Bioreactor Technology

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Bioreactor Technology
Conference on Leveraging Landfills
with Public-Private Partnerships Improving Local
Government Financial Performance by Protecting
the Environment LaGrange, Georgia June 7-9,
2006 Majdi Othman, Ph.D., P.E. mothman_at_geosyntec
.com
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Presentation Outline

• Background
• Bioreactor Concept
• Types of Bioreactors
• Benefits of Bioreactors
• Additional Costs of Bioreactors
• Conclusion

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Background-Use of Technology
Partial List of Landfills that applied
leachate recirculation or bioreactor technology
in the U.S.

• Over 50 leachate recirculation and bioreactor
  landfills in the U.S.
• Recent Passage of EPAs Research, Development,
  and Demonstration (RDD) Rule, created more
  opportunity to operate old and new landfill cells
  as bioreactors.
• EPA and many states have recognized the
  environmental benefits of liquid addition.
• Owners recognize the significant benefits.
• Guidance, regulation, and technical support are
  needed to support this technology.

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BackgroundWaste Degradation Process
I Initial Adjustment II Transition III Acid
IV Methane Fermentation V Maturation
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Bioreactor Concept

• Bioreactor technology accelerates the biological
  decomposition of food, paper and other organic
  wastes in a landfill by significantly increasing
  the moisture content in the landfill. The liquids
  create optimum conditions for the microorganisms
  to rapidly degrade the solid waste.
• 40-60 gallons of added liquid per ton of solid
  waste increases the water content of the waste
  from about 20 to about 40-50.

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Bioreactor Concept
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Types of Bioreactors

• Anaerobic
• Aerobic
• AerobicAnaerobic

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Anaerobic Bioreactor

• Degradation of waste is accelerated by optimizing
  conditions for anaerobic bacteria
• The anaerobic bacteria converts organic wastes
  into organic acids and ultimately into methane
  and carbon dioxide.
• Moisture is typically added in the form of
  leachate through a variety of delivery systems.
• Additional sources of moisture such as sewage
  sludge, storm water, and other non-hazardous
  liquid wastes may be necessary to augment the
  leachate available for recirculation.

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Aerobic Bioreactor

• Accelerates waste degradation by optimizing
  conditions for aerobes which are organisms that
  require oxygen for cellular respiration.
• Energy is delivered from organic molecules in a
  process that consumes oxygen and produces carbon
  dioxide.
• Aerobes require sufficient water to function just
  as anaerobes do.
• In landfills, aerobic activity is promoted
  through injection of air into the waste mass.
  Liquids are typically added through leachate
  recirculation.

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Aerobic-Anaerobic Bioreactor

• Rapid biodegradation of organic waste in the
  aerobic stage to reduce organic acids in the
  anaerobic stage resulting in the earlier onset of
  the methane fermentation phase.
• The uppermost lift or layer of waste is aerated,
  while the lift immediately below it receives
  liquids.
• Landfill gas is extracted from each lift below
  the lift receiving liquids.
• Horizontal wells that are installed in each lift
  during construction are used to transport air,
  liquids, and landfill gas.

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Benefits of Bioreactors
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Benefits of BioreactorsRapid Stabilization of
the Waste Mass
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Benefits of BioreactorsEnhancement of Landfill
Gas Generation for Gas to Energy Projects
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Benefits of BioreactorsEnhancement of Landfill
Gas Quality for Gas to Energy Projects
Source Yolo County, CA
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Benefits of BioreactorsImprovement of Leachate
Quality
Source Reinhart and Al-Yousfi, 1997.
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Benefits of BioreactorsIncreased Waste Settlement
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Benefits of BioreactorsIncreased Waste Settlement
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Benefits of BioreactorsIncreased Waste
Settlement leads to Increased Landfill Capacity
From SWANA Presentation by Gary Hater of WMI
(2006)
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Additional Costs of Bioreactors

• Added costs may include
• Larger leachate management system components
  (pumps, piping etc.)
• Installation of leachate recirculation
  trenches/wells and associated piping
• alternative daily cover
• alternative interim cover (e.g., exposed
  geomembrane)
• Operation costs for bioreactor (personnel,
  equipment, etc.)
• Additional monitoring (leachate quality and
  quantity, additional LFG quantity, etc.)
• Additional maintenance (seep repairs, odor
  prevention)
• Additional capital costs for a 1,150 tpd
  bioreactor landfill were estimated to be 3.5
  million by Hater, et. al.
• Actual cost is very site-specific.

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Conclusions

• Landfills can be successfully operated as
  bioreactors through proper design and operations.
• Bioreactor technology has many benefits
  including
• Accelerated and more complete decomposition of
  waste
• Associated settlement/capacity gain
• Enhanced gas generation for LFGTE projects
• Less leachate to treat
• Less contamination potential after landfill is
  closed
• Less long-term risk
• Reduced post-closure care requirements
• Bioreactors need additional capital and
  operations costs.