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11 – Methane capturing

11 Methane capturing

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11 – Methane capturing

“Landfill gas extraction system in the making”, Braambergen landfill

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11 – Methane capturing

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)

11.1 Types of extraction systems

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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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11 – Methane capturing

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

11.2 Operational aspects

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Landfill gas monitoring

Gas analyser can measure:

1. CH4

2. CO2

3. O2

4. N2 (= 100% - CH4% - CO2% - O2%)

11.2 Operational aspects

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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

11.2 Operational aspects

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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

11.3 Management and maintenance

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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