Fossil Fuels

Let’s move on to the practical aspect of how we use energy. Fossil fuels are probably the most common energy source and one that humans have been using for the longest time. The basic idea of fossil fuel energy is to take some carbon and combine it with oxygen, forming carbon dioxide along with some energy (which is the part we want). Yes, it’s true—you get energy from forming chemical bonds, not from breaking them. Of course the oxygen usually comes from the atmosphere (which is about 21 percent O₂), but where do you get the carbon? Well, you could chop down a tree and burn it. Or you could dig up some old trees that over time turned into coal, oil, or natural gas. Since these are super old trees, they are fossils—boom, fossil fuels.

So, what’s great about fossil-fuel-based energy? The best thing is that it’s easy. You just need to get this stuff out of the ground and then burn it. It’s like instant energy just waiting there for humans to use it. Most forms of fossil fuels also have a high energy density. There’s quite a bit of energy in gasoline, which has an energy density of 46.4 MJ/kg. Even though an automobile is only 25 percent efficient, just 1 kilogram of gasoline can give you 11.6 million joules of energy. Remember, it was 10 joules to lift a textbook ofg the ground and onto a table. This is why you can get a car to drive 20 to 50 miles on just a single gallon of gasoline. You have to admit that’s really impressive.

OK, then, what’s not great about fossil fuels? Hopefully, you already know the answer to this question. When you burn a fossil fuel, you produce carbon dioxide. Carbon dioxide is a greenhouse gas, and it contributes to climate change. If we keep burning fossil fuels, the increase in carbon dioxide is going to change the climate in a way that will make it difficult for humans to keep doing things we have always done—like living near the coast or growing crops in certain regions. So, that’s what’s bad about fossil fuels.

But let me just be clear. It’s not just the use of gasoline in automobiles. We also burn fossil fuels for the production of the electrical energy used in houses and stuff. The basic idea is to burn the fossil fuel to heat up water and convert it to steam. This steam then pushes on the blades of an electric turbine engine to spin it. These spinning turbines create electrical energy through an electromagnetic interaction (using loops of wires and magnets). A number of energy sources use spinning turbines, actually.