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“Landfill gas extraction system in the making”, Braambergen landfill
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Overview
11.1 Types of extraction systems
11.2 Operational aspects
11.3 Management and maintenance
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11 – Methane capturing 11.1 Types of extraction systems
11.1 Types of extractions systems
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Landfill gas dynamics
Three main factors influence the migration of landfill gases:
Pressure
Permeability and
Diffusion
11.1 Types of extraction systems
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Landfill gas extraction
Landfill gas is:
explosive in air
a Greenhouse Gas (GHG) and
toxic to humans
….and therefore should be controlled on landfills
11.1 Types of extraction systems
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Landfill gas extraction
There are two types of landfill gas extraction:
1. passive
2. active
11.1 Types of extraction systems
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Passive landfill gas extraction
11.1 Types of extraction systems
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Active landfill gas extraction
Active landfill gas extraction demands the following:
1. Extraction system
2. Compressor
3. Flare installation or
4. Landfill gas utilization
11.1 Types of extraction systems
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Extraction system
There are several types of active landfill gas extraction
systems:
1. Vertical
2. Horizontal
3. Slope
4. Point
11.1 Types of extraction systems
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VerticalConventional Cell wise
Build up Build up + early extractionGRAVEL
HDPE piping (perforated)
HDPE piping (non -perforated)
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Horizontal
11.1 Types of extraction systems
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Slope
11.1 Types of extraction systems
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Point
11.1 Types of extraction systems
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Gas well connection
RULE OF THUMB: 4 GAS WELLS PER HA
11.1 Types of extraction systems
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Gas well connection
11.1 Types of extraction systems
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Compressor
11.1 Types of extraction systems
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11 – Methane capturing 11.2 Operational aspects
11.2 Operational aspects
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Explosive conditions during start up
Due to safety procedures, explosive conditions must be avoided at all times. The start up procedure to avoid explosive conditions is as follows:
1. Every valve in the extraction system must be opened;
2. At the flare installation or the booster station venting piping needs to be constructed at safe place within landfill boundaries (NOT nearby housing, scavengers or registration offices) and
3. Under current conditions, landfill gas will force out the air naturally.
4. Flare and extraction system full with landfill gas
5. Start up flare at lowest extraction rate
6. Monitor landfill gas quality and explosion limits frequently
11.2 Operational aspects
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Explosive conditions
Landfill gas contains methane Explosive conditions of methane in air achieved between 5 - 15% Over extraction of the extraction system could result into high infiltration
of ambient air and explosive conditions could be reached
Monitoring again is essential!
11.2 Operational aspects
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Landfill gas monitoring
Monitoring equipment
Anemo meter Digital manometer Gas analyser
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Landfill gas monitoring
Gas analyser can measure:
1. CH4
2. CO2
3. O2
4. N2 (= 100% - CH4% - CO2% - O2%)
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Landfill gas monitoring
If CH4 and O2 concentration respectively in a gas
well is:
> 50% and < 1% then more extraction
< 50% and > 1% then less extraction
11.2 Operational aspects
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Landfill gas monitoring
If N2:O2 ratio is:
> 5 indicator suction of ambient air
< 4 indicator leakage piping extraction
system
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11.3 Management and Maintenance
11.3 Management and maintenance
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Check at the flare installation:
Flowmeter and indicator function (CDM requirements)
State O2 analyser
Automatic shut down in case of explosive mixtures
..on a regular basis
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Maintenance should be performed by: Maintenance scheme
Arrange spare part list critical items (compressor, flare,
extraction system)
The later enables planning and minimises down-time of
extraction system and, therefore, minimises greenhouse gas
emissions
11.3 Management and maintenance