi
If you are not particularly interested in precisely methane for some special
purpose or in the N P K content of food waste but more in the energy
content, than it is more efficient to burn it in a large incineration plant
and produce hot water or steam and electric power. The total energy
efficiency will be higher than what you can achieve in a digestion plant.
The hot water can be used for district heating, steam can be used for
district heating or sold to some nearby industries. Electricity can be sold
on the market for electric power. However incineration plants can not be
very small and the moisture content can not be very high. Usually the
technical maximum limit for the moisture in the total waste stream going
into a modern incineration furnace is about 65% and above that you may have
problems with the ignition and the required temperature level (850 C) of the
combustion. Waste with a moisture content of 38-40% is very good fuel unless
most of it is inert material. If a limited waste stream in the municipal
solid waste has higher moisture content than approximately 65% you can still
extract a lot of heat from it by co-combustion with dryer waste followed by
flue gas condensation. Flue gas condensation is a common method for
increasing the heat production from combustion and standard equipment in
Scandinavia to day on incineration plants and plants for burning wood
residues (branches and tree tops) from the forest industry. The absolutely
theoretical upper moisture content limit for extracting heat from solid
waste in a co-firing plant is around 80%. It is above that limit that
digestion of food waste is most competitive from energy point of view. Also
it can be competitive for cases where the waste supply is small, where the
transport distance to a big incineration plant is too long and where the
methane market is willing to pay a high price (e g city busses) and where
there is no market for district heating. So when it is question about
municipal solid waste there is room for both incineration and digestion but
one has too look carefully at the market conditions in each case and also
consider the societal cost of separating food waste from other waste at the
source, which is necessary if you want to digest in closed containers.
Municipal solid waste is one of the most difficult energy sources to use
irrespective of method but anything is better than landfill without
treatment. (Landfills can of course produce methane but the efficiency is
lower and the time required to complete the process is extremely long.) The
best use of digestion seems to be in agriculture and for treatment of high
moisture waste in the food industry.
Bjorn Dahlroth
-----Ursprungligt meddelande-----
Fr?n: digestion-bounces at listserv.repp.org
[mailto:digestion-bounces at listserv.repp.org] F?r mrcdb
Skickat: den 8 oktober 2007 18:27
Till: digestion at listserv.repp.org
?mne: 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
_______________________________________________
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
--
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Checked by AVG Free Edition.
Version: 7.5.488 / Virus Database: 269.14.5/1058 - Release Date: 08/10/2007
16:54
------------------------------
Message: 4
Date: Tue, 09 Oct 2007 16:25:34 -0200
From: "Katahdin Energy Works" <KatahdinEnergyWorks at verizon.net>
Subject: Re: [Digestion] Burning food waste
To: "'Duncan Martin'" <duncanjmartin at eircom.net>, 'Bj?rn Dahlroth'
<bjorn.dahlroth at telia.com>, "'mrcdb'" <mrcdb at charter.net>,
<digestion at listserv.repp.org>
Message-ID: <002a01c80aa1$c9107310$5b315930$@net>
Content-Type: text/plain; charset=iso-8859-1
Zero organic waste? Some say that over 50% is newsprint and other paper
products; some go up to 75%.
I've read a few advocacy pieces that indicate that AD is preferred to
burning for organics.
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 Duncan Martin
Sent: Wednesday, October 10, 2007 4:54 PM
To: Bj?rn Dahlroth; 'mrcdb'; digestion at listserv.repp.org
Subject: [Digestion] Burning food waste
Yes, it might be reasonable to burn food waste at 40% H20. But that's not
the scenario here.
The initial posting was about a landfill, which contains only a small % of
organic waste (tending to zero in the EU). Landfills can burn, of course -
but it's not recommended!
Duncan
----- Original Message -----
From: "Bj?rn Dahlroth" <bjorn.dahlroth at telia.com>
To: "'mrcdb'" <mrcdb at charter.net>; <digestion at listserv.repp.org>
Sent: Wednesday, October 10, 2007 4:29 PM
Subject: Re: [Digestion] Digestion Digest, Vol 16, Issue 1
Hi
If you are not particularly interested in precisely methane for some special
purpose or in the N P K content of food waste but more in the energy
content, than it is more efficient to burn it in a large incineration plant
and produce hot water or steam and electric power. The total energy
efficiency will be higher than what you can achieve in a digestion plant.
