Biofuel from manure and water
When you have completed these activities you will have produced and studied the biogas, methane (CH4).
You will need:
- Plastic drink bottle
- Mud from the bottom of a pond, or manure
- Fill a plastic drink bottle with mud or a mixture of manure and water. Screw the top on the bottle tightly and keep it in a warm place. Bubbles of methane will appear in the bottle. If the methane bubble in the top of the bottle is small, squeeze the bottle and (under your teacher’s supervision) try to set the gas alight. Methane burns with a pale blue flame.
You will need:
- Two plastic drink bottles
- Mud from the bottom of a pond or manure and water
- Wine cask inner bag
- Two-hole stoppers to fit into plastic bottles and wine cask bag, or plastic tubing
- Weak solution sodium hydroxide (caustic soda)
- Spring clothes peg
- Set up a model biogas generator (see the diagram). The manure mixture should be kept in a warm place or warmed with an aquarium heater.
The wine cask bag is used to store the gas. The sodium hydroxide solution absorbs carbon dioxide gas, which does not burn. The tubing from the wine cask bag should dip under the surface of the sodium hydroxide solution, because that bottle acts as a flashback trap. It prevents a flame at the gas nozzle from flashing back and exploding the gas stored in the wine cask bag. Pure methane has no smell, but there is always some smell associated with digesters.