Fossil fuels

Fossil fuels include coal, oil, and natural gas. They occur naturally in the Earth, and can be burned for energy. They currently provide over 80% of the world's energy, but at a heavy environmental cost.

Terminology

Natural gas is sometimes referred to as just gas. Not to be confused with gasoline.
Crude oil is also known as petroleum, and it can be refined into oil products such as gasoline and diesel.

Usage as an energy source

Climate change

Major problem

Burning fossil fuels is the main cause of climate change, due to the CO₂ it releases into the atmosphere.

For the same amount of energy, coal releases about twice as much CO₂ as natural gas, and oil is somewhere in between.

Other pollution

Sometimes manageable

Burning fossil fuels releases more than just CO₂.

Exhaust from cars and trucks
Exhaust from coal power plants

These contain particles that are harmful to people and ecosystems.^{[ELABORATION needed]}

Mitigation

Cars and trucks already have catalytic converters that eliminate some of this pollution - but not all of it.
For coal power plants, newer technologies could avoid most of this pollution (but still not the CO₂ that causes climate change).

Scarcity

Eventual problem

Oil reserves are expected to run out in less than a century, by most estimates.^{[QUANTIFICATION needed]} Coal and natural gas are similar. Fossil fuels are not considered renewable(...)( despite being fossilized organic matter that was originally dead plants & animals ), because existing oil reserves took millions of years to form.

Globally, per person, there is about 31 tonnes of oil (recoverable) somewhere in the Earth. oil.reserves(tonnes per capita)(world.population). Average production is about 1.5 kg/day per person oil.production(lbs/day per capita)(world.population). Rich countries consume a lot more, poor countries use a lot less.

Non-energy usage

Fossil fuels are also used in making plastic, most of which is disposable. Other uses include making thousands of different chemicals, but together they add up to only a small fraction of fossil fuel consumption. ^{[QUANTIFICATION needed]}