[Digestion] Negative Biogas Press

[David]

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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