Re: DIG-L: Thermophilic vs. Mesophilic (was: Anaerobic digestion)

[Paul Harris <paul.harris@adelaide.edu.au>]

Thankyou Brian for your kind words, I should point out that only some of
the "Beginners Tour " is my own work - the links take you around the
world to other good/useful sites (anyone got others to add?).

I have just run your figures through a Methane Calculator I have set up
and I got 350 cubic metres of methane per day (which is 160 kW of power
not considering conversion efficiencies), a bit more than your figures
but in the right area - if you have considered losses in storage you are
probably about right.

Brian Smyla wrote:
> 
> Greetings, all!
> 
> I am currently exploring the benefits of AD, and would like to build a
> test digester using the litter from a poultry farm.  I've
> located a farm that seems to be interested in working with me on the
> project.  I'm leaning towards a continuous flow digester,
> although I'm not sure whether to use the thermophilic or mesophilic
> model.  Here are some of  the requirements:
> 
> Replacement of LP gas (200 gallons / month average) with biogas for
> heating of the poultry houses.
> Enough effluent to provide fertilization for the farm's cattle grasses.
> Minimal time spent maintaining the digester.
> 
> Optional:
> Enough biogas for continuous operation of the farm's existing 100 kWh
> gasoline backup generator.
> 
> Farm Information:
> The amount of poultry litter produced by the farm is about 2000 Tons
> annually.  This litter is currently collected from the
> houses every 10 weeks, piled outside in the open and spread entirely on
> the fields as time allows throughout the year.  Our
> average annual temperature is 59 degrees F.
> 
> My preliminary calculations indicate that if digested, this amount of
> litter should generate enough biogas to equal the energy in
> 36,000 gallons of LP gas or about 90,000 cubic meters of biogas.
> 
> My questions are these:
> Are my calculations remotely accurate?
> Is there a possibility of meeting the listed requirements with the
> current volume of litter production?
> What size and type digester should I be looking at?
> Between thermophilic or mesophilic digestion, which would be the better
> choice for this application?
> What would be the best method of mixing and introducing the feedstock to
> the digester?
> 
> As for the debate between Horst Doelle and Chuck Steiner, I'd be
> interested to see data from actual test results in support of
> your claims.
> 
> I'm new to AD, and I've found this list and its archives to be very
> informative.  I'd also like to thank Paul Harris of the
> University of Adelaide for his web site and the information therein.  As
> my AD project takes shape, I'll be setting up and
> maintaining a web site to track its progress.  I'll post the URL to the
> list when it becomes available.  Thanks in advance for
> any help or information.
> 
> -brian smyla
> 
> doelle wrote:
> 
> > 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.
> >
> 
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-- 
Mr. Paul Harris,                                 Dept. of Agronomy &
Farming Systems,
ph +61 8 8303 7880,fx +61 8 8303 7979            Roseworthy Campus,
http://www.roseworthy.adelaide.edu.au/~pharris   The University of
Adelaide,
E-Mail: paul.harris@adelaide.edu.au              ROSEWORTHY, South
Australia, 5371
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