AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Anaerobic decay produces methane gas. Biogas generators can be used to…
Full specification wording
Decomposition (biology only): Anaerobic decay produces methane gas. Biogas generators can be used to produce methane gas as a fuel.
When microorganisms break down biological material without oxygen, the process is called anaerobic decay.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 5 of 7
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
When microorganisms break down biological material without oxygen, the process is called anaerobic decay. Anaerobic decay produces methane gas, which is a useful fuel. Biogas generators are designed to carry out anaerobic decay on a large scale. Waste biological material, such as animal manure or crop waste, is placed in an airtight digester so that oxygen is excluded. Microorganisms decompose the waste anaerobically and release methane, which is collected and burned as a fuel for heating, cooking or generating electricity. The remaining material can be used as fertiliser. The rate of methane production depends on temperature and the type of waste.
What earns the marks
- State that anaerobic decay occurs without oxygen and produces methane gas.
- Describe biogas generators as airtight vessels in which waste biological material undergoes anaerobic decay.
- Explain that methane produced by biogas generators is collected and burned as a fuel.
- Give uses of methane as a fuel, such as heating, cooking or generating electricity.
- Recognise that the material remaining after anaerobic decay can be used as fertiliser.
- Compare anaerobic decay with aerobic decay, noting that aerobic decay does not produce methane as a fuel.
Common mistakes and how to put them right
Stating that methane is produced by aerobic decay.
Put it right by linking methane production specifically to anaerobic decay.
Describing biogas generators as open containers.
Put it right by explaining that they must be airtight to exclude oxygen.
Confusing methane with carbon dioxide as the fuel gas.
Put it right by naming methane as the combustible gas produced.
Exam tips
- Use the term anaerobic precisely and state that oxygen is absent.
- Name methane as the fuel gas and give at least one practical use, such as heating or electricity generation.
- Link the design of the biogas generator, especially its airtight nature, to the need for anaerobic conditions.
Try the lesson
The start of the Decomposition (biology only): Anaerobic decay produces methane gas. Biogas generators can be used to produce methane gas as a fuel. lesson, made from checked teaching notes for this specification point.
Have a go first
Which gas is produced by anaerobic decay and can be burned as a fuel in a biogas generator?
Listen
When microorganisms break down biological material without oxygen, the process is called anaerobic decay. Anaerobic decay produces methane gas, which is a useful fuel. Biogas generators are designed to carry out anaerobic decay on a large scale. Waste biological material, such as animal manure or crop waste, is placed in an airtight digester so that oxygen is excluded. Microorganisms decompose the waste anaerobically and release methane, which is collected and burned as a fuel for heating, cooking or generating electricity. The remaining material can be used as fertiliser. The rate of methane production depends on temperature and the type of waste. A strong answer earns marks for these points. State that anaerobic decay occurs without oxygen and produces methane gas. Describe biogas generators as airtight vessels in which waste biological material undergoes anaerobic decay. Explain that methane produced by biogas generators is collected and burned as a fuel. Give uses of methane as a fuel, such as heating, cooking or generating electricity. A common slip: Stating that methane is produced by aerobic decay. Instead, linking methane production specifically to anaerobic decay. Exam tip: Use the term anaerobic precisely and state that oxygen is absent.
See it
Key words
Say what each word means before you turn the card.
Anaerobic decay
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Biogas generators
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Methane
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See every definition
- Anaerobic decay
- When microorganisms break down biological material without oxygen, the process is called anaerobic decay, which produces methane gas.
- Biogas generators
- These are airtight vessels designed to carry out anaerobic decay on a large scale, in which waste biological material is placed so that oxygen is excluded.
- Methane
- A gas produced by anaerobic decay that is collected and burned as a fuel for heating, cooking or generating electricity.
Label the diagram
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1Box 1
2Box 2
3Box 3
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