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

[Marc de Piolenc]

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
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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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