Landfill Gas Collection System DesignBRYAN WELDON P.E.

Permit Requirments01

Gas Models 02

Passive Gas Systems 03

Active Gas Systems 04

Economic Factors 05

Questions 06

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Permit Requirements

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Air Regulations for MSW Landfills – NSPS and EGs

NSPSXXX

NSPS WWW

EGCc

EG Cf

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When is a GCCS required by rule?• NSPS XXX minimum criteria that will require a GCCS:

• Landfill must have a design capacity > 2.5 million Mg AND > 2.5 million cubic meters.• Landfill must have begun physical construction AFTER July 17, 2014• Landfill must have the potential to generate 34 Mg/yr of NMOC emissions

• NSPS WWW minimum criteria that will require a GCCS:• Landfill must have a design capacity > 2.5 million Mg AND > 2.5 million cubic meters.• Landfill must have begun physical construction AFTER May 29, 1991• Landfill must have the potential to generate 50 Mg/yr of NMOC emissions

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When is a GCCS required by rule?• EG Cf minimum criteria that will require a GCCS:

• Landfill has accepted waste any time since November 8, 1987 or has design capacity for future waste acceptance.

• Landfill must have a design capacity > 2.5 million Mg AND > 2.5 million cubic meters.• Landfill must have begun physical construction BEFORE July 18, 2014• Active landfill must have the potential to generate 34 Mg/yr of NMOC emissions• Closed landfill must have the potential to generate 50 Mg/yr of NMOC emissions

• EG Cc minimum criteria that will require a GCCS:• Landfill has accepted waste any time since November 8, 1987 or has design capacity for

future waste acceptance.• Landfill must have a design capacity > 2.5 million Mg AND > 2.5 million cubic meters.• Landfill must have begun physical construction BEFORE May 30, 1991• Landfill must have the potential to generate 50 Mg/yr of NMOC emissions

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Gas Models

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• Official model used by the US EPA• Minimal Model Parameters/Variables/Inputs• Overly Conservative Gas Production Estimates• Generally, NOT the Best Indicator for Gas

Collection Design Systems

Landfill Gas Emission ModelL A N D G E M

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• Not Used for Permitting• More Dynamic Parameters/Variables/Inputs

• Moisture• Waste Composition

• Better Indicator of Actual Landfill Gas Production

Industry Specific ModelsG A S S I M

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Passive Gas Systems

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___Passive Gas System

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Solar Flares• Installed in Passive Gas Vents• Operate for Low Gas Flows• Localized Gas Flaring• Operate at Ambient Pressure• Difficult to Operate in Cold Weather Climates

• Heat Pads, Insulation and Running Power

Passive Gas SystemG A S F L A R I N G

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CONS• Less Gas Collection• Minimal or No Gas

Destruction• No Possibility for Energy

Production

PROS• Cheap to Construct• Can be Built During

Landfill Closure• Little to No Regular

Maintenance

Passive Gas System D E S I G N C R I T E R I A

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Active Gas Systems

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___Active Gas System

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___Active Gas SystemV E R T I C A L E X T R A C T I O N W E L L S

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___Active Gas SystemV E R T I C A L E X T R A C T I O N W E L L S

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• Must Provide Safe Access During Installation

• Spaced based on Radius of Influence (ROI)

• >15’ Above Liner

___Active Gas SystemH O R I Z O N TA L E X T R A C T I O N W E L L S

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• Trenched into Waste• Greater Gas Collection

than Vertical Wells• Best if Installed during

Waste Placement• Cannot be Modified after

Construction• Vulnerable to Waste

Settlement

___Active Gas SystemC O N D E N S AT E S U M P S

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• Provide Gas Knockout• Deep Enough to Not

Pull Condensate into Header

• Will Require Drainage Method

• Self Draining Into Waste• Self Draining into

leachate System• Pumping System

___Active Gas SystemH E A D E R A N D L AT E R A L P I P E W O R K

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• Always Maintain >5% Grade

• Design for Cover to Drive Over

• Ensure Grades Don’t Interfere with Cap

• Pressure Test all Pipework

• Be Conservative on Pipe Sizing

• Install Valves for Isolation

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• Enclosed Flare vs Candlestick • Cost vs Efficiency

• Sized Based on Gas Model Results• Placed in a Secure Location on Site• Immediately Down Stream of Condensate Sump

Active Gas SystemF L A R E / B L O W E R

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CONS• More Expensive to

Construct• Should be Designed with

Cell Landform• Regular Maintenance

and Upkeep

PROS• Targeted Gas

Collection • Odor Control• Migration Management

• Possible to Earn Capital to Offset Costs

Active Gas System D E S I G N C R I T E R I A

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Economic Factors

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• ~$15,000 Per WellIncludes all Associated Pipework

• >$100,000 for Flare• Regular Monitoring, Upkeep

• Wellfield Balancing• Permit Reporting• Replace Worn Pipes, Hosing, Valves, etc..

Economic FactorsC O S T T O C O N S T R U C T- A C T I V E S Y S T E M

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• Require Additional Infrastructure• Powerlines, Transformers, etc…• Additional Pipework to Possibly Sell Gas Offsite

• Minimum ~650 SCFM to Operate a Single 2 MW Generator• May Require Multiple Generators for Return on

Investment

• Requires More Stringent Gas Management

Economic FactorsL A N D F I L L G A S G E N E R AT O R S

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• Require Gas Plant Installed On Site• Refine Gas to >98% Methane• Pump Gas into Natural Gas Pipeline

• Extremely Stringent Gas Quality Requirements• Cost-Benefit Dependent on Price of Natural Gas

Economic FactorsH I G H B T U G A S P L A N T

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Questions?

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