Gas from waste
Bacteria without oxygen make biogas.
Waste in a closed tank
Some bacteria live in an oxygen-free place. They can decompose plant and animal waste or household wastewater.
What might these bacteria release as they decompose the waste?
What this lesson covers
The idea
Some bacteria living without oxygen decompose plant and animal waste or household wastewater, releasing biogas, a mixture of gases made up of carbon dioxide and a high proportion of methane.
Waste in a closed tank
Some bacteria live in an oxygen-free place. They can decompose plant and animal waste or household wastewater.
What might these bacteria release as they decompose the waste?
- A mixture of gases we can use as fuel
- Only a solid powder
- Nothing at all
Make biogas
Add the waste, close the lid so there is no oxygen, then wait. Tap each use of the gas.
A mixture of gases
Some bacteria that live without oxygen decompose plant and animal waste or household wastewater and release biogas: a mixture of gases made up of carbon dioxide and a high proportion of methane.
Biogas is used as a fuel for cooking, heating, generating electricity and even running vehicles.
- Gas in biogas | How much
- Methane | A high proportion
- Carbon dioxide | Also present
Notes
Bacteria that live without oxygen decompose plant and animal waste or household wastewater and release biogas: carbon dioxide and a high proportion of methane.
Check yourself
Which bacteria make biogas?
Biogas is a mixture of which gases?
Which of these is a use of biogas?
- Bacteria that live without oxygen — correct. Yes. They decompose waste in an oxygen-free place.
- Only bacteria that need a lot of oxygen. These bacteria live without oxygen, in a closed tank.
- Only bacteria that make food using sunlight. These bacteria decompose waste. They do not use sunlight.
- Carbon dioxide and a high proportion of methane — correct. Yes. Methane is the main part of the mixture.
- Oxygen and nitrogen. Biogas forms without oxygen. It is carbon dioxide and methane.
- Hydrogen and helium. Biogas is made of carbon dioxide and methane.
- A fuel for cooking — correct. Yes. Biogas is used as a fuel for cooking, heating, generating electricity and running vehicles.
- Making milk curdle. Lactobacillus bacteria make milk into curd. Biogas is a fuel.
- Making dough rise. Yeast makes dough rise. Biogas is a fuel.