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Landfill Wellfield and Project Components. Outline. Objectives of LFG Collection/Control Elements of a LFG collection System LFG Destruction/ Utilization Options. Objectives. Recover and utilize LFG Minimize potential environmental impacts Control off-site migration Control odors

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Landfill Wellfield and Project Components


Outline
Outline

  • Objectives of LFG Collection/Control

  • Elements of a LFG collection System

  • LFG Destruction/ Utilization Options


Objectives
Objectives

  • Recover and utilize LFG

  • Minimize potential environmental impacts

  • Control off-site migration

  • Control odors

  • Comply with regulatory requirements


Elements of an lfg collection system
Elements of an LFG Collection System

  • Network of interconnecting piping

  • LFG collection points

    • Vertical extraction wells

    • Horizontal collectors/trenches

    • Connection to existing vents, wells, etc.


Elements of an lfg collection system continued
Elements of an LFG Collection System (continued)

  • Elements of condensate management

  • Flow control

  • LFG blower/combustion device (flare, engine, etc.)


Landfill gas collection and control system
Landfill Gas Collection and Control System

  • Gas collection wells and blower – pull gas from landfill

  • Flares – greater than 95% destruction of landfill biogas

  • Monitoring equipment – used to balance well field and ensure proper operation


Vertical extraction wells
Vertical Extraction Wells

  • Most common approach for recovering LFG

  • Install in existing or operational disposal areas

  • Waste depth preferable >10 meters


Vertical extraction wells1
Vertical Extraction Wells

  • Install approx 2.5 wells per hectare(~ 1 well per 0.4 hectare)

  • May lose efficiency or not work in landfills with elevated leachate levels


Landfill gas collection control
Landfill Gas Collection & Control

Gas well and collection pipe.


Gas monitoring wells
Gas Monitoring Wells

  • Wells located on perimeter of landfill to monitor for off-site migration.

  • Placed in natural soil conditions.

  • Routine testing at same locations.

  • More reliable (uniform) results.

  • Verification through repetition.

  • Serves as a guide for system effectiveness.



Testing for gas quality and pressure
Testing for Gas Quality and Pressure

  • Performed on site at each well location

  • Portable equipment analyzes gas and measures pressure and flow.

  • Immediate results for maximizing balancing efforts.



Vertical extraction wells design features
Vertical Extraction Wells Design Features

  • In-refuse wells: 75% of the refuse depth

  • Depth of in-soil wells varies

    • Groundwater level

    • Bottom of refuse

    • Depth of gas migration


Vertical extraction wells design features continued
Vertical Extraction Wells - Design Features (continued)

  • Boreholes typically 60 cm to 90 cm in diameter

  • Casing is generally PVC or HDPE

  • Bottom perforated - start 6 meters below ground surface

  • Spacing depends upon “radius of influence” (typical 60 m - 122 m)


Typical vertical extraction well
Typical Vertical Extraction Well

  • Bentonite seal prevents air infiltration

  • Wellhead incorporates:

    • Flow control valve

    • Pressure monitoring port

    • Flow monitoring device (optional)

    • Thermometer (optional)


Vertical extraction wells examples

Auckland, New Zealand

Vertical Extraction Wells - Examples

  • Los Angeles, California


Vertical extraction wells examples1
Vertical Extraction Wells - Examples

Los Colorados Landfill near Santiago, Chile

Basural Landfill, Peru


Theoretical radius of influence of a landfill gas well
Theoretical Radius of Influence of a Landfill Gas Well

  • Radius of influence 2 to 2.5 times well depth

  • Increase vacuum to increase the radius of influence

  • Variations in vacuum are the operator’s only control tool


Actual radius of influence of a landfill gas well
Actual Radius of Influence of a Landfill Gas Well

  • A well’s radius of influence is unlikely to be ideal:

    • Variations in waste characteristics

    • Interim cover and cell configuration

    • Presence of leachate


Horizontal collectors
Horizontal Collectors

  • Alternative approach for LFG recovery

  • Install in shallow areas

  • Install in existing or operational disposal areas


Horizontal collectors continued
Horizontal Collectors (continued)

  • Install at a spacing of approx. 30 to 100 meters

  • Can be used in landfills with elevated leachate levels


Horizontal collectors design features
Horizontal Collectors - Design Features

  • Install in trenches or place on grade and cover with gravel and waste


Horizontal collectors design features continued
Horizontal Collectors - Design Features (continued)

  • Construct out of approx 100 mm slotted PVC or HDPE pipe

  • Alternatively construct out of “nested” 100 mm an 150 mm pipes



Examples
Examples

  • Bangkok, Thailand

  • Los Angeles, California


Laterals and headers
Laterals and Headers

  • Pathway for LFG from wellheads to blowers

  • Can be above-grade or underground

  • Generally HDPE - PVC sometimes used above-grade

  • Sized on flow rate and pressure drop


Laterals and headers continued
Laterals and Headers (continued)

