Hydrogen has been used as a rocket fuel Would you consider it a cleaner fuel than CNG

Q No. 2:

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

Ans:              

No doubt hydrogen gas is cleaner fuel than CNG as CNG contains hydrocarbons. Which contain carbon and it is a form of pollutant present in CNG.  But hydrogen is waste-free. The fusion of hydrogen does not produce any waste. Therefore hydrogen is cleaner than CNG.