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

[Paul Harris]

G'day Philip,

Without doing the sums anaerobic digestion wins, as it relaces fossil
fuels as well as capturing a 20 times more potent GHG!

The longer the retention time and the more steps/hosts waste goes
through the safer it is (and the more robust the system is!).

Hope this helps,
HOOROO

Philip Anderson wrote:
> 
> Greetings bioconversioneers!  I$B!G(Bm back after a year -Phil Anderson - and
> still working on a house plan which demonstrates living in partnership with
> Nature, including benign, site-produced energy and net zero greenhouse gas
> production.
> 
> I want to produce methane gas for cooking in the first cell of a constructed
> wetlands blackwater treatment system. This first cell is in effect a septic
> tank which I will seal (polyethylene tank) to use like ARTI$B!G(Bs 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$B!G(Bs uses.
> 
> I will construct two first cells (two $B!H(Bseptic tanks$B!I(B) 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$B!G(Bs
> 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:  $B!H(B 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 $B"*(B CO2 + 2H2O $B!H(B
> 
> Another way to phrase the question: given the same unit of feedstock is less
> C02 released to the atmosphere by the anaerobic-methane-combustion system
> than the aerobic system?
> 
> 2.  I$B!G(Bm thinking that at least the burning of the methane from the
> $B!H(Bseptic$B!I(B 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$B!G(B
> m aiming for?
> 
> Thanks,
> 
> Phil
> 
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-- 
Mr. Paul Harris
Room G8, Leske Building
Faculty of Sciences,
The  University of Adelaide, Roseworthy Campus, AUSTRALIA 5371
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