[Digestion] Negative Biogas Press
David
david at h4c.org
Mon Feb 14 17:29:18 CST 2011
Dear all,
With regard to the post by Alexander quoting two arguments against
biogas, as regards the first problem mentioned-- that conversion of
organic matter by AD might reduce humus-- I can't see the sense of
such an idea. After all, as we all know, biogas plants will not do
well with converting recalcitrant materials into biogas, for a number
of reasons. And if by the word "humus" we are addressing organic
material with any appreciable residence time in the soil-- then such
humus is not made from the easily digested or easily composted
fractions of any material. After all, these fractions are easily
converted into simpler chemical species in either a compost pile or
the soil, as well as in a digester. Rather, humus as defined must be
made primarily from the more recalcitrant fractions-- exactly what is
left as effluent.
If someone can show a well-done study that demonstrates a significant
reduction in humus in otherwise comparable lands comparably treated,
then perhaps it should be a matter of concern, but the mere statement
of opinion, to me, is unconvincing. (As well, speaking from a more
agricultural perspective, it should be obvious that most humus is
grown in, and not added to, the soil. It consists of decomposing
roots, for the most part. In natural forest or grassland soils with
good humus content, who is it that is plowing in the compost to make
the humus?)
As far as Clostridium, the biogas process does not /produce/ it; it
simply may fail to completely /remove/ it, especially in shorter HRT
mesophilic digesters. One may as well blame the plastic bottle for the
effect of the pesticide it holds.
If someone puts unsafe materials into a digester, and then is foolish
enough to put the effluent on land used for ag uses (whether to
produce human or animal foods), then it should be no surprise if that
effluent has bad consequences. How is it that biogas is to blame where
people have made foolish or ignorant choices?
d.
--
David William House
"The Complete Biogas Handbook" |www.completebiogas.com|
/Vahid Biogas/, an alternative energy consultancy |www.vahidbiogas.com
|
"Make no search for water. But find thirst,
And water from the very ground will burst."
(Rumi, a Persian mystic poet, quoted in /Delight of Hearts/, p. 77)
http://bahai.us/
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