[Digestion] Duncan's food for thoughtRe

Fri Aug 31 10:56:40 EDT 2007

To all,

In Digestion Digest, Vol 14, Issue 15 (30 August 2007), Duncan Martin
contributed the following memorable gem Re: biogas and its uses. It is
worth copying:

------------------------------------------------

> From: "Duncan Martin" <duncanjmartin at eircom.net

> Whatever method you think of using, do reflect first on the advice
> given by Paul Harris the few hours ago to consider very carefully
> why you should want to produce pure methane.

> Unless you want it for some kind of chemical feedstock, you
> presumably want it as a fuel.

> If you want it as a transport fuel, it is true that storage capacity
> would be enhanced by the use of pure methane.  However, it would
> not even be doubled, so the cost would have to be very low to make this
> worthwhile.

> Pure methane would be more energy efficient in any combustion device BUT
> the energy required to purify it might well exceed any efficiency gain
-->  and that is before you even consider the cost.

> Bear in mind too that the diluent effect of carbon dioxide in combustion
> is vastly exceeded by the diluent effect of the nitrogen in the
> combustion air.

> Consider the stoichiometry of combustion.

> With pure gases:
> CH4 + 2O2 = CO2 + 2H2O

> If the CH4 comes with some unwanted CO2 (lets say 2:1 for simplicity),
> the > eqn becomes:
> (CO2 + 2CH4) + 4O2 = 3CO2 + 4H2O

> Now the extra CO2 is indeed a 'passenger' in any boiler or gas engine,
> adding to the volume of the  hot gases that escape via the flue or
> exhaust pipe -and thus to the energy lost in them.

> BUT remember that the oxygen comes with a lot of unwanted gas too -
> nitrogen, in a 4:1 ratio, so the true equation for the combustion
> process is:
> (C02 + 2CH4) + (4O2 + 16N2) = 3CO2 + 4H2O + 16N2

> The nitrogen is just as much a passenger as the carbon dioxide is --
> and there is 16 times more of it (by volume). We all know that it is
> very rarely economic to supply an engine or any boiler with pure oxygen
> instead of air> (unless you work for NASA!), so this should be a warning
> that the removal of carbon dioxide is unlikely to make sense either.
Of > course, it might be economic if the removal of carbon dioxide was
very
> much cheaper than the removal of nitrogen. However, there is little
> point in considering one without considering the other, since for all
> you know you might be considering the less economic option.

> Food for thought?

