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BIOREACTOR LANDFILLS
Theoretical Advantages & Research Challenges
Thabet Tolaymat, PhD.U.S. Environmental Protection AgencyOffice of Research and Development
National Risk Management Laboratory
Bioreactor Landfills
Municipal solid waste landfills that utilize bulk liquids in an effort to accelerate the degradation of solid waste.
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Historical View of Bioreactor Landfill Technology
• US EPA sponsored research as early as 1974
• Preamble to Subtitle D regulations points to some of the benefits of moisture addition
• Uncertainty about long-term performance of MSW containment systems hindered full scale operations
Bioreactor Landfills• Bioreactor RD&D
Rule allows approved states to issue variances for the introduction of bulk liquid waste and air to MSW landfills
• Liquid introduction in landfills with alternate liner systems (other than composite liners)
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Landfill Site
Leachate
4
Bioreactor Landfill DesignFoundationsLiner systemsLeachate collection systemsStormwater control systemsSlope stability considerationsLeachate management systemsGas extraction systemsCapping and closure
AsAs--Built BioreactorBuilt Bioreactor
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NRMRL’s Research• EPA ORD, OSW and LMOP CRADA with
Waste ManagementPolk County Fl,
• Effects of Industrial Liquid and Various Sludge addition;Bench-scale tests (modified BMP);Lysimeter studies;
• Lysimeters are currently being constructed;• Studies should start late 2006 early 2007;
• Design Criteria for Bioreactor Landfills;• Bioreactor Landfill State of the Practice;
Project XL as well as few other bioreactor landfills.
Benefits of Bioreactor Landfills
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Leachate Treatment and Management
• Leachate from active or closed cell reintroduction into bioreactor landfill cells offers an economical disposal method
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Direct Wetting of Solid Waste
• Leachate can be sprayed or pumped onto the waste as it is tipped and compacted.
• Provides good means of moisture distribution.
• Potential concerns:Working conditionsExposure to workersRunoff
Landfill and Biogas
Biogas Plant
Landfill Site
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Enhancement of MSW Stabilization Rate
• Moisture in the solid waste massFacilitates the movement of
nutrientsMedium for Microbial growthActs as a seed
• Thus increasing the rate of decomposition and ultimately the stabilization rate.
<1 1-2 2-3 3-4 4-5 5-8 8-11
050
100
150
200
BM
P (m
L C
H4/
dry
g)
n=47 n=43 n=15 n=5 n=0 n=0 n=0
Waste Age (yr.)
<1 1-2 2-3 3-4 4-5 5-8 8-11
050
100
150
200
BM
P (m
L C
H4/
dry
g)
n=14 n=103 n=13 n=67 n=23 n=62 n=0
Waste Age (yr.)
Control Cells As-Built Bioreactor Cell A
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Year After Waste Placement
0.1 1 10 100
LFGG
d(%
)
0
20
40
60
80
100
k = 0.04 /yrk = 0.061 / yrk = 0.16 / yrk = 0.7 /yr
<1 1-2 2-3 3-4 4-5 5-8 8-11
050
100
150
200
BM
P (m
L C
H4/
dry
g)
n=47 n=43 n=15 n=5 n=0 n=0 n=0
Waste Age (yr.)
<1 1-2 2-3 3-4 4-5 5-8 8-11
050
100
150
200
BM
P (m
L C
H4/
dry
g)
n=14 n=103 n=13 n=67 n=23 n=62 n=0
Waste Age (yr.)
Control Cells As-Built Bioreactor Cell A
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Increase in Landfill Gas Generation Rate
• Increase in the rate of decomposition leads to an increase in the methane and carbon dioxide generation rate
• Potential gas to energy if gas collected efficiently
242 COCHOHMatter Organic +⇒+
Gas Generation is Enhanced
0 10 20 30 40Time (Years)
GasVolume
Bioreactor Landfill
Traditional Landfill
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Traditional Gas Collection Systems at Landfills
• Vertical gas wells are most common method of gas collection
Control Cells
1/1/2001
1/1/2002
1/1/2003
1/1/2004
1/1/2005
1/1/2006
1/1/2007
1/1/2008
1/1/2009
Cum
ulat
ive
Met
hane
(m3 )
0.0
2.0e+6
4.0e+6
6.0e+6
8.0e+6
1.0e+7
1.2e+7
1.4e+7
1.6e+7
1/1/2002
1/1/2003
1/1/2004
1/1/2005
1/1/2006
1/1/2007
1/1/2008
1/1/2009
1/1/2010
Cum
ulat
ive
Met
hane
(m3 )
0.0
5.0e+6
1.0e+7
1.5e+7
2.0e+7
2.5e+7
3.0e+7
3.5e+7
Bioreactor Cell
K = 0.16 / year
K = 0.04
K = 0.15
K = 0.20
K = 0.25
K = 0.28
K = 0.04
K = 0.05
K = 0.2
K = 0.05 /year
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Year After Waste Placement
0.1 1 10 100
LFGG
d(%
)
0
20
40
60
80
100
k = 0.04 /yrk = 0.061 / yrk = 0.16 / yrk = 0.7 /yr
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Increase in Landfill Capacity (Settlement)
• Increase in the settlement ratePrimary settlement caused by the added weight of the liquidsSecondary settlement caused by the increase in the rate of organic degradation of organic matter
Non-BiodegradableComponents
BiodegradableComponents
Non-BiodegradableComponents
BiodegradableComponents
BeforeStabilization
AfterStabilization
Converted to Gas*
* Some may be lost through leachate disposal if not recirculated
Increase in Landfill Capacity (Settlement)
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Potential Long-Term Risk Reduction
• Controlled short term decomposition rather than persistent long term emission
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Economics
• Increase landfill capacity• Industrial liquids• Leachate treatment• Potential reduction in post closure
care (PCC)• Gas to Energy
Concerns About Bioreactor Landfills
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Operational Concerns
• Increase in leachate break outs• Increase in odor• Increase in the potential of standing
water• Fires in aerobic systems• Record Keeping
Design Concerns
• Slope stabilityThe increase of moisture content and the concurrent increase in gas generation may result in an increase in pore water pressureHigh pore water pressure may lead to slope failure
• Perched liquids within the landfill• Head on the liner• Differential settlement• Watering out of gas collection lines
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Gas Emission
• If not collected efficiently, the increase in LFG generation rate may result in an increase surface emissions of
CH4CO2NMOC
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Conclusion• Increase in rate of degradation
provides a more economical source of green energy (methane and possibly hydrogen)
• Reduce long term risk associated with MSW landfills
• Maximizes utilization of land footprint for landfilling
• Bioreactor landfills may offer a sustainable solution for long term solid waste management
Questions?
Thabet Tolaymat [email protected]
Publication available on NRMRL scientific publication pagehttp://www.epa.gov/nrmrl/publications.html
