Across
- 2. Not suitable for places without enough ______ animals
- 5. A gas produced from cow dung and organic waste.
- 6. Biogas is a type of this energy that does not get finished.
Down
- 1. Biogas causes ____ effect.
- 3. Biogas is safe for this and reduces pollution.
- 4. Biogas plants need large amounts of animal ______.