Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel `CNG` ? Why or why not ?

Explanation

Hydrogen is a cleaner fuel than CNG. This is because the burning of hydrogen produces only water, which is totally harmless. On the other hand, burning of CNG produces carbon dioxide gas and water. This carbon dioxide can produce greenhouse effect in the atmosphere and lead to the excessive heating of the environment in the long run.
Some of the environmental consequences of the increasing demand for energy are the following :
1. The combusion of fossil fuels is producing acid rain and damaging plants (crops), soil and aquatic life.
2. The burning of fossil fuels is increasing the amount of greenhouse gas carbon dioxide in the atmosphere.
3. The cutting down of trees from the forest (deforestation) for obtaining fire-wood is causing soil erosion and destroying wild life.
4. The construction of hydro-power plants is disturbing ecological balance.
5. Nuclear power plants are increasing radioactivity in the environment.
The various factors which we should keep in mind while choosing a source of energy are : (i) the ease of extracting energy from that source, (ii) the cost of extracting energy from the source, (iii) the efficiency of technology available to extract energy from that source, and (iv) the damage to environment which will be caused by using that source.