> 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: "Warren Weisman" <weiswar at yahoo.com>
> To: <digestion at listserv.repp.org>
> Sent: Thursday, August 30, 2007 7:13 PM
> Subject: [Digestion] Scrubbing biogas into biomethane article
>
>
>>
>> Here's an article that covers a number of different
>> technologies to scrub biogas into biomethane.
>>
>> The simple, low-cost method of just bubbling your
>> biogas through a solution of lime and water is not
>> mentioned, but is in use in many countries.
>>
>> http://www.westernuniteddairymen.com/Biogas%20Fuel%20Report/Chapter%203.pdf
>>
>> Warren Weisman
>> USA
>>
>>
>>
>> ____________________________________________________________________________________
>> Pinpoint customers who are looking for what you sell.
>> http://searchmarketing.yahoo.com/
>>
>> _______________________________________________
>> 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: 7.5.484 / Virus Database: 269.12.12/979 - Release Date:
>> 29/08/2007 20:21
>>
>
>
>
>
> ------------------------------
>
> Message: 6
> Date: Thu, 30 Aug 2007 20:19:13 -0400
> From: Jaime Marti Herrero <tallerbiogas at hotmail.com>
> Subject: [Digestion] water manure rate
> To: <digestion at listserv.repp.org>
> Message-ID: <BAY116-W236610D24DEFAF6DC2F61CDCCE0 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi everybody.
>
> In the last moths im meeting people who is installing tubular biodigesters
> and they are using 1:2 manure:water rate to feed the biodigesters. From
> five years ago i started using 1:4 rate (recomended by Lylian Rodriguez
> and Preston), but from two years ago im using 1:3 because the in some
> places the are not that much water for 1:4.
>
> the reason tu use 1:3 or 1:4 is to avoid the formation of the foam that
> stop the production of biogas. But if really you can work wiyh a lower
> rate (1:2) without problems with the foam, this will be a great issue,
> because the volume required wil be lower and the cost os materials and
> biodigester as well.
>
> So please, have you got good expiriences with low rate manuere:water for
> long time with out foam?
>
> thanks everybody
> we keep in contact
> jaime
> _________________________________________________________________
> News, entertainment and everything you care about at Live.com. Get it now!
> http://www.live.com/getstarted.aspx
>
> ------------------------------
>
> Message: 7
> Date: Fri, 31 Aug 2007 07:04:13 +0530
> From: adkarve <adkarve at pn2.vsnl.net.in>
> Subject: Re: [Digestion] Scrubbing biogas
> To: digestion at listserv.repp.org
> Message-ID: <000701c7eb6f$41b7a4c0$4d69fea9 at adkarve>
> Content-Type: text/plain; charset=iso-8859-1
>
> Dear Biogas Workers,
> All over the world, efforts are on to use biogas as fuel in an internal
> combustion engine. We were told by an expert that there was no need to
> remove CO2 from the biogas. I would like to know, how important it was to
> remove H2S from biogas. In my system, where we produce biogas from food
> waste, we have only traces of H2S in our biogas. Due to oxidation, it is
> supposed to get converted into S02, and by combining with water vapour,
> perhaps into H2SO3. This is not as strong an acid as H2SO4. The cylinder,
> piston, piston rings and valves of an internal combustion engine are
> supposed to be coated by a film of lubricating oil. So how much is the
> danger of corrosion of the engine due to sulphurous acid? There is also
> nitrogen in the air, which goes into the engine, and a part of it gets
> converted into NOx.  Does this compound get converted into nitrous and
> perhaps also into nitric acid? Don't these acids harm the engine?  I shall
> be grateful to get answers to my questions.
> Yours
> A.D.Karve
>
> ----- Original Message -----
> From: Duncan Martin <duncanjmartin at eircom.net>
> To: Warren Weisman <weiswar at yahoo.com>; <digestion at listserv.repp.org>
> Sent: Friday, August 31, 2007 3:39 AM
> Subject: Re: [Digestion] Scrubbing biogas into biomethane article
>
>
>> Whatever method you think of using, do reflect first on the advice given
> by
>> Paul Harris the few hours ago to consider very carefully why you should
> want
>> to produce pure methane.
>>
>> Unless you want it for some kind of chemical feedstock, you presumably
> want
>> it as a fuel.
>>
>> If you want it as a transport fuel, it is true that storage capacity
>> would
>> be enhanced by the use of pure methane.  However, it would not even be
>> doubled, so the cost would have to be very low to make this worthwhile.
>>
>> Pure methane would be more energy efficient in any combustion device BUT
> the
>> energy required to purify it might well exceed any efficiency gain --
>> and
>> that is before you even consider the cost.
>>
>> Bear in mind too that the diluent effect of carbon dioxide in combustion
> is
>> vastly exceeded by the diluent effect of the nitrogen in the combustion
> air.
>>
>> Consider the stoichiometry of combustion.
>>
>> With pure gases:
>> CH4 + 2O2 = CO2 + 2H2O
>>
>> If the CH4 comes with some unwanted CO2 (lets say 2:1 for simplicity),
>> the
>> eqn becomes
>> (CO2 + 2CH4) + 4O2 = 3CO2 + 4H2O
>>
>> Now the extra CO2 is indeed a 'passenger' in any boiler or gas engine,
>> adding to the volume of the  hot gases that escape via the flue or
>> exhaust
>> pipe -and thus to the energy lost in them.
>>
>> BUT remember that the oxygen comes with a lot of unwanted gas too -
>> nitrogen, in a 4:1 ratio, so the true equation for the combustion
>> process
>> is:
>> (C02 + 2CH4) + (4O2 + 16N2) = 3CO2 + 4H2O + 16N2
>>
>> The nitrogen is just as much a passenger as the carbon dioxide is -- and
>> there is 16 times more of it (by volume). We all know that it is very
