Dear Dr. Fulford and others,
On 11/20/2010 9:22 AM, David Fulford wrote:
David and listers, Hello,
The microbes do not seem to be affected significantly by pressure,
at least up to the 1 atmosphere found in small dome plants as used
in India, Nepal and China. In the 1970s there were reports of some
earlier work in India that suggested less gas was generated at
higher pressures; but gas analysis demonstrated that the reduction
in volume at higher pressures was mainly due to carbon dioxide
dissolving in the slurry.... So, [perhaps] the answer is that the
relationship between pressure and biogas production seems rather
complicated.
It seems to me, then (all things considered) that pressure in the
great majority of situations is not worth any attention. Three things
lead me to this conclusion. First, most applications and appliances
that use biogas are satisfied with pressures that are measured in
inches of water, not feet, and second very few digesters are likely to
be built that exceed 30 feet in depth, at which point the pressure is
doubled. (The majority of those deep digesters-- which after all would
have to be quite large and which would therefore generally tend to be
fairly sophisticated-- would almost certainly be agitated, not
plug-flow.) Finally, since long experience, even if not multiple
studies, confirm that the effect even of a doubling of standard
atmospheric pressure tends to be so slight as to avoid notice, most of
us will never need to consider it as a factor.
I would still love to find some studies that discuss the matter, but
for the time being the sole driver is now simple curiosity, and no
longer the potential for practical impact.
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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