Natural gas is a fossil fuel formed when layers of buried plants and gases are exposed to intense heat and pressure over thousands of years. The energy that the plants originally obtained from the sun is stored in the form of chemical bonds in natural gas. It is a nonrenewable source because it cannot be replenished on a human time frame. Natural gas is a hydrocarbon gas mixture consisting primarily of methane, but it includes alkanes, carbon dioxide, nitrogen and/or hydrogen sulfide. It used for heating, cooking, and electricity generation. It is also used as fuel for vehicles and as chemical feedstock in the manufacture of plastics and other commercially important organic chemicals.
Coal is a combustible, sedimentary, organic rock, which is composed mainly of carbon, hydrogen and oxygen. Coal is used for electricity generation, steel production, cement manufacturing and as a liquid fuel.
Hydrogen fuel is a zero-emission fuel when burned with oxygen or used in a contained cell also capable of 'reversing' the reaction if needed. It often uses electrochemical cells, or combustion in internal engines, to power vehicles and electric devices.
Oil is one of the most highly consumed forms of nonrenewable energy.
Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human timescale, such as sun light, wind and water.
Nuclear energy uses fuel made from mined and processed uranium to make steam and generate electricity. It is the only source of electricity that can produce a large amount of power.