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

Tue Jun 12 10:54:57 CDT 2007

Hi Phil,
   Here are my thoughts on this greenhouse gas (GHG) issue.  To determine
your reduction in GHG emission, you need to select an alternative to compare
your system with, i.e. what approach would be used in the absence of your
system?  Assuming the wastes would be broken down aerobically otherwise,
without energy consumption ( i.e. not activated sludge system for the human
waste), with a similar conversion efficiency (i.e. organic matter
destruction), and that the methane produced in your system is completely
combusted to CO2 but there is no utilization of the energy produced, your
system does not provide a GHG emissions reduction.  Assuming there is some
leakage of CH4 from your system, it would even make a net contribution to
GHG emissions.  However, If you produce cooking fuel with your system that
would otherwise come from a fossil fuel source, you would be replacing
consumption of fossil fuel with a "carbon neutral" technology, and therefore
would be reducing GHG emissions, since the fossil fuel that would be
consumed in the absence of your system is not used.  Production of cooking
gas, electricity, or utilized heat would be the essential step in reduced
GHG effect in this scenario.  Lastly, if you compare your system to an
anaerobic treatment system with no biogas capture, then you are clearly
reducing GHG emissions as long as the captured CH4 is combusted.  Selection
of an alternative for comparison has a huge impact on the predicted net
effect of your system on GHG emissions.  It is my understanding that these
issues play a role in carbon trading/offsetting and you might look in this
area for more information.
   Regards,
       Sasha Hafner

On 6/12/07, Philip Anderson <solarphil at comcast.net> wrote:
>
> Thanks, Hooroo.
>
> Regarding the sums,the CO2 released by today's feedstock is today's CO2,
> which is better than introducing ancient CO2 from fossil fuel combustion,
> which is an unnatural addition to today's CO2 pool and cycle.  However, I
> would like to know if I am reducing today's CO2 release by
> anaerobic-methane-combustion-CO2 versus the release of CO2 of the same
> feed
> stock by decomposition in Nature.  This would be a great plus in a world
> where we need to not only reduce human-induced CO2 emmission but natural
> emission as well, since the atmosphere is overloaded and the Nature's
> carbon-fixers are depleted.
>
> Regarding the extent of conversion of human waste, you are saying the
> longer
> the anaerobic digestion takes place, the more complete the conversion to a
>
> benign compost.  Question is are we talking months or years after
> feedstock
> introduction ceases.  I need to know how long I need the offline tank rest
> to assure a benign compost.  The second, active tank can stay online for
> years if need be to allow the resting tank to complete the anaerobic
> digestion.
>
> PHil
>
>
> Philip Anderson
> Sustainable Living Design
>
>
> Life support & life style in partnership
> with Nature and in harmony with the heart
>
> 11801 Pine Court
> Monrovia, MD 21770-8802   USA
>
> Phone (301) 335-6051
> Fax (301) 865-3642
>
>   solarphil at comcast.net
>
>
> -----Original Message-----
> From: bioconversion-bounces at listserv.repp.org
> [mailto:bioconversion-bounces at listserv.repp.org] On Behalf Of Paul Harris
> Sent: Tuesday, June 12, 2007 2:09 AM
> To: Discussion of biological conversion to fuels and chemicals
> Subject: Re: [Bioconversion] methane digester and greenhouse gas reduction
> fordemonstration post-carbon world home
>
> 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'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
> >
> > _______________________________________________
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> >
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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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> Fax   : +61 8 8303 7979
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