Fossil fuels are non-renewable resources because they are derived from prehistoric plants and animals that died millions of years ago and have taken just as long to form under layers and layers of rock. There are different types of fossil fuels based on the type of organic matter, how long it was buried, and the temperature and pressure conditions as time passed. These are rich in stored carbon and when burned, release carbon dioxide into the atmosphere.
Before oil was used to power our various forms of transportation, it was used as a building material known as bitumen for thousands of years and was even used to help build the Great Pyramid. As a fuel, it was burned in lamps as early as 2000 years ago in China. Today bitumen is still used in asphalt, and for other products such as fertilizers, pesticides, plastics, and pharmaceuticals. Crude oil is found in reservoirs deep within the Earth and embedded in shale and tar sands. The United States imports 4.5 million barrels a day from exporters like, Canada, Mexico, Saudi Arabia, Venezuela, and Nigeria. Once crude oil is extracted, it is sent to an oil refinery to be turned into gasoline, fuel oil, and liquefied petroleum gas. Petroleum is responsible for 42% of greenhouse gas emissions in the United States. Outside of these gas emissions; destructive extractions toward ecosystems, combustion releasing harmful air particles for respiratory systems, and oil spills in the ocean are all other ways oil can be a very harmful material.
But regardless of its harm or potential harm, oil is a finite resource and we are quickly running out of availability. It is still a little unsure of the exact number of reserves left because it is based on what is currently discovered- there could be more. But what we do know is that at our current rate of consumption, the Earth has enough oil to supply us through 2050. There are more sources of oil, however, but they are all found within private land or federal reserves and natural preservation areas. It is our hope that these very few wild places left will not become threatened for extractions in the future.
Coal is that lump of dark brownish/blackish carbonized plant material extracted from deep mines in the Earth and from the Christmas stockings of bullies everywhere. 45% of the world's supply comes from China, making them the leader in coal exporters. The Chinese were also the first to mine coal around 1900-2200 BCE in modern day Mongolia and Shanxi provinces to be used for burning and carved ornamentation. Although, nearly all ancient societies used the material for fuel, including the Aztecs. Today, like oil, coal is also finite and when burned, releases sulfur dioxide, nitrogen oxides, mercury, and of course carbon dioxide into the atmosphere. Outside of this, mining for coal is extremely damaging to the surrounding environment with destruction to vegetation and poisoning streams, rivers, and other watery realms with high concentrations of minerals and mine wastes that quickly reach toxic levels.
The Department of Energy has reported that as our population grows with a desire of bigger houses that need to be powered, as well as more air conditioning units installed and more use of them as our global temperature continues to rise, the need for coal to provide electricity will rapidly grow until there is nothing left. Right now we have more than a quarter trillion tons of coal beneath us, from the Appalachians to the Rocky Mountains, which should last us another 250 years at our current rate of consumption. And more and more coal plants are being installed throughout the U.S. and China as the demand grows. However, coal emits the most carbon dioxide than any other fossil fuel, per unit of energy. There are, however, cleaner ways to burn coal that lessens the nitrogen oxide and sulfur dioxide, but does nothing for the carbon dioxide. Although there are considerations of building coal plants that gasify the material into electricity by releasing a fraction of the emissions, but the process is much costlier than traditional plants with less production results. So, the future of coal extraction and burning will most likely remain as it has been.
Natural gas was formed by marine beings around 550 million years ago and thus, a finite fossil fuel. It was used at the Oracle of Delphi around 1000 BCE and by the Chinese to boil water in 500 BCE. Natural gas emits about 50-60% less carbon dioxide than coal does, and 15-20% less than oil. However, when natural gas is extracted from their wells and transported by pipelines, methane is released which is 34 times stronger than carbon dioxide at trapping heat over 100 years, and 84 times stronger over 20 years. That said, natural gas is still the "cleanest" of the fossil fuels by also emitting less nitrogen oxide, as well as carbon dioxide when burned. However, residents living near natural gas wells have higher risks and reports of respiratory symptoms, cardiovascular disease, and cancer.
That we know of, there are currently a little less than 2,462 trillion cubic feet of dry natural gas left to extract in the world, which will last us about 90 years by current rate of consumption. Extraction of natural gas is similar to oil and coal mining; altering the landscape with sedimentation, erosion, and polluting nearby streams with harmful chemicals via runoff. When these pollutants contaminate the streams, they not only affect the water beings that live within, but these streams typically flow to larger bodies of water, including the drinking sources for the surrounding communities.
Nuclear energy is technically not a fossil fuel, per se, but it is a finite fuel resource and so it is listed on this page. Nuclear energy accounts for 14% of the world's energy but some countries rely on it more than others. France, for example, receives over 75% of their energy from nuclear, with the United States at around 20%. Because nuclear energy is not a fossil fuel, it does not emit harmful gas emissions (outside of whatever nuclear power plants generate, if not on nuclear) and so thus, it becomes the "cleanest" fuel source of all finite fuel resources. Nuclear energy is derived in a pretty sciencey way; by nuclear fission.
Within any atom we find the protons and neutrons that are housed within the nucleus- or the core of the atom. Surrounding the nucleus are what's called electrons. Protons have a positive charge and electrons a negative one. Neutrons are neutral, or no charge. Nuclear power plants induce fission by colliding a neutron with an atom, thereby splitting the atom into two new atoms and releasing the energy that had kept the original atom bonded. As this happens, more neutrons are released to collide with the two new atoms, splitting those and then they are split by more neutrons and so on. This is called a nuclear chain reaction that produces the heat that nuclear power plants convert to energy.
Now, atoms are found everywhere as tiny little things within the molecules that make up gases, liquids, and solids. So how is it finite? Because nuclear power plants only use the atoms derived from the metal, uranium. Uranium is found in rocks in plentiful amounts all over, but nuclear power plants use a specific kind of uranium called, U-235 and it is extracted by mining. Mining, like with coal, can damage the surrounding environment with water pollution and soil erosion. The highest amount of U-235 uranium is found in Australia, while the next highest amounts are in Kazakhstan, Canada, and Russia. Today, we know of about 5.5 million metric tons of uranium-235, with an estimated 10.5 million metric tons additional that have yet to be discovered. This will last us enough energy for about 230 years by current rate of consumption. As U-235 becomes less available, the price will likely increase. This may result with uranium being extracted from seawater in the future (currently, this procedure is too expensive) which would tack on an additional 60,000 years of energy supply! However, this could greatly disrupt the sea and harm the beings within, that which is already fragile and dealing with their own environmental degradation from pollution and rising temperatures.