[Bioconversion] methane digester and greenhouse gas reduction for demonstration post-carbon world home

[Philip Anderson]

Greetings bioconversioneers!  I’m back after a year -Phil Anderson - and
still working on a house plan which demonstrates living in partnership with
Nature, including benign, site-produced energy and net zero greenhouse gas
production.



I want to produce methane gas for cooking in the first cell of a constructed
wetlands blackwater treatment system. This first cell is in effect a septic
tank which I will seal (polyethylene tank) to use like ARTI’s domestic
biogas plant (http://www.arti-india.org/content/view/45/52/) which operates
without animal fodder (so it is feasible to be used off the farm in
America).  But our plant will also digest human waste in addition to food
scraps and landscape cuttings as ARTI’s uses.



I will construct two first cells (two “septic tanks”) in the wetlands
blackwater treatment system, so one can be online while the other rests and
its digested residue is harvested as compost.



Please comment:



1.  Is this system actually reducing the greenhouse effect which the
feedstock would have produced in Nature aerobically?  See Wikepedia’s
equation for methane combustion below.  Per unit of feedstock what produces
more greenhouse effect:   anaerobic digestion where the methane is captured
and burned releasing CO2 and water, or aerobic digestion where CO2 is
released without burning?



Per Wikepedia:  “ Burning <http://en.wikipedia.org/wiki/Combustion>  one
molecule <http://en.wikipedia.org/wiki/Molecule>  of methane in the presence
of oxygen <http://en.wikipedia.org/wiki/Oxygen>  releases one molecule of
CO2 (carbon <http://en.wikipedia.org/wiki/Carbon_dioxide>  dioxide) and two
molecules of H <http://en.wikipedia.org/wiki/Water> 2O:

CH4 + 2O2 → CO2 + 2H2O “



Another way to phrase the question: given the same unit of feedstock is less
C02 released to the atmosphere by the anaerobic-methane-combustion system
than the aerobic system?



2.  I’m thinking that at least the burning of the methane from the
“septic” cell /tank (rather than its finding its way out to the
atmosphere), is reducing the greenhouse effect since methane has about 20
times more greenhouse effect than C02, and the combustion formula shows one
methane molecule yielding only one carbon dioxide molecule in the combustion
reaction  --95% reduction in greenhouse effect?   Or would the same unit of
feedstock produce the same amount of CO2 via either process (aerobic
production of CO2 or anaerobic production of methane which is then burned to
produce CO2)?



3.  Is the feedstock in aerobic digestion converted to a material which can
be used as compost or is it unsafe sludge? How long does it take to produce
a safe compost, and how do we know when this process is complete?  Again, my
design calls for two anaerobic cells, one of which will be online /handling
blackwater while the other is cleared of the digested material for use as
compost.



Again, the benefits I would like to have from this system:   compost from
human waste, site-produced cooking fuel and net zero or even reduced
greenhouse effect as compared with the gases produced by the natural aerobic
and anaerobic decomposition of the same feedstock.  Do I have the system I’
m aiming for?



Thanks,



Phil