Re: DIG-L: Anaerobic digestion

[doelle <doelle@ozemail.com.au>]

Dear Chuck,

There is no difference in our science about thermophili and mesophilic digestion. I am well aware of the advantages of thermophilic over mesophilic and also the disadvantages. 
The question is, why do people install more and more mesophilic instead of thermophilic ? It is plainly economics.
In a socio-economic biotechnological outlook in developing countries we need all the by-products we can get. With mesophilic anaerobic digestion we are getting it. We reduce significantly pathogens and can run a very good aquaculture system as well as using cheap polyethylene material for the digesters. We also get a compost and vermiculture from the solid effluent. These are tremendous money resources for poor farmers in rural areas.

These by-products and cheap anaerobic digesters you simply cannot have with thermophilic digesters. I agree with you that thermophilic digesters may be get in developed countries where people have plenty of money and simply want to get rid of their waste, like burning the biogas instead of using it.

Every technology where it belongs to. It depends so much on your local conditions. I have seen all these digesters in China and now also in Vietnam and the Philippines. They are working excellent. You just have to go outside Shanghai and see the bif 1400 m3 anaerobic digester facility above ground with water jacket around to keep the water and digester temperature at 37C.

Please it is a bit irresponsible from you to suggest that I could use straight manure for fertilising, which would be the same as mesophilic digester effluent. I am strong opponent of such a practice and as a microbiologist I know a bit about pathogen contents.

On the other hand, if thermophilic digesters are so superior and better to operate as you say, why have they not been taken off ? My colleagues in SEAsia told me that they do not like 2-stage systems because of cost and operating problems. You may say they do not know, but these are very qualified personal. 

As I said before, every technology has its place in society. One should not generalise, as conditions in different Regions of the world are different. Also the demand or usage of waste products are different.
In developing countries, and I also believe in our countries, I can make more money out of socio-economic usage of waste management with minimal risk to health.
I love our conversation and hope that we both continue keeping an open mind.
Best wishes
Horst