> rarely
>> economic to supply an engine or any boiler with pure oxygen instead of
>> air
>> (unless you work for NASA!), so this should be a warning that the
>> removal
> of
>> carbon dioxide is unlikely to make sense either. Of course, it might be
>> economic if the removal of carbon dioxide was very much cheaper than the
>> removal of nitrogen. However, there is little point in considering one
>> without considering the other, since for all you know you might be
>> considering the less economic option.
>>
>> Food for thought?
>>
>>
>> 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
>> ================================
>
>
>
>
>
> ------------------------------
>
> Message: 8
> Date: Fri, 31 Aug 2007 10:11:09 +0100
> From: "alastair ward \(IGER-NW\)" <alastair.ward at bbsrc.ac.uk>
> Subject: Re: [Digestion] Scrubbing biogas
> To: "adkarve" <adkarve at pn2.vsnl.net.in>,	<digestion at listserv.repp.org>
> Message-ID:
> 	<13DEE40AE4BF764586DBF27022F0D6A701F8EB59 at nwe2ksrv1.igernet.bbsrc.ac.uk>
>
> Content-Type: text/plain;	charset="iso-8859-1"
>
> I read somewhere that the H2S is a problem for copper based components in
> an engine, including gaskets and some bearing surfaces so I would think
> that for this use scrubbing H2S is very important. I believe the waste
> water treatment industry has most experience with biogas engines?
>
> Alastair Ward
>
> ________________________________
>
> From: digestion-bounces at listserv.repp.org on behalf of adkarve
> Sent: Fri 31/08/2007 02:34
> To: digestion at listserv.repp.org
> Subject: Re: [Digestion] Scrubbing biogas
>
>
>
> Dear Biogas Workers,
> All over the world, efforts are on to use biogas as fuel in an internal
> combustion engine. We were told by an expert that there was no need to
> remove CO2 from the biogas. I would like to know, how important it was to
> remove H2S from biogas. In my system, where we produce biogas from food
> waste, we have only traces of H2S in our biogas. Due to oxidation, it is
> supposed to get converted into S02, and by combining with water vapour,
> perhaps into H2SO3. This is not as strong an acid as H2SO4. The cylinder,
> piston, piston rings and valves of an internal combustion engine are
> supposed to be coated by a film of lubricating oil. So how much is the
> danger of corrosion of the engine due to sulphurous acid? There is also
> nitrogen in the air, which goes into the engine, and a part of it gets
> converted into NOx.  Does this compound get converted into nitrous and
> perhaps also into nitric acid? Don't these acids harm the engine?  I shall
> be grateful to get answers to my questions.
> Yours
> A.D.Karve
>
> ----- Original Message -----
> From: Duncan Martin <duncanjmartin at eircom.net>
> To: Warren Weisman <weiswar at yahoo.com>; <digestion at listserv.repp.org>
> Sent: Friday, August 31, 2007 3:39 AM
> Subject: Re: [Digestion] Scrubbing biogas into biomethane article
>
>
>> Whatever method you think of using, do reflect first on the advice given
> by
>> Paul Harris the few hours ago to consider very carefully why you should
> want
>> to produce pure methane.
>>
>> Unless you want it for some kind of chemical feedstock, you presumably
> want
>> it as a fuel.
>>
>> If you want it as a transport fuel, it is true that storage capacity
>> would
>> be enhanced by the use of pure methane.  However, it would not even be
>> doubled, so the cost would have to be very low to make this worthwhile.
>>
>> Pure methane would be more energy efficient in any combustion device BUT
> the
>> energy required to purify it might well exceed any efficiency gain --
>> and
>> that is before you even consider the cost.
>>
>> Bear in mind too that the diluent effect of carbon dioxide in combustion
> is
>> vastly exceeded by the diluent effect of the nitrogen in the combustion
> air.
>>
>> Consider the stoichiometry of combustion.
>>
>> With pure gases:
>> CH4 + 2O2 = CO2 + 2H2O
>>
>> If the CH4 comes with some unwanted CO2 (lets say 2:1 for simplicity),
>> the
>> eqn becomes
>> (CO2 + 2CH4) + 4O2 = 3CO2 + 4H2O
>>
>> Now the extra CO2 is indeed a 'passenger' in any boiler or gas engine,
>> adding to the volume of the  hot gases that escape via the flue or
>> exhaust
>> pipe -and thus to the energy lost in them.
>>
>> BUT remember that the oxygen comes with a lot of unwanted gas too -
>> nitrogen, in a 4:1 ratio, so the true equation for the combustion
>> process
>> is:
>> (C02 + 2CH4) + (4O2 + 16N2) = 3CO2 + 4H2O + 16N2
>>
>> The nitrogen is just as much a passenger as the carbon dioxide is -- and
>> there is 16 times more of it (by volume). We all know that it is very
> rarely
>> economic to supply an engine or any boiler with pure oxygen instead of
>> air
>> (unless you work for NASA!), so this should be a warning that the
>> removal
> of
>> carbon dioxide is unlikely to make sense either. Of course, it might be
>> economic if the removal of carbon dioxide was very much cheaper than the
>> removal of nitrogen. However, there is little point in considering one
>> without considering the other, since for all you know you might be
>> considering the less economic option.
>>
>> Food for thought?
>>
>>
>> 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
>> ================================
>
>
>
> _______________________________________________
> 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
>
> End of Digestion Digest, Vol 14, Issue 15
> *****************************************
>

Melvin S. Finstein, Ph.D.
Emeritus Professor of Environmental Science
 Rutgers, The State University of New Jersey
Head, ArrowBio USA

105 Carmel Road
Wheeling, WV 26003
(304) 242-0341
Email: finstein at envsci.rutgers.edu
Skype: melvinfinstein