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[GreenYes] Landfill Gas
Bruce Middleton asks: "We are engaged in a broad LCA-type assessment of
domestic food waste management options for local city councils.  A key issue
seems to be whether landfill gas recovery systems actually capture any of
the methane from decomposition of food waste or if the food waste decomposes
too quickly for the methane to be captured. My research has uncovered
several mentions of reports on the issue but no definitive references. Any
ideas?"

You have put your finger on a part of the reasons why we are unable to
safely manage decomposable material in the ground, which is precisely why
the European Commission has already ordered a phase out of organics in
landfills, and Nova Scotia has implemented one.

That is the much vaunted systems for capturing landfill gas, in the real
world, are notoriously inefficient.  EPA has declined to produce actual
field data to document the real-world efficiencies, but, from all that is
known, it would be extremely difficult to explain how much more than 20% of
lifetime gas generation is actually captured, and the true number may well
be closer to 10%.

In the case of food waste, most of it decomposes in less than 2 years.
Below I have reproduced an analysis of the rate of food decomposition in the
Dane County Rodefeld Landfill done by the County's recycling manager John
Reindl.  This is of some import, because, under the EPA's air rules, for
those large landfills required to install gas collection systems, they are
not required to be operational for 5 years after waste emplacement.

That is to say, by the time the systems are required to be installed, only
0.9% of the food scraps remain undecomposed in ideal conditions (somewhat
more otherwise).  Moreover, in fact, most landfills are not able to actually
install the requisite piping for 7 - 10 years because of the geometry
constraints of the site.  This relates to the fact that the vertical gas
removal pipes cannot be perforated with slots through which to draw gas at
their top 100 feet for fear of drawing oxygen from the surface along with
gas from the waste load because oxygen would make an explosive mix with the
methane. Hence there has to be enough waste in the ground to encompass this
no-draw span before the pipes can be installed and operational.

Bottom line: none of the gases produced from the decomposition of food
scraps are captured.  All of that methane is emitted uncontrolled into the
atmosphere contributing to global warming, as well as the hazardous air
pollutants from the surrounding waste that the methane transports into the
atmosphere and which may be associated with the serious health effects that
have been observed in the few as yet inconclusive studies of landfill
neighbors.

But, please do not stop your consideration at this obvious conclusion, which
is to aggressively develop compost programs for food waste.  There is three
times as much unrecovered paper, on average,  than food scraps going to our
landfills, all of which also decomposes, and only a small part of which is
captured.

What is needed is a paradigm shift in which we see that the solution to one
of the intractable problems with landfills also can lift our recovery
programs to the next level.  Just like we already separate our bottles, cans
and newspapers for recycling, we will soon be separating our food scraps,
unrecovered paper and green waste for composting, thereby boosting today
30-35% recovery to more than 75% -- most of the way to zero waste.

Decomposition of Food in Landfill
Year Tons Percent
1    11654    60.3%
2    4625        23.9%
3    1835        9.5%
4    728            3.8%
5    289            1.5%
6    115            0.6%
7    46                0.2%
8    18                0.1%
9    7                    0.0%
10    3                0.0%
11   1                 0.0%
Total 19321 100.0%




______________________________
Peter Anderson
RECYCLEWORLDS CONSULTING Corp
4513 Vernon Blvd. Suite 15
Madison, WI 53705
Ph:    (608) 231-1100
Fax:   (608) 233-0011
Cell:   (608) 345-0381
email: anderson@recycleworlds.org
web:  www.recycleworlds.org

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