,O, Fac
"We see the potential to
transform landfills from
waste repositories to
waste treatment
systems."
A. Maurice Myers
Chairman and CEO of Waste
Management
Landfills
Enteric Fermenation
Natural Gas Systems
-------
fy potential problems such as whether
the cover can remain intact when
exposed to stresses, e.g., sloped land-
fill surfaces or foul weather conditions.
Another concern is what kind of vege-
tation, if any, will grow on the cover to
help stabilize it to prevent erosion.
After monitoring the physical prop-
erties of the plot during Phase I,
Waste Management expects to evalu-
ate the economic benefits. The com-
pany also will redesign the cover if
that proves necessary based on the
results from Phase I.
Benefits
Using a mobile landfill gas meter
and gas chromatography, Austrian
researchers Humer and Lechner
found that their system results in
complete decomposition of the
methane released from a 10-year-old
landfill site more than 65 feet deep.
They found that using a matured
compost characterized by a high
humic content, low ammonium and
salt concentrations, and adequate
pore volume yielded the best results.
Their emission reductions exceed
that of a landfill gas recovery sys-
tem, generally thought to collect
about 70 to 85 percent of the total
landfill gas generated.
Engineering measures for gas-to-
energy projects have a limited ser-
vice life, but Humer and Lechner
found that the effectiveness of com-
post in mitigating landfill methane
emissions improves with time. As
the outer compost layer of a landfill
dries up, it creates a barrier that
prevents temperature loss in the
lower compost layer and improves
conditions for methane oxidation.
Ancillary benefits may arise in the
compost market from this technique
if using compost as a landfill cover
becomes a widespread practice. The
use of compost as a landfill cover
could dramatically increase the mar-
ket for compost. If this practice
were employed in small landfills
expected to close over the next 10
years, the demand for compost
would exceed the currently available
supply. An increase in composting
could reduce the quantity of organic
waste disposed at municipal solid
waste landfills, thereby reducing
methane emissions and prolonging
the life of landfills.
Challenges
Since this technique is still in the
research stages, many facets of the
practical application of compost as
landfill cover have not been evaluat-
ed. For example, landfill owners con-
sidering this technique would need
to ensure that their cover complies
with Subtitle D regulations on cover
performance and maintenance of the
cover during the closure and post-
closure periods. As specified in 40
CFR 258:6.0, in order to use an
alternative cover, the landfill
owner/operator will need specific
approval of the state director.
Although research has found that
methanotrophic bacteria are most
active at temperatures ranging from
20 to 37 degrees Celsius and in
ambient conditions with a moisture
content of approximately 40 to 80
percent, questions still remain
regarding optimal conditions in a
non-experimental setting for the
compost to reduce methane emis-
sions. Further, quality of compost
varies considerably and should be
considered in the design of the
cover. It appears that mature, grade
A compost is best-suited as cover
material. Waste Management's
efforts should provide further infor-
mation on the selection of compost
as cover and how such a cover will
react to varied weather conditions,
temperatures, and the physical
stresses of the landfill environment.
Additional
Information
For information on the CRADA,
see Waste Management's press
release at http://www.wm.com/
docs/l/press0081.html, and the
company's bioreactor program page
at http://www.wm.com/bio.html.
EPA's Climate and Waste Program increases
awareness of climate change and its link to
waste management in order to (1) make green-
house gas emissions a factor in waste manage-
ment decisions and (2) employ waste manage-
ment as a mitigation action for reducing green-
house gas emissions. For additional information
on EPA's Climate and Waste Program, see
www.epa.gov/mswclimate.
Solid Waste and
Emergency Response
(5306W)
^ 1
EPA 530-F-02-022
July 2002
www.epa.gov
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(Minimum 50% Postconsumer)
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