What is natural gas, and what advantages and disadvantages does it have as a source of energy?

Flammable gas, consisting largely of methane and other hydrocarbons, occurring naturally underground Advantages & Disadvantages of Natural Gas. Natural gas burns cleaner than other fossil fuels, producing half the carbon dioxide as coal and about a third less than oil. It also emits fewer amounts of toxic chemicals like nitrogen oxides and sulfur dioxide.

81 is a composite number

There is a great difference between the windward and leeward side of a mountain. windward and leeward sides are opposites.