[Digestion] Dung burning vs. anaerobic digestion

[Anand Karve]

Dear Mr. Ward,
Thanks a lot for making us aware of the situation in Denmark. I agree with
you that situations differ from country to country and that one should do
what is best suited to one's needs and also what the environment allows.
Please remember that the posting that I reacted to refered specifically to
cow dung and its author complained about extremely low biogas yield. My
experience is mainly from India. In my posting I specifically refered to
dung of ruminents, i.e. bovine cattle and water buffalo. In India, these
animals mainly graze and they eat mainly grass, which is dry except for the
rainy season. The dung of such animals has very little digestible matter in
it. Excreta of poultry and pigs have much more digestible matter than those
of ruminents.   In India, dung cakes are made only from dung of cattle.
They are sun-dried. You must be aware of the fact that except for Muslims
and Cristians, dead bodies are cremated in India. There is a big market in
India for dung cakes as fuel for creamtion of dead bodies. Compressing
agricultural waste into fuel briquettes (as boiler fuel) has emerged as a
big Industry in India. Dung can also serve as boiler fuel.  People are even
looking at filter presses, which would squeeze the water out of dung, so
the solids can be coverted into burnable briquettes.
Yours
A.D.Karve

On Wed, Nov 14, 2012 at 2:35 PM, Alastair James Ward <
Alastair.Ward at agrsci.dk> wrote:

>  Dear A.D. Karve,****
>
> ** **
>
> I disagree that manure only consists of lignin, mucus and microorganisms.
> There is a lot of digestible but undigested protein, fat and carbohydrate
> in manure, not to mention a high concentration of fatty acids which are
> just one or two steps in the biological pathway away from methane
> production. It is not disputed that plant material usually produces more
> biogas than manure, but I think that you have to stand back and consider
> what factors are most important to the very varied users of this list. I
> live in northern Europe in a country with a high animal density. It has
> been calculated that if we could collect all manure produced, all organic
> wastes available and use all non-food producing land for energy crop
> production and put it all into biogas plants, we would still not make a
> very large impact on the national energy requirement (sorry but I forget
> the exact figures). However, we view anaerobic digestion as a method of
> treating wastes, with the recycling of nitrogen and phosphorous being of
> great importance. The fact that we can produce energy is a nice bonus that
> (hopefully) makes the whole process financially feasible. Burning manure is
> not a realistic option here. As an example, we produce in excess of 20
> million fattening pigs every year, in a country of less than 6 million
> people. As a result, we have a lot of wet manure to deal with and anaerobic
> digestion is widely viewed as the best available technology to do so. Pig
> manure has a low dry matter content so the energy input necessary for
> drying, not to mention space to do so and any other issues regarding odour
> emissions etc makes the drying and burning of wet manures impractical. We
> also want to keep the N to put back into the soil and thus reduce the need
> for artificial fertiliser and the non-degradable carbohydrates in digestate
> are useful in maintaining soil carbon levels.****
>
> As I understand, the original post was not from a northern European
> country but there are still many advantages to anaerobically digesting
> manure in warmer climates. Biogas is certainly a cleaner and more flexible
> fuel than dry material for burning, the fact that one can quite easily run
> lights and a small generator on biogas being major advantages. I came
> across a paper a couple of years ago that suggested the increased use of AD
> in preference to burning of organic material could be linked to an
> improvement in the health of people in rural Indian communities,
> specifically eye problems due to smoke as I remember.****
>
> Please, consider the motives of the people posting on this list before you
> tell us that we are wasting our time digesting manure. If Kyle has manure
> available I suggest he continues to use it in his digester, the low yield
> can be compensated for by having a large supply that is easily available.
> If he has any plant wastes available then certainly put these in as well to
> boost yield, but I would not recommend actively collecting large amounts of
> biomass from the surrounding area, the time and energy used to do so may
> negate the gain. ****
>
> ** **
>
> Med venlig hilsen ****
>
> *Alastair James Ward*
> Post doc.****
>
> *Inst. for Ingeniørvidenskab
> *Aarhus Universitet
> Blichers Allé 20, Postboks 50
> 8830 Tjele****
>
> ** **
>
> Tlf.: 8715 7645
> Mobil: 4112 2494
> Email: Alastair.Ward at agrsci.dk****
>
>
> Tlf.: 8715 6000
> Web: www.agrsci.au.dk <http://www.agrsci.dk/>****
>
> [image: Description: Logo]****
>
>
> --
> ***
> Dr. A.D. Karve
> Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)
>
>
>
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