,O,       Fac
                "We see the potential to
                 transform landfills from
                 waste repositories to
                 waste treatment
                 A. Maurice Myers
                 Chairman and CEO of Waste
            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.

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.

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.

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
  Solid Waste and
  Emergency Response
          ^  1
EPA 530-F-02-022
July 2002
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