At 05:49 14/02/00 -0600, you wrote: 
>>>>
> February 14, 2000
>   
> Dear Dr. Doelle:
>   
> Common nutrients are nitrogen, phosphorus, and several inorganic metals, not BOD.  If one wants residual organics in
> the solids and liquid effluents of mesophilic digesters, why not skip the digestion process altogether thereby obtaining
> at least twice the quantity of volatile solids?  And yes, more pathogens, odors, and sheer volume to use beneficially,
> and therein is the continuing challenge.  In reality, the principal purpose of digestion is to treat rather than generate
> beneficial biosolids.  The beneficial use of the residual biosolids must be viewed a secondary objective, not a primary one.
>   
> That six million mesophilic digesters are in achieving excellent results all over the world depends on your definition of 
> the word excellent.  If a specific digester can be converted to two-phase thermophilic and thereby enable the capability
> to generate 20 times the amount of methane gas (on a digester volume basis), how can you not embrace this better 
> technology?  Is more insulation required, yes.  With far greater gas production for sale or conversion to electricity, the 
> additional insulation is well worth the expenditure.  Is the process more difficult to control than mesophilic digestion, if 
> operated a single phase it is almost impossible to control.  If operated as two phase, its control is far easier than 
> single phase mesophilic digestion of the type you claim are doing a splendid job around the world.  My observation
> is that most single phase mesophilic anaerobic digesters are prone to upsets resulting in the loss of the gas flare and
> the associated methanogenic activity.  I haven't visited all six million and neither have you but to claim they are all
> doing A-OK is in my opinion a stretch. 
>
>
> On an organic loading basis, two-phase thermophilic digestion can be acquired at approximately one half the cost of
> traditional conventional high rate mesophilic digestion in common use throughout the world.  It is praiseworthy that you
> support anaerobic digestion as many beneficial results occur.  The facts, howver, support the assertion that mesophilic
> is but a stepping stone to the wonderful world of two-phase thermophilic digestion.   Learn more about this better
> technology as it represents the future of anaerobic digestion.  Regards-Chuck.     
>   
> > ----- Original Message ----- 
> > From: <mailto:doelle@ozemail.com.au>doelle 
> > To: <mailto:h2osmart@ix.netcom.com>Chuck Steiner 
> > Cc: <mailto:digestion@crest.org>digestion@crest.org 
> > Sent: Sunday, February 13, 2000 3:07 PM
> > Subject: Re: DIG-L: Anaerobic digestion
> >
> >
> > Would you please also compare the cost factor ?
> > I totally disagree with you saying that mesophilic anaerobic digestion is obsolete, when we have more than 6 million mesophilic digesters working in excellent conditoins with excellent results all over the world.
> > Please let us be rational and not push one's own pet.
> > If thermophilic digestion produces double the amount of biogas, with which I fully agree, you probably use more than you gain of the biogas in heating a thermophilic digester.
> > It is also not true that the liquid and solid effluent of mesophilic digestion has low nutrient value, since it has been used extremely efficiently for aquaculture. If BOD is 10% less in thermophilic effluent, how can nutrient content be higher ? Please give some comparative data. I learned that thermophili digestion removes 80% of the BOD compared with 60% of the mesophilic, thus nutrients must be much more in the effluent of the mesophilic. 
> > Please make a cost analysis of your claim and then we can much more reasoanably compare both systems.
> > best regards
> > Horst Doelle
> > At 09:20 13/02/00 -0600, you wrote: 
> > >>>>
> > > Dear All:
> > >
> > > To justify mesophilic over thermophilic digestion because of its claimed better process stability and beneficial nutrient yield represents
> > > incorrect thinking. The principal purpose of treatment is to maximize the removal of pollutants by conversion to solids. It goes without
> > > saying that the less the resulting solids the greater the efficiency of treatment. Biosolids and liquid effluents from mesophilic
> > > treatment can hardly be thought of as a useful source of nutrients as the nutrient concentrations are very low and both the solids 
> > > and liquids still contain pathogens. While traditional single-phase themophilic treatment is indeed difficult if not impossible to control, 
> > > two-phase thermophilic digestion can be very easy to control. At this higher temperature (60 degrees C) pathogens are virtually 
> > > eliminated from both the treated solids and liquids. The solids remaining are perhaps 5-10% of those left over after mesophilic 
> > > treatment. These few solids can, however, still be safely used as a soil conditioner or amendment, not a fertilizer. For those still interested
> > > in fertilizer values, the liquid effluent from thermophilic digestion contains far greater levels of ammonia-nitrogen than mesophilic treatment 
> > > as this specific nutrient is generated during anaerobic digestion. As such the liquid effluent from thermophilic digestion is a splendid 
> > > candidate for irrigation water so long as the ammonia-nitrogen nutrient uptake of the crop or grassland is equal to or exceeds the application loading to prevent nitrate contamination of groundwater. 
