[Digestion] Digestion Digest, Vol 2, Issue 33

Sumedh Bapat sumedh.bapat at gmail.com
Sat Oct 16 21:01:28 PDT 2010

Dear Srinivas,

Please consider the use of only chicken manure as a feedstock and then
see how important are C/N values are to the diegester. Please try using
only castor oil cake. There is 35% protein. you will see tremendous increase
of nitrogen infact if not measured or controlled, will lead to ammonia
toxicity of the digester. I have seen the pH shooting up to 8.2 sometimes,
The balance of Carbon and Nitrogen is vital for the running of biogas plant.
Also if you try to run biogas plants on single feed, there have been
problems of monodigestion. For the first 12 months/15 months you will get
gas but slolw the gas production will reduce. Food waste is anyhow a mixed
feed but it is also acidic. You do not have a control on the quality as
it comes from the public. Sometimes you have a boost of cheese or sometimes
tomato. i seasonal variations you get a boost of Citric fruits. We have
operated these digesters and although there is a possibility of loosing some
methane by predigesting and converting it to CO2 aerobically, you reduce the
risk of the digester going acidic. We have seen our scum problems have
vanished in two stage digesters, if designed properly. When we tried only
single stage, there were a lot of problems. Also we should not forget the
importance of Hygenisation. The reduction of pathogens is very crucial if
the waste has to be treated in a hygenic manner. You cannot just drive away
the "fetishes" of biogas plants by operating 1 - 5 m3 volumes digesters.
Please let us all try and "design & operate" plants on very large to medium
scale before been expertised in Biogas.
*Sumedh Bapat
On Sun, Oct 17, 2010 at 12:45 AM, Srinivas Kasulla <
srinivaskasulla at gmail.com> wrote:

> Dear Dr Karve,
> We are really proud of you being an INDIAN and making the entire Nation
> proud with the work you have done in the field of Biogas/Anaerobic digestion
> in India, but after reading some of your views it has confused me very much
> and even after 2-3 days of continuous research ONLINE and going thru some
> books i could find some of the answers for the data you have mentioned
> earlier, I would appreciate if you clear my doubts:
> 1) As am into this field from quite a long time but not as much as you have
> been and whatever you have mentioned about TS, VS, Cowdung, BOD etc is
> making me so confuse that it seems that i have to start from the basics and
> all my knowledge which i have accumulated till date will be waste.......
> you have mentioned that VS and BOD - neither of these are corelated to
> quantity of biogas generated?
> you said digestibility of the feedstock is to be considered for biogas
> generation? if not TS? if not VS? if not BOD? then what is this
> digestibility of the feedstock?
> I can agree that the mistake is to expect the same biogas yields per kg of
> VS or of BOD from a different feedstock may vary.
> 2) You have mentioned that DUNG cannot serve as a food for the methanogens
> because they are THROWN OUT of the body alongwith the dung??
> 3) The methanogens in the dung are very slow workers and they need
> retenntion time which we give in the digesters and which is missing (the
> number of days for holding - the gut of an animal is limited). the
> methanogens in dung keep on working even when the dung is thrown out of the
> body, and the process becomes slow due to exposure to the oxygen and once
> again they start producing the methane when they are put inside the
> digester........
> 4) you have mentioned that the FETISH C/N values should be discarded? how
> can I DISCARD THESE VALUES AND RATIOS? can you please teach me to discard
> the C/N values from my digesters? and you have mentioned the C/N values to
> be 10 or 5 but is it for C or for N?
> would be eagerly waiting for your answers to the above questions only, as
> in my earlier few mails i have asked you certain questions and had received
> answers from different experts in the blog and have received some answers
> from you which were not at all connected to my questions.
> with warm regards
> +91 9004689601
>  On Sat, Oct 16, 2010 at 12:30 AM, <
> digestion-request at lists.bioenergylists.org> wrote:
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>>   1. Re: Attachment to previous Article - More scientific based
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>> Date: Fri, 15 Oct 2010 12:37:37 +0800
>> From: Anand Karve <adkarve at gmail.com>
>> To: For Discussion of Anaerobic Digestion
>>        <digestion at lists.bioenergylists.org>
>> Subject: Re: [Digestion] Attachment to previous Article - More
>>        scientific based research and questions
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>> Dear Alex,
>> I give below the philosophy of our biogas work. Our first assumption is
>> that
>> because the methanogenic archaea reside in the guts of animals, they eat
>> what the animals eat. Our second assumption is that these organisms are
>> universally found in the fecal matter of animals because they are thrown
>> out
>> of the body along with the dung. Therefore we do not accept that dung
>> serves
>> as food for the methanogenic archaea. In fact, it is mentioned in the
>> textbooks on biogas technology that several species of bacteria are
>> involved
>> in reducing the dung to acetic acid and that the methanogens turn the
>> acetic
>> acid into methane. Our third assumption is that using the terms VS and BOD
>> to describe the feedstock are wrong. Neither of these parameters is
>> correlated with the quantity of the biogas generated. The use of these
>> parameters in biogas work is comparable to using the phlogiston theory in
>> chemistry. We therefore propose that digestibility of the feedstock be
>> considered as the correct parameter to describe the feedstock. Methods are
>> available to determine the in vitro dry matter digestibility (IVDMD) and
>> these values are available in books on cattle fodder. We ask the users of
>> our biogas plants to ask themselves the question if the feedstock would be
>> digested by animals. If the answer is yes, it is the right feedstock. We
>> also feel that the fetish of C/N ratio should be discarded. We have
>> operated
>> our biogas system for months on end, using only green leaves, or oilseed
>> cake, which have a C/N value of less than 10, some time as low as 5.
>> We make only sparing use of a biphasic system. In fact, my advice is to
>> avoid the use of a biphasic system. In a biphasic system, in order to
>> break
>> down the difficult to digest material, one makes use of an aerobic
>> fermenter. In this phase, a lot of the easy to digest material, which
>> would
>> have yielded methane in the anaerobic phase, is lost, being converted into
>> carbon dioxide.
>> You can now understand, why the biogas workers hoot me out and don't
>> believe
>> in me.
>> Yours
>> A.D.Karve
>> >
>> >> On 07/10/2010 01:39, Alexander Eaton wrote:
>> >>
>> >> Dr Karve,
>> >>
>> >> Your innovation and work in the field is quite appreciated, and your
>> >> system really opens doors for us who are also not technically focused
>> in the
>> >> biology of biogas, but rather its application to families and
>> communities.
>> >> That is why it seems your use of food waste and loading rates based on
>> gas
>> >> production for a family really widens the populations we may be able to
>> work
>> >> with globally.  Do you have a paper or document that has this data and
>> other
>> >> user data available?
>> >>
>> >> Best,
>> >>
>> >> Alex
>> >>
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