Environmental Engineering Reference
In-Depth Information
settlement data. The leachate composition is analyzed on a regular basis. A gas collection
system is installed for landfill gas collection and emission control. The produced biogas is
collected using this gas collection system comprised of a combination of vertical wells and
horizontal trenches. The collected bio-gas is used to produce electrical energy. This gas
collection system will also be used to pump air into the waste matrix during the second stage
aerobic operation to accelerate biological degradation. A low permeable final biocover was
installed to prevent gas escape from the top surface prior to extraction of biogas. Gas/energy
recovery has commenced after filling and construction of the final cover.
CO2
emissions
CO2
emissions
CH
4
& CO
2
emissions
CH
4
& CO
2
emissions
Oxidation in
landfill bio-cover
(Methanotrophs)
Oxidation in
landfill bio-cover
(Methanotrophs)
Commercial
recovery
Commercial
recovery
Final bio-cover
Final bio-cover
CH
4
& CO
2
generation
CH
4
& CO
2
generation
Solid waste-3
rd
lift (8 m)
Solid waste-3
rd
lift (8 m)
GL
GL
GL
GL
2
nd
Intermediate thin
biocover (30 cm)
2
nd
Intermediate thin
biocover (30 cm)
CH
4
& CO
2
generation
CH
4
& CO
2
generation
Solid waste-2
nd
lift (5 m)
Solid waste-2
nd
lift (5 m)
1
st
Intermediate thin
biocover (30 cm)
1
st
Intermediate thin
biocover (30 cm)
CH
4
& CO
2
generation
CH
4
& CO
2
generation
Solid waste-1
st
lift (5m)
Solid waste-1
st
lift (5m)
Figure 10. Schematic diagram of the Calgary Biocell
The biocell is located at the Shepard landfill owned and operated by the City of Calgary,
Canada. Construction of the biocell started in the summer of 2004. The biocell started
receiving domestic municipal solid waste in April 2005. The 1
st
intermediate cover consisted
of a mixture of partly stabilized leaf compost and soil (6:4 wet weight) and was placed in July
2005 over the 1st lift, with a depth of 5 m. Similarly, a 2
nd
intermediate cover of tree branch
mulch was placed in December 2005 over the 2
nd
lift which was also 5 m in depth. A mixture
of stabilized compost and tree mulch (9:1 wet weight) was placed in an area of 10m x 10m in
the northwest quadrant. The thickness of both intermediate covers ranged from 30 to 40 cm.
The placement of the third and final lift of waste commenced during the third week of
January 2006. The materials for the landfill final cover and leachate collection system were
selected to facilitate convenient excavation, and to recover, and to reuse all components of the
biocell. The biocell reached its final design elevations by April 2006 and was capped initially
with a 0.5 m biocover, a granular medium to support methanotrophic bacteria that oxidize
methane to carbon dioxoide without producing harmful by-products. The construction was
completed in summer 2006 and operation started in September 2006 with gas recovery. The
Calgary biocell pilot project used real-time instrumentation to measure settlement during the
