[Digestion] landfill vs. AD
mylesacc at comcast.net
mylesacc at comcast.net
Wed May 2 11:12:39 CDT 2007
Bjorn,
You are quite right about the "return on investment" I work with a company www.NESI.biz that has developed & patented a system to convert ADG to natural gas or to hydrogen.The hardest thing is to convince people, investors or dairy farmers to try new ideas even when there is a three year return on the investment. The return is longer if you do not use the produced gas on site, do to carrier fees & mark up on the natural gas product. We have also designed a system on a trailer, which can be used at winerys or food processors that do batch processing. The system can be used for 30 days or more, pickup and moved to another location. Word of caution is gas suppliers need to have constant monitoring for contaminents, percentage of CO2, rate of gas flow and purity of methane. If you use the gas on site either directly in burners for heat, etc or compress it for vehicles you may be able to use a lower percentage, typically 98% or lower for CNG. Feeding the pipeline may need 99 to 99.92%
methane.
My favorite source of anerobic digester gas is dairy cows. Their feed is very stable and the bacteria can be fine tuned to produce a greater amount of methane is a shorter digestion period. Most dairy farmers are good source of experience and knowledge of feeds to digestion times.
Oddly enough I am not a fan of composting. Due to the fact that composting releases methane in the atmosphere, generally small amounts over a long period. Still direct venting is almost the same as spilling any fuel source and letting it air dry. The more we capture, the more we save.
Cheers to everyone.
Peter Z
New Energy Solutions Inc
-------------- Original message --------------
From: gp baron <gpbaron4091 at yahoo.com>
> When I saw the International Expo in Japan in 2005 that had an environmental
> theme, I had a fond memory of seeing Japanese nationals diligently queing up to
> sort and discard their garbage: 1 bin for food waste, 1 bin for cans, 1 bin for
> plastics, 1 bin for styro containers, 1 bin for glass bottles, 1 bin for papers,
> etc.. Yes, in addition, a lot of patience was involved because the process took
> some time.
>
> In Ontario, Canada some cities are implementing a three-stream system of waste
> disposal: the traditional green garbage bag, the blue box and a new green bin
> for wet kitchen scraps. (see: http://www.yorkregion.com/News/article/20785)
>
> Green bins are used for organic waste such as fruits, vegetable scraps, meat,
> fish, coffee grounds, pasta, house plants, animal waste and soiled diapers. The
> organic material will be made into high-quality compost.
>
> I think there's the answer we're looking for: composting.
>
> Bjorn Dahlroth wrote:
> Hi
> Don't forget that cow manure is already digested.
>
> Regarding the digestion efficiency one must not forget that this is also a
> matter of economy. Normally the turn over time in a digestior is around 20 days
> but then all the digestibel matter is not completely digested. I you want to get
> a higher efficiecy it takes a longer time and then the treatment capacity in
> tons per day will be less and one must remember that for a commercial plant
> digesting for instance MSW the main income is the gate fee in spite of the fact
> that the methane gas can be sold as a fuel for city buses or for electricity
> production. What the owner of a commercial digestion plant wants is not
> necessarily high efficiency but return on the invested capital. There is a
> similar effect if you landfill and suck out the gas. After some 15 - 25 years
> the methane production has gone down so much that it is not economical to suck
> it out any more, but the lanfill will continue to produce methane gas at a low
> rate for many many years after that.
>
> One thing one must also think about is the method of digesion in cells. A Cell
> could be a big concrete box filled with waste and covered by a gastight
> membrane. The digestion process would take 1,5 up to a couple of years. When the
> gas production goes down you take away the membrane or exchange it for a
> permeable type and ventilate so that the process turns into composting. Finally
> you dig out. Still the main income is the gate fee - as always.
>
> So there are many ways of doing it.
>
> Regards
> Bjorn Dahlroth
>
>
>
> -----Ursprungligt meddelande-----
> Från: digestion-bounces at listserv.repp.org
> [mailto:digestion-bounces at listserv.repp.org] För Jason Perry
> Skickat: Sunday, April 29, 2007 7:19 PM
> Till: digestion at listserv.repp.org
> Ämne: Re: [Digestion] landfill vs. AD
>
> Thanks Duncan. This is purely academic at this stage, and I appreciate
> your input. My question is really more about comparing the efficacy of
> the two methods in terms of useful methane output per amount of matter
> input. I agree, the transport schemes won't be exactly the same.
>
> However, in this particular town there is no landfill, just a transfer
> station -- the landfill is run by the county in a different town. Most
> residents drive their rubbish and separated recyclables to the transfer
> station every Saturday. There is some curbside collection (taken
> directly to the landfill) but I think it's the exception. So, if people
> were convinced to source separate their food waste in a different
> container, and a central AD were set up at/near/on the way to the
> transfer station, then the transport scheme would be about the same.
>
> As it is there is no official separation of kitchen waste, and the
> county does not plan to encourage it because they are implementing a LFG
> energy recovery system this year. There is some voluntary home composting.
>
> The reason I suggested co-digestion with cow manure is that the town has
> nearly as many dairy animals (about 4500) as it does people (about
> 6000). Unless I am grossly mistaken the amount of food waste from
> households is dwarfed by the quantity of cow manure.
>
> Cheers,
> Jason
>
> Duncan Martin wrote:
> > Hi Jason
> >
> > But a similar transport scheme seems highly illogical. Have I read
> > your proposal aright?
> >
> > If the vast majority householders can be persuaded to segregate their
> > biowaste efficiently (challenging!) and you set and pay for a separate
> > collection system, then an AD plant is a good option. It would be daft
> > to go all that trouble then dump it in a landfill - with all the stuff
> > you've kept it apart from.
> >
> > Landfill with LFG collection and use might be preferable (under US law
> > - but not in EU) where the biowaste is left in mixed waste or in a
> > residual waste fraction.
> >
> > However, if you had in mind some kind of biowaste AD cell within a
> > landfill site, my own research suggests that it would biodegrade much
> > more slowly than in a mixed landfill, because rapid acidification
> > would effectively ensile it.
> >
> > Duncan J Martin
> >
> > Chair
> > Republic of Ireland Centre
> > Chartered Institution of Wastes Management
> >
> > ================================
> > CONTACT DETAILS
> > Duncan J Martin, PhD, CEng, CSci, MIEI, MCIWM, MIChemE
> > 24 Townsfield, Cloughjordan, N Tipperary, Ireland
> > Mobile: +353 86 8377 906
> > Home: +353 505 42087
> > Email: duncanjmartin at eircom.net
> > ================================
> >
> >
> >
> >
> >
> >
> > ----- Original Message ----- From: "Jason Perry"
>
> > To:
> > Sent: Friday, April 27, 2007 4:54 PM
> > Subject: [Digestion] landfill vs. AD
> >
> >
> >> Dear AD Listers,
> >>
> >> I may have asked this question in some form before, but I thought I'd
> >> rephrase it.
> >>
> >> Consider a rural town in the Northeastern US. If you had a choice
> >> between 1) sending the town's domestic food waste to a landfill that
> >> collects its gas and runs a generator, or 2) sending it to a central AD
> >> that co-digests food waste and dairy manure and runs a generator, which
> >> do you think is a better use of the food waste in terms of energy
> >> production? Assume similar transport schemes between the two.
> >>
> >> Many thanks,
> >> Jason Perry
> >>
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> >>
> >>
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> >
> >
>
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