> > >
> > > It is true that thermophilic treatment requires greater heating than mesophilic treatment. Two-phase thermophilic digestion generates 
> > > twice the quantity of methane as mesophilic because of its ability to achieve twice the level of volatile solids reduction. This greater 
> > > gas production easily produces the additional energy required to heat the digester. Additionally, there should be no credible concern 
> > > over the higher operating temperature because of the ease of capturing the vast majority of the exit heat through the use of heat exchangers.
> > >
> > > In short, mesophilic digestion represents obsolete technology compared with the far greater efficiencies and associated pathogenic 
> > > destruction resulting from two-phase thermophilic digestion. As an example, a two-phase thermophilic digester utilizing fixed growth 
> > > bacteria can successfully treat at least ten (10) times the organic loading of a traditional high rate single phase mesophilic digester. 
> > > The good news is that most mesophilic digesters can generally be converted or upgraded to this type of a treatment dynamo. The true
> > > potential of anaerobic digestion if far greater than most of us realized a few short years ago. Eliminating thermophilic digestion is but
> > > a technology step backwards regardless of how its justification is formulated. Regards-Chuck Steiner, WaterSmart Environmental, Inc. 
> > >
> > > > ----- Original Message ----- 
> > > > From: <mailto:doelle@ozemail.com.au>doelle 
> > > > To: <mailto:greenfinch@burford.co.uk>greenfinch@burford.co.uk 
> > > > Cc: <mailto:digestion@crest.org>digestion@crest.org 
> > > > Sent: Sunday, February 13, 2000 4:55 AM
> > > > Subject: Re: DIG-L: Anaerobic digestion
> > > >
> > > > Dear Lisa,
> > > >
> > > > In a cold climate like Europe I would never recommend a thermophilic digester, particularly if you require the by-products.
> > > > As I mentioned in an earlier message, mesophilic digesters reduce pathogens significantly and as you know, also the BOD by approx. 60%. Thus you have enough nutrients left in the solid and liquid effluents to compost or use it as an excellent resource for aquaculture, eg algae and fish. Also the biogas requirement to keep your temperature all year round at 35-37C is far lower and you can sell the rest or use the rest of the energy for other purposes.
> > > >
> > > > In the case of a thermophilic digestion, it has been claimed that the BOD can be reduced by 80% +, pathogens are of course further reduced, biogas yield is higher, BUT you require a much higher amount of biogas for heating your digester. Your by-product opportunities are significantly reduced, since the solid and liquid effluents are much poorer in nutrients.
> > > >
> > > > Both types have their place. I prefer the mesophilic one because the economics appear to be much better, IF you believe in an integrated biosystem. Thermophilic digesters are good if you do not believe in an integrated biosystem.
> > > >
> > > > I hope this helps.
> > > > Best regards
> > > > Horst Doelle
> > > >
> > > >
> > > > At 11:51 12/02/00 +0000, you wrote:
> > > > >Dear all,
> > > > >
> > > > >My name is Lisa Pritchard and I currently work for a company called
> > > > >GreenfinchLtd based in Shropshire, UK. Our demonstration plant is a 20m3
> > > > >anaerobic digester which treats 5-7 tonnes of source-separated household
> > > > >kitchen waste (biowaste) each week from approximately 1500 households. 
> > > > >
> > > > >One of our objectives is to recycle and reuse of by-products of the AD
> > > > >process. This does not include agricultural land application. As you
> > > > >know regulations are getting tighter so we do not want to rely on land
> > > > >application to reuse the nutrients effectively. Hence we are reusing our
> > > > >by-products through various processes including aquaculture and
> > > > >vermiculture.
> > > > >
> > > > >Our digester is mesophilc. Do you see any clear advantages for running our
> > > > >digester at thermophilic temperatures, bearing in mind our climate and
> > > > >need to reuse all by-products?
> > > > >
> > > > >Thankyou and look forward to any replies,
> > > > >
> > > > >Lisa Pritchard
> > > > >
> > > > >
> > > > > 
> > > > >*** greenfinch@burford.co.uk using SmartMail v4.00.15 *** 
> > > > >--------------------------------------------------
> > > > >
> > > > >
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> > > > >http://WWW.roseworthy.adelaide.edu.au/~pharris/biogas/beginners
> > > > >
> > > > >
> > > > Horst W.Doelle, D.Sc., D.Sc. [h.c.]
> > > > Chairman, IOBB
> > > > Director, MIRCEN-Biotechnology
> > > > FAX: +617-38783230
> > > > Email: doelle@ozemail.com.au DIGESTION List Sponsors, Archive and Information http://www.crest.org/renewables/digestion-list-archive http://www.crest.org/renewables/biomass-info/ Beginners Tour of Biogas http://WWW.roseworthy.adelaide.edu.au/~pharris/biogas/beginners
> > <<<<
> >
> >
> >
> > Horst W.Doelle, D.Sc., D.Sc. [h.c.]
> > Chairman, IOBB
> > Director, MIRCEN-Biotechnology
> > FAX: +617-38783230
> > Email: doelle@ozemail.com.au
<<<<



Horst W.Doelle, D.Sc., D.Sc. [h.c.]
Chairman, IOBB
Director, MIRCEN-Biotechnology
FAX: +617-38783230
Email: doelle@ozemail.com.au DIGESTION List Sponsors, Archive and Information http://www.crest.org/renewables/digestion-list-archive http://www.crest.org/renewables/biomass-info/ Beginners Tour of Biogas http://WWW.roseworthy.adelaide.edu.au/~pharris/biogas/beginners