[Digestion] Lessons Learned from the dissemination of Biodigesters for Sanitation in Haiti, form 2010 to 2013.

[Anand Karve]

Dear Marc,
the slurry from a biogas plant can certainly serve as a source of
minerals to the plants, but please remember that dung is a residue
from which most of the minerals and digestible matter has already been
removed. Therefore one must weigh the economics of using cattle dung
either as a source of biogas or as manure, versus its economic value
as cooking fuel. A family needs daily about 40 kg dung to generate
enough biogas to cook two meals in a day, whereas two meals can be
cooked with about 4 kg dung cakes. In the city where I live, dung
cakes made from 40 kg dung sell for almost one US$. Therefore selling
dung cakes as fuel is more remunerative than using dung for any other
purpose. I have no experience with fecal matter of pigs either as
feedstock for biogas or as fuel for direct combustion, so I cannot
express any opinion on the example cited by you. I can however make
one comment,  that using biogas for cooking makes more economic sense
than generating electricity from it. But it all depends on the
opportunities available. If one produces biogas at a location, where
one cannot use it for cooking, then one has to find an alternative use
for it.
Yours
A.D.Karve
***
Dr. A.D. Karve

Chairman, Samuchit Enviro Tech Pvt Ltd (www.samuchit.com)

Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)


On Mon, Jan 12, 2015 at 9:55 AM, Marc de Piolenc <piolenc at archivale.com> wrote:
> Dr. Karve,
>
> This is something of a shock. If I'm reading you correctly, the only value
> of anaerobic digestion as applied to human or animal wastes is sanitary
> disposal of the waste, with gas as the by-product hopefully helping to
> offset some of the cost.
>
> Yet I recently visited a piggery on the outskirts of Iligan City which has
> been generating all of its electricity, and even sometimes selling a surplus
> to the grid, from biogas generated from a single feedstock: pig excrement.
> The owner doesn't sell the slurry, but does use it himself in his orchards
> and gardens, and from the look of them there is a benefit.
>
> Cordially,
>
> Marc de Piolenc
> Philippines
> --------------------------------------------------------------------------
> Let me explain the background of my thoughts. I am an agricultural
> scientist and I started working on biogas in 2003, at the age of 67. The
> reason was my realization that if we wanted the methane  producing
> organisms to produce a high calorie substance like methane we must feed
> them with a high calorie material. I therefore constructed a biogas plant
> and when I fed it with sugar, I found that I could get the same amount of
> biogas from 1 kg sugar as from 40 kg cattle dung. I then tested starch,
> proteins, fats, cellulose and got more or less the same results. In 2004 we
> installed these biogas plants in 40 urban households, which had no access
> to cattle dung. In 2005, I read a paper on our work in a conference. The
> audience just did not believe me. They said that food would produce biogas
> only if it was co-fermented with cattle dung. Since then I have been
> advocating that if dung is to be used as a source of energy, it should be
> burned and not converted into biogas. My detractors then countered my views
> with the argument that the slurry of a dung based biogas plant could be
> used as fertilizer. I showed that this too was a wrong notion. If one
> wanted to feed the soil microbes with an organic source of food, one should
> use a substance with high nutritive value. Just 25 kg sugar added to a ha
> of agricultural land, would give the same results as a 10 tons of compost.
> In fact, this method of farming has now become quite popular in India and
> there are thousands of farmers who apply neither compost nor chemical
> fertilizers to their field, but just 25 kg sugar per ha, once every 3
> months. One can equally well apply 125 kg green leaves per ha and get the
> same results.
>
> Yours
>
> A.D.Karve
>
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