A piece of coal is around 440 million years old. All that time ago, it was part of a fern or primitive tree growing in a bog. When it died and was buried, it was eventually compacted into layers of rock. Natural gas formed from gases released from decaying matter into pockets between the rocks. Oil is a sludgy deposit that is similar in composition to oil, but which was not compressed so that it became solid.
Fossil fuels, because they were formed from the decayed remains of organisms that were once alive, are rich in carbon. When they are burned, that carbon is released as carbon dioxide, a natural greenhouse gas. Human activity that has burned up fossil fuels in the last 100 years has increased the atmospheric level of carbon dioxide, leading to global warming and climate change.
Contribution of Fossil Fuels to our Energy NeedsCoal provides 28% of the energy that we use in developed countries, slightly less than oil, which currently provides about 40%. Natural gas contributes about 20% of our total energy consumption. This only leaves 12% that is, at the moment, provided by renewable energy sources. This must change however, as all three fossil fuels are finite and they will run out.
The History of Fossil Fuels
Although we are now worried about fossil fuels running out, we have not been dependent on them for very long. Gas, oil and coal all existed before humans evolved but we did not use them as energy sources until the latter part of the 19th century. Even then, the human race hardly made a dent in reserves.
It is during the last 80 years or so that our consumption of fossil fuels has grown unbelievably to the extent that reserves may not last for another 20 years. The fossil fuel age for humans may only last for barely a century of our existence.
The key turning point in history that led to our current fossil fuel frenzy was World War II, the first war to be fought using aircraft and tanks – the age of the modern vehicle followed, and then the electronics revolution.
The World’s Leading Oil Producers
In the brief window that may become known as the fossil fuel era, the USA has produced an astounding 170 billion barrels of oil, the former Soviet Union 125 billion barrels and Saudi Arabia 74 billion barrels. When we have used up all the oil, Saudi Arabia will probably come out as the lead producer because it has the largest reserves – 189 of the 800 billion barrels of all the remaining oil in the world. Another 200 billion barrels remain in the rest of the Middle East and there are just 84 billion barrels left in Russia.
When Will Fossil Fuels Run Out?
There are many estimates of this but it is a big unknown because it depends on how fast we actually use what it left. There is enough oil still left in our reserves to power the world for another 15 years or so, assuming that developing countries increase their consumption to double the current US level in the next few years. This seems unlikely. At the other end of the spectrum, assuming we manage to use oil sensibly, it might last for another 60 years. Some would say this is equally unlikely. In reality, the final date that oil runs out will probably be somewhere in the middle of these two extremes.
There are around six thousand trillion cubic feet of natural gas left on Earth. Experts think that natural gas could last longer than oil as demand is lower – gas is used only as a fuel whereas oil is also used as a raw material for the chemical industry, but some think we only have another 50 years of gas left. Coal has more reserves. In total 97% of all the reserves of fossil fuels we have on Earth are coal deposits. If we use coal at the rate we do today, it could last as long as 1500 years. However, if usage rises by 5 per cent each year, which it could as our reliance on coal could increase as oil and gas run out, we could only have 87 years worth of coal still to burn.