The hot water can be used for district heating, steam can be used for
district heating or sold to some nearby industries. Electricity can be sold
on the market for electric power. However incineration plants can not be
very small and the moisture content can not be very high. Usually the
technical maximum limit for the moisture in the total waste stream going
into a modern incineration furnace is about 65% and above that you may have
problems with the ignition and the required temperature level (850 C) of the
combustion. Waste with a moisture content of 38-40% is very good fuel unless
most of it is inert material. If a limited waste stream in the municipal
solid waste has higher moisture content than approximately 65% you can still
extract a lot of heat from it by co-combustion with dryer waste followed by
flue gas condensation. Flue gas condensation is a common method for
increasing the heat production from combustion and standard equipment in
Scandinavia to day on incineration plants and plants for burning wood
residues (branches and tree tops) from the forest industry. The absolutely
theoretical upper moisture content limit for extracting heat from solid
waste in a co-firing plant is around 80%. It is above that limit that
digestion of food waste is most competitive from energy point of view. Also
it can be competitive for cases where the waste supply is small, where the
transport distance to a big incineration plant is too long and where the
methane market is willing to pay a high price (e g city busses) and where
there is no market for district heating. So when it is question about
municipal solid waste there is room for both incineration and digestion but
one has too look carefully at the market conditions in each case and also
consider the societal cost of separating food waste from other waste at the
source, which is necessary if you want to digest in closed containers.
Municipal solid waste is one of the most difficult energy sources to use
irrespective of method but anything is better than landfill without
treatment. (Landfills can of course produce methane but the efficiency is
lower and the time required to complete the process is extremely long.) The
best use of digestion seems to be in agriculture and for treatment of high
moisture waste in the food industry.
Bjorn Dahlroth
-----Ursprungligt meddelande-----
Fr?n: digestion-bounces at listserv.repp.org
[mailto:digestion-bounces at listserv.repp.org] F?r mrcdb
Skickat: den 8 oktober 2007 18:27
Till: digestion at listserv.repp.org
?mne: 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
_______________________________________________
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
--
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_______________________________________________
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
------------------------------
Message: 5
Date: Thu, 11 Oct 2007 07:01:40 +0200
From: "Zietsman, Rex" <Rex at Process.co.za>
Subject: [Digestion] Digesting MSW
To: <digestion at listserv.repp.org>
Cc: finstein at envsci.rutgers.edu
Message-ID:
<15158807F724CB4593BF508C151108CC01613168 at scalpel.imsgroup.local>
Content-Type: text/plain; charset="us-ascii"
Bjorn wrote:
"Hi
If you are not particularly interested in precisely methane for some
special purpose or in the N P K content of food waste but more in the
energy content, than it is more efficient to burn it in a large
incineration plant and produce hot water or steam and electric power.
The total energy efficiency will be higher than what you can achieve in
a digestion plant. The hot water can be used for district heating, steam
can be used for district heating or sold to some nearby industries.
Electricity can be sold on the market for electric power. However
incineration plants can not be very small and the moisture content can
not be very high. Usually the technical maximum limit for the moisture
in the total waste stream going into a modern incineration furnace is
about 65% and above that you may have problems with the ignition and the
required temperature level (850 C) of the combustion. Waste with a
moisture content of 38-40% is very good fuel unless most of it is inert
material. If a limited waste stream in the municipal solid waste has
higher moisture content than approximately 65% you can still extract a
lot of heat from it by co-combustion with dryer waste followed by flue
gas condensation. Flue gas condensation is a common method for
increasing the heat production from combustion and standard equipment in
Scandinavia to day on incineration plants and plants for burning wood
residues (branches and tree tops) from the forest industry. The
absolutely theoretical upper moisture content limit for extracting heat
from solid waste in a co-firing plant is around 80%. It is above that
limit that digestion of food waste is most competitive from energy point
of view. Also it can be competitive for cases where the waste supply is
small, where the transport distance to a big incineration plant is too
long and where the methane market is willing to pay a high price (e g
city busses) and where there is no market for district heating. So when
it is question about municipal solid waste there is room for both
incineration and digestion but one has too look carefully at the market
conditions in each case and also consider the societal cost of
separating food waste from other waste at the source, which is necessary
if you want to digest in closed containers. Municipal solid waste is one
of the most difficult energy sources to use irrespective of method but
anything is better than landfill without treatment. (Landfills can of
course produce methane but the efficiency is lower and the time required
to complete the process is extremely long.) The best use of digestion
seems to be in agriculture and for treatment of high moisture waste in
the food industry.
Bjorn Dahlroth"
Bjorn,
There is an Israeli technology that takes unsorted MSW, sorts the
"heavies" from the "lights" by dropping the MSW into a water bath -> the
plastics float off while the heavies are sucked out and subjected metal
and glass recovery. The organics are broken up by shear in the water
bath using water jets. The organic laden water is then sent to a two
stage AD process of which the second stage is a UASB treating filtered
water from the first stage. This system works remarkably well but, as
you noted, does not generate as much energy (plastics are not burnt and
the co-production of CO2 leads to energy loss).
For more information, contact Mel Finstein: see contact details below
Kind regards
Rex
Melvin S. Finstein, Ph.D.
Emeritus Professor of Environmental Science
Rutgers, The State University of New Jersey
Head, ArrowBio USA
Email: finstein at envsci.rutgers.edu
------------------------------
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End of Digestion Digest, Vol 16, Issue 4
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