|It's gettin' hot in here
“”"Oil? An emergency? Ha! It's about time the people who run this planet of yours realised that to be dependent on a mineral slime just doesn't make sense."
|—The Fourth Doctor, Terror of the Zygons
Fossil fuels consist of biological material that had decomposed and been placed under extreme pressure for extremely long periods of time (millions of years). They include coal, natural gas, and petroleum. Fossil fuels are of great importance to the world's energy production, as they account for 86% of it. There is great concern over what happens when we run out (peak oil). Use of fossils fuels also has damaging environmental effects (pollution and greenhouse gases).
How does it work?
When plants or animals die, some of the potential chemical energy in them remains. This matter may sink to the bottom of the ocean or lakes and be covered with sediment. Over millions of years, it is compressed by layers of earth, and the same amount of energy will occupy the now smaller space. This in turn makes the matter give off far larger energy output than the more recently deceased. However, as we still are burning almost pure carbon, the main byproduct is carbon dioxide, a greenhouse gas.
First discovered by Santa to give to naughty kids,[citation NOT needed] coal is one of the older sources of fuel. There's various qualities of coal ranging from filthy lignite to relatively clean-burning anthracite. In terms of energy efficiency, coal has to boil water into steam rather than exploding directly, meaning it's pretty much the dirtiest fossil fuel there is. Worse still, there's no "pure" coal — it all contains things such as sulfur, and some sources are so dirty that CO2 isn't the most problematic issue.
Natural gas is the cleanest energy source, as the gaseous nature allows for the most efficient generator designs. It can be used for cars in a liquified state, though it's not the most stable. It's also used in the Bosch-Haber process to make fertilizers and 'splosions. Removing its use completely while maintaining crop production is a concern; there's potential from GMO's to develop, say, wheat that can fix nitrogen, but this hasn't been proven yet. There's also the issue of leaking into the atmosphere during mining; methane is far, far worse than carbon itself.
Pretty useful for transportation. Oil derivative can also be used for other purposes, such as plastics. Helium is extracted from oil, which is an actual concern about a zero-carbon world when helium is so important for medicine and nuclear physics.
Also known as "shale oil", this is better thought of as a fourth type of fossil fuel. Kerogen is the precursor to the other fuels, and there is also more of it. But as the precursor, it needs to be processed, and that processing ain't pretty. It's much dirtier than oil.
Problems with fossil fuels
As mentioned before, using fossils fuels contributes to two major problems:
- the byproducts leave a mess (smoke, greenhouse gases, ash, waste from extraction)
- for all practical purposes, fossil fuels are non-renewable
The most common method of using coal to produce electricity releases large amounts of the greenhouse gases emitted straight into the atmosphere. While the process seems relatively cheap at the moment, it certainly doesn't diminish global warming. (Nor does burning any other fossil fuel.) Other methods of using coal may cause less harm — mainly clean coal-burning — but due to the ever-increasing depletion of coal resources, it seems an unlikely long-term solution.
Due to the process in which fossil fuels form they have a limited supply before the "stockpile" must be left to replenish — for another few millions of years. This would mean essentially a permanent switch from fossil fuels to another — renewable — energy source. Currently, there are no viable alternatives that can be implemented in all cases where fossil fuels are used, so energy-suppliers may have to diversify — shock! horror!.