  • Pipe configuration often “looped” to provide alternative flow paths

  • Pipe sloped to promote condensate drainage

  • Unusual drops in vacuum normally due to condensate blockages


Condensate system
Condensate System

  • Condensate volume depends on LFG temperature and flow

  • LFG is assumed to be 100% saturated with water

  • LFG temperature is typically 32° to 54° C


Condensate removal design features

LFG cools in the LFG collection piping and the moisture condenses out into the piping

Piping designed to allow condensate to drain

Traps allow for drainage by gravity

Sumps collect condensate

Condensate Removal - Design Features


Landfill gas flaring
Landfill Gas Flaring condenses out into the piping

  • Flaring

    • Open flares (candle-stick flares)

    • Enclosed flares (ground flares)


Blower flare station

Combusts methane gas condenses out into the piping

Open or enclosed flame

Blower/Flare Station


Blower flare station continued
Blower/Flare Station condenses out into the piping(continued)

  • May be used in combination with beneficial use system

  • Needed during utilization system startup and downtime


Blower flare station design features

Location should be central to collection system, close to potential end user or utility service, away from trees

Design with flexibility to handle future gas flows

Blower/Flare Station - Design Features


Blower flare station typical elements
Blower/Flare Station – potential end user or utility service, away from treesTypical Elements

  • Moisture separator

  • Blowers

  • Flare (open or enclosed)

  • LFG piping and flame arrestor

  • Flow meter

  • Pilot fuel supply

  • Control panel (controls both blower and flare)

  • Auto shutoff valve


Landfill gas flares
Landfill Gas Flares potential end user or utility service, away from trees


Example potential end user or utility service, away from trees


Landfill gas blowers
Landfill Gas Blowers potential end user or utility service, away from trees


Enclosed ground flares
Enclosed Ground Flares potential end user or utility service, away from trees

  • Flare body usually circular: 9 to 12 meters high

  • LFG combusted close to ground

  • Flame not visible from outside

  • Air louvers near stack base


Enclosed ground flares continued
Enclosed Ground Flares potential end user or utility service, away from trees(continued)

  • Typical operating temperature range:

    760 C to 870 C

  • Typical destruction of 98 to 99 percent (or greater)

  • More expensive than candlestick flares


Open candlestick flare components
Open (Candlestick) Flare Components potential end user or utility service, away from trees

  • Vertical pipe

  • Flare tip at top of pipe - flame visible

  • Smaller than enclosed flare


Landfill gas beneficial use
Landfill Gas Beneficial Use potential end user or utility service, away from trees

  • Methane is a valuable energy source.

  • Can be used to generate electricity in an internal combustion engine or turbine.

  • Can be used as a fuel in boilers or thermal kilns or dryers.

  • Can be used in infrared heaters.


Landfill gas beneficial use1
Landfill Gas Beneficial Use potential end user or utility service, away from trees

  • Dual benefit  destroys methane and other organic compounds in LFG

  • Offsets use of nonrenewable resources (coal, oil, gas) reducing emissions of

    • SO2, NOX, PM, CO2

  • Landfill gas is generated 24 hours a day, seven days a week.

  • LFG can act as a long-term price and volatility hedge against fossil fuels


Landfill gas electricity generation
Landfill Gas potential end user or utility service, away from treesElectricity Generation

Internal

Combustion Engine

(range from 100 kW to 3 MW)

Gas Turbine

(range from 800 kW to 10.5 MW)

Microturbine

(range from 30 kW to 250 kW)


Diversity of project types direct use of lfg

Pottery Studio Sugar Grove, NC potential end user or utility service, away from trees

LFG-fired Boiler Ft. Wayne, IN

Diversity of Project TypesDirect Use of LFG

  • Direct-use projects are growing!

    • Boiler applications – replace natural gas, coal, fuel oil

    • Combined heat & power (CHP)

    • Direct thermal (dryers, kilns)

    • Natural gas pipeline injection

      • Medium & high Btu

    • Greenhouse

    • Leachate evaporation

    • Vehicle fuel

      (LNG, CNG)

    • Artist studio

    • Hydroponics

    • Aquaculture (fish farming)

Greenhouse Burlington, NJ


Carbon credit benefits
Carbon Credit Benefits potential end user or utility service, away from trees

  • Carbon Credit Markets

    • Through the Kyoto CDM/JI Mechanism

    • Tons of CO2 offsets are sold on an exchange market


Summary

LFG collection system design - site specific potential end user or utility service, away from trees

Basic Concept

Provide path for LFG collection

Manage condensate

Burn or utilize the gas

Always consider your operating goals

Summary


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