Introduction to fuels

Humans and our ancestors have used fire for a very long time. Maybe even for over a million years, long before the advent of modern humans. Learning to set a piece of wood on fire gave us several benefits: we could cook our food, scare away wild animals, on a cold night we could get warm and comfortable. We could carry on doing things after sunset, and make pottery, and stronger building materials. Think about it: a tree takes decades to grow, by gathering energy from the sun.

Then we come along and release that energy in just a few hours: fifty years of sunshine, gathered and concentrated, into a few evenings of warmth and spicy casserole. No wonder we humans have always liked to burn wood! In some places people burned so much wood that they used up all the trees and without trees there’s not much to keep the soil in place – not a very good idea – especially not if you live on an island. It’s a better idea to cut down trees no faster than they can grow back again. That’s what it means when we say a fuel source is renewable.

Later, people found an alternative to firewood right under our feet! It was a hard rocky substance, made up mostly of carbon – coal. And it seemed to be in unlimited supply. Coal burns like wood, but we can get a lot more energy from coal compared to wood. These two things – lots of energy and large supply – turned out to be important when the coal-burning steam engine was introduced.

With the help of this invention, we could do even more things. Now, burning stuff could replace muscle power to lift, press, cut, and move things. And people got greedy for fuels! But as useful as coal has been, it has some drawbacks. When we burn coal, we don’t just get heat.

A lot of other stuff is released too: ashes, sulphur oxides, nitrogen oxides, carbon dioxide, and toxic heavy metals like mercury and lead. Sure, many of these things are released when we burn wood too. It’s just that suddenly we burned waaaay more coal than we ever burned wood. Since then, humans have been great at digging and drilling in the ground, to get hold of even more fuels that we can set fire to, to get what we want. We burn petrol, which we get from oil, to get cars to move.

And we burn kerosene, which also comes from oil, to get aeroplanes into the air. Natural gas is burned to generate electricity, and to heat homes. And just like coal, these fuels leave things other than energy behind when we burn them including carbon dioxide, which adds to climate change. Fuels that we dig or pump up from the ground – coal, oil and gas – are called fossil fuels. They are the remains of plants and algae, that lived a very long time ago, most of them even before the dinosaurs.

These plants and algae gathered energy from the sunshine, died, sank to the bottom of the ocean, and then slowly turned into coal, oil, or gas. This went on for more than a hundred million years. Imagine: nature has spent a hundred million years, farming these plants and algae. And now we’re harvesting it in just a few hundred years. Eventually, we’ll run out of fossil fuels.

Because unlike trees, the fossil fuels aren’t renewed any time soon. So why do we even use fossil fuels, if they are non-renewable, and pollute the environment? Well, a few pieces of firewood, is enough to cook a dinner but with a few litres of kerosene, you can cook your food, for several weeks. Sunshine from a hundred million years, concentrated, and stored in substances that we can burn and make useful in an instant – no wonder it’s so hard to replace fossil fuels.