What is the typical composition of landfill gas in the stable methane-producing stage?

Landfill gas in the stable stage is roughly 50–60% methane and 40–50% carbon dioxide. Traces of hydrogen sulfide and organic compounds cause its odour.

What happens in the final stage of landfill decomposition?

Biodegradable material runs out and gas production declines. Air slowly returns to the waste, and aerobic conditions may resume.

Why is methane from landfill a concern?

Methane is a powerful greenhouse gas, around 28 times as strong as carbon dioxide over 100 years. Methane is also explosive at 5–15% in air and can migrate into nearby buildings.

CCEA A-Level Environmental Technology 3930

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Waste Management

Landfill decomposition, methane and leachate

3 things to know
A2 1

Overview

The aerobic, acid and methane-producing stages of decomposition, the composition of landfill gas, methane as a greenhouse gas, leachate, and how moisture, waste type, temperature, pH, rainfall and compaction control breakdown.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Process

What happens during the first, aerobic stage of waste breakdown in landfill?

Key term

What happens once the oxygen in landfill waste has been used up?

Key term

How does methane production develop as landfill waste ages?

Questions from this subtopic

Each one with the model answer underneath.

1
What happens during the first, aerobic stage of waste breakdown in landfill?
Model answer
Aerobic bacteria use the oxygen trapped in the waste to break down organic matter. Carbon dioxide, water and heat are produced, and the oxygen is used up within days or weeks.
2
What happens once the oxygen in landfill waste has been used up?
Model answer
Anaerobic bacteria take over and ferment the organic matter into organic acids, hydrogen and carbon dioxide. The pH falls, and the leachate becomes strongly polluting.
3
How does methane production develop as landfill waste ages?
Model answer
Methanogenic archaea convert the acids and hydrogen into methane and carbon dioxide. Methane output rises over months to years, then stays steady for decades.
4
What is the typical composition of landfill gas in the stable methane-producing stage?
Model answer
Landfill gas in the stable stage is roughly 50–60% methane and 40–50% carbon dioxide. Traces of hydrogen sulfide and organic compounds cause its odour.
5
What happens in the final stage of landfill decomposition?
Model answer
Biodegradable material runs out and gas production declines. Air slowly returns to the waste, and aerobic conditions may resume.
6
Why is methane from landfill a concern?
Model answer
Methane is a powerful greenhouse gas, around 28 times as strong as carbon dioxide over 100 years. Methane is also explosive at 5–15% in air and can migrate into nearby buildings.

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Global Action on Energy Conservation and Climate Change

Macrogeneration

Microgeneration

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